CF6-80 Thrust reverser deactivation
 

hi guys
I would really like some info regarding thrust reverser deactivation on the CF6-80C engines. The procedure is fairly straight forward. My question actualy is what happens when you have any of the top or bottom ball screw actuators completely jammed in the fully extended position. Is it legal to completely remove the actutor, retract the thrust reverser and dispatch the aircraft with one actuator missing? If so can any one assiistt me with any reference material with regards to this, and if not also any reference to that. I have been facing this situation too many times and i have not found the refrerence material to support it. The third party ailine we handle keep refering me to MEL 78-31, but no where does it say you can remove an actutor and lock out the reverser.
Any info will be much appreciated
Thanks
Engg4life

I would hazard a guess here but I reckon the sleeve integrity is compromised by removing an actuator.
However someone who is 'up to speed' with the CF6 installation is bound to make things clear!:ok:

Thank you
 

Thank you for your response. Hopefully we will get someone to shed more light on the subject.. Im sure its a question that needs more research. Being in a line station we are limited to material. The procedure employed was proposed by the base maintenance station of the affected airline which i also felt was very unsafe. Thanks again
engg4life

The screw jack actuators are what hold the T/R halves in place on the slide tracks.
So if you remove one actuator, how would you hold the C-duct half in place?
If one half moved backwards in flight, YOU WILL KILL EVERYONE ONBOARD.

What is the name of this airline you are dealing with?

There is no way you are going to remove the screw jack!! The structural integrity of the reverser system will be compromised. The flex drive shafts from the CDU to the upper and lower screwjacks do sometimes get damaged or worn but I am not aware of a screwjack being jammed in the deployed position. I may stand corrected on this however! Change the actuator/drive shafts is the best option.

just trying to get the fact
 

AINTSAYIN,
im not trying to justify what was done on the aircraft, the airline responsible claims that removing one of either the top or bottom screwjack will not affect the integrity of the sleeve since you still have the cdu and one more actutor.
I am in complete agreement with you guys its just that i need the facts to support my protest against the maintenance action carrried out..

Engg4life

Perrin
 

Good for you, hope your Airline who operate the A/C take on board what you tell them. Simple thing the MEL, if its not in it then there's no sign off. :=

Keep them up boys

:ok:
Thank you all for your input . Much appreciated.
Engg4life

The CDU does not hold the T/R half in place. The screw jacks are the mechanical linkage between the movable T/R half and the non-moving T/R inner half.

Who is this airline that carried out the screw jack removal and then dispatched the aircraft?

Back in around 1990, a BWIA Tristar Thrust reverser was locked out in Frankfurt after disconnecting an actuator. On rotation the whole thrust reverser assembly departed the engine and hit the stabiliser. The aircraft carried on, but diverted to LHR. There is a UK CAA accident report about it.

On a Boeing 744 RR RB211 application they have the mother of all lock-out brackets that you can install to 'replace' the integrity of a missing screwjack. Which basically bolts the sleeve to the FWD firewall to prevent deployment in flight. Sorry no gen on the CF6-80. Only other bit of advice I can give is, we once tried to ask GE if we could dispatch a CF6-50 powered 747 with 2 screws of one reverser lockout plate missing and they nearly died...

Brgd's

N1 Vibes

Say what?
 

Don't have the MEL or MMEL available to me at this point in time but this engine installation on the B767 requires for MEL 78-31-1 application that the TRAS brake be funtionally checked operative for MEL application which is in addition to the CDU being mechanically baulked by the installation of the hex drive lock. Belts and braces I guess as well as checking the integrity of the flex shafts.

As previosly alluded to removing a ballscrew actuator would seriously compromise the integrity of the deactivation of that particular sleeve.:ok:

Remind me not to travel with these jokers!

The sentiments of all comments above are correct. Not in the MEL and associated despatch maintenance requirements - no go. Removing the actuator as the operator suggested could alter the design and certification configuration of the aircraft. It's all very well for an operator to stipulate what has to be done but it has to be within rules and regs; the AMO - and maintenance staff - remain responsible for accomplishment of the task.
Stand firm, ENGG4LIFE, I know what it feels like making a stand like this.:D

And are these "airline responsible" willing to sign for the "fix"?

hi mate have u tried to grease the jack screw because i remembered the incident of alaska airline in which they havent bother to grease there elevators jack screw and while on flight its all treads get worn up and elevator is stuck and had an crash.

I believe you could safely remove the lower jack screw.
No there is no MEL provision for it so I do not propose to make it standard practice but with a one flight home Engineering Authority from your tech services dept would be enough to cover the paper work legalities

The CF6-80 744 767 and A330 have a pneumatically driven T/R.
The (CDU) Centre Drive Unit provides the drive and the braking to the upper and lower jack screws via flex drive shafts.
A TRAS brake is fitted above the upper drive actuator to add belts and braces to the system.
I believe the T/R system has enough redundancy built in, that it’s stow forward integrity would not be impaired by one of these flex drive shafts shearing.

So if you had the situation where a jack screw had seized I think it would be feasible to send the aircraft home with the lower jack screw missing after checking the integrity of the other to jack screws, the drive shafts and the T/R brakes plus fit all the locking screws thru the forward edge of the sleeve.
This of course is well outside the authority of my LAE license and I would not carry this out without a piece of paper giving authority to do it.

In my time I have spent many hours on these T/R systems and have often found TRAS lock (short) flex drive shaft sheared and occasionally a long flex drive end sheared but what is most common is the CDU failing it's brake torque check with no associated problems written in the incoming tech log

My 2 cents :ok:

I just noticed the original post was made April 1st

Bolty,
Even if you were to adopt that method, usual process is to obtain an NTO, TV or equivalent form the TC/STC holder but that in itself does not allow despatch.
The AMO does what the operator wants - the operator is responsible for ensuring required maintenance is accomplished - within the limits of the rules of the regulations and the limits of their maintenance approval. The operator would have to issue a concession, if approved, or go to the regulator. Unless an operator or contracted AMO is so approved to authorise such despatch, it can't happen.
We can't make decisons to despatch on our judgement alone; aircraft have to remain within the approved configuration (and that includes despatch in accorance with the MEL; you can't fly commercially outside the MEL).

BUS429
Thanks for the lesson in air leg much appreciated.
In my case the AMO and the operator are the same.
I did say the action is out of the scope of my license and would require an approval from a "tech services" dept of the operator for a concession, as would dispatch for an over head bin removed in the cabin.... Any part missing from an aircraft that is not in the CDL = concession BFD
A concession is only a bit of paper it does not make the aircraft any safer.

My point was to add some balance to what had been written in this thread.
With the lower jack screw removed (not advisable) and T/R locked out as I described I don't believe in the very short term the the sleeve security would be compromised as I have found the lower flex drive shaft "square" end sheared during inspections of these T/R assy in my time. The CDU provides the locking and the lower jack screw is held in place by the flex drive shaft via the CDU locking.

Judging by the topic of this thread this event has already happened and we can argue the merits of a jack screw removed all day but it looks to me like its history

Care to fill in some details ENGG4LIFE ?

HEy guys,

I just started my career as a mechanic. Well I wud like to know hw to deactivate the T/R for dispatch.

contact Boeing AOG desk..
tell them what you want to do and they will tell you if you can do it or not...
normally if it is not mentioned in the manual as a fix.. then they will not allow it