Bell 412 inflight loss of Collective Control [Archive]

SASless

21st Jul 2010, 15:45

The photos beg a few questions for sure!

I sure hope the FAA/NTSB do a stress crack failure analysis on the broken bits to determine the propagation of the failure......review maintenance records and historical data for the part, chase down the lot number of the item and do an AD requiring an immediate one time inspection of all related parts. That being said....I would hope Engineers world wide would be doing it on their own as a precautionary measure.

Was there any indication of a problem seen during the maintenance action, daily inspection, or preflight?

Any history of incidents or accidents involving that part? Was there a metallurgical failure, manufacting fault, casting problem?

Big chunks of metal just do not break like that without there being a "real" cause that can be found if properly investigated?

Hand salute to the pilot for getting the aircraft down safely!

It would be nice to hear his account of the flight and the technique he used to accomplish the landing.....as it would be a very good learning tool for the rest of us.

sox6

21st Jul 2010, 17:37

I would like to here more about the 412 photos. When and where did that happen? Are they recent?

oldbeefer

21st Jul 2010, 18:22

Whew - I'm glad I've just retired

Graviman

22nd Jul 2010, 11:43

From the beach wash marks it looks like the crack initiated near that central web on both sides. Unless part is resonating, i would expect highest stresses to have been near section top and bottom. :confused:

Bespoke

28th Jul 2010, 04:08

Heard from Qatar,

Bell 412 suffering loss of control on return from offshore with passengers.:eek:

Who knows more?

Bespoke

28th Jul 2010, 10:55

So its true.......... I thought this would be an aviation urban myth.Cannot find the thread though................. I did find reference to a 206 L4. How can one fly a rotory aircraft without collective? Is it something about Bell Aircraft?

Encyclo

28th Jul 2010, 22:07

"How can one fly a rotory aircraft without collective? Is it something about Bell Aircraft?"

I guess the answer could be yes; the safety design of the 412 (having the throttles on the collective) probably made the difference here.

You might have heard that the same (loss of collective control) happened to a 206L-4 a few days later in the GOM; in that case a control bolt fell out. Same outcome as the 412, all aboard unharmed. :ok:

stickysunrise

29th Jul 2010, 03:48

the safety design of the 412 (having the throttles on the collective) probably made the difference here.

if the collective isn't working :uhoh: i don't believe it would make any difference where the throttles are!

EBCAU

29th Jul 2010, 05:48

BlenderPilot

29th Jul 2010, 06:18

It also happened in Mexico about 5 years ago, landed safely, total loss of collective control. XA-TNE belonging to ASESA, and the helicopter was part of a recently purchased set of 10 412's

ASN Aircraft accident 13-APR-2006 Bell 412EP XA-TNE (http://aviation-safety.net/wikibase/wiki.php?id=66598)

fly911

29th Jul 2010, 10:24

if the collective isn't working http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/worry.gif i don't believe it would make any difference where the throttles are!
It sure would to me. But that might just be me. It's the way I learned and the way I practiced manipulating the throttles. Reaching up to the roof or down to the floor might work too, but for me at least, not as well. Point taken though.

Could you give us another option that would allow the safe landing of a "collectiveless helicopter" that would not involve the use of throttles?
Reduce altitude by increasing airspeed, use power pedal and uncoordinated flight (slip) to aid in slowing airspeed before touchdown, find a long, wide hard surface runway with crash equipment, anticipate runway friction to slow you down after initial contact, anticipate ground effect and the possibility of becoming airborne again, be ready to cut power by fuel or throttle(s). Burning off fuel before landing will make you less likely to burn, but should be weighed against lighter and consequently faster landing speed. Use a crosswind / headwind combination to allow you to use more power pedal to rob more main rotor lift. If at altitude, consider that OGE hover requires more power than forward flight. An OGE hover may be a way to lose altitude, but may require you to shuffel in and out of settling with power on the way down. Settling will reduce your altitude but could get out of control if allowed to progress too far. Remember, you can't reduce collective to aid in recovery and must rely on airspeed only to come out of settling. All of the above, by the way, is if your power settings are too high, such as in cruise flight when collective is lost.
If on the other hand you lose collective in a reduced power scenario such as in a decent but still have sufficient power to maintain some forward flight and maintain altitude, your landing might be considerably less challenging.

Bespoke

29th Jul 2010, 13:24

Sandyhelmet, Thats very Interesting that this is an event that is trained for, am I correct that the pics on the 206 thread are indeed 206 pics and you train for component failure?

Fly911, your explanation seems very involved compared to sandyelmets, have you actually experienced this failure?

Blenderpilot, I checked your link and it doesnt actually mention the collective from what I see.

Thud_and_Blunder

29th Jul 2010, 19:47

Must be a Bell thing - ISTR a ROPAW 214ST having a similar experience with an equally safe outcome not long after it entered service in the mid-80s.

SASless

30th Jul 2010, 12:13

Duiring the Vietnam War....a US Army UH-1H aircraft crew found themselves confronted with the absolute worse case scenario of "stuck collective"....that being the collective stuck at the maximum up position.

The aircraft was in the process of taking off from a "Hot" LZ....took numerous bullet hits from hostile forces....and upon reaching a safe altitude...discovered they could not lower the collective.

They were able to fly the machine to an airfield and landed it by means of reducing Rotor RPM. The old Huey with its amazing strength coped with the situation quite well.

As to location of throttles....it is of no matter as the left hand is going to be free to manipulate the throttles and not be required to move the collective. I have done the maneuver in Bell type helicopters and Sikorsky S-76's.

A thing to remember....as you decrease Rotor RPM you will find the Tail Rotor begins to lose thrust as well making the Pedals less effective.

It is truely a balancing act in multiple parameters.

Bespoke

30th Jul 2010, 13:57

All has become much clearer now that the thread has become whole I appreciate that as a novice my comprehension of the problem and the means to solve it is unclear. An instructor has mentioned that the rotors would be free flying and have the ability to change angle depending on the loads applied and would make the control of the machine vague with variations of rotor speed and flight speed.

stickysunrise

30th Jul 2010, 17:54

is pilot a ppruner? would appreciate his/her insight

It would be nice to hear his account of the flight and the technique he used to accomplish the landing.....as it would be a very good learning tool for the rest of us.

hear hear SASless

:ouch:

fly911

30th Jul 2010, 22:36

Bespoke: Fly911, your explanation seems very involved compared to sandyelmets, have you actually experienced this failure?

Well, Sandyelmets explained the process using throttles but no collectine.
I was answering the following question by EBCAU: Could you give us another option that would allow the safe landing of a "collectiveless helicopter" that would not involve the use of throttles?
No, I have never run into this situation while flying thankfully.

Something witty

31st Jul 2010, 16:14

"if the collective isn't working http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/worry.gif i don't believe it would make any difference where the throttles are!"

Could you give us another option that would allow the safe landing of a "collectiveless helicopter" that would not involve the use of throttles?

For any helo where there are hydraulic jacks about the MRGB then, assuming it is possible, selecting that hydraulic circuit off will cause the sloppy links to collapse down under flight loads and thus induce a collective reduction in pitch (with possible attendant slight attitude change in pitch and roll). DONT go off and do this because I said it was a good idea before checking the wisdom on your particular type!!

However, it is a recognised (and once used, due siezed friction) technique on Sea Kings (S-61) where you knock out the Primaries to initaiate a descent in the high power case. Playing with Nr, speed, balance etc are also other methods, a combination of which might be needed.

Of course, the above assumes that the failure is below those jacks!

rupigill

1st Aug 2010, 14:06

A job well done in a most professional manner GOD bless and happy landings

Could somebody or the pilot give the full detals of the incident ,symptoms like vibrations or any other useful information which might help the community of offshore pilots with very limited choice available.

Squat switch

1st Aug 2010, 15:33

Hats off to the crew not an easy problem to deal with.

I was given a stuck/frozen collective many years ago and went through the various options of reducing power with throttle, reducing Nr, playing with hydraulics.

Eventually I got to playing with the speed and working along the power curve, to maintain any sort of cotrol over the ROD you need to be on the lower speed side and then it works a treat, but to get there you could end up climbing a long way!!

It is possible to get it all the way down to a running landing.

One to try on your next Training session or base check??

IntheTin

1st Aug 2010, 16:38

It is possible to get it all the way down to a running landing.

That's how he got it down. Three attempts........:ok:

MightyGem

6th Aug 2010, 13:28

Eventually I got to playing with the speed and working along the power curve, to maintain any sort of cotrol over the ROD you need to be on the lower speed side and then it works a treat, but to get there you could end up climbing a long way!!

That's the way that I would have tried, but as you say you can get very high. Not so good with low cloud.

Then I was shown how to do it by doing very steep, tight 360deg turns, gradually bringing the speed back to get on the backside of the power curve. However, you do get quite close to the ground at some extreme bank angles.

Bespoke

6th Aug 2010, 17:40

Considering that in this instance the collective was disconnected/broken and ineffective and the rotor disc was, as was explained to me, free to do its own thing changing pitch angle without control, harsh inputs and manouevres could give unexpected reaction.
Wasnt this also a passenger flight, surely such an entertaining display dismay those passengers or create at minimum some anxiety.

outhouse

7th Aug 2010, 06:38

A very nasty situation handled in a very professional and competent way, well done bringing all your passengers and crew home safely.:ok:

jetA1pilot

7th Aug 2010, 07:35

Outhouse:

* Any word from Bell yet on the reponse to the collective lever failure?

* Is the lever & associated parts in the Cp control link chain on condition or tbo'd?

FYI our 430 fleet was also grounded yesterday following the failure of the collective servo link in a GOM B430 a couple of days ago. Looking at the 430 pictures & the failure of that control rod, it looks like pretty similar metal fatigue/stress fracture type failure to this 412 Cp lever i.e. clean shear....quite worrying, no way to pick that up with normal visual pre-flight inspection. Fortunately the 430 was on the deck and was about to start #2 when the collective came up under his armpit and he just shut down. I'm sure a thread will start on that one soon, if it hasn't already, and those pics will be put up. I can scan them in if anyone is interested.

I hope some alarm bells are warming up somewhere wrt current ideas on high stress parts & metal fatigue & part life spans on the high stress items, in the harsh offshore environment. Maybe time for Bell to reduce some of those part lifetimes or institute better fatigue testing than "on visual condition"?

Re this incident; I was lucky enough to fly with this captain a few years back; one of the most professional & competent guys I've had the pleasure of flying with & learning from. Well done mate, great outcome.

outhouse

7th Aug 2010, 09:36

Jet, I don't think Bell have made any comment as yet, having viewed the snaps available to us all, has anyone any info on the collective failure re 214 on the NSea many years ago? I seem to remember that two incidences occurred, my memory seems to have dulled over the years. Failure of this type on what seems a substantial casting with no pre indications needs attention I feel. I suspect that it's OC with the usual NDT inspections on scheduled intervals? Engineers viewing info please.
As indicated on previous comment, a great job done by ---------- .
:ok:

BlenderPilot

7th Aug 2010, 14:56

For those who understand Spanish . . . . .

This is the audio where a Bell 412 pilot calls ATC to declare an emergency due to the fact that he has lost collective control, he describes how the collective control does nothing, he gives his position, states that he's going to try to put it down in the water and then asks the people on the frequency to tell his family that he loves them in case he doesn't make it.

http://homepage.mac.com/helipilot/PPRuNe/TorredeControl.wav

SuperF

9th Aug 2010, 04:04

A couple of part answers to a couple of questions:
re life on Collective levers, 204, 205 and 212 collective levers are lifed, varying retirements depending upon p/n and a/c installed upon. sorry don't have 412 lives, however part looks very similar to 212 part so "should" be lifed.

As to passenger comfort getting them home. in an emergency, if you get them back alive then forget how they felt on the way in. I don't know how many pax would be too happy if you had to do an auto with them onboard, but as long as they walked away they would thank you, maybe after a couple of drinks and changing their shorts...

And congrats to the pilot on this one.

stacey_s

9th Aug 2010, 08:49

Outhouse & SuperF

The part in question is lifed at 10,000hrs with an NDT inspection each 2500hrs, the particular part that failed had accrured 8037hrs total time in service and had last been NDT'd 617hrs prior to failure by Abu Dhabi Aviation with no fault found.

the Collective lever was dismantled along with the M/R/H, Hub & Sleeve & Swashplate and support under the supervision of the Bell rep the following morning with the local Authority in attendance, with no fault found, the parts were then sent immediately to Bells Field Investigation Laboratory for analysis.

All maintenance records and activities were reviewed by the same personnel and all was correct.

Gulf's 412 fleet were inspected visually prior to their next flights with no other anomalies found.

Spinwing, mmmmmm! sorry for the delay in replying I'm on holiday and have been out of e-mail contact for a while

Best Rgards

S

outhouse

9th Aug 2010, 12:28

Many thanks Stacy, seems all the Ts crossed and Is dotted. One of those occurrences that needs the boffins look at the part and do magical things and maybe come up with an answer.
I remember the AIB at Farnborough many years ago looked at a S 61 MGB combiner gear and it turned out the failure was caused by the manufacturing process during the smelting process in 1965 ish. Nitrogen something ( can't spell it). Also tracked three other gears from the same batch, one on a shelf at Sk one in service and the other In one of our MGBS. clever sods.
Looking forward to further news S.
:ok:

spinwing

9th Aug 2010, 18:41

Mmmm ...

Perhaps the word was embrittlement?

Stacey ... nice to have you back mate! :ok:

technoprat

10th Aug 2010, 02:26

The collective lever on 212 & 412 are quite different.
412 is one piece (casting I think).
212 is 2 pieces + a bolt & spacer between them.
Also they pivot differently on the swashplate support.

I would guess 204 & 205 are similar to the 212 type.

nonac

10th Aug 2010, 10:09

Mast Seal looks good in the pickies:hmm:

vaqueroaero

10th Aug 2010, 20:07

Blenderpilot - do you have any more specifics on the the clip you posted? Maybe a link to an accident report?

Thanks.

AdamFrisch

11th Aug 2010, 02:44

I seem to remember the H300C in the north of Sweden that lost its collective pitch horn and where the blades defaulted to max alfa as per the design. I assumed this would be a certification requirement for all helicopters - at least then you have a fighting chance. But is that not the case? Can they default willy nilly to any alfa?

BlenderPilot

12th Aug 2010, 01:49

Vaquero . . .

It was one of ASESA's Bell 412's, took place around 2005 to one of I think it was 12 new Bell 412's that ASESA purchased back then, I could find out the exact serial number if you would like?

vaqueroaero

12th Aug 2010, 17:18

Blender - That would be great if you could.

Gracias!

SuperF

13th Aug 2010, 06:36

technoprat, 205 runs 204 levers. virtually the same as 212 and interchangable, up generally with better lives. i doubt a 212 can run the 204 levers. 212 levers are obviously stronger, also they have a larger pin, or larger bolt through the pin as levers and pins can't be interchanged. looking at pics i can now see the diffs with the 412 levers.

BlenderPilot

14th Aug 2010, 09:53

Vaquero I think it's this one . . .

For sale: Bell Bell 412 (7195000 USD), USA, New Mexico, Clovis - JamesList (http://www.jameslist.com/advert/1798/for-sale-bell-bell-412)

it's the one SN listed on the accident report, plus as you can see this one that's for sale had a complete overhaul, rewire, and interiors, the one Bell 412 flipped over in the water during recovery from the incident.

cobrajock

5th Mar 2011, 00:21

In the case of the 412 , that lost collective control because of collective lever severance , I have seen this many times in the past , and it has been attributed mostly to improper rigging of the collective flight control , which allows the collective levers to bottom out on top of the swash plate mounting bolts when the collective is in the full down position . This clearance is critical especially during the auto-rotative rpm check during the test flight , and after rigging has been accomplished . if this clearance is not there , and the levers bottom out on the mounting bolts , coupled with the 1500 psi hydraulic boost , the collective levers will be stressed to the point of fracture , and eventual complete severance , and failure .