Bell 412

[TeaCup]

I am wondering as a general enquiry what the operating cost of a B412 would be approximately just as a pax mover machine per hour. I have heard several wearied and wonderful figures that vary by 400%. They look damn expensive little feller's to run. Roughly what kind of pay load would you have to play with on a 150NM run with a 1hr IFR reserve? Thanks, and nothing to technical please !! ;)

[TeaCup]

c'mon, roll up- roll up, someone out there must know something.

Teacup

[gulliBell]

Bell Helicopter quotes the "direct operating cost" of the B412EP at $750.18USD per flight hour, based on fuel @ $1.50/gal and maintenance labor at $50/hr. For operational purposes you would also have to add indirect operating costs such as insurance, crewing, financing costs, depreciation, facilities etc etc. What did I hear you say, "Ripley's believe it or not??"

[leading edge]

How many hours do you want to fly per month?

Single Pilot or 2 Pilot ops, day only or day and night, 5 days per week or 7 day per week, EP, HP or SP???

I will work it out for you based on real world costs if you have that information available.

LE

[Ian Corrigible]

TC -

If you're after detailed data, suggest you try Conklin & Decker (www.conklindd.com). Addition of indirect costs takes the hourly rate for the 412 to ~ $900/hr.

[Phoinix]

Can anyone help me with B412 rotor blades data?

I'm looking for root&tip chord line, and construction angle of attack difference betwen tip&root.

Thanks for any info!

[sprocket]

This all that I have found, does it help?

From this site ... EngTips (http://www.eng-tips.com/faqs.cfm?fid=645)

Wing Root Airfoil - Boeing VR-7

Wing Tip Airfoil - Wortmann FX 69-H-080

[Phoinix]

I'm amazed that data like that exists. Thanks fot the help, but i would need the actual length of chord line.

I managed sort of get the angle out of some photos. Thanks for the tip on airfoil sprocket. I got 10° difference between root and tip chord line. Can anyone confirm this?

If i got this far, chord line length shouldn't be a problem. :}

[Recuperator]

Scenario: [B] Take off from a oil platform that is at 100' amsl.

Helicopter: Bell 412 SP, 11400 lbs TOW. (2 crew, 10 pax + baggage/freight.)

Weather: Sea level, OAT-32 degrees C, Wind-Light and variable, QNH-1013 Mbar.

On rotation you loose an engine and through your superior handling skills, knife edge reactions, you prevent ditching and after nursing your helicopter, climbing at the guaranteed 150 feet/minute ROC at 65 kts, you eventually reach a safe flight condition and altitude.

Now having to fly back to a onshore alternate for a single engine landing, what would the realistic figures be one can expect for indicated airspeed in kts and fuel consumption in lbs/hr?

Data I have been given to work on is 90 kts and 700lbs/hr single engine at loiter power? Loiter power, then you will never reach your destination and I think 90 kts is pushing it? :confused:

Some expert advice will be appreciated please!

(I hope I didn't bring back to many scary nightmares:\ )

[SASless]

OAT Minus 32C ?

[Nigerian Expat Outlaw]

Hope you mean +32, but if it was me I'd plan on max approx 80kts IAS @ 600lbs/hr.

Hope it helps.

[Recuperator]

Sea level, OAT-32 degrees C, Wind-Light and variable, QNH-1013 Mbar. = Sea level, OAT- +32 degrees C, Wind- Light and variable, QNH- 1013 Mbar.

Thanks NEO, what do you base the figure of 600lbs/hr on, experience or from the FM?

I looked again and the 700lbs/hr at loiterpower is a twin engine figure, but it is also the figure stated for single engine operations?:ugh: RTFM!

[Nigerian Expat Outlaw]

Glad to be of assistance. Unfortunately it's based on experience, over around 50 miles of unlandable/unditchable swamp. I have never found anything in the FM that covers SE fuel consumption adequately, although you can contact BHT directly on their website. Maybe they have some accurate SE cruise fuel figures ?

Cheers.:ok:

[Recuperator]

Let me, guess, Warri, PH, Eket area... say no more! Been there done that, mostly on singles... glad not to have had any trouble and lived to move on to the next level of fear and trepidation.:eek: :ooh:

[Old Man Rotor]

Tell me the secret please!!!

What magic are you using to get a heavy 412 away from a platform on a ISA +17 nil wind day in the OEI, at the critical point.!!!!

[Assumming you have standard 3B engines?]

My experience would have you upside down after hitting your tail on the edge, or sitting happily on the floats looking smugly at each other.

[Nigerian Expat Outlaw]

OMR,

I agree. I was talking about cruise figures. Getting away from a platform at those weights etc would be a real feat with -3Bs.

[Recuperator]

OMR,

I saidthrough your superior handling skills, knife edge reactions, you prevent ditching and after nursing your helicopter All hypothetically speaking off course, to get to the figures for OEI flight fuel consumption and IAS in the cruise as NEO rightly helped with.


You saidMy experience would have you upside down after hitting your tail on the edge, or sitting happily on the floats looking smugly at each other.
I assume that you had the latter as your experience, as very few people survive the drop from a hundred foot inverted coming of the rig after hitting their tails on the deck. I have seen the evidence of that happening, and it wasn’t pretty.

Now if you have had the “My experience” part, please share it and make a wiser man out of me and at the same time offer your OEI figures for the cruise flight home as described in the post.

Your handle, OMR, is probably not because you are a bold pilot, but rather a old pilot as I know very few old and bold pilots. Sharing your story and your experience will be highly appreciated and I could very well learn something from it.


:ooh:

The engines that we house are PT6T-3BF engines.

Pretty reliable in the twinpack configuration, I would say.

OMR, NEO, Pretty low on power as you would say.

I agree fully. The nice thing though of the reliability of the remaining engine is that it\'s lack of power will most probably take you to the scene of the accident/ditching...:mad:

[SASless]

Get some of the Aramco pilots to explain their magic....they fly the 412EP's at 11,900 and do not cut weight except for night flying....and it gets rather warm in Saudi....

Their operation (off-shoot of PHI according to most folks in the know) does not consider CAT A performance at all....nor do they use any sort of identifiable CAT A profiles.

As I recall...with some clarity due to the lack of adult malt beverages in that part of the world....they basically used miminal climb and accelerated as quickly as possible to 60 kts....on takeoff from the rig and then considered that CDP of sorts. Lofting off some of the elevated decks there that were all of 25 feet above the briny....that could be an interesting proposition in my view.

[Old Man Rotor]

Sorry, I cant highlight an actual event, otherwise I may not be here to report the magic!!

My experience has been around Test Flying the various profiles at various Weights, Temperatures, AMSL and Crew Experience [discipline] levels.

The scenario described by yourself would be nearly impossible to execute successfully, regardless of the competence of the crew. There are many variables to consider in “your” departure, but if all goes wrong at the worse time, then you will not get safely away.

Sassy, as you know those machines are on the N Register.

The mention of the: WAT Chart, OEI Climb, MTOW and 100% Torque is a revelation. Shudder!!!

Remember this is a SP with 3B's, not an EP with DF engines.

[Recuperator]

Thanks for the input, will definately keep it in mind next time they want to load everything and the kitchen zinc in the back! Sometimes I wonder if it is worth it, especially in the Middle East under Sharia law...:\

[DSpice]

Had the single engine fuel consumption question come up in preparing for a new contract. After doing a lot of work with FlightSafety and Bell Helicopters it was determined that the fuel consumption single engine at max cont. was the same in the PT6T-3b as twin engine consumption. The airspeed will depend at on what you can maintain but we had come up with 90 knots in the simulator.

Hope this helps.

[Recuperator]

Thanks mate, it's a bit scary considering the distances you have to go sometimes to the rigs, with limited fuel and maximum payload. That onshore alternate can seem like a mighty long way to go!

Changing the post a bit, any comments; pros and cons in taking off from the centre of the deck compared to moving as close as possible to the edge of the deck before commencing the rotation into forward flight.

Your imputs will be highly appreciated!:ooh:

[Red Wine]

This was an interesting airing of views from a while back:

http://www.pprune.org/forums/showthread.php?s=&threadid=54120

[Gomer Pylot]

The usual technique over here is to get as close to the edge as possible, with the rotor over the water, and the toes of the skids just barely inside the edge of the deck. The rationale for this is that the wind hits the wall below and is deflected up and into the rotor, providing some additional lift. The wind usually goes up, and then on the downwind side of the heliport is actually blowing down, much reducing lift, so the best place to be is as close to the edge as possible. All this is assuming a standard production platform heliport, but the same effect is usually felt coming off a drilling rig. The technique used when at 11,899 lb, little or no wind, and very hot, is to get to the edge, and move nothing. It's important to be very smooth, and to move neither the cyclic, the collective, nor the pedals unless absolutely necessary, and then as little as possible. Stirring things around destroys lift. We hover there at 100% torque, and eventually some lift comes along, which can be felt as the helicopter starts to rise. As this happens, smoothly lower the nose to move off the deck, and do nothing quickly, or else the deck may rise up and strike the tail. If 100% torque provides enough power, then the takeoff is made in one continuous movement. You usually know before the skids break contact whether there is enough power to go immediately, but it's still a good idea to do things slowly.

Some may be horrified at the technique, but it works, as evidenced by tens of thousands of takeoffs annually, without a single accident that I'm aware of during the past 20 years. The exposure time is minimal, a couple of seconds at most, and everyone involved has accepted the risk.

[Recuperator]

Thanks RW, not trying to reinvent the wheel sometimes makes life easier!:ok:

GP, it's the same techique I use when heavy, by moving forward till the blades are over the sea and skids just inside the deck. The wind does make a huge difference!

Company policy dictates 85% IGE max to ensure enough power in hand to be able to get to 15-20 feet vertical, before rotating. But some of the SP's just can't do it from 85%, without a lot of praying, nursing and swearing in the same breath. :mad:
Thanks for the input!

Anything said on approach angles somewhere?

Especially taking into consideration wind / no wind, heavy / light load, turbulence and cross wind landings (especially wind from the right side) with the Bell 412's? :\

[Old Man Rotor]

Your not writing a book by any chance are you???

Please don't think that the standard upheld in the GOM is the accepted International Standard, it is not.

If you have to wait for a gust of wind to become airborne, then your far to heavy, and negligent. But maybe don’t know it!!!

[SASless]

OMR....It is amazing how one large company....OLOG...with its two major companies...Bristow and Air Log ...can operate so differently. Not only between companies...but within the company itself at its various bases. The local management has as much effect on operating practice as does the Home Office crowd (if not more so).

Throw in the different governmental agencies overseeing the operations and you get a whole different twist yet again.

The FAA sees things much differently than does the CAA...thus Gomers approach the same tasks from a different viewpoint than do their UK licensed brothers (and sisters).

What is right one place...is poison at another...what came out of the Elevated Deck thread seemed to indicate that different techiques seem to yield very similar results but with lots of arguing about which side had the best way.

The GOM method of diving off the decks...and making flat approaches took some getting used to...after doing the Bristow steep...steep...steep approaches. In Nigeria...the takeoffs were not much different beyond the fact we reduced weight for temps in general and greatly reduced weight for Mud Barges surrounded by tall trees....not sure the Gomers would be allowed to do that by company and customer mandate.

[Old Man Rotor]

Your not saying that our GOM colleagues would be forced to trade off their meager safety margins in favor of increased profits?

Surely not.

Its been ten years since I was down in the Gulf, and now fully recognize there are Companies, Authorities and Flightcrew that demand and achieve a higher safety standard.

Cheap safety will cost significantly more in the longer term.

[Gomer Pylot]

OMR, since the incentive bonuses of most upper level managers, both helicopter and oil companies, are based on quarterly performance, there is little reason for them to care about long-term costs. With the profit levels being posted, lawsuits are only minor annoyances, and there is little evidence that the managers care about the safety of employees other than from an economic standpoint.

Perhaps I'm too cynical, but I've been observing the actions of these companies at close range for well over 20 years, and that has been my consistent impression.

[Nigerian Expat Outlaw]

Problem is, the "companies" call the shots !! Like it or not, operators are coerced by them and then go to the authorities to get a "dispensation". Fact of life. Nobody is wrong:mad:

[SASless]

I was not able to attend the PHPA Safety Conference...but heard some good reports about it. One of the statistics advertised there was the helicopter industry kills about 59 pilots per year....and that trend seems to be relatively constant.

Maybe someone that attended can enlighten us on that presentation of statistics?

[Nigerian Expat Outlaw]

Regardless of profiles/numbers/manuals etc, there are some things you can't budget for.

[Recuperator]

OMR :ooh: No, definately not writing a book, and not taking anybodies advice as accepted International standard. This forum lends itself to learning more, as there is a vast amount of experience out there.

I am merely fishing for information to take, evaluate and to assimilate, then to use the best from everyone for my own use to improve on my own knowledge and skill, within or as close to company regulations as possible.

As for flying over MAUW, I don't go there! We work on Class 2 and OGE figures for take off, depending on location and with the temperature of the moment, we then calculate what we can lift. The OEW, fuel and manifest weights are added to together to determine TOW and then compared with take off data. Weight then gets adjusted or reduced to stay within allowable TOW parameters. This gets done before every leg on every flight. So there is never a doubt or any guess work involved what our actual TOW is or what figure will give us Class 2 take off performance or OGE performance. I am sure most pilots work on that basis in the offshore industry.

I have been very fortunate to have flown with pilots of various nationalities that have flown in the North Sea, GOM, Nigeria and Middle East, Australia and South Africa and have learnt from each and every one of them! Wasn't all good, some of it was kept as experience on how not to do it. :uhoh:

As SASless said there are differences in the same company. I have seen the flat approaches, the dive off the decks, the steep, steep approaches and have prayed many times! As said in the post Red Wine was refering to:"Flying and helicopter flying per say on and off decks/rigs/ships/mud barges/airfields are not black and white and every situation merits it's own tecnique.

I thoroughly believe that the day you think, as a pilot, that you know everything about helicopter aviation, it's best to step down before your attitude kills yourself, or worse some innocent passenger, who is relying on your skill and knowledge as a professional to get him to his destination safely. He is usually just a worker, a pawn in the system, like you and me and not usually directly involved in management with hidden agendas, short term planning and incentive bonusses.

Unfortunately safety margins do get "adjusted" to make up for profit. Maybe the Sikorsky S92's will be the answer to all this, with it's Cat A performance, with full fuel and full pax, and go capabilities.

But will the companies pay that kind of money, cut into their profits for their workers safety sake?
:confused:

I would still like to hear the pro's and cons on approach profiles though, anybody willing to stick their necks out?:\

[NickLappos]

At risk of poking again at the hornet's nest, who said that operating with full Cat A from a rig would measurably improve safety?

The data I have seen says that OEI enroute, with minimal exposure time at takeoff and landing is quite sufficient, since we are far more clever at making crashes than to simply wait for an engine to quit.

Yet again, I do wish we were willing to actually fix what causes crashes, rather than what we train for, which is burned into our collective brain, and therefore has our deepest concern, however unreasoned.

[SASless]

Nick,

Why then the full Cat A performance of the 92.....? What drove that decision.....or design criteria?

[JimL]

Notwithstanding that this will raise the hornets from slumber; Nick has managed to avoid comment on Gomer Pylot's post and remark only on the aspirations of Recuperator.

Compared to Recuperator's considered approach (which is based on the practical procedures contained in JAR-OPS 3), the description of the take-off procedure in the GOM results (for me) in a sharp intake of breath.

It might first be appropriate to highlight one particular element of Gomer's post; it has been observed from flight tests that a wind of up to10kts does not give the additional lift that one would expect (hence no wind accountability in the S76C+ Category A helideck procedure for winds below 10kts). Putting the disc over the deck edge might improve on this situation but would it compensate for the loss of lift that would result from the dissipation of ground cushion? Nick probably has the answer to this.

The fact that the authors of JAR-OPS 3 settled for second segment performance (climb performance of 150ft/min at Vy at 1000ft above the take-off altitude) or AEO HOGE was no accident, it ensured that vertical acceleration would be possible and the decision to pull above a limit would not be required.

If one is already applying the take-off Tq of 100% (and going no-where vertically) what if the sudden improvement in lift, due to a transient wind, disappears at the time that the helicopter is in transition over the deck edge? Isn’t this the Las Vegas approach to performance?

How many pilots, faced with this situation, would allow the helicopter to descend rather than pull a ‘transient Tq’! This might not be reportable but is it good practice?

[Recuperator]

Maybe all areas of the offshore market needs some attention to detail when it comes to flight operations, human factor, maintenance and training to improve safety and standards in our industry.

Some interesting reading.

The 2004 report for 2002 from the OGP at http://www.ogp.org.uk/pubs/354.pdf
:eek:

[NickLappos]

JimL is right, but I use the same logic on this thread that I did when my young son asked me where the knives were kept. I asked him, "Why do you want to know?"


SASless, please understand that my questioning here has NOTHING to do with the performance of ANY aircraft. I am not the S-92, I am a person. I have opinions and ideas that I share here that do not infer ANYTHING about ANY helicopter. I believe the S-92 has the best OEI performance of any aircraft in its class.

I contend that we are channeled by our training from the first flight to think of engines as safety, and this creates an automatic response that hurts us.

More engines, More OEI performance, More safety. This builds in our minds the belief that no other investment in our machines will pay bigger benifits. Our regulators grow from our pilot pool, they are part of our self-hypnosis, so the safety rules grow from this same delusion.

I ask anyone to show the data to prove this wrong-

For twins that have basic OEI capability:

The safety of those aircraft will NOT be increased in any measurable way by adding full OEI performance. If we invest in full OEI performance, we will FAIL to make our aircraft safer, we will just make sure an aircraft with bigger engines crashes in the same way it now does, with all engines running happily while the real cause has been ignored.

[SASless]

Nick,

We have discussed this before...and actually agree about having a focus upon "real" accident causes....vice grinding away with the same old wheel. My point was merely to point out that in previous posts to other threads you have talked of the 92's load it up and go capability. Believe me when I say as an oldtime pilot...I understand the beauty of that capability....but....following your logic that we are only exposed to an engine failure during the critical phase in takeoffs for .0000008 percent of the time...or some such number....then why all the wonderful performance for the 92....maybe some of that weight and power could have been expended upon range and cargo volume and thus step back to the current status of most twin engined helicopters wherein we all risk a saltwater dip should one of the Donks give up the ghost during a takeoff at "max" weight?

[Nigerian Expat Outlaw]

Nick, I agree with you on may of the points you've raised, but in that case why haven't the big operators taken on the EH-101 ? 3 engines, total redundancy (so they say) ? Sounds too good to be true.....................

[NickLappos]

Nigerian Expat Outlaw,

I guess I wasn't clear enough. The third engine costs so much in lost range, and gains so little in safety (arguably zero) that it is totally rejected by all commercial opeators. The newest commercial jets are all 2 engined for that reason as well.

SASless, the OEI capability of the S-92 allows about 330 NM from a rig at zero wind on an ISA+10 degree day with full pax and baggage, which is great. If we loaded it to enroute OEI, the aircraft would have about 1000 lbs more payload. That is the price paid for the full OEI. The military H-92 has the same systems, and loads up at 2100 lbs more payload. That 1/2 to 1 ton loss is the "cost" of full Cat A.

That being said, our job at any manufacturer is not to argue with the customer, it is to deliver what he wants. Since full Cat A is so popular 9and was required a few years ago) we designed it in. But we made the EGPWS standard just for real safety.

[SASless]

Nick,

Interesting point you made....Ground Proximity Warning system shoved onto the customer by the manufactuer....rather than by the Customer demanding it. That system would have saved at least one S76 in the Gulf of Mexico this year....and a bunch of lives. Funny how the Big Time corporate helicopters get outfitted with all the gadgets while the Offshore birds do without. I guess all the IFR flying in the Northeast corridor requires that stuff and the Gulf of Mexico doesn't.

[Gomer Pylot]

I have to agree with Nick. If you look at accidents here over the past years, engine failures in twins are not killing people. Flying into the water, into rigs, into thunderstorms, etc are killing people. Mechanical failures of other components are killing people, and merely frightening others, because of the skill of some pilots. I'd far prefer an engine failure to a tail rotor failure.

I don't spend much time worrying about an engine failure, if any, except on checkrides when I know it's going to happen. A simple engine failure enroute is an annoyance, nothing more. On takeoff it can be critical, but it seldom happens there, despite what anyone may want to believe. Look at all the reports you want, and you will find very few in which an engine failed on takeoff. There have been none at all that I know of in which the result was the tail hitting the heliport. Focusing on engine failure to the exclusion of all else, especially to the exclusion of CFIT, is incredibly short-sighted.

And now back to your regularly scheduled hand-wringing.

[Recuperator]

Does the S92 have TCAS or similar and HUMS as standard fit?

[NickLappos]

HUMS is standard, TCAS is available. See

http://www.s-92heliport.com

[Scorpiones Pungunt]

We operate the Bell 412 EP in a variety of roles and have a question regarding the pre flight hydraulic systems checks.

According to the Bell flight manual there are 2 checks to be carried out. The preliminary check with the throttles at idle to check for uncommanded control movement or motoring whilst either system is selected off and a second check at 100%rpm to determine proper operation of the hydraulic actuators.

During the second check you are also required to check the electrical interlock, which prevents both systems from being switched off at the same time. To do this you are required to select the second system’s switch to off whilst the first is already isolated to check that the second system remains operational and vice versa.

For those of you not familiar with this aircraft the hydraulic switch panel is located on the centre console on the co-pilots side. Therefore as we operate the aircraft single pilot, this check is conducted with the left hand away from the collective.

Our concern is that whilst the likelihood of this electrical interlock failing is no doubt extremely rare, if there is a check in place to ensure the interlock is working then logically there must be a risk of it not! As the procedure stands if it did fail the aircraft would have no hydraulic assistance at 100%rpm and the collective unguarded.

Our question is could the interlock part of the second hydraulic check be carried out during the preliminary hydraulic check when the throttles are at idle?

Are there any other 412 operators out there who share our concern or are we being over cautious?

[Nigerian Expat Outlaw]

Scorp,

I may be wrong (and I'm sure I'll be corrected if I am !!), but we do another check at idle called a "Stick Jump" check which should give the pilot some assurance that your scenario won't happen.

All we do is switch off each system in turn while guarding the collective with our knee, i.e. both feet are still on the pedals but the left knee is bent over to prevent the collective rising uncommanded. This is done at the same stage as the "Creep Check".

Hope this helps.

Cheers,

NEO.

[Matthew Parsons]

On the second check, if both systems fail, it won't matter if your hand is on the stick or not. If it doesn't move, no problem. If it does move, you won't be strong enough to stop it. Your instinct then should be to undo the last switch selection you made rather than fighting the controls.

What you should do is keep your left leg lightly touching the collective so that you can feel if there is any unusual movement.

I doubt if the check is valid at low rpm because the loads are appreciably different. If it is valid, the possible uncommanded movement of controls at low rpm could be quite damaging.

I'd recommend sticking to the manual.

[Nigerian Expat Outlaw]

Ah ha. That makes sense to me. Thanks a lot.

NEO:ok:

[NickLappos]

This does underscore the question of exactly how often you must check things to see if they are broken. Considering the very low failure rate of hard wired switches, you must wonder why you check that interconnect every day.

I have always wondered exactly how much time we waste in the cockpit doing daily checks that could be done weekly or monthly or yearly, depending on the inherent reliability of the system being checked. As manfacturers, we are stuck because there is only one paper checklist, with the "first start of the day" and the "through flight" checks.

With computer cockpits, it should be possible for the manufacturer to group the system checks by prompting you to do the required check on the required interval. This could allow a much briefer checklist.

Comments?

[212man]

How would you differentiate between 7 starts and shutdown in a day, and 7 days of one flight each?

Slightly off topic, but if you do the hydraulic check in the 212 at 100% Nr but turn off an engine governor switch instead (very close to Hyd panel) it will wake you up very quickly!

[Broadcast Control]

SP, you have a good point. If the loss of hydraulig pressure would cause an abrupt movement of the controls I would rather be at idle than at 100% Nr.
Trusting the Bell engineers, the explanation must be that there is no significant feedback from the rotors if hydraulic pressure is lost.

[Matthew Parsons]

I don't have a checklist in front of me, but I believe the initial check is every flight and the full check is first flight of the day.

I completely agree with the comments about scheduling the checks. We've seen a reduction in certain parts of maintenance by reducing the scope of pre-flight checks. If you open one panel four times between each flight, not much will change, but the closures will certainly show more wear.

I wouldn't be surprised to see similar results with some of the cockpit checks that are done.

[detgnome]

To continue from SP's initial post...The resting position for a 412 collective is around 1/2 travel, which is where it naturally goes to once hyd assistance is removed; I would assume this is the neutral position for the elastomeric bearings. If all hydraulic assistance is removed when at 100% NR, will the collective naturally revert to this position ? If this is the case it is extremely unlikely that any pilot would be able to stop it due to the forces involved.

The flight manual warns that flight with no hydraulic assistance is not possible (no surprises there!). Therefore why do we carry out a check that if succesful (ie the check proves there there is a malfunction) will potentially make the aircraft uncontrollable, possibly leaping into the air?

answers on a postcard....

[Buitenzorg]

You’ve probably already done this, but…

Try contacting the BHT rep for your area; you can find them through the Bell website www.bellhelicopter.textron.com . If they don’t know the answers themselves they’ll certainly know whom within Bell to ask and both BHT reps I’ve had occasion to deal with myself couldn’t have been more helpful. Alternatively, if one of you is going to the factory school soon, this would be great discussion fodder for the class and instructor.

As an aside, and following Nick’s point, I remember reading an article about tech delays on the USAF C-5 Galaxy fleet – the majority of which were due to the Air Force insisting on exercising emergency systems each flight that had been designed as emergency systems, i.e. for one-time use…:rolleyes:

[chuckolamofola]

I am not a Bell rep so the information below is worth what you paid for it.

1. The check at idle checks the timing between the two systems pilot valves so that you know that one hydraulic system is not fighting the other. As you know the servo is actually two servos mounted together and redundant. If the timing or pilot valve centering is not the same, when you turn off one system the control will jump the distance needed to recenter the pilot valve.

2. For the check at 100% you needn't be concerned about the controls jumping as you have already confirmed this at idle. The real check here is to ensure that you can't turn off both hydraulic systems at the same time. Bell wants to make sure that you can't turn off both hydraulic systems by mistake. This has happened in the past via improper maintenance or other items installed by people that supply the necessary ground in order to turn the system off. When you turn off the hydraulic system you are actually powering the solenoid valve to the off position. Hyd #1 valve actually supplies the ground for the #2 valve and #2 supplies #1's ground. That way if one system is already off, then the other system can't be turned off unless the original system's switch is positioned back into the on postion. By using power to turn the system off, acts as a fail safe, so that if you loose all electrical power you won't loose hydralulics. As you know the 412 can't fly without the red stuff flowing through its tubes...

[exwessex]

I know this is strictly off topic-but why do Eurocopter not install hydraulic cut-off switches in the 355/365-how could you isolate a possible restriction?

[GLSNightPilot]

Both the preliminary and the full check are done on the first flight of the day, not every flight. And as to Nick's question of why they need to be done that often, I have no idea. Obviously Bell has some concern about it, but I've never been able to turn off both systems at the same time. There are a number of systems checks in the 412 that seem rather needless to me, but they're on the checklist, so I do them. The 412 hydraulics check is little different from the S76 check, and that is done daily also. Total loss of hydraulic power is one of those things that will kill you, unlike engine failure. It's obviously not likely, but the check only takes a few seconds, so I don't worry about it.

As for Scorpiones Pungunt's original question, I don't think you will have a serious problem on the ground, as long as the controls are neutral or very close. You wouldn't be able to move them, but on the ground you don't have to. I'm not sure there would be that much difference between 80% and 100% Nr anyway, and 80% is the minimum RPM for a 412 (another consequence of the remarkably poorly designed main rotor system). In general, I think it's a good idea to do things the way the manufacturer recommends, because there is usually a good reason for doing them that way.

[detgnome]

Ah yes Hammer Headed, don't forget you are talking about Bell where evolution not revolution is the way of life! I'm told that the handle on the tail boom baggage door on the 412 is the same as the handle originally use on the Bell 47!

Anyway, back to the discussion. My point is that whilst testing/checking a system is fine, in the case of the Hyd system interlock failing at 100% NR, what is the outcome? Nobody seems to have a definitive answer and I am still not convinced that the cab will still sit on the ground and not thrash itself to death. If this is the case does it not question the validity of the check in the first place?

[Aesir]

"detgnome" you know Bell keep´s it simple, if it ain´t broke don´t fix it ;)

I see many comments telling to stick to the manual... but I wonder how many PT6´s have been incinerated due to that HYD test at 100% because the GOV Manual/AUTO switch was moved instead of the HYD switch which is just above.

The 212 has no hyd system isolate function as it can be flown with both hyd system´s off (its tough, yeah I know) and I really can´t see the point in the test at 100% except make more money for Pratt & Whitney.

[GLSNightPilot]

It's not really that difficult to move the hydraulics panel. Our 412s have it on the left side of the console, all the way to the front, well away from the governors.

[glimmerman_alpha]

We are currently conducting an indepent study on 412's worldwide.

If you have information of 412's/registration/location it will be greatly appreciated.

Fly Safe

:ok:

[glimmerman_alpha]

We are currently conducting an indepent study on 412's worldwide.

If you have information of 412's/registration/location it will be greatly appreciated.

Fly Safe

:ok:

[BlenderPilot]

I would buy the latest RotorRooster, its amaizingly accurate, and it will tell you where most if not all 412's are, who owns them, serial, etc. (and all other helicopters)

[BlenderPilot]

I would buy the latest RotorRooster, its amaizingly accurate, and it will tell you where most if not all 412's are, who owns them, serial, etc. (and all other helicopters)

[glimmerman_alpha]

Thanks BlenderPilot. Where will I find the RotorRooster? Will I find a copy in Africa?

[glimmerman_alpha]

Thanks BlenderPilot. Where will I find the RotorRooster? Will I find a copy in Africa?

[Collective Bias]

I think you can find it on the HAI homepage, (rotor.com) or just buy it from the Rotor roster people.


CB

[Collective Bias]

I think you can find it on the HAI homepage, (rotor.com) or just buy it from the Rotor roster people.


CB

[chuckolamofola]

http://www.airtrack.com/

Try the link above. You can download a free copy if you are an HAI member. You can also purchase a copy for $25.00

Regards,

Chuck

[chuckolamofola]

http://www.airtrack.com/

Try the link above. You can download a free copy if you are an HAI member. You can also purchase a copy for $25.00

Regards,

Chuck

[BlenderPilot]

See there you go! This is why I love PPRuNe Rotorheads, plenty of smart educated people to help you.

Imagine if this question would have been asked in JH?!

[BlenderPilot]

See there you go! This is why I love PPRuNe Rotorheads, plenty of smart educated people to help you.

Imagine if this question would have been asked in JH?!

[glimmerman_alpha]

Thank guys!:ok:

That will help me out. I ordered it and hopefully receiving it in 10 days.

Cheers;)

Fly Safe

[glimmerman_alpha]

Thank guys!:ok:

That will help me out. I ordered it and hopefully receiving it in 10 days.

Cheers;)

Fly Safe

[Skitso]

:ok: Hi guys new to the pprune thing...what im lookin for is if anyone has got a training manual for sale etc...on the Bell 412 ep type...Or some help on locating 1....thanks guys

[outhouse]

Skitso,
My experience is that the manuals available from Flight Safety are the best, certainly regarding pilot tec subjects; they cover all the B 412 series in one volume. Check on the Flight Safety web site under Training Materials available for sale. Failing that copies are around on CD, I found it once on the net but do not remember the web address. Best of luck in your quest, outhouse.

[Skitso]

:ok: thanx outie i will give them a try...all the best mate

[Jez]

Skitso

I see you are in QLD.

If you are near CareFlight (Coolangatta) they may be able to lend you one. All the guys have just completed a recurrent Flight Safety course and they now produce a nice little "refresher" manual that takes into account all B412 variants.

QLD Rescue at Archerfield may even help??

[Skitso]

To the guys that have responded thanks heaps:ok: ...had a few trails out there . 1 was Bell itself and the other was Flight Safety, all they wanted to offer me was their ground school course,(which had a training manual) too much bucks????...

So by the looks of it I might have to grab a shovel and start lookin underground....any 1 out there got a good decent manual that could be bought or duped as a colour copy..

get back or personal message me if you want to would be kool...

May your beers be always cold, and your women hot hehehe

[cl12pv2s]

Contact a guy named Tank. You'll find him somewhere in the Matrix. He has training programs for all types of helicopter.

Give him a ring and ask for a "Pilot Training Program for the B412 helicopter".

In 30 seconds all the knowledge you need to be able to fly the helicopter will be uploaded to your brain via the telephone network!

Clever, eh?!

[Skitso]

MMMM... WE MEET AGAIN "MR ANDERSON" or should i say Neo...

[ConwayB]

Hi,

Do you want any manual in particular or just the Flight Manual?

I bought a flight manual on CD ROM from a guy in Toronto on EBay. He had a whole selection of manuals copied onto CDROM. I can't guarantee it was legal, but he had his own business that specialised in that so I can only assume it was legit. If not, I'm sure Bell are onto him.

I did the usual Ebay thing and I had it in my grubby little hands in 10 days.

Do a google search or a search on ebay for flight manuals or pilot operating handbooks.

If you don't have any luck, PM me and I'll see if I can dig it up and give you more info.

Cheers
CB

[Skitso]

Con...roger that thanks mate i will give it a go, and basiscally i'm trying to get a training manual on the a/c to start with....I can get my grubby hands on a " fright manual" at work. but the disk copies sound kool:ok:

[outhouse]

Skitso,
Look I do have an acrobat copy of the FS 412 manual, I scanned the latest version and its on disk, saves lugging the two books about when on trips. However the files are rather large and not any good to send over the Internet, too slow and costly from my backwater of the unknown world. However if you want to PM me maybe we can sort an alternative.
Outhouse

[Aser]

Did you ever hear of a ground resonance incident in a 412?

I've done a search in the ntsb site without results.


Thanks
Aser

[Ned-Air2Air]

Aser - Your havent been bouncing the Malta Gozo machine have you :confused:

[212man]

In the absence of drag dampers, undercarriage oleos or pneumatic tyres, it would seem unlikely to be a problem.

[SASless]

But the RFM does make mention of it....something to do with the ability of the skids to slip in the rubber mounts or something as I recall....thus setting up a lateral input to the rotor system similar to an oleo.

[Blackhawk9]

The Aft cross tube on the 412 has a support beam fitted not fitted to the 205 and 212, to give a single point attachment to the airframe to counter ground resonance if the elastomeric dampers sticks (fails) in the leading or laging mode. Thats what gives the 412 its rock from side to side when you move around on top the aircraft as the cross tube rolls within the support beam.

[idle stop]

It's not unusual for a perfectly tracked and balanced 412 to 'pad' markedly on the ground at min collective pitch, particularly on concrete. Whilst it may be uncomfortable it is not divergent and can be stopped by raising the collective slightly.

[Aser]

idle stop I know what you are talking about, I had the experience in one 412 and I thought it was going to self destroy
:}

I believe the possibility of ground resonance in a 412 although very remote , exists.
The dampers , rubber in the crosstube, or one drop restrainer not in locked position after the previous shutdown... something can fail.
Maybe a pilot react intending to lift the helicopter and find himself hitting a nearby tree... ? :E
What do you think guys?
Ned-Air2Air: The machine is fine , I was just speculating about something I heard...

Thanks for your responses

[Yabu]

In early stages of vertical bounce, place cyclic right aft, if this does not work as it often will, pull a little collective as was suggested earlier. Be aware that you can increase the bounce if you hold the collective tightly causing it to have a pilot induced factor as well , Cheers Yabu

[Spanish Waltzer]

Yabu

I would imagine if you pull the cyclic 'right aft' then your early stages of vertical bounce may well be replaced by broken tail rotor;)

[Oogle]

As all Bell 412 pilots know - those things LEAK with oil underneath. The rubber dampers on the aft crosstube gets hammered by this oil and can eat them away fairly quickly.

This can increase the ground bounce as well.

I have never had anything close to ground resonance in the aircraft in over 1000 hours of flying them. :)

[Yabu]

Spanish Waltzer, Moving the cyclic right aft is not to be read as a harsh manuever, and you will normally find a "sweet spot" at which time early stages of bounce will cease. I am only trying to aid, with my 4000 hours on the 412. If you think it is not a reasonable suggestion, then so be it. Regards

[Aser]

Yabu, right and aft is where usually I move the stick to turn off the Cyc Center light, so what you are suggesting in finding the sweet spot sounds like a good idea , I was taught just to add a little bit of collective.

Best regards.
Aser

[NickLappos]

Ground resonance is a term we misuse the way we misuse LTE and Settling with power. Every time a guy runs close to pedal limits he calls LTE, every time he starts falling through on approach it is VRS and every time the aircraft wiggles on the ground it is ground resonance.

Some thoughts on true ground resonance:

1) It is possible to get it in any aircraft that has a lag degree of freedom, even the 412.

2) It takes something mis-adjusted or mis-maintained to get it, because all helos that have lag hinges have systems to quell it. Manufacturers have to prove they are immune to ground resonance to themselves and to the FAA. Those systems (oleos, dampers on skids, dampers on blades, elastomers on all the previous) do not cause ground resonance, they prevent it.

3) It is a destructive resonance where the blade goes out of lag position, and the ground restraint (gear, skids, chocks/chains) reflects the out of balance back to the rotor in such a way as to drive the blade further away from the center. This means the vibration amplifies with each cycle.

4) True ground resonance is fast, vicious and destructive. Usually the number of cycles is few (maybe 10 seconds) and the cure is to leap airborne (stops the ground from reflecting the wave back to the head) or shut down fast, slapping on the rotor brake (which drives all the blades forward and again breaks the cycle).

5) Some helos have spots where the main rotor dampers are less effective (sweet spots in the cyclic) while on the ground, and they shuffle or bounce in yaw, roll or pitch enough to be noticed by the crew. These areas of lower damping are not ground resonance.

[Oogle]

Nick

I think the point that everyone has been talking about with the last few replies was in conjunction with the "Ground Bounce" (not ground resonance) which can feel a little harsh dependant on the track and balance of the particular aircraft, wind direction, quality of dampers on the rear crosstube, etc.

:}

[NickLappos]

Oogle,
Agreed! You can get it in a BlackHawk at very aft stick, for instance, when you land down-slope. It is a combination of dampers that are stroking alot, tail wheel lateral compliance and AFCS activity.

[Aser]

So to resume:

1- The 412 has the possibility of ground resonance as any other helo with lead-lag movement in the blades.In the first post I was looking for a previous incident without luck.

2- The replies derived to the 412 well known Ground Bouncing capability :}

3- Nick: 2) It takes something mis-adjusted or mis-maintained to get it, because all helos that have lag hinges have systems to quell it. Manufacturers have to prove they are immune to ground resonance to themselves and to the FAA. Those systems (oleos, dampers on skids, dampers on blades, elastomers on all the previous) do not cause ground resonance, they prevent it.

This is something... I was missing, I was thinking that a blade with a bad lead-lag damper will develop the ground resonance, but not, it's there just to preven it, Thanks.

Best regards.
Aser
;)

[Yabu]

I agree that generally with the 412 we are talking bounce which is not resonance. Both cyclic position, and to a larger degree some addition of collective will help. We have found the bounce can become quite a thump particulary on wooden wellheads, where some movement of the deck allows the situation to worsen. In cases like these pilots do tend to hold the collective tightly and while they bounce, unconciously bounce the collective as well increasing the effect. I personally have not heard of this developing into resonance as such, but it does get your attention for sure. Some good technical feedback on this has come thru, Thanks guys.

[nutcracker43]

Many of the 412's I have gound run have been prone to some form of bouncing. It has always happened on concrete and starts at about 95%+ with min pitch. Invariably the aircraft has been lightly loaded (empty actually). Certainly there was the thought that this could develop into full ground reasonance if it were allowed to continue Raising the collective slightly seems to be the cure. It was very uncomfortable and I am not able to say whether the condition is divergent, or not.

I have never experienced this problem on either a B212 or a B205 although I have experienced collective bounce on a B205. The situation there was a gentle run on on a bank of shells/stones caused by insufficient friction on the collective.

Hope this helps.

NC43

[goaround7]

Hi guys,

I've got the manufacturer's and 'blue book' type costs but can a couple of you give me some real world gen on operating costs for 212/412 in harsh(ish) desert environment but with hangar and daily maintenance available doing pax and equipment transfer with one to two hour flights, 100 hours a month - minimal sling, no high cycles, nothing unusual ?

Eg. real maintenance, unplanned spares, fuel, oil, blades etc.

Thanks,

G7

[BlenderPilot]

Go with Conklin and D's estimates and you will do more than well, the 412/212 has no surprises.

The desert should not pose any problem for the 212/412 its one of the most dependable aircraft this world and its surroundings have available for you to make money with it.

[goaround7]

Thanks, we got those.

Recent newsletter reckons US$ 606 per hour for 412 then ?

[Gomer Pylot]

Came to this somewhat late, but why not jump in anyway!

IME the 412 ground bounce is usually caused by track/balance problems, and can't always be eliminated no matter how long you try. I've seen it caused by a t/r imbalance. We worked on the m/r track/balance for weeks, with no success in lowering the ground bounce. Then when the t/r balance was done as part of the scheduled maintenance, it was found to be well out of tolerance, and when balanced the ground bounce was gone.

It's a miracle when a 412 has no vibrations anyway, considering that it starts out with the blades in different planes. Sometimes you just have to live with a ground bounce, but I try to get it tracked out. Raising the collective slightly usually helps, as already mentioned.

[Phoinix]

What is the difference in performance and structure between these 412 versions? Is there any other that i might not know about?

J

[noooby]

How much time have you got :-)
Engines are different across the 3 models, although engine models are sometimes common between SP/HP (-3BE/BF/BG), and between HP/EP (-3D). SP uses 212 tail rotor driveshafts with driveshaft clamps. HP/EP uses Thomas Couplings on the tailrotor driveshafts. HP/EP have ITT trim for Engine #2, SP has the 212 setup. EP has different Damper Bridges on the Main Rotor Head, but I think this can be retrofitted back to HP/SP. EP cannot fly with older style Damper Bridges though. EP measures rotor torque at the Main Rotor Shaft output to the Main Rotor Head. SP measure at the MGB input from the engines. Structurally, from memory, they are the same. Components are upgraded for each successive model, and engine horsepower increases with each model to hide the fact that the later models are heavier :-)
As far as perfomance goes, you'd have to speak to a driver.

noooby

[Encyclo]

Quite right except both the HP and EP have mast torque wich uses mast twist to determine torque with a lot more accuracy than the "No P" and SP wich totalize the torquemeter from eng #1 & #2 as on the Bell 212.

The "412 No P" or "412 Straight" or "412 Classic" how ever you want to call it, is structurally very close to the Bell 212 not having the aft center fuel cell (five fuel cells in lieu of 10).

[SASless]

Does anyone care to discuss the fuel system and how it works?:uhoh:

[Blackhawk9]

Yes, the Bell fuel system!!
Well it's not that bad ,to start with the 412 Classic is basically the same as the 205 and 212 fuel system with 5 main tanks giving approx 1450lbs fuel.
The 412 SP/HP/EP, has a ten tank system 6 floor tanks, with fwd, centre and aft floor tanks on each side, the centre and aft tanks take the same space as the 2 floor tanks in the 205 /212/ 412Classic with the fwd tanks fitting into the floor cavity behind the pilots seats.
3 of the 4 aft tanks are the same as the 205 /212/ 412 Classic with the extra tank befind situated in the rear hellhole area. With the fuel system extended fwd and rear in the airframe longitudinal CofG became a problem , so Bell came up with a series of stand pipes and valves to keep the CofG move to a minimum (a total move of approx 4 ". between 136.0 -140.0)
To do this Bell do it in a series of 6 "Burns"
Burn 1 is approx the top 1/4 of the 4 rear tank as the flow into the floor tanks
Burn 2 is the centre floor tank on each
Burn 3 the next 1/4 of the aft 4 tanks
Burn 4 is the fwd floor tank on each side (approx 800lbs left at end of burn 4)
Burn 5 last 1/2 (rest) of 4 aft tanks
Burn 6 remaining fuel in aft floor tanks.
Hope that helps and isn't too confusing, it had me stuffed to when i first did the course!!

Oh yeah and the main reason for the fuel system change?
More fuel Classic 1450lbs approx 225 nm
SP/HP/EP 2150lbs approx 350nm

[noooby]

Simple really!!!! :) Until the underfloor Jet Pump clogs or fails and you find that you can't get fuel out of the center underfloor tank!! DOH!! Stoopid stoopid stooopid system. But hey, that's the price you pay for continually modifying a UH-1!!! :eek:

[Blackhawk9]

Its not that bad the fwd floor tanks on each side and centre floor tanks on each side are conected together by the standpipe interconect to maintain even fuel on each side and you have the interconnect valve on the rear floor tanks and crossfeed after the pumps so you can still get justabout all your fuel if a jetpump or boost pump fail !
If you want to see a sh1t fuel system just look at the Super Puma ,7 tanks, no direct crossfeed to the engines and only a mickey mouse "crossfeed" pump between tanks if it fails and the crew don't monitor the fuel levels between sides you have the potential of running fuel out on one engine and still having heaps to the other engine , this has disastrous potential if you are running a long range internal tank as it only feeds into one side!! not so in a Bell!

[Phoinix]

Thanks guys. Only one info is puzzeling me. What does SP/HP/EP stand for exactly? The more i ask, the more different explanations i get :confused:

[Blackhawk9]

SP-Special Performance
HP-High Performance
EP-Extra Performance

[DSpice]

In my Flight Safety manual it shows the following infor:

PT6T-3B PT6T-3D
100%Torque Twin engine torque limit

1800 SHP !800 SHP

Continuous Twin engine Torque limit

1600 SHP 1600 SHP

Continuous OEI Torque Limit

970 SHP 970 SHP
765 C ITT 820 C ITT

30 minute OEI ITT Limit

970 SHP none
822 C ITT
2.5 minute OEI ITT LIMIT

1025 SHP 1100 SHP
850 C ITT 925 C ITT


Hope this helps

[Phoinix]

Thank you all. That should do it.

[Yabu]

Not that its important, but I think the correct designation for EP is Enhanced performance.

[Induced Drag]

Any truth that the NSW Police are going to purchase 412's to replace their aging AStar fleet

[Disguise Delimit]

Why would they?

Rescue is a minimal part of their job these days, and the largest part is covert surveillance - not something you use a large, noisy and easily-distinguished 412 for!

Maybe there is a change of heart coming?

[blade root]

Why wouldn't they look at a 412 ?

Do you know how many C/T members you can fit in the back of a BK, with all their bombs, bullets and bullsh!t ?

Answer : Not many

[sprocket]

... And the 412 would have more appeal for rappelling, no? ;)

[SLBAGAGE]

blade root,

How many do fit in? What is not many?
Are you talking about C/T or PAG?
Tell me, how heavy are their bombs, bullets and bullsh!t? or are you collectively referring to "their Kit"
Which 412, standard, SP,or EP?

[blade root]

SLBAGAGE,

Get up on the wrong side of the bed did we?

How many can you carry ? 4-5, depending on the configuration of the a/c, fuel requirements etc. (refering to a BK-117B1).

Yes, I was refering to their "kit".

As to which 412, you are asking the wrong bloke, how much money have they got.......


Kind regards

Blade Root

[Dynamic Component]

A little birdy from France tells me they have a new B2 on order:}
So I can't see why they'd be retiering the AStars:confused:

[Disguise Delimit]

Don't Astars have LTS101 engines?

Aussie's Pigs in Space have Squirrels as the Pork Choppers.

[rotorque]

There is definately potential for the introduction of a larger aircraft withing the airwing, although I believe we won't see anything for at least 5 years.

Interesting to note that when originally sourcing an aircraft for the CT role they did in fact have the funding to purchase a 412. It was decided that the long term operational costs of a BK were more affordable ..... especially when concidering the 'here today, gone tomorrow' funding whims of the government. I think anyone would agree, it would be a shame to have a 412 as a hanger queen......

Cheers


P.S The BK is actually a B2 not a B1

[Dynamic Component]

Don't Astars have LTS101 engines?

No. Those are called Falling Stars:hmm:
AStar and Squirrel are the same thing:}

[goof]

Anyone know the VNE for a 412 with both rear doors open?

[Kim Il Jong]

Our company policy and limit in our FRC's is 100Kt. (60 Kt to open our close though, then 100)

[detgnome]

Kim - not sure if your company is the same as mine (debrief in Mom's?) but concur with 100kts both open, assuming they are metal doors. Newer, composite, doors are available but caused a few problems when fitted with 'panting'.

[HueyHerc]

Have a Keo for me....

HH
(O.C.O.H. Ret):ok:

[Oogle]

Remember that the flight manual makes note of the type of seating that is installed in the aircraft.

As said before - 100 kts doors open and 60 kts for opening and closing.

[800]

1. Check the flight manual in the first instance regards the model type etc.
2. The type of seating installed (cushions!), as mentioned earlier will determine if you can fly/open them at all.
Use 60Kts maximum door opening and closing speed.
I have a feeling that the flight manual states the following;
80kts Asymmetrical open door(latched)
100kts Symmetrical open door (latched)

[goof]

Thanks very much fellas

[Broadcast Control]

Hello, any experts out there willing to share experience on Bell 412 main rotor track and balance. (Despite using the RADS system recommended by Bell I find that the task is much more time consuming than on other helicopter types.)

[SASless]

Unless maybe a recalcitrant Hughes 500D/E is considered!

[Matthew Parsons]

I don't want to label myself an expert on it, but I have flown a few T&B's on the 412.

Be very precise with the ground track and then the hover track. With those two regimes done well, the rest should follow. Then focus on the forward flight. Try to get all regimes on each flight. Also, remember to compare the results of each flight to make sure you're not going back to an earlier condition.

It can take a long time, but it does give you a smooth ride that tends to stay smooth for many hours.

Matthew.

[Rusty Bifilar]

Good luck, 412 dynamic balance can be a real pain. Before you start flying do a very close inspection of everything from the transmission mounts up. Check all of the control rod bearings, swashplate bearings and bridge dampers very close. Water in a main rotor blade can cause major headaches, you can spend time balancing just to have the water get out of the blade and put you back where you started.

[spinwing]

Mmmmm....

If its giving you trouble check thru the maint records to see if any of the elastomerics have recently been changed.

Some machines with mismatched (ie hard/soft) elastomers have been known to drive mechanics NUTS trying to get them to fly smooth.

Good Luck ....;) ;)

[OverTq]

Get it the best you can at 62 and 100 before even thinking about a hover. Progress then to the full range (except VNE unless it's very smooth). Edit out the product balance unless it just won't come in without them. On a good day, after component changes, it takes my team about 6 runs on the ground and up to four flights to get the beast in limits. Bonne Chance!

[Wunper]

Whatlimit
There are no short cuts to RTB on the 412 the key is making sure you are using the right program for your aircraft Landing gear (high or Lo gear) and pylon mount configuration.
The donkeywork is done on the ground and the hover using the initial flight plan before attempting the full flight.
The test condition FPOG means Collective FULLY DOWN and not lifted to ease the ground bounce.
Also pay attention to the MM AUM range stated for the procedure as the RADS response sensitivities are set for that AUM.
Here is a list of tips from Chuck Kemp who is the doyen of 412 RADS RTB and another list from Dave Burch from Bell, if these don't answer your questions then you will have to pick up the phone to Mirabel..
Cheers W
"""""
Use the scripts on the following aircraft:
1. 412_41 (For those aircraft with soft pylon mounts (-105) and standard
landing gear low or high.
2. 412F (For those aircraft with soft pylon mounts (-105) and float style
landing gear.
3. 412_50 (For those aircraft with hard pylon mounts (-107) all landing gear
types.
Perform a visual inspection to determine which type of pylon mount
you have. Olive drab green are the soft mounts (-105) and Epoxy Polyamide
Yellow are hard mounts (-107). You also need to determine if you have dual swashplate drive links installed.
If you have single drive links this can give a problem where the ips level
will tend to bias around only one phase angle. Bell gave out dual drive links
for free when they introduced them but some AB412 customers still have
single drive links. If you don't have hard mounts or dual drive links then
you need to get them for a consistent rt&b solution.
If you go into flight with high vibration levels and a track split larger
than 45 mm's the machine is not ready for the forward flight flight plan.
The proper way to perform the initial is:
1. Determine which type of pylon mounts you have and use the appropriate script file
2. Obtain a perfect track of +20 m/m's on RED/BLU and -20 mm's on ORG/GRN +/- 1mm using p/c link at 62% idle. Turn off Tabs, Hub Weights & Product Balance at
this point using the diagnostic editor.
3. Run aircraft at idle and 100%FPG and 100TQ if high gear. Stop track change from idle to 100% using Outboard tabs. Turn off product Balance at this time using the diagnostic editor.
Don't make p/c links changes of less than two flats Don't proceed to Hover
until track change is less than 2 mm's and lateral balance is below 0.2ips (low
skid) or f/a is below 0.2 ips (high skid gear).
4. Now run idle, FPOG, 100TQ and Hover. Stop track change between FPOG and
HOVER using product balance. Hover lateral is not so important here instead we
are interested in stopping the track change. Keep performing this until the
track change is less than 4 mm's or you can't make a product balance move. All
test states should still be in limits. If all are good proceed to forward
flight.
Forward Flight (Soft Mounts using 412_41 or 412F scripts)
1. Perform forward flight taking data at all test states!
2. Set Auto-rotation on very first flight. Setting it last can cause 1 per
rev. and a couple more flights to fix.
3. Look at initial adjustments and predictions. On the first flight you will
probably do what the CADU comes up with.
4. On the second flight usually the verticals are down but you still have some
lateral. If vertical is down turn off Tabs leaving on P/C and Hub Weights.
P/C's will work you lateral in flight and hub weights will work your lateral on
the ground and let down.
Forward Flight (Hard Mounts using 412_50 script)
1. Perform forward flight taking data at all test states
2. Set Auto-rotation on very first flight. Setting it last can cause 1 per
rev. and a couple more flights to fix.
3. CADU will default down to a maximum of 6 adjustments. Usually these are
what you end up using.
4. Instead of playing with edit adjustables, use Max # and adjust that number
up or down to get you favored predictions. This will allow the CADU to pick
adjustments with the maximum effect and not what you think it will need thus
keeping track split close and vibe levels down.""""""""""
And here are extracts from a list of more tips from Bell CSR Dave Burch I hope he doesn't mind my posting it.
"""
412 MAIN ROTOR VIBRATION CHECKLIST
1. Insure that the tail rotor is in track and balance. An out of balance or track tail rotor is often felt as a roughness or a one per rev vibration in the cabin in forward flight and not as a medium (or high) frequency vibration. Feel the left hand elevator at 100% on the ground. Don't take the pilots word for it. Because of the hydraulics most pilots won't feel a tail rotor buzz until it is in the 0.6 IPS range.
2. Insure that the engine to transmission input drive shaft is balanced. The drive shaft will make a pulsating low frequency noise at about 1.25 second intervals in flight that will make the passengers and pilots feel very tired and uncomfortable in flight. This may be perceived as a one per rev vibration. Again many times this will not be noticeable to the pilots as a specific high frequency vibration in the airframe.
3. Wash and wax the blades. The 412 airfoil is very critical. It is not unusual to see 0.2/0.3 IPS vibration changes by just cleaning the blades. Be sure to use non-silicone wax per MIL-W-18723. Insure that the product balance weight pocket covers are sealed properly with no squeeze out above the surface of the blade while insuring that the gap around the pocket cover is filled evenly and smooth with the upper surface of the blade.
4. Inspect the skid gear cap assemblies for condition of the rubber. If the latest dash number elastomer (P/N: 412-030-437-103) are not installed; then they should be at the earliest possible date. Bad or old style (P/N: 412-030-437-101) elastomer/rubber will cause/feed vibrations and make it very difficult to work the rotor. Insure that any caps sent to Lord for rework are reworked to the -103 assembly.
5. Loose doors, cowlings, elevators or external equipment will amplify any vibrations and particularly the four per rev. Insure that they are tight. There are several Technical Bulletins to help reduce the noise and rattles from the doors that should be complied with on older aircraft. The latch pin rods in the hinge panels often rattle against the inside of the panel. These can be covered with plastic tubing which often decreases the cabin noise level considerably.
6. Check the elevators for looseness in the spar to horn and at the horn to fuselage mount bearings. It is necessary to disconnect the spring cartridge in order to check the preload. Be aware that the inspection criteria for axial play in the maintenance manual is currently incorrect.
7. Check that the pilot/co-pilot seats are tight on the rails and that the vertical lock pins or holes are not worn out. Many times the seats will be loose enough to increase the feeling of an acceptable vibration to an unacceptable one.
8. Insure that all the passenger seats and cabinets are tight. In particular, the high back seats used in the EMS sector give false visual clues by the tops moving excessively even though the vibration is not actually there.
9. Insure that there are not any pieces of equipment or cords in the cabin or cockpit area that are loose or can shake or move where they will give false visual clues to the pilots or passengers that there are excessive vibrations when there are none. Map light cords, windshield wipers and fire extinguishers are notorious for this.
10. Insure that all the equipment in the nose compartment is tight and in particular check for loose ballast or batteries. These make very uncomfortable vibrations and make it very difficult to work the rotor.
11. Insure that the hydraulic actuators are tight and aligned properly. Check that the universal bearings on the extension tubes are tight. This is difficult to check with the pitch links connected due to the loads of the elastomerics of the main rotor. Ensure that the pivot bearings on the input levers are tight. Check the lower mount for elongated bushings or worn bearings or bolts.
12. Insure that the minimum collective friction is adjusted correctly. A slight collective bounce will cause a lot of problems. On the 412SP and 412HP be sure that the droop compensator cable is not giving you a false friction.
13. Check the four pylon mounts for sheared rubber or obvious delamination or deterioration. Check the two friction dampers for proper operation and for loose bearings in the damper or the airframe mount. Loose bearings in the dampers or mount and/or bad or soft pylon mounts will increase the sensitivity of the airframe to the point that it may not be possible to get a good ride and really hurt laterals in the let down.
14. Check the lift link for loose bearings and for any damage to the mounts. Insure that the spacer washer is installed between the upper lift link bearing and the inside of the right side of the transmission mount. If this is not installed the link chaffs the mount and makes a thunk with power changes and adds to the four per rev vibration level.
15. Inspect the instrument panel mounting structure for security and tightness. Insure that all the mounting screws are installed and that the side braces are secure and have no cracks (particularly behind the plastic on the door post.) Insure that the glare shield is in good condition with no cracks or looseness. If the frahm damper is still installed on the instrument panel, insure that it is securely mounted and that the springs are in good condition or that it has been locked out.
16. Insure that the trailing edge expandable bolts on the main rotor hub are set for the proper tension and at the proper dimension from the yokes. This is a repetitive problem. If the customer wishes, PSE can authorize replacement of the expandable bolts with the normal bolt, washer and nut combination.
17. On aircraft with the elastomeric control system links, insure that the serrated rod ends and bushings engage properly and the bearings are set at zero preload at full down collective. Refer to the Maintenance Manual.
18. Insure that the collective levers to sleeve pivot bearings are tight and that pins to bearings are shimmed for the proper clamp up.
19. Insure that the collective lever and two swashplate horn universal bearings are tight.
20. Verify that the swashplate support, gimbal ring and inner ring mount bolts, bushings, and bearings are tight and the shims for the supports show no signs of deterioration or looseness of the mount screws.
21. Verify that the droop stops are rigged properly. Insure that the clevis arms are centered on the cams and do not contact the sides of the cams. If necessary, the thru bolts can be loosened and the lower support rotated to center the clevis to cam. Check the bushings for flat spots. Check the bearings for free movement and proper lubrication.
22. Inspect the elastomers carefully in the main rotor hub. Refer to the maintenance manual for inspection criteria. Insure that the spindle bearing to lead-lag damper joint is secure. Check for evidence of the lead-lag damper working in the damper bridge. Insure that the through bolts are tight and there is no evidence of the yokes moving on the center drive hub or upper or lower cone seats.
23. Insure that any cracks or erosion in the finish of the main rotor blade are filled properly. These can allow water intrusion into the core of the blade which will cause the blade to become unworkable. Check for cracks in the trim tabs or the tab mounting area. Check that the tabs have not lost their rigidity (become soft tabs) that will not hold their settings.
24. If the blades have been reworked, insure that the Bell Helicopter procedures were followed for sanding, repairs, rework, refinishing and re- balancing of the blades. Improperly reworked blades may not be able to behave properly in flight.
25. Insure that the simple pendulum absorbers are lubricated and that the bearings are free. Check by pulling outboard and aft on the weight arms and then check for roughness of the bearings or excessive fore and aft movement.
Hub Weights:
Maximum:
* 8 weights any location.
* 16 weights per yoke end.
Once you get to eight weights on trailing edge add to leading edge.
Product Balance:
Trailing edge weight adjustment does all the track change from ground to hover.
Leading edge balance pocket is just to offset the weight move to keep span wise balance equal.
* 1 weight move= 0.5 IPS hover lateral
* 1/2 weight move=4mm-5mm track change ground to hover
Standard Load:
Leading edge pocket: 135 grams (One thick flat and one thin flat washer)
Trailing edge pocket: 158 grams (One wedge and one thin flat washer)
Ratios:
Trailing edge to leading edge x 0.85
Leading edge to trailing edge x 1.17
It takes approximately nine (9) grams at the hub weight mount arm to offset a one (1) gram mistake at the trailing edge product balance pocket. It takes approximately ten and one half (10.5) grams at the hub weight arm to offset one (1) gram at the leading edge product balance pocket
412 Rotor Working Information
Try to work rotor at 800 to 1200 pounds of fuel, External Auxiliary Fuel Tanks empty and no more than three people on board. Make sure inboard tabs are set to zero before tracking.
On Initial:
1. Get maximum of 2mm track change between 62% FPG and 100% FPG.
If possible, get maximum of 4mm track change or less between 100% FPG and hover.
2. Try for total maximum change between 62% FPG and hover of 4mm if at all possible.
3. Initial does not work lateral in hover, only works track at 62%, 100% and hover and lateral at 100FPG on "412 F & 412_41" programs and fore/aft at 100TQ on the "412_50" program.
4. RADS phase angle is plus 62.5 degrees of the standard Chadwick to compare to charts. (2:00-2:15 on RADS is 12:00 on Chadwick charts, or 12:00 Chadwick = 62.5 degrees (RADS)
5. Concentrate on vertical on first flight before lateral.
6. Significant change in ride level with changes in gross weight indicate a product balance problem or bad rubber.
7. 412 normally indicates 19% to 21% torque at flat pitch on the ground if autorotation is correct. Check Auto rotation RPM on flight, first. Do not make rotor smoothing adjustments until auto revs are set.
8. When getting close to completing a rotor, turn tabs off (412F & 412_41). Concentrate on roll and hub weights.
9. Significant phase angle change from ground to hover indicates product balance needed. Watch phase angles for proper directions of move.
10. Excessive inboard tab may cause ground bounce.
11. Worn swashplate gimbal ring bearings or bores may show up as a lateral in let down.
12. Sudden severe lateral on pickup to a hover is probably a hung droop stop.
13. If you have shifting weight clock angle call out, then look at the opposite pair of blades lead lag dampers.
412_50 ver 5.3 or higher
This program differs in that it has a couple of states that are different than 412_41.
Listed below are the extra states:
1. 100TQ - This is 100% NR on the ground with 5% torque pulled in from the flat pitch reading. With the -107 mounts the aircraft may have more of a ground bounce than a standard aircraft. This will reduce ground bounce and allow you to balance the rotor.
2. 120/97 - This is 120 KIAS with the rotor beeped back to 97% Nr. This state can be skipped until your last flight. No rotor smoothing is accomplished with this reading. (Do not forget to beep back to 100% Nr upon completion!)
This program works diagnostics differently than 412F. It will automatically count down to the smallest amount of adjustments, usually about 6. You can do those adjustments or go into the "edit defaults" on the diagnostic menu.
Once there, turn the best number of adjustments to best 04 and "resolve to limits" off. Press DO, it will then give you the best 4 adjustments or less that will make the rotor smoother. Check the predictions if it is better than "default moves", do those. Try best 3 or 2 moves, they may be better. Just be careful and do not get caught up in trying to reduce the predictions that you are just dropping the vibrations .05 ips between the different adjustments. You are finished when the screen says you are below all set limits or you cannot obtain a smoother ride.
Installation: Install the RADS for 412F ver 1.40 the same as the Bell maintenance manual chapter 65, Install the RADS for 412_50 ver 5.3 the same as above but add a fore/aft accelerometer on the bottom of the instrument panel under the lateral accelerometer. The connector must point fwd. Attach it to channel 3. Reference Technical Bulletin 412-92-111 Rev. A.
412_41 ver 5.3
This program works the same as 412F ver 1.4 yet is to be used on soft mounted aircraft without external tanks and floats
Using The RADS At Night: Install the reflective tape supplied with the kit on the bottom of all four blades trailing edge. It must start at 9" inboard of the mid span tab and be 24" long. Turn the Day/Night test knob on the DAU to "Night."
Using a mini mag light ( something with a small focused beam ) align it with the UTD and adjust the angle of the UTD so that the beam of light hits the middle of the tape. (67 degrees from co-pilots seat rail) You are now ready to track at night!
Common Rotor Adjustment Mistakes: The RADS will only give hub weight adjustments for blue/org blades. If you have weight on red/green don't add to blue/org. Just remove from red/green. Mid span tabs move the blade about the same as outboard. You can use these to adjust track in lieu of outboard tab. Make sure you are not adjusting it opposite of the outboard tab and you are using the correct scale on the tab tool. Do not use inboard tabs. It may or may not work. It's not worth the gamble if you are getting the aircraft smooth without them.
If you have not made the aircraft significantly smoother in 4 or 5 flights, you have a problem. Start checking for loose drive link bearings, loose p/c link bearings, bad rubber, etc. All the bearings (hard) are .007 radial and .015 axial play. If all of these bearings are loose, they add up to a lot of play, which can make your job harder to accomplish.
On a freshly installed M/R head make sure that you retorque between each flight until bolts do not move.
To be certain which program you should use visually check to see which pylon mounts are installed. Hard mounts (-107's) are yellow and Soft mounts (-105's) are green.
You will be better prepared if you will watch the video tape titled "412 Rotor Inspection and Troubleshooting/Rotor Analysis and Diagnostic System", Chapter 65-03-00 through 65-05-00 of the Bell Maintenance Manual. and the Operators Manual supplied with each RADS. There is quite a bit of data that you could find useful in working 412 Rotors...

[Broadcast Control]

Thanks to everybody for valuable inputs. Wunper - excellent!

[pa42]

Off-the-wall cute obscure website urls, V.1.

www.onefinalcoat.com

Now, would you think that had to do with helicopters? Guess again--it's Bell's 412 LUH advertisement! The "onefinalcoat" turns out to be the hypnotic suggestion that it has everything you could possibly need except that one final coat of your paint scheme!

Some chuckles available on the tech specifications .pdf button, also: the 412 is "based on the four-rotor, twin-engine 412EP" -- wow FOUR ROTORS, what a lifter! Somebody didn't proof-read this, helicopters with 4 rotors are significantly rare in history. (A few lines down they do get to "4-bladed rotor" but that comes after you're fininshed ROFL.)

In a masterstroke of customer reassurance, the Cabin Size options include either 6 or 8 "crashworthy seats." Nice to know, isn't it, that they are subliminally putting you on alert that you WILL crash! Other helicopters, one presumes, have seats not worthy of crashing. Or, perhaps, all the seats are good for is crashing?

The ship "routinely performs multiple same-day missions." How unusual for a helicopter. Must be in contrast to the OTHER helicopters that only do one mission a day? Who wrote this thing?

"Titanium yoke for smoother ride." Hey, everybody should have a titanium yoke, smooths out all those obnoxious jolts and bumps, finaly a smooth-as-silk helicopter.

OK, rant completed, we now return control of your browser to you.

[airspeed alive]

In 1997 or therabouts, the titanium yoke on a Gulf Helicopters machine, Doha, Qatar broke, whilst proceeding offshore. They all survived, surprisingly enough, although if they had been any higher than approx.1,500' agl they probably wouldn't be here now.
The pilot was a Kiwi who's now resident in Perth, WA, I believe. If he's reading this sometime, could he give me a PM & refresh my memory regarding the registration of this machine & the date of the accident?
Yours aye, airspeed alive:ok:

[SASless]

I liked the "ambulatory attendant" comment. Reckon that is opposed to a "non-ambulatory attendant".

This was probably written by a Texan afterall.;)

[widgeon]

anyone close to rucker know how the fly off is going ?.

[TheFlyingSquirrel]

Click here !

http://www.onefinalcoat.com/PDF/UsArmyStencil.pdf

that's real tack !

[Sax412]

Just a simple question about the topic above: if experienced a start up wihout removing one or both of the engine air inlet covers what actions should be taken before the next flight?
I was told that it depends wether the ITT has exceeded the maximum permitted temperature or not and I was told also that there is a standard procedure on the manual dealing exactly with this case more than explaining what to do in case of a "normal" FOD during the start up or the flight.

I've looked all the documents I got in order to find this specific procedure but I found nothing ...
Does anyone of you has ever experienced this kind of issue and is aware of the correct procedure to follow and where I can find it ?

I hope not to be OT ...:uhoh: ... by the way it's a very important point to discuss about do you agree with me ? :O

Thanks a lot to you all,
Sax

[SASless]

Step one would be to firmly kick some butts about the ramp for being stupid!

I would worry first about basic safety procedures and adherence to checklist requirements before starting engines.

At first glance, however, it would seem a standard FOD inspection would suffice assuming the ITT and other start parameters were not exceeded.

Some of our Techie friends might have better ideas and hopefully will pass them along.

[Sax412]

... I forgot to tell that even if ITT and other limits were not exceeded a good part of the cover had gone into the engine air inlet. Part of it stopped on the net at the entrance of the turbine but where is the missing part we hadn't find? has it been expelled out of the turbine or it's stucked somewhere in some compressor's stage?
The actions taken have been: removal of the cover's part melted and stucked on the first air filter, visual check just of the first air compressor stage, start up and power check and 15' test flight.

I'm wondering if this actions suffice or if the turbine should be further checked opening it to be sure no parts of the cover got stacked inside the engine ... I'm know I'm a little bit too much strict but , you know, 110 miles on the sea during day or night time need this kind of issue to be fixed for sure!

[Spanish Waltzer]

Try not to turn it into an issue of cost. If you are concerned that some of the cover has gone into the engine then the ONLY course of action I believe is to have the engine opened up to check for damage and/or remaining debris. Otherwise you will never know and you are risking the lives of all those that fly in it as either crew or pax. Made doubly more important if you are doing long sea transits where quick landing options are significantly reduced. But thats just my opinion....:ooh:

[Sax412]

The point is that I fully agree with you but I'm not in charge of anything more than stressing as much as I can the possible negative sides of the story ... so also for me this is just my point of view!
Thank you very much though!:D

[What Limits]

So make an entry in the technical log along the lines of ' Suspect FOD to engine no 1 during start'

Then an engineer has to do something and everyone is covered.

[Matthew Parsons]

To prevent recurrence, tell the pilots to count the rivets on the particle bypass doors during the pre-flight. If they can't count them, then tell them to remove the inlet plugs.

Although this seems like an easy one to avoid, once you're seated in the cockpit it's not an easy one to diagnose. Failure to light may be the only symptom you notice, so you go through a dry run then a second start attempt. Maybe you even decide to try the other engine to get a generator online before you go through that process on the first engine. Point is, its a simple cause but can lead to costly outcome.

[Sax412]

An engineer has already performed some check, the point is if these checks are all what he shoud have done or not... that's it!

[Spanish Waltzer]

Simple then - tell the engineer and your boss that you want them to accompany you on the next flight and tell them it will be a long over sea night transit. If they start squirming and making excuses about not wanting to be home late for dinner then strongly suggest a second opinion from the engine manufacturer is sought.....:ok:

[TukTuk BoomBoom]

Hey dont ask people on an internet forum would be my first suggestion.

Call your Bell or PWC tech rep thats what they are there for.
If its just a personal thing do it without mentioning the company. Most of the tech reps ive dealt with are very helpful.

(15 minutes test flight sounds pretty conclusive though.)

[noooby]

15 minute test flight sounds a bit silly to me, especially if part of the cover was missing!!
Call tech rep first, if you can't find a procedure for suspected FOD injestion.

Start with the easy stuff. Remove the mesh grill from the intake and feel for damage on the first stage compressor. Insert borescope down compressor and check further stages, and impeller, if you can.
Remove an ignitor plug and borescope the combustion liner checking for damage. Insert the borescope guide into said igniter hole, and check the Nozzle Guide Vane, and Compressor Turbine.
Any damage found, refer PT6T manual for limits. No damage found, ITT was in limits, compressor didn't surge, then all should be OK.

Spanish Waltzer, if you don't trust your engineers, maybe you should change jobs. They undergo 10,000 hours of practical and theory training just to get a basic licence, then extra requirements for each type rating on top.

Call Agusta (there should be a P&W rep there), or call P&W direct. They should be able to help. And pleeeeeaaassssseeee tell them EVERYTHING. I have been involved in fault finding where the pilot didn't want to tell us everything because he thought he would look silly. After 5 days trying to trace and replicate the fault, we finally got the whole story, and went straight to the problem.
Apart from the 15 minute trest flight, I agree with tuk tuk boom boom.

Regards

[Downupside]

I agree with Nooby
In any case do not forget that an engine is not just an assembly of compressors and turbines!
If there is a possibility of foreign material ingestion (even with no scratch or dent on the compressor), all the air system, pipes, pressure sensors,etc. must be duly checked. You never know when the least expected piece of fabric will be stuck into an air tapping, a pressure sensor, an oil jet... ruining your long over sea night transit!
Being a bit conservative never reduce flight safety level!
Cheers
Kami

[Rich Lee]

The only advice that matters is that of the engine manufacuturer. Provide them all the details and follow their recommendations to the letter. Failure to do so will risk the life of anyone subsequently operating the aircraft.

FOD and overtemperature are not the only terms of the equation. Much of the stresses in a turbine engine occur during start and shutdown. Starting with an inlet cover disturbs the delicate balance of air and creates situations that may lead to significant fatigue related failures.

Starting an engine with inlet covers installed is something the happens more than you might believe.

[Two_Squirrels]

Can any kind soul tell me what the differences are between the Bell 412HP and EP please?

Thanks in advance!

[oldbeefer]

Transmission improvements allow more power to be applied to main rotor. PT6T-3D engines give higher power and 2.5 min OEI N1 and ITT limits. Improved 3 axis AP with options of 4 axis and EFIS. Torque matching no longer automatic - beeper switch now moves lateraly as well as fore and aft to match the torques in flight (can also be used to control an engine approaching it's ITT limit when hovering hot and high).

[Encyclo]

Bell 412 HP & EP share the same drivetrain...no difference (including the the ITT/N1/Tq trim switch). They both use a mast torque (phase shift) system.
Differences are: PT6T-3D engine providing substantially more OEI power and DDAFCS (dual digital AFCS) which allows for optional 4 axis helipilot system. This provides search & rescue modes including auto-hover:cool: .

[Aser]

Humm...

The new ITT/TQ trim is also on HPs but I can't remember if the transmission was changed from SP to HP or HP to EP. :ugh:

[800]

the gingerbeers may well say that the EP stands for extra problems but from what i hear, not so for the pilots.

try extra performance! (over the old lot)

[Oracle]

The BELL 412 Series grew like this: 212 + 2 more blades (bolted another pair with a flex-beam on top of the original pair!)= 412 Classic (useless and non-upgradable to the more powerful/capable DF engine and drivetrain). Better off with a 212! At least then you have a High Inertia Rotor rather than the Low (as in NO) Inertia Rotor of the 412!

412 Classic 'upgraded to 412 SP (SUPER POWER!!!) with slightly better design to stop the airframe cracking up, but still with the old 212's BF engines and inability (due airframe tolerances) to upgrade to DF engines and upgraded powertrain.

412SP then upgraded to HP (HIGH POWER!!-marginally better engine power with later model BF engines - a/c handles better but still only single AFCS). The HP models onward equipped with overtorque warning system (co-pilots always comes on first - go figure!). The HP is easily upgradable to DF engines - becoming in effect the best performing of the 412 series as it works out (with DF engines & associated powertrain upgrade) about 450 lbs on average below the 412 EP basic weight. Changes include strengthened main box, shaft and drivetrain, + upgraded (but more sensitive) Mast torque system (split-type torquemeter replaces the old BF engine/212 Delta Torque type indicator).

Most models now retrofitted to the newer 8 hour digital CVR system - so that the boss can hear everything!
Last Model:

The 412 EP (EXTRA/EXTREME/ENDLESS POWER) now comes standard with the DF engines, Upgraded trannie etc, yaw trim (useless Bell crap), Dual Digital AFCS as opposed to the old single steam-valve-driven item in the Classic/SP/HP - which makes all the difference for decent 3 axis/ 4 axis (SAR models) IFR flight. EP gives you dual digital FD selectors as opposed to the previous single analogue unit. New bells and whistles, twitchier pedal actuator, left/right N2 governor beeper trim (also retrofitted to upgraded DF engined HP models) functions only by tweaking #2 engine up or down a tad and primarily to fix torque splits inherent with the far more lively/twitchy/hotter starting DF FCUs! Better compass system and gyros. If you want you can get the very nice aircon upgrade with the new EPs - but at a 450 lbs penalty - making a DF equipped HP about 900 lbs less in basic airframe weight than the full-option new EP! Future US military variant is supposed to have FADEC, Glass cookpit (can't write it properly or it gets edited out!), improved (possibly Cobra Z) head and blades to replace the old boltontopoftheotherbastard Bell bodge (rather than a single in-plane starflex like the fwoggy machines) and a new quieter and more powerful tail rotor. Still to be seen yet though. Bell should just have taken their best biggest machine ever after the Huey (the 214B) and got Soloy to do a twin engine fit with 4 Burping Blades and and air conditioner!

The joy (!) of the DF-engined aircraft is their ability (with at least 5 to 8 knots of wind) to operate off a helideck at MAUW up to about 42 degrees C. Good enough for most places. The BF engined SP/HP will start to lose HOGE power/load lifting ability above about 34 to 38 degrees. They are noticeably less foregiving! The DF has single-growth crystal Hot-end blades - so has a much spicier top-end/OEI performance when the SH1T does hit the fan! All of the 412 series suffer from crappy pedal performance though in the hover, as that second bolt-on set of blades induces naughty interference to the tail rotor - nasty when the relative wind gets past the beam or the aircraft gets too high in the hover! 4 feet is really the safe max for hovering a 412! It ain't got the manners of the 205 or 212, sadly!


If you can - avoid the airline seat fit - there's nothing like the flexibility of the old troop seats - and customers eventually realize this!

Hope this makes everything as clear as muck!!!

[MiracleAvn]

Hey Oracle, You seem to be up on the 412s, If you don't mind me asking you where do you work? (Company or Country)

Thanks in advance,
KM

[Salusa]

You may be interested to hear that there is an FAA STC to drop in a 3DF Twin-Pac into a 212 or 412.

Held by Heliponents I believe.

Pretty sure ADA bought a couple of the kits a few years ago for 212's.

[spinwing]

Mmmm Oh yes the 412 can really buck around with a right crosswind on a turbulent helideck!..... so ....

Are there any Ppruners out there that have any experience with the "Boundary LayerTechnologies" (?) tailboom slat STC which is said to very much tame the 205,212,& 412 twitchy tail rotor control behaviour ?


:)

[split pin]

Oracle just about covered it all. Only extra to add is HP S/No's are Pre 36087 and EP's are Post & inclusive 36087.

SP

[SASless]

Spin,

Currently Bell is fussing with the folks that build the tailboom slat you mention.

The issue is some cracking on the tail boom (as if that is new to Bell"s) and Bell blames the mod....the mod folks blame Bell.

I flew them on 212's but really could not tell the difference as the machines I flew with them did not have any SAS...and all the other 212's I ever flew had SAS so it was hard to compare.

[crop duster]

Spin,
Currently Bell is fussing with the folks that build the tailboom slat you mention.
The issue is some cracking on the tail boom (as if that is new to Bell"s) and Bell blames the mod....the mod folks blame Bell.
I flew them on 212's but really could not tell the difference as the machines I flew with them did not have any SAS...and all the other 212's I ever flew had SAS so it was hard to compare.
SAS, please enlighten this one ignernt red neck, what is SAS. :confused: Thanks,
barryb

[spinwing]

SASsy........... thanks,

Would be nice to try one of those kits out on a 412 ....... with the EPs I fly at the moment manouvering out of wind (and of course below the 90% Tq limit!!!) can be a neck snapping experience due to the airflow breakdowns around the boom and t'rotor ..... :eek: :yuk: ..... and I just LUV how the master caution flashes just as you rotate off the deck when the fuel state gets to 920 lbs or so .... one of the Bells less desirable features!!! :(

Cheers :ugh:

[Bat-Off]

SAS, please enlighten this one ignernt red neck, what is SAS. :confused: Thanks,
barryb

Stability Augmentation System

[SASless]

What I always liked was trying to remember the unusable fuel when the fuel system went south....not that the 412HP/EP fuel system is confusing or anything.

[SirVivr]

Chaps:

Any tips on Sling Loads and Winching with the EP?

Moving from 212 to 412EP. We have 412 Classics but haven't been usuing them for the interesting work.

Chas A

[800]

winching in the ep is easy!

just check your RFM supplement for limitations:ok:

[spinwing]

Be VERY VERY careful doing any MAXIMUM weight sling loads in turbulent air with the EP ....

Also be VERY cautious if the governors are not working as advertised ...cos you will have that yellow over Torque light flashing as the governors argue over who is in charge! (causeing Tq oscillations and the above mentioned Yellow light or even worse the dreaded "Dolls Eye"!!!) := :=

Cheers :(

[Gomer Pylot]

I can't believe Bell got that fuel transfer light thing certified. At 2AM, on short final or just clearing the deck on takeoff, it is brighter than the sun. Even if you know it's going to come on, it causes a very sudden increase in heartrate, and distracts both pilots at a critical phase of flight, because you have to verify what the master caution light was. I've cursed the :mad: idiot(s) who designed the 412 fuel system more times than I can count. Rube Goldberg had nothing on them, and it's all caused by the simple failure to put the :mad: fuel underneath the mast, and thus the problem of CG movement when fuel is burned. The entire machine is one huge kludge, cobbled together without any apparent forethought.

[tribal]

When slinging heavy loads with the HP or EP, you really need to pull up to near 94 or 95% mast torque. Now with the way the torque needle swings between various helicopters you need to be careful around 94 to 100%.
If the load is starting to move while holding this power, wait, it will come away gently without much need for addition to collective.( As the disc settles and becomes more efficient)
3 items will cause her to overtorque, 1, addition of collective obviously, 2, using your feet ( so be very stable on those pedals) and 3, addition of forward cyclic. Now, you may think well thats a load of good because I need to fly the load away right? Once you get lift on the load near 95% MTq, very gently add the forward cyclic, the 5 -6% up your sleeve will normally be enough to allow the torque needle to spike up to the 100% limit. What it is doing is measuring the added aerodynamic force to the rotor system by your forward cyclic input.
Now add turbulence to the equation and you will need to allow for this as well, however generally if your load is not moving at 94 to 95% Mtq it may well be a little heavy for you to carry out successfully without setting off the overtorque light.
Hope this is of help

[Oracle]

Hi Guys,
Further to Tribals excellent advice, I would also warn you that most 412 HP/EP aircraft with DF engines have very twitchy FCU's - so once you do get above that steady 95% Mast Tq on lift, you are into the 'twitch range' and need to pull in your remaining 5% power very gently to avoid an overtorque (which does you no good whatsoever in this aircraft anyway - except result in nasty interviews with the Boss!). The co-pilot's overtorque light tends to be the first one to illiminate - usually as the P1's is oscillating gently about 98-99% - so even though your TQ Meter says you've got something left in hand, you haven't! Use the co to call the Torques as his will normally be the slightly higher reading of the two! Also if you have slightly different speed FCU's this in the range within which the engine torques might split - so you will have to trim your N2 lateral beeps (DF engined aircraft only) or even carefully tweak a throttle slightly to ensure the needles stay together through to 100%. Sometimes the naughty ones oscillate in this range also! What fun!
Tribal is spot on with the pedal input/torque demand problems too. If you have good vertical motion with the load (which you must aim to lift from the deck at or below about 85% Mast Tq to have the required power in hand for a safe transition with low wind/90% with a higher wind)) you will need to start your rotation (into wind, or preferably with the wind from Red 30 to Green 10) before you lose vertical motion, - in order to get the requisite nose-down for a safe transition. In normal pax operations, modern proposed JAR Perf E recommendations now point to using 95% to max available Mast TQ (carefully!) and then using a whole 15 to 20 degrees nose-down for the transition to Vy/VBROC (70KIAS, not 60 as some people insist on thinking!) within the 9 seconds of the 'Exposure Profile' ('Rotation' to 'Vy' time - not TDP or Vtoss off a helideck!). For Underslung Loads, - particularly long-lines from a deck (or land surface) your will only be able to put in a gentle nose-forward pitch at the rotation point of about 5 to 10/15 degrees. Unlike the 205/212/214B, the four-bladed messy 412 monster hasn't the inertia in the head to allow you to happily 'pull to the bells' and chuck in a huge nose down attitude on departure to 'pendulum' the load off the ground and then accelerate through Translational Lift speed using the 'sling-shot' effect of that 'pendulum-effect' departure. Ah! - Such halcyon days of Yore!
Le Slug 412 however, will fall out of the sky doing this - due to its 'LO (i.e. NO) -Inertia Head! Remember that the 412 likes to have at least 8 knots of wind to attain MTOW graph performance -especially with OATs above 25 degrees. Winds above that -no worries - except that the flight deck turbulence will require you to shuffle at very low skid height about the deck to get into wind before departure with pax/internal cargo. No 10-foot hovers in this beast at MAUW! Best not to turn off the wind at all for deck landings in wind speeds above 20 knots or in the Classic or older SP/HPs you won't have the torque on lift to turn back into wind as the tail rotor input will overtorque you quite quickly and alarmingly! Remember your TR charts in the PFM - the 412 hates winds from abaft the beam and likes to fall out of the sky at that point, leaving you pedaling like you're in a kids go-cart!
As the fixed USL mirrors are crap for long-line work - particularly to offshore platforms/decks, I would recommend that you take a suitably competent and well-briefed co-pilot in the LHS, then on the run-in for the deck with the load, <45 KIAS (and also during the initial take-off to position over the load) he loosens his lap-strap about 12 inches, which allows him to turn slightly in the seat, grip the leather door strap firmly with his right hand, while opening (and firmly gripping!) his lower door handle with his left hand - and between those two 'geometrically locked' hands he can firmly hold the door partially open and at the same time look out and talk you down with the load to the desired landing point giving the usual con 'patter' with reference to height and speed for the load (Word-Picture-Information as my old mate Robbo used to say!). He can also confirm proper subsequent release/unhooking of the load and or strop without any nasty lateral/fore/aft drift over the load. This is particularly effective for changing out flare heads on offshore platforms, where very accurate positioning is required for safe installation. Of course if you have a proper 'bubble' load door in the LHS with instrumentation included, then just fly the load from the LHS like a 212! What joy! Just remember that if you are flying a 412 Classic or an SP (or HP with BF engines) you won't have the same engine/torque response/pulling power for the same amount of lever movement that you would have had in a DF-engined aircraft, nor will you have the same level of power margin under any set circumstances. As the Older Classic and SP aircraft - in particular - age, the machine will not normally perform to graph expectations (especially in low wind conditions) and you will, by necessity, have to work at minimal fuel loads or with reduced MAUWs (usually by reducing the published weight by about 600 to 800 lbs depending on the ambient wind conditions). The older (212-type) torquemeter instruments are much steadier but have no overtorque warning lights and will - effectively - give you much less raw 'grunt' or 'pulling power' than the more reactive (and excitable) DF-equipped HP and EP split-type Mast Torquemeters.
Happy humping! Any more questions - fire away!

[tribal]

Interestingly enough, I have found that when working the 412 EP / HP very heavy and in light winds ( not underslung) it is possible to fly the aircraft away with a right quartering tail wind, at a considerably reduced Mast torque. You do need a drop down height available, to gain airspeed, so I am talking platforms and the like. I call it putting the wind in your back right pocket.
Others I know have used the technique with success, but as we are mere drivers none of us have an idea as to WHY it works.
I know there is added exposure of risk in using drop down for airspeed, being near downwind, so this requires judgement, however it will get you away when very heavy and hot. ( Im not after a slagging from so called experts here on the technique, but does anyone actually know why it works?)

[Oracle]

Yes, well........... what a brave chap you are! Of course if your TOW is low and your tail wind is below 5to 8 knots, then this is certainly possible, but I wouldn't recommend it as a regular occurrence and certainly never with an Underslung Load - which is what I was primarily talking about above. The 'drop-down’ use for trading height to speed during departure is great with pax/internal cargo - (when you actually have a decent deck height to give you the drop-down option) - but the aim of the act of rotation is to get the tail clear of the deck in the event of a critical engine failure after the nose-down rotation has been input. During a downwind deck departure (pax/frt) this would be pretty-well guaranteed, because of your exaggerated tail-up, nose down attitude from the downwind departure (just about where you feel your butt-puckering rate increasing quickly!) will ensure this, however you are still downwind and therefore will sink more rapidly after an actual EFATO and your subsequent ability to fly away safely from an engine failure after rotation will therefore not be quite so cozy. It will take you longer to carry out your fly away, and if you were (horrors!) at MAUW it is highly likely that you would not make your 70 KIAS VBROC/Vy at Max SE Torque before you impacted the water, in which case, you would then be faced with converting to a down-wind run-on into de briny blue (whilst maintaining translational lift iaw with the PFM!) In a 412? No thanks mate!
Purely as a guide to pilots new to these 412 helideck operations and especially Underslinging to/from offshore platforms, I would say NEVER do a downwind departure in a 412 unless you are light and the winds are below 5 Knots. As for the pedal input - yes, you can do this during any deck departure, - downwind or otherwise, but from vast experience teaching new guys offshore, it is far less stressful for them (and for me) to depart on a steady chosen heading (especially at night) into wind or within the 'nice' relative wind arc for the 412 (Red 30 to Green 10) without making pedal inputs during this departure. Such inputs tend - until they have frightened themselves sufficiently in a 412 offshore - to be excessively applied and the cause of quite alarming and wholly unexpected Torque 'spikes'/overtorques after rotation which they are usually wholly unprepared for! Sorry, - but the machine flies like a dog compared with its illustrious predecessors and therefore needs to be mollycoddled off the deck in the smoothest, gentlest way possible. We helicopter Gods are meant to be smooth, of course! Downwind departures with excessive rates of pedal input on departure are liable to end up with passengers submitting complaints after flight - so lily-livered and chicken-hearted, those oilies!
The gentle, expert use of pedal by an experienced pilot is another matter entirely, of course - and one which shows the devastating skill and experience of the 412 operator involved!
When you do have sufficient experience offshore to be skilled at, and be comfortable with, doing downwind departures off decks, then you will know exactly where that very fine dividing line is. However, within a company employing over 15 different nationalities, I personally find that the safest standard to set is usually the most straight-forward and sensible one. - K.I.S.S. (Keep-It-Simple-Stupid) - it works well for new guys, especially when one only has one pair of instructional brown-corduroy trousers supplied by the company!
In the end - operating the Bell 412 (especially above 44 degrees C) is all about getting enough hands-on experience on the type, - in all winds and weathers, without going swimming or bending the machine, and then using that expertise to try always to operate the aircraft with the most suitable (fine) margin of power/weight and fuel 'insurance' in-hand to provide for the wife and kids!
Fond regards,
O

[tribal]

Oracle, I think you and I have a very similar job, and you add a wealth of knowledge in your threads.
Now let me be more specific with the right quartering tailwind takeoff. Ok as I said earlier, No underslung loads, Im talking 11,900 pounds, Internal load,temps 30+.
I have found at offshore facilities, where due to obstructions nearby or in the takeoff flight path, that an into wind takeoff is either precluded or not the best option. Now I know your thinking, drop the weight, however its not necessary in every case. By turning the aircraft, (to the left, ideally for tail rotor effectiveness) and placing the wind in your back right pocket, hover power (MTq) will considerably reduce, 5 - 10%.
Try this without effecting the takeoff and you will see that it is true.
To carry out the takeoff, this allows you to clear the deck edge gaining more height over airspeed in that critical phase....ie without fear of overtorque , and allowing safe passage for the tail. Now it is true that once the deck is cleared you will need to make a transition to gaining airspeed, so to nullify the effect of a larger forward cyclic adding to torque required, you may check collective down a touch ( Now I mean, check it , not drop it, Im talking 1/4 of an inch) You will get more dropdown height for sure, you can re-evaluate your takeoff decision point, depending on height available, and airspeed. Or more correctly your judged ditch/fly away point. To my way of thinking getting off the deck at maximum power is the worst part of exposure in the event of failure.
The point was, why does the aircraft use a lot less Mast torque in a right quartering downwind while heavy in the hover? I will add that although I know 3 pilots who also use this technique occasionally, I do not teach the technique to those new to the 412, but have added it here so for those of you who have a lot of time on this aircraft to look at it as an option and see for yourselves. I dont know why aerodynamically it works.
Thanks for your input fellow drivers, it makes interesting and valuable reading.

[GLSNightPilot]

The 412 really hates crosswinds. I've lifted up off tankers where there was no way to turn the tail until at a very high hover, and it took gobs of power to get up there, but a simple pedal turn resulted in a rather exciting rate of climb, immediately. The rotor system doesn't know where the wind is, but the fuselage does. Either a headwind or a tailwind requires less power than a direct crosswind, IME.

[Matthew Parsons]

Tribal,

What is a typical location of your cg when you do this? The helicopter attitude may become more level with the aft right wind, which may show a slight decrease in required mast torque. However, I doubt the magnitude of this effect will be as large as what you're finding.

I think the most likely area for the savings is the power requirement of the tail rotor. The aft right wind may direct the tail rotor wash away from the vertical stab, or even around it in such a way that favourable yaw forces are generated. Again 5-10% seems high, since I would have thought that would represent the total power requirement of the tail rotor.

One caution, everything you're saying suggests you only get this excess power with a tail wind. As you translate forward, you're necessarily eliminating that excess, and arriving at a minimum wind condition (also max power required) with a rate of descent established. You'd be better off starting at that max power condition being level or with a rate of climb.

Just my thoughts,
Matthew.

[SirVivr]

I appreciate all comments and ideas in this thread. It gives me a lot to sift through and many questions to cause beads of sweat on the forehead of the instructor when I go to Flight Safety soon.

We all have to earn our money.

8,000+ hrs on the 212, 2,000+ on the 412 Classic, and learning a lot from this thread.

Please keep going, I don't have many years left to experience all the mistakes myself.

Chas A

[tribal]

Matthew, Thanks for your thoughts.
As far as translating forward is concerned, like I said you need drop down height, and with smooth controlling it doesnt present a great deal of problem, provided you are aware of your actions prior to and after your selected fly away point, to ditch or to fly in the event of a failure. Thats the second part of the equation.
However like most things mechanical, they have a tendancy to fail at the time of most stress, under the highest power requirement, and to me on the edge of the deck or on the way over the edge, is probably worse than in flight clear of the deck.
Now I didnt say that this excess power was available only with the wind on the right tail quarter. I do agree a headwind is always the best option, IF it is available ( obstructions etc...). I have noted that wind within a 360 arc around the aircraft that from the angle I suggest you will note a considerably less torque requirement. Try it without effecting your takeoff and you may become a believer.
As far as CG is concerned, I can only say within limits, because with this operation we effect up to 70 takeoffs and landings per day at offshore facilities with many varying numbers of pax and freight. To work out CG closely to figures becomes impractical.
Having said that, with the extremely high numbers of t/o's and landings, we do find many situations in which one can find little nuances such as this one Ive passed to this forum.
The thoughts on the tail rotor wash may be the answer as to why this works. Appreciate the input. Thanks

[Matthew Parsons]

I thought I was in meetings today. Show up at work and discover I'm doing low speed performance work-ups in the 412. It was done just for technique so the data gathering was far from rigorous, but I saw the numbers you mentioned.

We flew cardinals and subcardinals at 10 and 20 knots relative wind. Unfortunately, I thought the FTE was recording perf...he wasn't. So I only had the green and red 135° and the 180° data, at 20 knots. With those three data points the effect was seen, about 7% less mast torque at the green 135° than at the red 135.

[Shawn Coyle]

A slightly different subject related to the 412. Does anyone have problems with the gimbal ring and related swashplate parts starting to fail at 300-500 hours?

[Encyclo]

Not if it's maintained properly:ugh:
Refer to: http://www.bellcustomer.com/files/Storage/TB%20412-05-201.pdf
:ok:

[Oracle]

Shawn,

Just a consideration.

Some years back many (ex-212) 412 operators were beeping down to 97% NR for cruise flight (which really does nothing for you with 4 blades except get very exciting trim actuator-induced TQ spikes in the >105KIAS mast torque limitation range!). When the EP came along, the same cruise reduction started causing noticeably increased wear on the rotating components of the head, some of which were being damaged quite markedly within very low flight times.

Bell then advised that the probable cause was pilots climbing the aircraft regularly (and at varying ROC!) at less than 100%NR, which was damaging said components in very short order. Subsequently, Bell advised 412 operators not to beep down at all for cruise flight in any 412 variant and to maintain 100% throughout the normal twin-engine flight envelope. My own company and many others subsequently withdrew any reduced-NR cruise operations. No further occurrences of such increased wear in rotating components were subsequently encountered. The climb at 97%NR in the EP model was the particular hard-wearing activity. (Of course, any prolongued operation of a 412 with poor tracking/rotor balance will also speed such wear.)
FYI

[Matthew Parsons]

Oracle,
Subsequently, Bell advised 412 operators not to beep down at all for cruise flight in any 412 variant and to maintain 100% throughout the normal twin-engine flight envelope.

Do you have a reference for that advisory? We still have 97% cruise in our books.

[tottigol]

Oracle,
Do you have a reference for that advisory? We still have 97% cruise in our books.

Likewise, I've been flying the 412 for years and I've never stumbled on anything like that.

[Aser]

I'd like to see the advice.

Related to this thread http://www.pprune.org/forums/showthread.php?t=189116&highlight=cruise

[Gomer Pylot]

We still beep down to 97% as per the flight manual. It results in increased speed and a smoother ride. Anything you can do to smooth out the 412 is worth doing.

[800]

The "EP" RFM says for;
"In-Flight Operations"; ENG - 97 to 100% RPM (N11).
"ROTOR RPM - POWER ON"; Continuous operation 97 to 100%
"FUEL FLOW VS. AIRSPEED" graphs; ENGINE RPM = 97%
Now that all said and done, I do prefer to only beep down when I am cruising at a sufficient cruise altitude to have time to beep back up if something happens.
800

[Oracle]

Hi Guys,

- Amazed to find so many people still beeping down in the 412! Old habits (like helicopter pilots) die hard!

I will indeed attempt to find the communication from Bell about this although it was some three years ago!

However, at that time we did approach Bell directly with regards to over-fast wear/way-short life expectancy experienced on the rotating head components' of our new 412 EPs at that time and they came back with the very definite advice and recommendations that they considered it unwise and quite uneccesary to beep down to less than 100% NR for cruise flight in any model 412, and particularly in the EP Variant, which would definitiely sustain excessive wear - particularly during sustained climbs at less than 100%NR.

Meanwhile, I must say that removing such cruise reductions from our company checklists and SOPs has made the whole excessive wear issue go away and also made for much easier day-to-day operations, particularly as this outfit doesn't rate-time their N2 beep actuators (as we used to do in my old 205 and 212 Fleet).

I am sure that some of you will already have been shocked at the 2-nanosecond min-to-max beep rates on some new actuator units! I have actually had one so bad after instalation that it turned the aircraft on its skids on the ground in less than 2 seconds! By removing the beeping up and down during each flight, my heart-attack rate has subsequently been reduced - as newbies seem to insist on holding the beep-up button (rather than tapping at it gently) whilst tooling along at 79% Mast Torque at full chat, thereby exceeding the 'top of the green' Mast Torque Limitation above 105 KIAS. Such exceedences were commonplace before we lost the 97% NR cruise, and we are therefore saving ourselves wear an tear from that angle as well as from the obvious transient torque-spike transmission wear during 'savage' beep actuator operations. Life is FAR more sedate and comfortable now, - and the fuel saving was never really noticeable over a 200 mile sector in the 412 anyhow!

One thing I should add though (as my single random 'duty brain cell' suddenly kicks in) is that part of our change to continuous 100% NR operations (twin-engine) in our 412 fleet was that we had to change our engineering practices and air test schedules to reflect the fact that our FRAM Dampers would now be re-tuned to 100% so that RADS workups and in-flight-tracking would reflect our cruise speed requirements (although we do still check the RADS at 97% to ensure there are no naughty vibes in the OEI range!). All of our 412s subsequently display red cockpit decals on either side showing 'FRAM DAMPER TUNED TO 100%NR'.

I'll see if I can dig out the original response from Bell from way back and get back to thee if I am successful!

Happy Beeping meanwhile!

Cheers,

'O'

[Oracle]

Greeting fellow 412-ers!

Sorry nothing still on file from Bell, but I did get confirmation that Bell had definitely come back to our company and pointed out that they recommended all 412 operators maintain 100%NR throughout the flight range and that particular attention had to be paid to the 412 EP model to ensure that no climbs with RRPM less than 100%NR were carried out (non-emergency, that is!) .

I can, therefore, only suggest that you guys who are still ''beeping for victory'' in the cruise consider getting your companies to contact Bell directly on this subject if you have any doubt - or otherwise just to change your SOPs and FRAM damper tunings to 100% as covered in my previous posting. . I suspect that you will indeed find that such a common-sense move will result in much less wear and tear being experienced on both the rotating components of the rotorhead and on your gearboxes/power trains.

Salaams,

[BJC]

Oracle, does your 412 fleet have any external kit mounted (skis, floats, hoist, etc)? We were advised by Bell a few years ago to only operate at 100% Nr with external kit, but in a clean bird 97% is still authorized. Food for thought...

[Oracle]

Yup - all of them have external floats fitted. No hoists. But Bell knew that when they gave us the advice!
Cheers...

[Oracle]

Of course, there is a definite difference between what Bell ''authorizes'' and 'recommends'''with regards to 100% NR operations! - Wonderful thing, product liability! :}

[Matthew Parsons]

ahhh...external kits.

Guess that's why I'm testing aircraft and you're changing diapers.

Welcome aboard, BJC!

[BJC]

Ya Matt, I just took a few months off to let you catch up to me in your knowledge of the 412. Looks like you might be needing to get back into the books again :) or maybe I should stay at home longer to give you more time? Enjoy your three weeks of classes :bored:

[Rocket Surgeon]

So.....any update or enlightenment on the 97% vs. 100%?

[Oracle]

G'day!
Well, in the end you guys will have to make your own minds up! However, as I have said before, Bell 'strongly recommends' that 412 operators maintain their RRPM at 100% throughout the flight envelope. The particular known problem of excessive head component wear on the 412EP Model in particular during climbs made at 97% RRPM would seem to suggest that the sensible option for all variant operators is to stick with 100% RRPM as a standard for all non-OEI flight phases and to minimize OEI rate of climb for training purposes (not that one needs much help with that!).
Apart from amending your company's maintenance and flight test procedures to retune your aircraft's FRAM dampers to 100% for the cruise/Vne segment of the vibro (part of the vibro is obviously still done at 97% to ensure that nothing shakes itself to bits during OEI ops!) and adding a decal on the instrument panel to indicate this change (and educating your staff that not cruising at 97% is in their best interests), there seems little to be gained from retaining the old 204/205/212/214B twin-blade cruise RRPM setting.
Besides the fact that fuel saving with the composite blades on the 412 is marginal/minimal at 97% as opposed to the normal 100%NR, if your company's engineers don't strictly 'time' your beep trim actuators, you might/will undoubtedly find that even the most fleeting operation of an over-excitable 'beep' actator [especially when torque is already at or near the 'top of the green'] might lead to accidental/inadvertent overtorquing of the main rotor (>105 KIAS). Particularly when the beep is used to restore 100%NR from a cruise setting of 97%NR. This 'beeping up' can lead to a nasty, if not positively savage, degree of rapid mast torque fluctuation in EP's that do have such a 2 to 5 second full-range beep timing (Bell recommends 8 to 11 seconds, I believe, - like the 205/212). In some companies, the beep actuator timings on their fleet aircraft are all different! Someone getting out of a sedentary SP therefore and straight into a 'hyper' EP might easily ruin their whole day/career in a moment of tired inattention at the end of an 11-hour day! Not worth it in my humble opinion!
In the end, choice of cruise NR setting is still left up to the individual operator, but one suspects that by 'advising' customers to operate their EPs (and therefore their whole 412 fleet for sensible standardisation) in this manner, Bell have covered their liability 'Six' and will not entertain any prospective cries of premature or excessive wear, or other inexplicable damage to rotating components from customers who have not complied with their 'advice'! Having seen such components removed from a new EP with less that 100 hours on the clock, I am quite convinced that maintaining a steady 100% NR throughout the normal operating envelope is the most sensible way to go!
I hope that this post may help you decide likewise!

[Matthew Parsons]

Oracle, the post really does nothing without the advice from Bell. Have you found any correspondance that actually details this, or is this change to your companies maintenance and operational procedures merely based on word of mouth?

[Oracle]

Well, my dears, I wasn't going to waste more time wading through 4 years of correspondance to find the actual letter from Bell, - but if you choose not to believe me (despite the halo) and are SO durned desperate for written proof, why don't you just drop Bell Customer Support a line yourselves - or don't you guys talk to them at all?

Unless you are based in Iran, Bell will probably respond and may even satisfy your every need (within the constraints of product liability legalities)!!! If you are, then best not to email or call them at all - you might find some GPS targeted munitions from GWB incoming onto your bonce!

Seek and ye shall find, Glasshopper!

[Matthew Parsons]

I think that's our points as well. You seem to be the only one that has heard of this. You have no correspondance to verify this. We're all in regular contact with Bell. We still have 97% cruise in our manuals.

What if I told you that Bell said you can't start engine #2 first (they didn't say this). Would you then change your procedures? Even if nobody provides evidence or even supports this claim?

It's not that we don't trust you, just that a change like this requires more than one opinion from the internet.

[spinwing]

Mmmmm....

Well I am going to have to side with Oracle on this one .....

The company I work for has also been advised by Bell to do the 100% Nr operating RPM thing and it makes quite a difference!

With 15 odd 412s (mostly EPs) it has made life much easier for the maintenance crews and with our higher (than most) DA ops it seems to me the aircraft like it better too!

Cheers :D :E

P.S. ...... just 'cos Bell have advised the operating RPM change does NOT mean they have to ammend Flight Manuals to reflect that opinion.

[Oracle]

Thank you SPINWING!

Dudes - just ASK BELL and find out for yourselves!!!!!!! We did and that's what they came back with some 4 or 5 years ago.

Is that TOO difficult? Don't keep on qveching at me to go did into 20 years of correspondance for the letter from Bell - no time for that, I am only trying to help you (as requested in the original thread) by telling you what has gone on in my company for the last 7 years. You must be responsible for your own flight operations/SOPs and how you decide to operate your aircraft.

A Bell recommendation - as my friend SPINWING points out - is not necessarily going to appear in the PTM or Flight Manual! We live in a litigious world, my friend! 30% of your spares' cost is to cover possible litigation!

Also - if you haven't renewed or updated your 412 Flight Manual since you got your aircraft, its worth getting the latest EP ones from Bell (about $200 each I think) because it has some extras -OEI Fuel burn charts etc. which many opeators haven't seen yet because they haven't amended or renewed their Manuals in the aircraft since they took delivery!

So - drop Bell an email and find out what they say!

[Waag]

Hi there guys!

Just wonderin'; What's the BEW of your 412? And in what config, and type?

Trying to compare with our 412

Thanks!
Waag

[wazz'n'zoom]

Interesting to read 7 yrs of 412 EP ops. RAF Shawbury's DHFS experienced operators beep down on nav sorties to reduce the mast Tq and therefore achieve even more IAS but moreover in this PC world less noise from the extemely loud tail rotor. We did an unofficial trial last year and the difference was you could get about 2nm closer to the bad guys before you were heard at 120kts. But flying at 97% in OIE condition is not good, but that's wehy it's in the FRC's to ensure that you beep back up to 100% post an engine failure.
Blue skies and light landings.

[wazz'n'zoom]

Does your 412 have a 2S11 switch to enable you to couple the busbar post an under volt/ flat battery otherwise you ain't going to commit aviation? We start o ur 412's #1 engineon odd days and #2 on even days without any probs.:)

[Oracle]

Yup, Wings, the 2S11 switch is pretty standard these days. Anyone who ever suffered from the old 212 roof relays failing during starter load, with the resultant loss of 5 to 8 volts during the critical phase of start will remember why! (The engine hangs up at @12% NR, you have no voltage left to blow it through and the hot end burns out happily as the ITT passes 900 degrees C going UP!). Starting one of those puppies with flat ni-cads was a one-armed paperhanging exercise! The 2s11 switch 'remedies' this problem as only Bell (Product Liability) Textron Corp could. Problem is, all Bells were designed to start Number 1 engine first and 2 second (an Army pilot arithmentical logic process, I believe) so there is that bias in the (il)logic of the electrical system design, rather than true parity. As most 212 and 412 operators alternate 'first start' engines each day to spread wear, this can make it 'interesting' when starting number 2 first - especially on the odd-ball machine having a reluctance in its No 2 self-energizing generator relay! This is why it is often easier when starting Number 2 to quickly 'whip' the No. 2 start/gen switch straight up to reset and then straight back down to ON without stopping halfway (after 70% has been attained) to get the genny on line. When starting No 1, the Start/Gen switch will normally just switch straight on as advertised without resetting first. Similarly, some starter-generators will drop the respective battery bus switch off when start button has been engaged. This often confuses newbies until the magic finger reaches up, reselects the affected Bat Bus Bar Switch back ON and the start continues as advertised. - It was so just so much easier on the UH-1/B205!!! Of course then you had to remember NOT to try selecting the starter/generator on if you had been foolish enough to start with a falling battery voltage during crank (<14v) as one of my old Squadron Commanders proved when - despite warnings - he did this and several horrified people (inlcuding himself) watched the nosedoor and battery blow off the front of the aircraft! The Halcyon Days of knackered Ni-Cads! Lead-acids are the real deal!

As for 412 EP fits. -Standard offshore machines with external float kit, internal ADELTs (as all are now, I believe). I gather some operators without the floats do get slightly more from beeping down for cruise, but as I warned of before, the damage done to the rotating components (EP especially in climb) at 97% by far outweighs the perceived minimal fuel-burn saving, let alone the transient beep switch torque spikes which have been known to catch far too many tired 7-hour a day offhsore pilots without their brains-in-gear! As for quietness - well, man - IT'S A BELL! A little blade-slap is your personal acoustic signature! Heading Front Line with a 412? Definitely want 100% on!!!! (and clean underwear and lots of Kevlar Armour-plating - preferably in a 412B!)

In the end, Keep It Simple Stupid usually works better as a company policy in mixed-crew reality - so 100%NR across the non-OEI board is easier, safer and protects the aircraft, crew and passengers better from unintentional transient 'beeping' damage and excessive wear on your precious rotating 'bits'!

Happy Trails!

[gittijan]

ORACLE and Spinwing are on track. The latest information from BHT is that they are planning to amend the Flight Manual to say that 100% N2/NR is to be set for all Normal operations.

[Oracle]

Excellent news! Thanks for that, mate!

I had written to Bell last week about this, but not had any reply yet - perhaps they have now decided to make it 'official' at last!

Cheers,

Oracle:}

[outhouse]

About time it was official, flogging around at 97% NR/N2 never made any sense to me, lots of disadvantages and bugger all advantages in my book. Though I am sure some will disagree!!!:uhoh:
outhouse

[Oracle]

Greetings All,
This just in from my own Bell Rep this week for your edification:
On the issue operation at 97% NR, In order to standardize operations, Bell Helicopter will be issuing a rev to the flight manual that will limit rotor RPM to 100 % during all operations. Normal governor excursions above or below 100 % will be acceptable but continuous ops shall be at 100%.
At this point in time normal rotor RPM limits (Green arc) can be anywhere from 97 to 100 %. There is no restriction. There is a perceived ride quality 4/rev improvement at 97 % if the aircraft is not equipped with a FRAHM damper (412-SI-47) as well as a slight fuel burn improvement. At 100% rotor blade lift is optimized .At high altitude, high gross weights and airspeeds at or near VNE, control system loads increase dramatically as the rotor approaches retreating blade stall. Because retreating blade stall occurs at a lower airspeed at 97%, operation at 100 % will reduce these loads and will be stipulated as the RPM limit used for continuous ops.
A revision to the flight manual, plus a decal to install on the instrument panel will be release thru ASB shortly advising operators.
Hope this helps those of you who are still flogging about at 97% to start changing your checklists now!
Cheers,
Oracle

[C-David]

:8I would like to learn more about this unique aircraft. I notice, that in addition to somewhat unique engine fuel controller, it had (has) an unusual avionics suite. How many of these aircraft were built? Where are they today?

[C-David]

I have Bell 412EP RSAF Flight Manual and Bell 412EP-Specifications Neither has much detail on the Rogerson Kratos Avionics that seems to be somewhat unique to this limited production aircraft.
:8I'm particular interested to know about the digital bus structure and what specific data one might be able to capture by monitoring and recording bus activity.

[JUANK]

hi all.
Excuse my english. I´m a spanish helicopter pilot, i was looking for any incident about groun resonance in 412 and find you.
In spain we have four incidents by ground resonance. well no ground resonance, i think there were greats bounces in ground, because when we try to take of whith the helicopter bounce and it separate of the ground it continue flying jumping (or bounce) and the only way to stop bounce was shutdown engines (autorrotacion).
The four helicopters were working in firefighting and all were without persons on board at 100% N/R.
I was flying two of there four (same helicopter)
The first time i complete succesfull the helicopter´s control fighting about one minute with it and maintenance don´t find something inussual. two days later in ground in a sand filed it become to bounce and this time i have to shutdown the engines in flight because it was imposible regain control.
in several flights with anothers 412 we have the same problems,with light and medium bounces and the only way to cut this situation was turnning throtles to idle and try to pass to flight gently aplly a lot of collective.
Excuse my english and thanks to all for your forum

[Oldlae]

Juank,
I might be out of order here, but you may be getting bouncing because your collective friction is too light and you maybe a litttle bit too gentle with the collective lever. I had a similar case with the Bell 205A-1, the pilot's seat is flexible and if you are holding the collective, as you probably are, any bounce in your seat is transmitted to the collective. You say that your maintenance crew cannot find anything wrong, please ask them if the static friction clamp on the left side of the collective torque tube is correctly set? There is a panel just below the left hand side crew door which gives access to the clamp. I apologise if this has been checked before.

[RVDT]

Oldlae is on the money.

JUANK

The dreaded "collective bounce". I have taken 2 aircraft straight to maintenance because of low minimum collective friction.

Afterwards when other pilots return to fly the aircraft the "whining" about the collective friction is louder than the engines.

The "chorizo's" in the pilot seat are too SOFT!

It is not "optional" - get used to it.

This issue is not limited to Bell medium products, it affects the Super Puma as well.

It has destroyed a few aircraft - if all else fails RTFM!!!!!!!!!!!!!!

[Oracle]

Hi Gents,

Whilst slack collective friction MAY often lead to PIO's (Pilot Induced Oscillations) of the vertical kind (especially when the pilot's seat IS loose vertically, or the pilot sits very high on the seat and then his overly stiff collective arm magnifies any existing aircraft vertical 'bounce' quite quickly), the 412 is subject to other factors which can lead to considerable and quite scary Ground Resonance or Low Hover Resonance with a severe vertical vibration.

Two cases in point:

1. The Main Rotor blades are not well statically or dynamically balanced, nor weight-matched and the MR tuning has placed them in an 'out-of phase-harmonic' with the skid gear. This is accentuated when such poor blade dynamics and mix are combined with worn cross-tubes. I have known one such particular aircraft that would enter Ground Resonance at the drop of a hat and frequently did so, with scary results, usually during OEI run-on landings onto a tarmac or concrete surface - at which time it would enter a SEVERE vertical oscillation, which had it reached the third such oscillation would have been impossible to contain/recover from. The situation was only remedied by swiftly re-engaging the second engine at the onset of the oscillation and quickly lifting the aircraft smartly up to a ten feet hover. (- Change of underwear subsequently required -THAT bad!)

2. Many pilots fail to notice when one (or more) Main Rotor Droop Restrainers fail to disengage properly from their static position during run-up. Because we are all so used to having 412's shaking us to death on the ground anyway with bad tracking, and the fact that our backsides are also definitely 'attuned' to a certain basic level of 'shake, rattle and roll', the failure of a droop-stop to come out properly and cleanly during engine/rotor run-up is therefore often masked. The vibration this causes is, however, quite a marked, constant, equal and very regular WHUMPER (One-Per-Rev) vertical vibe whilst on the ground. If this problem is not noticed or correctly diagnosed and addressed whilst on the ground [by winding the engines back to idle, giving the stick a gentle 'stir' and then winding the rotor back up to 100% again slightly faster (normally this disengages the sticky restrainer, sometimes with a slight 'clunk' or control jump)] then any subsequent attempt to lift the aircraft into a hover with the droop stop(s) still engaged will demonstrate a serious level of One-Per vertical vibration, very similar to that described above. The 'stuck' droop restrainer cannot normally be cleared in flight, but only on the ground. Continued flight will just damage the stuck restraining mechanism even more and scare the pilots markedly. Usually, a total shut-down and maintenance attention will be necessitated, as worn parts or stuck bearing on the mechanism often cause this problem in the first place. The more polluted your operating environment, the more likely this is to occur unless specific attention is paid to cleaning and properly maintaining the blade droop restrainer mechanisms. The RFM DOES warn about this occurrence but this is often forgotten on a daily basis, as a droop-stop sticking is usually a quite rare occurrence.

The RFM States (Pre-Flight): "DURING LIFT-OFF TO HOVER, ANY ABNORMAL INCREASE IN ONE PER REV VIBRATION MAY INDICATE ONE OR MORE DROOP-STOP RESTRAINERS HAVE FAILED TO DISENGAGE FROM THE STATIC POSITION. VERIFY PROPER OPERATION PRIOR TO FLIGHT."

Obviously these two forms of induced vibration are just two causes of nasty vertical vibrations, but I would suggest that our Spanish pal gets his engineers to check his droop stop restrainer mechanisms for worn or stuck parts or bearings.'' Fire pollution gums things up!

If you have one of those rare beasts that just likes shaking itself to death as in (1) above, then the only answer is often to deliberately 'detune' the main rotor (all blades equally adjusted) within the available limits of the Auto RRPM, such that it no longer sings in harmony with the cross-tubes. Changing the cross-tubes is another option if they exceed lateral max spread.

Those other old 205 & 212 drivers out there may well remember the wonderful vertical bounce encountered whilst flying underslung loads with a two-bladed system, when the load and rotor got into 'synch' and tried to vertically vibrate themselves to equality! With the 412's unforgiving (and gutless) main rotor blades, it is also prone to induced vertical bounce with an underslung load, particularly with a long line. The only answer here is to change the length of the line/sling to change the induced frequency.

Hope this helps our Fire-Fighter buddies in Espana!

Cheers,

O :}

[Oldlae]

Juanta,
Whilst checking the good stuff from Oracle, get your maintainers to check the rubber mounts of the cross-tubes.

[BJC]

Oracle, it’s taken over a year, but we’ve now received the amendment from Bell on 97% Nr, although it is slightly different then what you’ve described. You can bet as the largest 412EP operator in the world we’ve been in regular contact with Bell and we’ve only recently received the amendments. The amendment to our flight manual now states power on Nr continuous operation 97-100% below 6000’ DA, continuous operation 100% Nr 6000’ DA or above.

The reason I wanted to see your correspondence with Bell is because our flight manual has always restricted us to 100%Nr when operating with any external kit installed (hoist, night sun, FLIR, skis etc). Since you stated that all your aircraft have external kits it made us 412CF operators sceptical. It’s hard to suppress that scepticism when our flight manual has guidance such as:

Operation at 97% is considered best for cruise flight while hovering and other flight manoeuvres are best accomplished at 100% NR.
Cruise charts are presented for 100% engine and rotor rpm and standard configuration. Often better range (higher speed and reduced fuel consumption) may be achieved by reducing rpm to 97%. If rpm is beeped down 3% and speed remains same at a constant torque setting, then fuel consumption is reduced by over 1% and actual SHP required has been reduced by 3%. At certain operating conditions, speed actually increases 6 to 8 knots while beeping down at a constant torque. When this happens, range gain can be over 5%.

For your “ground resonance” example #1 above, were your autopilots engaged? Were you in SAS or ATT mode? Our flight manual was the following caution: “Run-on landings may result in roll oscillations while on the ground. If this occurs, lowering the collective full down or disengaging AP1 and AP2 will stop the oscillation”. Holding the force trim release button also helps.
It feels very similar to landing on very rough terrain and could be what you’ve described.

[JUANK]

thanks to all for your answers.
thanks oracle, i think it will be caused by the cross-tube but there were one think that i can´t understand. i don´t understand why i continued bouncing flying (bigs bounces one-per-rev of SEVERE vertical oscillations)?.
the droop stop restriners i think there were right because i was flying three hours in fire-fighting when happened the first time (two hours of flyght, 40 minutes of rest and one hour of flyght in fire-fighting until i descend to recover the firefighters). i was flying only whith one hp engage in SAS mode (BJC). the landig zone was ten degrees of slope (left side), the collective was not full down because the slope, i need to apply collective to avoid slipping and the ciclyc styc was to the left to maintain the slope.but the helicopter was stable and without vibrations. When the firefighters open the basket to save the bambi bucket the helicopter started to severe verticals ascillations. i maintain in that position to
allow firefighters to derogate, and when i was close to dump i take of but the helicopter continued whit verticals oscilaciones and we lose the tail rotor control during 30 or 40 seconds. when i regain the tail rotor control the verticals continiun in all the time and i could disconnect the hp1 and all verticals disappeared. i go to my base and change hp1 box control, and we make a one hour test flight testing hp1.
maintenance not found anything abnormal and they thought that was due to a wrong behavior of hp1.
The next flight was a cruise flight and it was fine.
The next one was fine until i landed. helicopter at ground, collective full down, hp1 off (in caution to prevent a system fail), 100%NR, no vibration, one minute to descend all firefighters, and when they open the basket to draw the bambi bucket the helicopter sudenly become to jump, a big jumps. i take of fast, when the fire fighters broke the helicopter, to prevent ground resonance but it continued jumping, i had full control but the helicopter has several verticals vibrations one-per-rev. i try to take of but noises in the transmission were increasing (i think was the lift link) and when i was over 30 knots and one hundred feet the helicopter try to yaw 30º to the right in a jump, I fixed that position but it try to another jump to the right in 30º. i had to shutdown the engines and try to land in autorotation and crashed the helicopter.
two more helicopters in other company has similar problems and crashed the helicopters.(2005, 2006, 2006 and 2007).
I did not have communication maintenance.
i continue flying 412 with caution in ground.
i was sure that all verticals vibrations disappear with throttles in iddle posittion or shutdown engines. Now bell recommended 4º slopes.
thanks to all

[Oracle]

BJC,

Thanks for your comments - it has been a long frustrating wait for the final word from Bell, although they gave the same advice over three years ago in a letter.


If you read the full text of the ALERT SERVICE BULLETIN 412-07-125, the last paragraph goes on to say:

"Bell Helicopter recommends standardizing operations by operating the aircraft at 100% NR at all altitudes during all flight operations. In the past operators operated at 97% NR for a perceived ride quality improvement of the 4/rev vibrations and a slight fuel burn improvement. The 4/rev vibration levels vary with the aircraft configuration, if operators wish to reduce these vibration levels they may install FRAHM damper per BHT-SI- 47 as required."

Having contacted Bell about placing our own Decal on the dash to reflect this policy (100%NR throughout the AEO envelope) they have no objection as long as the '6000 FT HD' decal also remains displayed iaw the ASB. I suspect that the original letter they gave us in 2005 was a reflection of their knowledge of problems with excessive head rotating component wear on new EP Models being climbed to cruise at 97%NR, particularly with external floats kit on the SLED-type offshore skids. Anyway - hope you have found life easier also by moving to 100% throughout. This saves time and transient wear on the gearboxes through twitchy beep actuators and avoids all prospective transient mast torque exceedences by pilots beeping back up to 100%NR WITHOUT first reducing mast torque to a safe level (70-75% or less) on the EP.

Oh - and NO-ONE in their right mind EVER runs on a 412 in ATT Mode, unless they are Japanese and are wearing a headband!! If you ever do it once by mistake (like not checking your newby has selected an HP/SP to SAS) then you will NEVER do it ever, ever again! More clean underwear required!

As regards our good friend JUANK, - hey mano, I suspect your aircraft are in sore need of a good Autopilot overhaul and some real engineering TLC.

Firstly no-one in their right mind operates a 412 on only ONE autopilot at a time - this feeds back at least 50% more Pilot Induced Oscillations into the system, depending on how good your actuators are. You should definitely not get the random inputs you described. However, if your aircraft is old and tired and has weak FLUX UNITS on the compasses, this coupled with worn Autopilot Trim Actuator motors can give you a sudden jump in YAW in ATT Mode. Of course, with a Bell 205/212 & 412 (without a 4-axis Autopilot) you should NEVER - as handling pilot - take your feet off the yaw pedals in flight. The only thing holding this puppy straight is the yaw trim part of the Stick Trim system. If you have a large disagreement between FD HDG Hold and YAW Trim/Stick Trim, or the compass 'suddenly' kicks large degree changes due to erratic compass system inputs/corrections/problems, you will get either a very fast repetitive shunting of yaw left and right up to 90 degrees, or may actually (unless you are quick) lose effective tail rotor control momentarily - which will scare you ****less unless you have your feet on the controls. I have had this happen three times in 412's enev with my feet on the pedals -usually older SP/HP machines with very tired compass systems which have wandered abnormally and very quickly offshore on pig-iron rigs. This just shows their susceptibility to yaw instability. However, it also happened once when the HDG Hold and Compass fell out with each other, (compass jumped 170 degrees in 1 second)resulting in a very quick and nasty 5 seconds of wrestling before the AP's were disengaged.

With regard to the hover problems, the 412 just cannot cope with OGE high-hover lifting situations out of the wind. Once out of a safe 4 feet ground cushion and out of wind, you are inviting 'Big G' to smite you mightily and undoubtedly he will! Hover the 412 into wind. Best with the wind between RED 75 and Green 45 relative to the nose. For underslungs essential. For slope landings - this is essentially a RIGID-ROTOR System. You just can't fly it like a 212 and it will NOT behave like one. Approach the lateral cyclic control stops and you will run out of everything , including breath/life. Dynamic Rollover is further complicated by the crappy out-of wind/crosswind performance as published for this beast. Low hover into wind and let the buggers jump out off the skids - far safer and it will preserve your life longer.

I won't lecture you on sloping ground landings, but it's always safer to be pilot's side (starboard) UP slope and to land 45 degrees across the slope if you can.

Lastly, if you do have significant wear in your Lift Link (a favourite for horrible vertical vibes), worn swachplate assembly, PLUS Autopilot problems AND perhaps a loose seat/light collective friction, the cumulative totals of all of these vertical vibes might send you to meet your maker earlier than you had previously expected. Methinks you need some serious money spent on spares, Amigo!

Find a new company to fly for with better aircraft!

[Shawn Coyle]

Oracle:
Beg to differ with you. Flying a 412 in ATT mode is the only way you'll get any modes of the autopilot to work.
It works just fine in all modes of flight, including the hover. You just need to learn how to use it.

[outhouse]

Agree with SC. Check the Flight Manual, and I suspect your Ops manual on your company procedures.
outhouse

[Bomber ARIS]

If you read his post, I think you'll find that Oracle is referring to the use of ATT mode during a run on landing.

[Turkeyslapper]

SC

Haven't got a reference with me but I thought that prolonged hover operations in ATT mode were not recommended.

I have flown helicopters which stay in an ATT type of mode for hover ops and I certainly find it easier for some applications, winching, boat transfer etc - Does it actually say you shouldn't and why not ATT mode for the 412 in prolonged hover ops? or have I got this totally wrong?

Thanks

Turkey

[Shawn Coyle]

I think you'll find that prolonged ground operations in ATT mode are what you're thinking of. The actuators can motor the stick to try and make the helicopter maintain a constant attitude and with some drift on the gyros and sensors, can result in a lot more out of center than the hub and associated components would like.

[Oracle]

Greetings, 412 Drivers All,

Thank you muchly, Bomber, for pointing out that I WAS indeed (quite clearly) talking about the inherent dangers of RUNNING LANDINGS in ATT Mode.

Hovering in ATT Mode is actually bloody daft if you are a Bell pilot. Precision maneuvering, winching by day, landings, take-offs, underslung and ops close to the ground are all recommended by Bell as being carried out in SAS MODE. Although some pilots insist on using ATT all the time, you will end up with thumb-strain and will never be as smooth as the 'sloppy-stick' pilot using SAS. This is the way Bells were designed to be flown - 'free and easy'!

'Clunking' the 412 Force-Trim in and out in ATT Mode does not make for smooth or comfortable flight and unnecessarily wears out the Trim Release Switch & your thumb! Must be a Sea King/MIL driver, perhaps? Do you like that huge lump of hard skin on your thumb?

Today's reading is from the first book of the Bell 412 RFM (Before Take-Off):

"AFCS - Select ATT or SAS mode as desired (ATT mode shall be used during IFR Flight; SAS mode recommended for ground operation, hover and take-off)."

If you MUST (dementedly) continue to fly in ATT Mode for landing, then I would recommend (as Bell themselves do) that you do NOT do OEI run-on landings in that mode or you will likely need:

a) New skid shoes/cross-tubes/aircraft/job &
b) new underwear.

In ATT Mode, if you do not keep the Stick Trim Released during the smoothest of greasy-ace landings, you WILL find the aircraft/AFCS inputting exactly equal and opposite roll/pitching movements to the normal 'wobbles, bumps and grinds' encountered during this landing procedure. It is quite easy to thereby enter Ground Resonance, or into a joint aircraft/Pilot Induced oscillation of the very worst sort. That's why Bell specifically warns in the Bell 412 RFM (Before Landing):

"RUN ON LANDINGS MAY RESULT IN ROLL OSCILLATIONS WHILE ON THE GROUND. IF THIS OCCURS, LOWERING COLLECTIVE FULL DOWN OR TURNING SCAS OFF WILL STOP THE OSCILLATIONS."

I rest my case and go back to playing with my sloppy stick..........:}


O

[Shawn Coyle]

Oracle:
Having flown the 412 in ATT mode in hover and some quite precise landings (but not running landings - you're right), I had no particular difficulty in controlling the helicopter smoothly. The secret is, once you've got the machine roughly trimmed - do not use the force trim - merely fly against the forces and hold the stick where you want it. You will probably have to change your grip from a 'fist around the grip' to using just fingers, but I've never seen anyone who wasn't shown how to do that revert to the other way of flying.
Works like a charm. But if you insist on using the force trim switch all the time, you'll not like the results.
Those who've flown a Hughes 500 or Enstrom where you can't turn the stick forces off and who have learned to fly holding a force for short durations where it didn't make sense to retrim learned how to do that.
The real problem is that the spring gradient and forces in the stick are just a bit too high. Ditto on the A109 series - those forces are even higher, and result in folks who were brought up without a trim system turning off the trim without realizing that the trim is necessary for any of the AFCS to work properly.
But ATT mode works quite well in the hover if you know how to use it.

[Ascend Charlie]

While comparing the Flight Manual to the numerous other bits of paper claiming to be checklists, I found an interesting bit which the engineers couldn't resolve:

After starting Engine 1, the RFM says to increase N2 to 77-85% before starting Eng 2.

BUT! It says that if Eng 2 is started first, the N2 MUST be 85% before engine 1 start.

Why the difference? The engineers say that a lower RPM, around 80%, for engagement is preferable to stay away from the band of vibrations.

Nick Lappos, you might be in the ideal position to answer this one?:8

[RVDT]

Sure it's not a typo?

[helix47]

I must be bored. Try this lot.
A quick check of all 4 Bell 412 Flight Manuals showed the following.
The 85% N2 on the No 2 engine if started first appears only in FM1 (Classic 412).
The others, FM2 412SP, FM3 412HP, FM4 412EP, do NOT mention this bit. The rest of the numbers, 77% to 85%N2/NR etc are common to all 4 manuals. ALTHOUGH the wording in all 4 manuals is slightly different.?????

Personally, I have always gone for the 85% N2. One reason is that I am a convert from the 212 where this is the norm. More importantly, being at 85% N2/NR allows more time and control for a SOFT C Box engagement. Reason - Some of the AFCUs accelerate quickly to idle from the “about” 35%N1 position. This causes the N2 on the second engine to have a corresponding quick acceleration and an UNSOFT engagement if the N2/NR is at 77% on the first engine.

As for SAS vs ATT selection. Just prior to take off I select ATT. I then hold the Force Trim button in for all hovering, take off, until I am stable in the climb, then release. Any time I need to do in flight maneuvering I push the FT button. Come landing time I push the FT button, hold it in till on the ground. The only time I turn it off is when I am on the ground at an intermediate stop or shutting down. I have flown with SOME pilots who never use ATT when VFR and come the Night IFR flying when they MUST use ATT they have trouble remembering when to push the FT button and then we get the cyclic (and helicopter) jumping around. With ATT mode selected, and the FT button is pushed the ATT mode is cancelled BUT the SAS is operating happily. In flight, the moment I release the FT button I get ALL the assistance of the ATT function immediately. I don’t have worry about resetting the ATT selector. No, my thumb does NOT hurt. I cannot imagine, why, if doing any hovering or running landing, with ATT mode selected, the pilot would NOT have the FT button pushed ( and KEEP it pushed till the machine is at rest). It is so much easier to fly that way rather than ‘muscling’ the cyclic around.
Care needs to be taken when making a definitive statement about the 412s. As with the wording on the engine starting numbers, with the different AFCS systems over the 4 different 412s the reactions of the helicopters will be different. The original 412 with the roll oscillations during run on landings says turn off SCAS. The later models say turn off HeliPilots.
Yes, flying the 500, especially on very short sling ops, I would muscle the cyclic around. Mainly because the trim system cannot be cancelled and beeping the cyclic is too slow. The 212/412 have the system that allows the pilot to push the FT button, so, why not.

Re the 3 or 4 412s going into “ ground resonance” hover instability” whatever you want to call it. I believe they were all OLD 412s or 412SPs. NO HPs or EPs. Also, At least 2 of them were operating on training, with BOTH HeliPilots OFF. Any others heard along these lines?

QUESTION. With the 412 shutdown the collective can be raised easily to about half up (the neutral point for the rotor head elastomerics). At this point you CANNOT move the collective up or down. I understand that this is why a single hydraulic system failure is treated as a critical emergency. The machine cannot be flown with both hydraulics out.
What would happen, when doing the 100% NR Hydraulic interlock check, the interlock failed and you end up with BOTH hydraulics OFF.
I think with the rotor turning at 100% the aerodynamic forces would quickly bring the collective to the neutral elastomeric position and you would be in a hover with NO HYDRAULICS. This possibility was pointed out by a Bell production test pilot on loan to our company. Unofficially he suggested doing the interlock check at idle NR.
What you think???

[Matthew Parsons]

As for the controls moving to the neutral point in the event of a double hydraulics failure, we have done these failures in sim, and there is never any movement through any of the controls - they simply freeze in place.

As always, the sim may or may not model that accurately.

That neutral point of the elastomerics is without any aerodynamic forces, until someone experiences this I don't think we can be sure of what would happen in a full hydraulic failure. I do think that frozen controls is the most likely outcome, but I would expect some feedback.


If the interlock fails, just move the switch that you last moved. Your finger should still be on it.

Some of the AFCUs accelerate quickly to idle from the “about” 35%N1 position.

If the engine is accelerating too quickly, that should be adjusted.




When I see a range such as 77-85%N2/Nr I usually target the middle of the range. Assuming that there is a reason for the maximum, as there is for the minimum, I choose to avoid both extremes.

Following what the flight manual says, and not strangers on the internet, is a good idea.

Matthew.

[Gomer Pylot]

Experienced 412 pilots tend to have large right thumbs, from pressing and releasing the interrupt switch repeatedly. I sometimes just keep it pressed down, but get smoother results from pressing it, making a small movement, and releasing it. I never, ever move the cyclic without having the interrupt pressed when in ATT mode. Bell recommends against it, and it seems to confuse the helipilots. I've seen the sim crash when flown against the helipilots. I fly in ATT mode all the time, going to SAS only when on the ground, and I turn the force trim off only for the hydraulics check. Happily, I don't often have to fly a 412 these days.

[Shawn Coyle]

Gomer:
Sounds like someone understood the AFCS!
My only complaint was that the stick forces working against the force trim were too high, and that the system didn't do a really good job of maintaining attitude in the hover. Otherwise, like you, I never turned ATT mode off.

[Gomer Pylot]

The 412 AFCS doesn't really do a good job of anything. It doesn't maintain attitude for very long in cruise, and seemingly wasn't designed to do much of anything in a hover. It's better than nothing, of course, but it's a rather poor system. IME flying against it is an exercise in futility, but you have to keep a very close eye on it at all times.

[shilka]

Guys , this could be a good debate. Just being curious about how different pilots may have different views about this situation.:confused:
Bell 412 ...No. 1 Hyd. failed at 4-5 miles inbound to your airfield .
Would you like to put her down immediately at an "unknown but available" surface in the middle of a town:confused: OR would you consider it worth flying her back because you 're only 2 mins from the base?

[maeroda]

BHT 412 RFM says "land as soon as possible" in case of hydraulics failure and everybody knows this rotorcraft can't be driven with both systems OFF.:eek:

For me it means I should land as soon as I get in sight of a suitable surface and a congested environment in a town maybe it is not the right place, even if my home base is located there inside.:\

Personaly I have had a HYD 1 failure at 40kts in landing and nothing appened apart of feeling some hard pedal force as aspected.
No need to brainstom that time.:O

Maeroda

[John Eacott]

Land ASAP.

But.... what altitude are you at? If you're cruising at 5000ft, the descent to your base 4-5 miles away would take the same flight time as a descent to a spot right below you. You are going to reduce control loads as much as possible (no steep turns to spiral down to the nearest spot!), so why not make for home in a steady descent?

But.... if you're at 500ft, then a minute down to the nearest open space is the choice to make :ok:

[shilka]

We know the helicopter s not flyable with both hyd.s failed.The RFM says it all.
But what are the chances of both failing at the same time?? Aren't they independent systems , Each with its own pump.
Don't we fly the helicopter in case of a OEI?? There is no doubt that if that field was 25 miles away one would choose to select a field and land. The question here is whether it is prudent to land at an unknown place which during short final phase may prove to be not as good as it looked like from above due to wires /cables etc in a town like environment as against going to your airfield which is 5 miles away.
Opinions please..

[spinwing]

Mmmmm ....

I thought John Eacott just answered that question for you ... "Airmanship" dear boy!

2 minutes away ... continue ...... any further perhaps have a good think about it !


:ooh: