DOES THE A320,330 or A340 USE A MECHANICAL BACKUP SYSTEM FOR THEIR FBW ?

[used2flyboeing]

Dear Learned Colleagues,

What kind of mechanical redundency does AIRBUS use on their fly-by-wire aircrafts ? Do they, like the 777, have a backup set of panels driven by cables ? I think the rudder is the only thing cable-actuated on AIRBUS

THanks in advance ..

[Sheikh Your Bootie]

You think right. On Airbus FBW conversion courses mechanical back up is demonstrated, and you can land it using just rudder and engines, tricky but it can be done. Handy as well if there is no xwind :p

Airbus have claculated that the chances of getting to mechanical back up are infitessimally small. Possible but extrememly remote.

SyB :zzz:

[A-3TWENTY]

Rudder, engines and Manual pitch trim..

[As I See It]

I think you'll find the only cables connected to the engine are elctrical ones, you could try pulling on them, but you'll find they are not much use in controlling the donk when all else is lost.


Remember; It's only As I See It

[idg]

Latest A340-500/600 and A330s have all electric rudder now so no cables to the rudder. There is a back-up electric power supply driven from the hydraulic system at the rudder to maintain control even in the event of loss of all generators.:oh:

[CV880]

Airbus use mechanically connected Stab Trim and rudder pedals but as stated above latest models of A330/340 have deleted the mechanical rudder cables. 777 uses mechanical cables for stab trim and one pair of flight spoilers.

[Max Angle]

Interesetingly the manual back-up system was not required for orginal certification and was only put in to reassure the airlines. Can't say I mind having it though.

[MANTHRUST]

As I see it
You are quite correct,the thrust levers are only connected by wires to the FADECS and hence the engines, however, the FADECS are self powered as long as the engines are turning.
So the question is, can you control your engines when ALL electrical power is lost? ( that is no engine/APU generators no emergency generator and the poor old batteries are flat)
Do the FADECS supply the thrust lever quadrant to allow the thrust lever position to be monitored?

[catchup]

To my limited knowledge "backup systems" are designed as a temporaly feature to fly the aircraft until normal systems are restored.
Pls correct me if I'm wrong.

regards

[As I See It]

Maybe I should have clarified my answer, there is no mechanical backup for the engines should there be a total electrical failure as they are not mechanically connected. However I have not got to the bottom of a total electrical failure and whether the DDG will power the engines, as the FADEC is powered by the battery in a total electrical failure as too is ignition, but only ign A, if the batteries were lost then I guess you are now piloting a glider!


Not only is it As I See It, but I've checked one or two books!

[swh]

As I See It,

Thought FADEC was self powered above 10% N1 ?

Thought the mechanical backup still drives a manual hydraulic valve, remember that you can fly the aircraft without computers, but cannot fly the aircraft without hydraulics ?

[Techman]

Strange question from someone who supposedly is A320 rated.

[used2flyboeing]

don't have the latest FCOMS .. was curious about the modern AIRBUS aircrafts & what lengths they were going to to save weight ( cable are heavy - especially ones that run the length of the airplane ) .. Boeing took all their cables out incrementally on some of their cable backup systems on the 757 & 767s: stab trim ( cables to STCM replaced with duel concentrically wound electrically actuated - arm and control valve solenoids.. AIRBUS has a tendency to do little fixeys & design improvements that are spread hither & yon amongst the fleet - IE like the PIP package on the early A340-200 & 300s - was implemented on a small block of 1--20 airplanes - then superceeded by a redesigned skins which incorporated said PIP improvements .. so, often with AIRBUS - you have to look under the hood to see what is there because of all the variation in the effectivity numbers ..

[swh]

Techman,

Its not that strange a question, a typical FCOM will say something like that mechanical pitch control is achieved by applying manual trim to the THS, and lateral control using rudder pedals. The nuts and bolts of how this works is not clearly stated.

However looking at the diagrams of the pitch and rudder control, it appears that hydraulic systems are still required for mechanical backup for the rudder and THS, mechanical backup is a backup to the flight control computers, not the hydraulic systems.

I dont have the 345/346 manuals what I have indicated is true for earlier airbuses.

:ok:

[Trash Hauler]

I don't know about the FADECs used on the engines for the Airbus fleet however I have some experience with FADECs on C130J.

They are guaranteed to be self sufficient above 12% Ng, powered by the permenant magnet generator on the engine. The power levers and fire handles are hardwired to the FADECs so engine control is maintained in the event of total electrical failure.

On a maintenance run we shut off all generators and then the both batteries. The flight deck was dark, all computers powered down but the engines were still operating and full control in the flight range was available from the power levers. The final part of our little test was shutting down with the fire handle. Again it worked as advertised.

I suspect the same type of system on the Airbus fleet.

Hope this helps

[As I See It]

Mr Trash Hauler, you are correct in your assumption with regard to the A320 (have done some reading on this, believe me), but the fact remains there is no mechanical back up and it would seem the same with the C130. Lets assume worst case the DDG failed as well, then gliding would follow.
As it happens an inop DDG is a no go, kind of makes sense now!

It is not only As I See It, but it would also seem As It Is

[Techman]

I still find it a strange question or perhaps more accurately put, a worrying question.

Also,

"However looking at the diagrams of the pitch and rudder control, it appears that hydraulic systems are still required for mechanical backup for the rudder and THS, mechanical backup is a backup to the flight control computers, not the hydraulic systems."

Shows, at least to me, the level of system understanding required these days as worrying.

[alatriste]

Mechanical backup ( THS and rudder) is ONLY usable if HYD power is available.
It permits the pilot to control the aircraft during a complete loss of ELECTRICAL POWER. (all computers are gone)

Just think the reason why AIRBUS named the HYD system as Green, Blue and Yellow instead of the classic Left, Center and Right. Green, Blue and Yellow in this precise order cause if you loose all Hyd systems you are DEAD, and then AIRBUS just tell you:

" God Bless You"

[swh]

alatriste,

The airbus A300 that had a missile hit after takoff landed back on the runway in bagdad, had no HYD, with fire and structural damage, the guys walked away unhurt.

:rolleyes:

[used2flyboeing]

Techman said:

[ I still find it a strange question or perhaps more accurately put, a worrying question.

Also,

"However looking at the diagrams of the pitch and rudder control, it appears that hydraulic systems are still required for mechanical backup for the rudder and THS, mechanical backup is a backup to the flight control computers, not the hydraulic systems."

Shows, at least to me, the level of system understanding required these days as worrying. ]

1) Based on where the industry has been & the downward trend in pilot salarys - worrying & following the QRH is all yer gonna get when your world comes unstuck ..

2) Boeing & AIRBUS training has made it clear that they really dont want pilots to have too much systems knowledge b/c they dont want pilots troubleshooting problems in the air

3) All modern Fly By Wire flight control systems & cockpit commonality reinforce these ideas - by making low time, low skilled pilots viable and competitant on the flight deck - regardless if the last thing they operated was a bicycle in Tenneman square ..

4) you know, they say the light deckof the future will have a dog and a pilot - the pilots job will be to feed the dog & the dogs job is to bite the pilot if he tries to operate the controls ..

[alatriste]

Thanks SWH but I´m sure you know that A300 is not FWB, still some cables around..... there must be an emergency checklist for a complete HYD failure, not available for A320. The only choice is GBY.