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???

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.

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.

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.

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.

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.

Bell 412 : Hyd Failure
 

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?

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

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:

Bell 412
 

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..

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:

As long as the landing isn't more dangerous than continued flight, then landing where you are is acceptable and probably the right choice. If you are going to continue, consider what you're flying over, keep loads down, and monitor the good system. If anything shows on the second system, then you have absolutely no choice, and you may regret leaving that field behind you.

412EP MR track and Balance
 

Ive been having several problems with my helo. It just wont track.....it has a horrible lateral vibration in the 60kts letdown and a bit of vert in the 120kts str8 and level flt regime. Ground resonance seems to occur everywhere it has landed. The techs have done almost everything from changing the elastomeric bearings, Xmsn mounts, MR blades, tracking the TR blades. The aircraft also has an overall high frequency vibration within the airframe. Advice anyone??

Mmmm ......

With the M/R blades ..... were/are they a matched set or a mixed bag?

Was the Lift Link checked at the same time as the main transmission mounts?

How many hours "time in service" has the machine?

:confused:

At one point in my brief career at Bell, I was assigned to flying the 'flying whirl stand' Bell 412.
We had a 'rogue' blade that wouldn't track, and in desparation, I had the mechanic watch while I changed airspeed at the same power setting. The blade went way out of track, and we ended up using balance weights against the tab at the outer tab. That worked.
Not sure if that will help your situation, but every little bit helps.

Food for Thought:
 

Shilka,

Just for info, we have had an occasion with a B412 which had a Hyd Sys fail and the aircraft was landed ASAP (thankfully) on a beach about 7nm from the field. After shutdown it was noted that lots of Hyd oil under the aircraft. Closer inspection revealed that both Hyd lines had been chaffing together where they run close together up the hell hole and are supposed to be kept separated by Adel Clamps, until one finally perforated with the inevitable result.

The second line was also chaffed almost through the wall thickness. How long would the second system have lasted....how long is a piece of string? But with my luck, I'm sure Murphy would step in and stuff my day......

So I'll treat a system which is grandfather on 1950's technology, which has no decent, well designed Leak/Detection/Isolation system with huge suspicion . Especially when it relies on a serviceable Hyd System to maintain controlled flight and only gives you 2 x systems each which run close beside each other.......too much room for potential problems for my liking.

I think the Huehy system (1 x Hyd sys) was inherently safer, at least you could fly it when it did fail....

Food for Thought......

Shak'n

Yes, we do fly the helicopter in case of a OEI; but if the remaining one fails we still have a good chance of walking away from an autorotation, unlike in a 412 that becomes un-flyable if the No2 hydraulics fail as well.
The post above by shak'n seems to prove the point: what's the reason the initial failure happened in the first place? Good airmanship as suggested by John Eacott is key.

Bell 412 Maintenance Programme
 

I wonder the maintenance programme of Military 412 helicopters.

Is there any Bell 412 Military operator who is able to explain maintenance programme of military 412 helicopters?

Is there mandatory preflight inspection performed by technicians apart from flight crew performing before each flight?

What is daily inspection consept and validaty?

Is any airframe overhaul (or other type of inspections) scheduled beyond 3000hrs/5year inspections?

Does any military format MM exist for 412 helicopters?

What about maintenance test flight requirements? Do -6CF and -6CL manuals exist for 412 helicopters?

Any help/information will be higly appriciated...:D

412EP MR track and balance
 

A tech rep from Bell Helicopter came and looked at the aircraft. After several checks and isolating the Main drive shaft Vibration. It was realized that the rotor brake disc was warped. That has gotten rid of the high frequency vibration throughout the airframe. The aircraft has subsequently smoothed out a bit. I only experience a slight lateral vibration in the 60 kts letdown.

Deviator

I have seen the reported rotor problems when certain RT&B equipment is being used. What were you using Chadwick, RADS, Bell's HVM?

In most cases it is just a lead-lag damper.

Also unless you have 20 year old blades all are interchangable and not as reported in pairs unless they get cocked up during refurb.:ok:

The Sultan

Special Inspections for Bell 412 in Military Ops
 

The answer: NO

All Bell 412s, what ever the paint scheme, have the same inspection requirements. Some customers have elected to slightly modify their schedule because of past incidents/events. And yes, the highest interval is the 5 year/3000 Hr inspection.

Bell 412 unusual engine problem
 

Hello there. Just picking up our Bell 412 from contractor following a 600 hr inspection. The #1 engine was taken out because it was reported that engine stalling / popping was occurring. Some of the compressor blades were changed out and the engine got a new combustion liner.

We started doing our post 600 hr ground runs and noticed that the #1 engine was still popping since repair! It seemed to pop like a machine gun going off between 61% to 70% Ng (N1) on a normal wind up of the #1 engine throttle. If the pilot wound up the throttle quickly like if we were doing an accel check, it wouldn't pop. Also if he brought up the throttle slowly, it wouldn't happen. It would only happen during a "normal" wind up of the throttle and it didn't matter if the governor was in auto or manual.

So far we have swapped fuel clusters from our #2 side since it was proven serviceable during ground runs, changed bleed valves, fuel surge accumulator, fuel dump valve, checked P3 filter, checked for air leaks, changed the setting on the accel dome 3 clicks in either direction and still has the symptoms!

So any input on the cause of this problem would be very helpful because i think we've changed about everything that we can before we change the engine!

Thanks.

Check the inlet system?

How olds (hrs) the Engine and was it popping before the inspection? if not what was done to the engine during the check? has it had an HSI recently where the CT vane ring was changed?

Well, oddly enough, before we changed fuel clusters it wouldn't pop with the intake cowling off!! I guess P&W do say that these birds do have a problem with the intake system with the 3D engines.

Anyways, got word back from the P&W guys and our Bell Rep. They have concluded that our "surge margin" in the engine was too close and it was running too rich. This was evident because we pulled one fuel nozzle and it was covered in black powdery carbon!

So the decision was to pull the engine and replace it. I'm just glad that i'm not forking the bill for this mess. Thanks for the input.

Pleasure dear Chap, give my regards to your Pratt rep (Rob Pobjoy?)
Stacey

Errrmmm... The Canadian Defence Forces? (CH-148 Griffon).

CH 148 is the Cyclone/S92

CH 146 is the Griffon/412

and.... Surete du Quebec (Quebec Provincial Police), NRC (National Research Council, fly by wire, flying simulator), Allied Wings (commercial, de-militarized CH-146 flying as trainers)...

Bell 412 Maintenance /year 700 fh.
 

Hi there,
Is there any info out there regarding how much maintenance a Bell 412 need´s on a yearly basics for doing around 700 f/h .
we are talking about a Full SAR 4 Axis EP Heli.

My figures are so far 70 Day´s(ground time) schedule maintenance , and normally around 14-35 days (groundtime)unschedule maintanance.

Pls advise if you have any Idea where such info is avali!

Tump´s rule if you need one rolling have 3 on the line right ;)

412 Helicopter Maintenance Tasks
 

We're government 412 helicopter operator in Turkey. We perform all scheduled maintenance requirements iaw tasks in MM chapter 05. Tasks in MM is not well defined and are mostly full of general wordings. ın order to optimize maintenance performances we're looking for job cards for scheduled maintenance requişrements of 412 helicopters?

Has somebody heard, used or seen well detailed maintenance tasks (job cards) to apply 300/600 Hrs and lower and higer level scheduled maintenance requirements of Bell 412 helicopters?

Where ? How can I reach / buy / see ?

The aircraft is a B412SP with PT6T-3B engines. When making a power change engine 1 hunts high and low (torque, ITT and N1) about four times before settling down; engine 2 settles down after only one cycle.

Is there a prescribed minimum (either in seconds or number of cycles) before which the engine should be in a stable state? If so, where can I find it? I’ve looked through both the B412 and PT6T Maintenance Manuals and failed to find any hard data.

Thanks for any pointers.

Mmmmm ...

Not quite sure what you mean by 'cycle' ...BUT .... engines should be stable (within reason) during pwr changes at all times ....

Need to know a bit about the TSN/TSOH of the engines and AFCU/Gov components to really try to diagnose this .... BUT... it may be that the fault is actually with the No.2 engine AFCU/Gov as it may be the 'slow' (sticky) operator which is making the No1 do all the work .... need to see what is happening with the Nr while all this is going on ....

One method to determine which engine is operating correctly is to set (say) Eng No1 into MANUAL Gov and set it @20% Tq lower than No2 and see if with (gentle) pwr changes the other engine responds normally then vice versa etc.

If you are operating in a very dusty envoironment get your engineers to look at the TCU bleeds for blockages etc ...

Cheers ... Good luck :}

Rainbrave.
Check your PM's.

Frank
Pleased you answered before I did!!
Stace

Thanks spinwing,

My question was prompted by the following observations: with the aircraft on the ground, well ballasted, one throttle at idle and the other fully open, rapidly raise the collective to 35-40% engine torque, and observe how long it takes for the parameters (NR, torque, N1, ITT) to settle down at the new setting. Initially the NR will droop somewhat, then surge higher than before, drop again, etc., before settling down. The #1 engine took about 4 times as long (both in seconds and in number of high-low surges) to stabilize as the #2 engine; however, it does eventually stabilize.

What I was hoping for is a hard number (either seconds or number of surges or “cycles”) before which the engine must stabilize following a power change. At the moment we’re not sure if this is a fault that needs to be rectified, or just not as good as the other engine but acceptable.

I have flown a few B412s whose engines just wouldn’t stop hunting, from +/- 3% N1 at flat pitch to +/- 1% in cruise even in dead calm air, and they all required an AFCU change on one engine to rectify that problem.

Mmmm ...

Buitenzorg.....


Well there is your answer .... No.1 AFCU or Gov. FKD! (this is a technical term for 'not working correctly') .... Engineering dept. will have M&O requirements to hand?

In the organisation (?) I work for the requirement for us to carry out slinging task with loads that put the a/c at MTOWA mean we have no margin for sloppy AFCU/Governor performance .... so they are kept very well looked after.


StacyS of this forum will have the detail you require at his finger tips ..... perhaps :}

Cheers ;)

yes , lots of fingertips, but on holiday in Abu Dhabi till 2nd Jan?!!!!
S

Mmmm ....


ROFL ..... AND I'm on holiday AWAY from Abu Dhabi .... Have fun! :E


:D

If you've warmed up the engines, then icing in the air lines shouldn't be a problem.
We had an iced up air line after a blizzard many years ago. -The engine went from idle to 117% N2 in less than three seconds when the throttle was cracked from idle. Ripped the tail rotor drive shaft into several sections.

when will P&W make a digital fuel control for the 212 / 412? The world waits!

Aren't the latest "Super EP" equipped with a EEC similar to the 119s and 139s?
I believe few of those were built for the Saudi Kingdom and came with a full glass cockpit.