LMML 14/32 From Malta, joined Jan 2001, 2559 posts, RR: 7 Posted (8 years 1 week 13 hours ago) and read 6412 times:
I mean can you actually switch off all 5 (?) computers, the FADEC, Alpha floor etc and fly the aircraft the old fashioned way? If so how do you switch off the computers?
Prebennorholm From Denmark, joined Mar 2000, 6019 posts, RR: 55 Reply 2, posted (8 years 1 week 13 hours ago) and read 6334 times:
Not the oldfashioned way. With all FBW systems inoperative the following controls is available.
- Cable control of the rudder - gives some roll control in non-turbulent weather.
- Engines will give some pitch control. Differential engine thrust can also be a control input.
A friend on mine, who is an A320 driver, has tested it for fun in the sim, and he claims that in most cases they would bring a plane down in one piece. But it takes the power of strong legs from both flight crew members.
The A380 doesn't have the wire backup on the rudder. It would be useless since all four legs of the flight crews couldn't move the rudder. No way.
That's nothing special for FBW planes like "busses" and B777. The hydraulics are in any case by far the most prone to fail, and they are in principle identical on all large airliners. A couple of DC-10's have been "landed", or at least not crashed vertically, with all three hydraulic systems inoperative.
Always keep your number of landings equal to your number of take-offs, Preben Norholm
B744F From Germany, joined Jan 2006, 0 posts, RR: 0 Reply 3, posted (8 years 1 week 9 hours ago) and read 5988 times:
Hydraulics may fail, but computer systems are always error free! That is an accident waiting to happen unfortunately if you can't control the bird by hand
Nwafflyer From United States of America, joined Jul 2004, 1050 posts, RR: 2 Reply 4, posted (8 years 1 week 9 hours ago) and read 5979 times:
Again, I am not a pilot, nor an engineer -- however, I feel strongly that on all major airlines, there are adequate safety devices to cover for all but human failure
XXXX10 From United Kingdom, joined Jan 2000, 777 posts, RR: 0 Reply 7, posted (8 years 1 week 3 hours ago) and read 5836 times:
As I understand it you can switch off all of the computers, the aircraft will go into Direct law where the side-stick inputs directly control the control surfaces as they would in a normal plane.
Fadec, I'm not sure if you can disable this although I would guess that some redundancy is built in.
The above of course assumes that the hydraulics are working. If there were a failure of all systems then you are in trouble but then you are in trouble on any large plane with no hydraulics.
HAL From United States of America, joined Jan 2002, 2467 posts, RR: 53 Reply 8, posted (8 years 1 week 2 hours ago) and read 5825 times:
To clear this up:
Switching off the computers (and there are seven of them) would not result in direct law, but mechanical reversion. Direct law results if you did switch off some of the computers, and also if certain combinations of them fail, or certain components in the plane. Lesser failures result in Alternate law. There are switches on the overhead panel for all seven computers.
If ALL the computers failed (or were switched off), you still have cable control of the rudders as mentioned above for lateral control, and also cable control of the stabilizer trim through the trim wheel for vertical control.
I am an A320/319 pilot for America West, and they make us go through that scenario during training. It's a pain in the a$$ to control, but it can be done.
HAL
[Edited 2005-05-19 10:05:34]
One smooth landing is skill. Two in a row is luck. Three in a row and someone is lying.
CactusTECH From , joined Dec 1969, posts, RR: Reply 10, posted (8 years 6 days 20 hours ago) and read 5717 times:
Hi all I owrk on A320's and it is possible to fly it manually. Its called direct law and in case you lose your Air Data Inertial Reference Units you can use the joystick to fly it. Its actually a procedure at the simulator for checkrides at America West.
LMML 14/32 From Malta, joined Jan 2001, 2559 posts, RR: 7 Reply 11, posted (8 years 6 days 16 hours ago) and read 5596 times:
So, if I understand correctly, if you loose the ADIRU an A320 can be flown manually using the joysticks. If that is so what drives the servos when there is no direct command? The joystick only provides electrical input and this cannot be termed as direct law. What am I missing?
HAL From United States of America, joined Jan 2002, 2467 posts, RR: 53 Reply 12, posted (8 years 6 days 10 hours ago) and read 5479 times:
LMML 14/32,
I think there are some misconceptions going on here with terminology.
The ADIRU's are inertial navigation computers. They just tell us where we are and which way we are going.
The seven (7) flight control computers are the 3 SEC's (Spoiler Elevator Computers), the 2 ELAC's (Elevator Aileron Computers) and 2 FAC's (Flight Augmentation Computers.
Their uses:
ELAC = Normal elevator and stabilizer control. Aileron control.
SEC = Spoiler control. Standby elevator and stabilizer control
FAC = Electrical Rudder control.
It is through these seven computers and their associated software that programs like Alpha Floor and speed & attitude protection work. If one or more of those computers fail or are switched off, you may lose some of the protections thereby going into alternate or direct law. But if all seven fail or there is a complete electrical failure or if you switch all seven off, then you are in mechanical reversion as I described above. At that point you only have cable operated rudder and cable operated stabilizer trim available for control. The sidestick would be so much useless plastic because you need at least one of those computers running for it to work.
HAL
One smooth landing is skill. Two in a row is luck. Three in a row and someone is lying.
HAL From United States of America, joined Jan 2002, 2467 posts, RR: 53 Reply 15, posted (8 years 6 days 2 hours ago) and read 5386 times:
Quoting Gasman (Reply 13): Thanks HAL - for the benefit of us without your obvious high degree of technical knowledge, what is alpha control?
Quoting Captoveur (Reply 14): Correct me if I am wrong but isn't that angle of attack control?
Thanks for your optimistic opinion of my abilities, but I'm just another Airbus pilot that's been through the ground school.
Alpha Floor is one of the many 'protections' provided by the multiple & redundant flight control computers. What it does is protect the plane from getting into a high angle of attack/low power situation that might cause a stall. The computers are constantly assessing things such as the current angle of attack, current airspeed, airspeed trend and much more to judge when the plane may be getting close to a low speed stall situation. When that high angle of attack is sensed, the computers automatically set TOGA thrust (full power) no matter what the thrust levers are set at. It is trying to power the plane out of a possible stall configuration.
To answer Captoveur, the word Alpha refers to the engineering term describing the angle of attack of the wing of the plane. Airbus uses Alpha Floor to label the protection I described above.
HAL
One smooth landing is skill. Two in a row is luck. Three in a row and someone is lying.
Starlionblue From Hong Kong, joined Feb 2004, 15872 posts, RR: 66 Reply 16, posted (8 years 5 days 12 hours ago) and read 5219 times:
Quoting B744F (Reply 3): Hydraulics may fail, but computer systems are always error free! That is an accident waiting to happen unfortunately if you can't control the bird by hand
Pfft. Decades of FBW history with not a single fatal crash due to computer failure says you're wrong. I can't prove it will never happen, but you're more likely to be hit by a meteor.
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
AussieAMEgirl From Australia, joined Apr 2005, 61 posts, RR: 1 Reply 20, posted (8 years 4 days 10 hours ago) and read 5011 times:
Yeah the good old scarebus has 2 cables...it was so much easier to do a cable lube on the A320 than the 727!!....Oh and heres another interesting little titbit....next time any of you you ever has the chance to play in an A320 sim...get the motion turned off and turn off ELAC1 and ELAC2 and the bird handles like a fighter!! (It makes for a fun nightshift buzzing and rolling in an A320!) Although I wouldnt try that with a real one as the thing starts screaming error messages at you in the cockpit.
Another safety bit added was the manual fuel off/on. When I was an apprentice I remember one of the LAME's on type telling me that the pilots were not too impressed with Airbus's original plans of having the engines totally controlled by computer, including fuel input so they had to add a manual fuel shutoff switch in the centre console, so in the event of emergency they can manually shut off fuel.
HAL From United States of America, joined Jan 2002, 2467 posts, RR: 53 Reply 21, posted (8 years 4 days ago) and read 4956 times:
Quoting HAWK21M (Reply 18): BTW why HAL......reminds me of Hindustan Aeronautics Limited BLR.
When I first started posting on this board, I was flying for Hawaiian Airlines (HAL). The nickname seemed pretty obvious. Of course I didn't count on getting furloughed and going to work for a couple more airlines in the process - but such is the life of the airline pilot these days.
HAL
One smooth landing is skill. Two in a row is luck. Three in a row and someone is lying.
Pihero From France, joined Jan 2005, 3496 posts, RR: 72 Reply 22, posted (8 years 3 days 22 hours ago) and read 4942 times:
AussieAMEgirl :"Another safety bit added was the manual fuel off/on. When I was an apprentice I remember one of the LAME's on type telling me that the pilots were not too impressed with Airbus's original plans of having the engines totally controlled by computer, including fuel input so they had to add a manual fuel shutoff switch in the centre console, so in the event of emergency they can manually shut off fuel"
That guy was telling you stories. There's a lot more functions to that ENG MASTER switch than just fuel s/o.
HAL From United States of America, joined Jan 2002, 2467 posts, RR: 53 Reply 23, posted (8 years 3 days 13 hours ago) and read 4892 times:
Quoting Pihero (Reply 22): That guy was telling you stories. There's a lot more functions to that ENG MASTER switch than just fuel s/o.
I think he's right. Remember, we have to shut off the engines when we arrive at the gate, so there has to be some way of turning the darned things off besides politely asking the computer.
I can just imagine a conversation like that in 2001 a Space Odyssey:
"Hal, shut off the engines please"
"No Dave, I can not do that"
"Hal, shut off the engines. We're at the gate now"
"Dave, I think you need to take a stress pill, sit down, and think things over"
"Hal, the jetbridge is at the door. Shut down the engines"
"Dave, I have the upmost enthusiasm for the mission"
"Hal, don't make me pull your circuit breaker again"
"Stop Dave, stop dave, stop...."
HAL (Not the computer)
One smooth landing is skill. Two in a row is luck. Three in a row and someone is lying.
Pihero From France, joined Jan 2005, 3496 posts, RR: 72 Reply 24, posted (8 years 3 days 11 hours ago) and read 4867 times:
Love it, Love it !
And I don't really want to add more.
My previous post had to do with a perceived joke from some rather biased people :Everything was ok as long as it could add to the 'Bus bashing that was fashionable.
Having since early in the 320 program been kept "au fait" of the tech specs, I've never heard of a full Fadec control over the engine including the start-up and the shutting down.
My biggest problem is I fell in love nineteen years ago with a plane people call "scarebus" in 2005, which I find at least unfair. But that's just me.
That said, Hal, you just demonstrated in a way I could never have achieved the fallacy of certain assumptions, and whether you're my favourite computer or one of the few on this forum to have the experience of CWS - AND could tell of it- welcome to my respected list!
Regards
Contrail designer
25 Kaddyuk: It is true that in the Airbus cockpit, the Master Fuel Cut Off Switch is the only physical connection between pilot control and the engine...
26 Pihero: Kaddyuk, Sorry but you're wrong too.You just forgot there is a fire P/B for each engine on the overhead panel, and among other things ,it controls the
27 Starlionblue: And Arthur C. Clarke said it was just a fluke. Nobody wanted to believe him for years.
28 AussieAMEgirl: er why do I fell I was taken out of context? I love the A320, I think it beats the Boeing fleet from a maintenance standpoint hands down. I dont parta
29 LMML 14/32: On the newer 'busses two horizontal magenta lines appear equidistantly (I think 15 knots either side) from the speed bug during descent. From what I h
30 LongHauler: You are correct with the lower speed limit. If when maintaining the profile descent path, the airspeed drops to the lower limit, trust will be added
31 WindowSeat: HAL, do you know if there have been instances that this has actually happened in the past, and not just simulated in the sim?? ROFL! If anyone has th
32 HAL: As far as I know, there hasn't been a complete failure of all seven computers in flight in an Airbus - at least on a flight with passengers. It's pos
33 LMML 14/32: LOL !! That reminds me. Someone I know has recorded the callouts on his cell phone and now uses them as a ring tone.
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