Helicopter down outside Leicester City Football Club
Avoid imitations
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That is why a tail rotor control failure can be far worse than a tail rotor drive failure.
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That is why a tail rotor control failure can be far worse than a tail rotor drive failure.
None of you guys have ever tried this??? With training aircraft like the B47 we'd do lots of simulated tail-rotor failures from 500' by jamming in full right pedal, pointing out the pedal position was not going to move again until on the ground, and then slowing down until keel effect was lost and it snapped around. Let it go around a time or two (any more and the student would lose horizontal plane reference and bad things would happen) then roll throttle off to stop rotation, bottom collective to hang onto rpm, and pitch for some airspeed. From 500' you'd get about 10 mph per 100, so you'd have enough to flare and skid it on full-auto. It would veer a little to the right but not bad, at which point you'd point out to the student that the pedals hadn't moved. Most pedal goes to counter right yaw, in an auto it's almost full right. 212's weren't much different, but all this stuff used collective throttles.
Who knows whether a sim is going to replicate reality or not. You have pilots chatting with programmers on what they think will happen, nobody has hard data. And after all, the only failure we're concerned about now is an engine failure (but only if you have two), anything else is as JimL describes beyond the probability where it is worthy of much attention. On the S76 we tried jamming right pedal in a hover and having the copilot chopping throttles but it didn't work all that well with experienced trainers and there was low probability of success with a plebeian crew, hence the new world order of just lowering collective. We never did zero airspeed simulated by right pedal tail rotor failures at altitude either, too hard. So we always trained with enough speed for keel effect where the lowering of collective had some merit an gave time to bring the throttles back.
Discussions on takeoff profiles again, comparing the statistical exposure time. Jungle ops we started out verticalling some distance above the canopy before transitioning to forward flight, but gave up on that due to what felt like a lifetime of exposure for that extra hundred feet and the reality that you weren't going to find your way back down that keyhole anyway. Judgement call based on wide consideration of environmental factors, something we can't do anymore - each specific case has to be in the RFM.
In this one, I saw nothing wrong with Eric's departure profile. In the absence of any RFM or regulatory Class 1 guidance I would have flown the same. Raising the gear, I don't know if it had any significance or not. The S76 has a priority valve to deal with extra demand on hydraulics during gear retraction. The 139 deals with it by bolting on an extra hydraulic pump.
Who knows whether a sim is going to replicate reality or not. You have pilots chatting with programmers on what they think will happen, nobody has hard data. And after all, the only failure we're concerned about now is an engine failure (but only if you have two), anything else is as JimL describes beyond the probability where it is worthy of much attention. On the S76 we tried jamming right pedal in a hover and having the copilot chopping throttles but it didn't work all that well with experienced trainers and there was low probability of success with a plebeian crew, hence the new world order of just lowering collective. We never did zero airspeed simulated by right pedal tail rotor failures at altitude either, too hard. So we always trained with enough speed for keel effect where the lowering of collective had some merit an gave time to bring the throttles back.
Discussions on takeoff profiles again, comparing the statistical exposure time. Jungle ops we started out verticalling some distance above the canopy before transitioning to forward flight, but gave up on that due to what felt like a lifetime of exposure for that extra hundred feet and the reality that you weren't going to find your way back down that keyhole anyway. Judgement call based on wide consideration of environmental factors, something we can't do anymore - each specific case has to be in the RFM.
In this one, I saw nothing wrong with Eric's departure profile. In the absence of any RFM or regulatory Class 1 guidance I would have flown the same. Raising the gear, I don't know if it had any significance or not. The S76 has a priority valve to deal with extra demand on hydraulics during gear retraction. The 139 deals with it by bolting on an extra hydraulic pump.
so you’re worried about exposure to TR problems in a Cat A profile but now you’re advocating sticking explosive bolts in the assembly? You couldn’t write this stuff!!!!
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Yes, if full un commanded pedal is worse than loss of drive, perhaps a "drive disconnect" switch could be an option on the way down.
Another EASA AD issued with expansion -
Emergency Airworthiness Directive
AD No.: 2018-0261-E
Issued: 30 November 2018
Emergency Airworthiness Directive
AD No.: 2018-0261-E
Issued: 30 November 2018
Required as indicated, unless accomplished previously:
Repetitive inspection:
(1) Within 10 flight hours (FH) after the effective date of this AD, and, thereafter, at intervals not exceeding 10 hours, inspect the slippage marking of the castellated nut installed on the back-end of the TR servo actuator in accordance with the instructions of Part I, and inspect the roughness and breakaway force of the TR duplex bearing in accordance with the instructions of Part II, of the applicable ASB at intervals not exceeding 30 hours.
Repetitive inspection:
(1) Within 10 flight hours (FH) after the effective date of this AD, and, thereafter, at intervals not exceeding 10 hours, inspect the slippage marking of the castellated nut installed on the back-end of the TR servo actuator in accordance with the instructions of Part I, and inspect the roughness and breakaway force of the TR duplex bearing in accordance with the instructions of Part II, of the applicable ASB at intervals not exceeding 30 hours.
Part Removal and Send to Leonardo:
(5) From the effective date of this AD, within 2 days after removal of a TR duplex bearing, if part of the corrective actions as required by paragraph (2) or (3) of this AD, as applicable, send the TR duplex bearing and the collecting containers of the grease to Leonardo for in-shop inspection. This can be done by using the instructions of the applicable ASB.
(5) From the effective date of this AD, within 2 days after removal of a TR duplex bearing, if part of the corrective actions as required by paragraph (2) or (3) of this AD, as applicable, send the TR duplex bearing and the collecting containers of the grease to Leonardo for in-shop inspection. This can be done by using the instructions of the applicable ASB.
Yes, if full un commanded pedal is worse than loss of drive, perhaps a "drive disconnect" switch could be an option on the way down.
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Originally Posted by [email protected]
so you want to add to the complexity of the TR system, adding weight and more potential points of failure, into something that already has a low probability of failure in any form, just to guard against an even more remote type of failure.............c'mon chopjock- get real!
I love you choppy - you should have your own show. The last dozen posts have all been about real professionals tying themselves up in knots trying to win you over. 
For someone who actually poles one of these contraptions, your technical and practical insight and knowledge of rotary wing operations is excrutiatingly lacking.
You've been like this for years on Pprune and I for one love watching proper pilots froth at the mouth trying to convince you .
Great show choppy - love it.
For someone who actually poles one of these contraptions, your technical and practical insight and knowledge of rotary wing operations is excrutiatingly lacking.
You've been like this for years on Pprune and I for one love watching proper pilots froth at the mouth trying to convince you .
Great show choppy - love it.
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crab
I think they are all doing it wrong. It would be much simpler if there was an electric motor out on the boom and simply switch it off when not needed...
so you want to add to the complexity of the TR system
Avoid imitations
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Chopjock, the RAF SAR Wessex which crashed into the lake in Wales with cadet passengers on board had a tail rotor dis-connectable coupling failure.
First of all you complained that a tail rotor drive system is too unreliable but now you want to make it more complicated and therefore by definition less reliable...what sort of logic is that?
First of all you complained that a tail rotor drive system is too unreliable but now you want to make it more complicated and therefore by definition less reliable...what sort of logic is that?
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ADNo.: 2018-0261E
“For the reasons described above, this AD requires repetitive inspections of the TR servo actuator’s back-end castellated nut slippage marking, and of the roughness and breakaway force of the TR duplex bearing and, depending on findings, accomplishment of applicable corrective action(s). This AD is still considered to be an interim action and further AD action may follow.”
part 1 every 10 flight hrs
part 2 every 30 flight hrs
“For the reasons described above, this AD requires repetitive inspections of the TR servo actuator’s back-end castellated nut slippage marking, and of the roughness and breakaway force of the TR duplex bearing and, depending on findings, accomplishment of applicable corrective action(s). This AD is still considered to be an interim action and further AD action may follow.”
part 1 every 10 flight hrs
part 2 every 30 flight hrs
send the TR duplex bearing and the collecting containers of the grease to Leonardo for in-shop inspection
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unlike oil, where you can run a chip plug and filters to collect debris, grease holds onto those particles.
if a bearing has started to fail, those chips/flakes will continue to beat around the bearing. collecting the grease for inspection will help determine whats breaking down. whether its the bearing cage, the rollers themselves or the races. It may even determine that it's a foreign material that shouldnt be in there to begin with.
if a bearing has started to fail, those chips/flakes will continue to beat around the bearing. collecting the grease for inspection will help determine whats breaking down. whether its the bearing cage, the rollers themselves or the races. It may even determine that it's a foreign material that shouldnt be in there to begin with.
Or even if there was no grease or the wrong grease....or other kinds of contamination.
The scientific name is 'tribology'. It studies lubricants, and effectiveness. If there is a failure of a lubricant, the examination of the fluid(grease) and contaminants may point to a specific failure mode.