Bell 412 inflight loss of Collective Control
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"if the collective isn't working 
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!
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!
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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.
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.
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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??
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??
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!!
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.
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Oh Yeah
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.
Wasnt this also a passenger flight, surely such an entertaining display dismay those passengers or create at minimum some anxiety.
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Bell response?
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.
* 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.
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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 ---------- .
As indicated on previous comment, a great job done by ---------- .
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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/PP...edeControl.wav
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/PP...edeControl.wav
Last edited by BlenderPilot; 9th Aug 2010 at 14:22.
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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.
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.
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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
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
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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.
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.
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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.
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.
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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?
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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?
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?