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Helicopter down outside Leicester City Football Club

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Helicopter down outside Leicester City Football Club

Old 30th Nov 2018, 17:16
  #881 (permalink)  

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Originally Posted by Non-PC Plod
Agree - it would be interesting to see if that was even worse than having zero rotor thrust -Just wondering whether you can get negative pitch on the tail rotor at extreme pedal inputs?
Yes, of course you can get negative pitch! Any helicopter has to be able to turn in both directions, both at high power and in autorotation. As I stated a long way back in this thread, the tail rotor of a Puma helicopter, as one example, can go between +35 degrees to -17 degrees of pitch.

That is why a tail rotor control failure can be far worse than a tail rotor drive failure.
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Old 30th Nov 2018, 17:29
  #882 (permalink)  
 
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That is why a tail rotor control failure can be far worse than a tail rotor drive failure.
Perhaps there should be an explosive bolt or a quick release dog clutch on the tail drive shaft then...
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Old 30th Nov 2018, 17:30
  #883 (permalink)  
 
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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.
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Old 30th Nov 2018, 18:06
  #884 (permalink)  
 
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Originally Posted by chopjock
Perhaps there should be an explosive bolt or a quick release dog clutch on the tail drive shaft then...
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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Old 30th Nov 2018, 18:28
  #885 (permalink)  
 
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Originally Posted by 212man

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!!!!
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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Old 30th Nov 2018, 19:17
  #886 (permalink)  
 
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Malabo
Just to eliminate your query on landing gear vs hydraulics. The landing gear on an AW169 is moved by electric motored actuators. No hydraulics involved at all.
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Old 30th Nov 2018, 20:18
  #887 (permalink)  
 
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Another EASA AD issued with expansion -



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.
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.
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Old 30th Nov 2018, 20:59
  #888 (permalink)  
 
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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.
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!
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Old 30th Nov 2018, 21:19
  #889 (permalink)  
 
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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!
If you have an un commanded stuck full pedal and you don't have easy throttle control or perhaps a bird strike on a tail blade causing severe vibration with tail rotor imminently about to fall off etc and high up in the cruise, how do you maximise your chances to land safely? Presumably this is when you do not want a turning tail rotor? Just for discussion ...
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Old 30th Nov 2018, 22:05
  #890 (permalink)  
 
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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.
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Old 30th Nov 2018, 22:16
  #891 (permalink)  
 
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crab
so you want to add to the complexity of the TR system
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...
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Old 30th Nov 2018, 22:18
  #892 (permalink)  

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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?
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Old 30th Nov 2018, 23:27
  #893 (permalink)  
 
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Originally Posted by chopjock
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...
Everybody relax, the above statement should make it perfectly clear that he's just trolling you.
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Old 3rd Dec 2018, 13:08
  #894 (permalink)  
 
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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
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Old 4th Dec 2018, 12:08
  #895 (permalink)  
 
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send the TR duplex bearing and the collecting containers of the grease to Leonardo for in-shop inspection
Just an ordinary SLF here and I wonder if anyone can explain why the grease containers are also required?
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Old 4th Dec 2018, 12:47
  #896 (permalink)  
 
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Originally Posted by SamYeager
Just an ordinary SLF here and I wonder if anyone can explain why the grease containers are also required?
If things are wearing unexpectedly then it may leave traces in the lubricant that can be found by analysis.
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Old 4th Dec 2018, 13:32
  #897 (permalink)  
 
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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.
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Old 4th Dec 2018, 13:46
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Or even if there was no grease or the wrong grease....or other kinds of contamination.
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Old 4th Dec 2018, 19:36
  #899 (permalink)  
 
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Originally Posted by SamYeager
Just an ordinary SLF here and I wonder if anyone can explain why the grease containers are also required?
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.
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Old 5th Dec 2018, 15:00
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Thanks to all that answered my query.
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