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A-320 Flight Management Computers  
User currently offlineCapt_smith From United States of America, joined May 2000, 65 posts, RR: 0
Posted (15 years 2 weeks 4 hours ago) and read 3135 times:

I understand that the A-320 flight management computers are redundant. I know it's near impossible, but what if something caused a complete failure? Is there some kind of hydraulic back up? How would the pilot fly the plane or control the flight surfaces without the computer?

10 replies: All unread, jump to last
User currently offlineGreenArc From United States of America, joined May 2000, 83 posts, RR: 1
Reply 1, posted (15 years 2 weeks 4 hours ago) and read 2815 times:

Capt. Smith,

I believe you are confusing the flight management computers with the flight control computers (FCC's).

IIRC, there are five FCC's. If all five were to fail or lose power, the plane can be controlled using rudder and trimmable horizontal stabilizer, both of which are independant of the FBW chain.

The A3XX will do away with this redundancy as it has proved unnecessary.


User currently offlineNKP S2 From United States of America, joined Dec 1999, 1714 posts, RR: 5
Reply 2, posted (15 years 2 weeks 3 hours ago) and read 2785 times:

RE: "Hydraulic backup" I want to clear something up here. It should be noted that on FBW aircraft,only the control,or shall I say command of flight control surfaces are electronic. The surfaces themselves are still physically actuated hydraulically. Instead of a cable or rod commanding a hydraulic power control unit metering valve as on a 'traditional' a/c,the said metering valve is moved by an electrical servo. So you see,it's not a matter of "cables vs. wires" actually moving flight controls as some think it may be. Yeah,the 319-321 horizontal stab and rudder have cable control for redundancy. (the brake metering valves are also cable operated BTW) When we first got the A319's,I made it a point to crawl up in the E&E bay to verify for my own curiosity that yes,there are cables on a 320 family a/c!  

User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3719 posts, RR: 33
Reply 3, posted (15 years 1 week 6 days 20 hours ago) and read 2731 times:
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I have to disagree with you regarding the A320 Brake System. There are no mechanical cables in this system, braking is normally acheived (excepting auto-brake) by electrical transducers on the brake pedals transmitting the pedal postion to the Brake & Steering Control Unit and the brake pressure and anti-skid function being controlled by this unit. Should this system fail there is alternate brakes. In this case a low pressure hydraulic circuit from the master cylinders on the pedals control a Dual Brake Metering Valve in the u/c bay that ports the main system hydraulics to the brake units.

User currently offlineAirbuspilot From Belgium, joined Apr 2000, 416 posts, RR: 2
Reply 4, posted (15 years 3 days 3 hours ago) and read 2673 times:

Only rudder and stabilisers have a mechanical backup with cables. But this was done only because it was needed for US approaval. I can assure you that the aircraft becomes almost impossible to fly when you loose all hydraulics. When i am flying ,the mechanical backup is NO option!!!

User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3719 posts, RR: 33
Reply 5, posted (15 years 3 days 2 hours ago) and read 2649 times:
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The cables operate the servo's for the stab & rudder, so hyds are still rqd. So no hyds no control.

User currently offlineA330 From Belgium, joined May 1999, 649 posts, RR: 7
Reply 6, posted (15 years 2 days 21 hours ago) and read 2642 times:

Airbuspilot, Capt. L. Bondroit (I think you know him...) says "it works". Off course, THE pilot of Sabena has some experience...! (great man, btw.)
Using rudder for heading, trim for pitch!! How long does it take to get it right in the sim??

User currently offlineAirbuspilot From Belgium, joined Apr 2000, 416 posts, RR: 2
Reply 7, posted (15 years 5 hours ago) and read 2615 times:

Off course I know Luc Bondroit. I know him rather well and I have a huge respect for the man. If you know him you should know that he is an airbus addict! I love airbus but I am not an addict. We exercised the mechanical backup in the sim several times and I must say, I managed ONCE to set it on the ground but it was nearly a crash-landing. So as I said before , for me this is no option anymore.
A330, are you studying at SFA? My guess is you do.Good luck anyway with the atpl!!! Been there, done that. Prom7 day.

User currently offlineFlyBoeing From United States of America, joined May 2000, 866 posts, RR: 2
Reply 8, posted (14 years 12 months 4 days 17 hours ago) and read 2589 times:

Oh, my God. Remind me to NOT fly on any Airbus planes. Admittedly, fly-by-wire reduces weight and makes the aircraft more efficient, but not having a backup that works is kind of scary. Is this situation different in Boeing aircraft?

User currently offlineDL_Mech From United States of America, joined Feb 2000, 2091 posts, RR: 9
Reply 9, posted (14 years 12 months 4 days 15 hours ago) and read 2585 times:

The only cable operated systems on the 777 are for spoilers four and eleven (one on each wing) and alternate stabilizer pitch trim control. This Direct mode can be selected by the pilot or is automatic in case of total FBW failure (this can't happen right?). The 757/767 have FBW spoiler systems.

This plane is built to withstand anything... except a bad pilot.
User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3719 posts, RR: 33
Reply 10, posted (14 years 12 months 3 days 18 hours ago) and read 2565 times:
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Airbus or Boeing, you still require hydraulics to actually move the control surface

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