Go Back  PPRuNe Forums > Aircrew Forums > Rotorheads
Reload this Page >

Helicopter down outside Leicester City Football Club

Rotorheads A haven for helicopter professionals to discuss the things that affect them

Helicopter down outside Leicester City Football Club

Old 30th Nov 2018, 22:16
  #921 (permalink)  
 
Join Date: Nov 2008
Location: UK
Age: 61
Posts: 894
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...
chopjock is online now  
Old 30th Nov 2018, 22:18
  #922 (permalink)  

Avoid imitations
 
Join Date: Nov 2000
Location: Wandering the FIR and cyberspace often at highly unsociable times
Posts: 12,068
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?
ShyTorque is offline  
Old 30th Nov 2018, 23:27
  #923 (permalink)  
 
Join Date: May 2016
Location: Norway
Posts: 33
Originally Posted by chopjock View Post
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.
Nadar is offline  
Old 3rd Dec 2018, 13:08
  #924 (permalink)  
 
Join Date: Jun 2008
Location: England & Scotland
Age: 58
Posts: 1,341
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
John R81 is offline  
Old 4th Dec 2018, 12:08
  #925 (permalink)  
 
Join Date: Jan 2010
Location: UK
Posts: 101
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?
SamYeager is offline  
Old 4th Dec 2018, 12:47
  #926 (permalink)  
 
Join Date: Jan 2011
Location: on the cusp
Age: 47
Posts: 217
Originally Posted by SamYeager View Post
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.
dClbydalpha is offline  
Old 4th Dec 2018, 13:32
  #927 (permalink)  
 
Join Date: Sep 2017
Location: Canada
Posts: 259
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.
GrayHorizonsHeli is offline  
Old 4th Dec 2018, 13:46
  #928 (permalink)  
 
Join Date: May 2002
Location: "Deplorable but happy as a drunken Monkey!
Age: 70
Posts: 15,936
Or even if there was no grease or the wrong grease....or other kinds of contamination.
SASless is online now  
Old 4th Dec 2018, 19:36
  #929 (permalink)  
 
Join Date: Feb 2017
Location: Republic of Texas
Posts: 92
Originally Posted by SamYeager View Post
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.
ethicalconundrum is offline  
Old 5th Dec 2018, 15:00
  #930 (permalink)  
 
Join Date: Jan 2010
Location: UK
Posts: 101
Thanks to all that answered my query.
SamYeager is offline  
Old 6th Dec 2018, 13:04
  #931 (permalink)  
 
Join Date: May 2008
Location: LEIC
Posts: 23
Further info on AAIB website released today at 1400
ROC man is offline  
Old 6th Dec 2018, 13:15
  #932 (permalink)  
 
Join Date: Jun 2012
Location: Teesside
Posts: 151
Originally Posted by ROC man View Post
Further info on AAIB website released today at 1400
AAIB Special Bulletin here ; https://assets.publishing.service.go...018_G-VSKP.pdf .

Already reported on the BBC .
David Thompson is offline  
Old 6th Dec 2018, 13:33
  #933 (permalink)  
 
Join Date: Oct 1999
Location: Nigeria
Age: 52
Posts: 4,395
Originally Posted by David Thompson View Post
AAIB Special Bulletin here ; https://assets.publishing.service.go...018_G-VSKP.pdf .

Already reported on the BBC .
so clearly the EADs were not based on speculation
212man is offline  
Old 6th Dec 2018, 13:34
  #934 (permalink)  
 
Join Date: Oct 2018
Location: South West
Posts: 3
If I read this right, the yaw went full travel to the right. Since the limit of right yaw is usually set for the ability to yaw right in autorotation, it would probably mean it was still yawing right even in auto with engines shutdown (normal recovery actions for a tail rotor drive fail in the high hover). Thoughts?
gipsymagpie is offline  
Old 6th Dec 2018, 13:55
  #935 (permalink)  
 
Join Date: Oct 2018
Location: UK
Posts: 7
“Sufficient force and torque had been applied to the castellated nut on the actuator end of the control shaft to friction weld it to the pin carrier and to shear the installed split pin. The observed condition of the duplex bearing and the increased torque load on the castellated nut that remained on the spider end of the shaft is consistent with rotation of the tail rotor actuator control shaft. Whilst the shaft was rotating and a yaw control input was applied, the shaft “unscrewed” from the nut, disconnecting the shaft from the actuator lever mechanism, and causing the nut to become welded to the pin carrier.”

So... what provided the force and torque which welded the actuator-end nut and broke split pin? Failure of the duplex bearing locking the inner shaft to the outer shaft?
Slowclimb is offline  
Old 6th Dec 2018, 14:10
  #936 (permalink)  
 
Join Date: Apr 2000
Location: EGDC
Posts: 7,197
My reading of this is that the duplex bearing was overheating, binding and then seizing, causing rotation of the control shaft which undid the castellated nut and removed the pitch control of the TR allowing the servo to go to the 'full right pedal' position.

I don't care how many times you practice in the sim, that one is pretty unrecoverable from that height and speed.

The question is - is this an assembly issue (bearing end nut over torqued) or a maintenance issue? The aircraft was quite young.......
crab@SAAvn.co.uk is offline  
Old 6th Dec 2018, 14:23
  #937 (permalink)  
 
Join Date: Jul 2002
Location: Ireland
Posts: 429
The rent-an-idiot David Learmount has just been on the BBC News saying that the report reveals that the control cable between the pedals and the tail rotor had snapped!

Really?

Why would somebody agree to an interview about a very short bulletin without taking five minutes to read and understand it?

Looking at the photos and CAT scans of the bearing and carrier, I tend to agree that the bearing failed for some reason and the actuator linkage became disconnected as a result of this failure.
Speed of Sound is offline  
Old 6th Dec 2018, 14:39
  #938 (permalink)  
 
Join Date: Jan 2010
Location: Edinburgh
Age: 80
Posts: 38
Looks like it should have been a left hand thread, although that might just have postponed disaster.
DType is offline  
Old 6th Dec 2018, 14:42
  #939 (permalink)  
 
Join Date: Jan 2018
Location: Leatherhead
Posts: 6
Originally Posted by [email protected] View Post
My reading of this is that the duplex bearing was overheating, binding and then seizing, causing rotation of the control shaft which undid the castellated nut and removed the pitch control of the TR allowing the servo to go to the 'full right pedal' position.

I don't care how many times you practice in the sim, that one is pretty unrecoverable from that height and speed.

The question is - is this an assembly issue (bearing end nut over torqued) or a maintenance issue? The aircraft was quite young.......
​​​​​​From the Special Update "The observed condition of the duplex bearing and the increased torque load on the castellated nut that remained on the spider end of the shaft is consistent with rotation of the tail rotor actuator control shaft."

I read that to mean that they think the increased torque on that nut was caused by the rotation of the control shaft - for the reasons you gave. Maintenance issue or defective bearing ??
GAPU is offline  
Old 6th Dec 2018, 14:43
  #940 (permalink)  
 
Join Date: Nov 2001
Location: 1000ft above you, giving you the bird!
Posts: 488
What sober and horrible reading the S2 bulletin is - if only they had a few more minutes to transition into forward flight.... RIP!! Horrible sad loss for all involved
Jetscream 32 is offline  

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.