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rgamurot

777 Mechanical Flight Controls

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I know the 777 is a fly by wire aircraft but if the entire electrical system were to fail, the manual says there are mechanical linkages to enable the pilots to maintain straight and level until the electrical system can be restarted. My question is, if the only way to fly the aircraft was by the mechanical links due to some sort of catistrophic failure could one still land? I'm sure if anything it would be sloppy but at least make it safely?


Ryan Gamurot
 

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My question is, if the only way to fly the aircraft was by the mechanical links due to some sort of catistrophic failure could one still land? I'm sure if anything it would be sloppy but at least make it safely?

 

Yep, in fact an Airbus crew used engine thrust alone to make a successful landing after losing all hydraulic fluid due to a missile strike. 

 

http://www.youtube.com/watch?v=Dqnrkvl9MNg


Alex Jevdic KORD/KHOT/KPWK

A<380 love at first flight

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That was an analogue A300B2 non flyby wire aircraft but still a great example of airmanship.

 

If fbw is degraded yes you can still land, you will still have a proper degree of controllability.


Will Reynolds

 

Flight Sim Addict

 

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Yep even the modern Airbuses have something called direct law where the pilots can relay on the mechanically linked rudder and trim controls if the computers somehow fail completely, not sure how it works on the 777 and 787 but I'm sure the back up is similar. As for FBW or analog it wouldn't have mattered for the DHL crew, with no hydraulic fluid there is no movement of flight control surfaces. 


Alex Jevdic KORD/KHOT/KPWK

A<380 love at first flight

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You are talking about mechanical backup not direct law.. Direct law only requires manual pitch trim, the gear also needs to be lowered. If you lose all hyd pressure on the new busses you are still a lawn dart with engine thrust only.


Rob Prest

 

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You are talking about mechanical backup not direct law.. Direct law only requires manual pitch trim, the gear also needs to be lowered. If you lose all hyd pressure on the new busses you are still a lawn dart with engine thrust only.

Exactly the same is true on non FBW aircraft with no mechanical backup (the DC-10 and 747 for example).  Which is why so much attention is paid to backup hydraulic systems.  Many aircraft have RATs.  The A380 has some surfaces powered by self contained hydraulics, independent of the main hydraulic systems.  An echo of the VC10's flight control system from the 1960s.

 

 

My question is, if the only way to fly the aircraft was by the mechanical links due to some sort of catistrophic failure could one still land? I'm sure if anything it would be sloppy but at least make it safely?

You would have limited pitch and roll control.  No yaw control apart from thrust asymmetry.  As long as you have little turbulence and no crosswind I think a safe landing is highly likely.


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You are talking about mechanical backup not direct law.. Direct law only requires manual pitch trim, the gear also needs to be lowered. If you lose all hyd pressure on the new busses you are still a lawn dart with engine thrust only.

 

Yeah that's right, I still got the names mixed up even after looking it up on Airbusdriver.net, that's what you get for lack of sleep lol


Alex Jevdic KORD/KHOT/KPWK

A<380 love at first flight

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I know the 777 is a fly by wire aircraft but if the entire electrical system were to fail, the manual says there are mechanical linkages to enable the pilots to maintain straight and level until the electrical system can be restarted. My question is, if the only way to fly the aircraft was by the mechanical links due to some sort of catistrophic failure could one still land? I'm sure if anything it would be sloppy but at least make it safely?

 

The mechanical backup in the 777 gives you control of a single spoiler on each side (4 and 11 iirc) for roll control via the yoke, and pitch control via the backup pitch trim controls on the centre pedestal. Control will be limited; it's designed for you to be able remain straight and level, not to land. 


Jordan Forrest

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