Well this was all pretty entertaining to read.

There's a slight chance that this video will cause fear to develop. ^_^ But maybe it just gives an outlook on what can be done with some flexible systems in place. Imagine blocked control surfaces or even severely damaged structures but, on the control stick, a normal response to the commands from the pilot.

Who needs wings anyway?

 

On another occasion, after the DC-10 accidents I think, NASA developed a system being able to steer the plane only by the use of differential thrust. Means no control surface deflection involved. They've assumed a complete loss of hydraulics. Propulsion-Controlled Aircraft (PCA) system. http://www.nasa.gov/.../PCA/index.html

 

A rather short video on it. A nice example on why not to use music on ordinary YT videos by the way. ^_^

http://www.youtube.com/watch?v=jIyIqAf0Ddc

A nice example on why not to use music on ordinary YT videos by the way. ^_^

+1.

I found this in an A330 FCOM

 

 

I found this in an A330 FCOM

 

 

 

Read what the captain said about the mechanical backup law above:

 

http://forum.avsim.n...50#entry2561347

 

 

Guy

Read what the captain said about the mechanical backup law above:

 

http://forum.avsim.n...50#entry2561347

 

 

Guy

 

I did. Note the use of the word temporary in the FCOM and the additional information.

I did. Note the use of the word temporary in the FCOM and the additional information.

 

You are right !

 

From A320 manual:

"mechanical back-up (through rudder and

stabilizer control) will ensure adequate control in case of

TEMPORARY loss of all electrical power sources including

batteries"

 

Guy

I did. Note the use of the word temporary in the FCOM and the additional information.

The temporary thing is because if you actually tried to land it in mechanical back up, as I said it'd be semi-controlled crashing. You're aim would be to restore flight controls to direct law at a minimum before attempting a landing, hence the use of the word temporary. It's not intended for you to continue flying the bus for extended periods in, as it is really there for you to try and maintain level flight till you get your controls back.

 

Regards,

Ró.

A Concorde captain once told me about a time the flight controls dropped into mechanical just as the aircraft got airborne on a JFK 31L Canarsie Climb. Said he'd never heard so many expletives from the F/O (PF). Fortunately they got one of the electrical flight control channels back.

A Concorde captain once told me about a time the flight controls dropped into mechanical just as the aircraft got airborne on a JFK 31L Canarsie Climb. Said he'd never heard so many expletives from the F/O (PF). Fortunately they got one of the electrical flight control channels back.

If it's anything like an Airbus I can imagine the feeling, they're about as manouverable as a 100,000 ton cargo ship in mechanical law. Fine if you're in the cruise and just need to keep her steady for a few moments, but on the climb out on the Carnasty is another thing... :mellow:

 

Regards,

Ró.

Never said it was easy LOL... ^_^ Fact is most of the time, 99.999999999999999999999% that he'll have no need to over ride it, it will do exactly as he says or else do the correct thing, but where there's a will there's a way. Making it easy to override the computer even when it's doing the correct thing would defeat the purpose of the flight envelope protections.

 

Regards,

Ró.

 

To SUMMARIZE and conclude our discussion from yesterday, I think I must modify

my statement from above a bit. This must be about right now :

 

It is NOT possible to fly the Airbus in NORMAL conditions like a conventional aircraft

(that is in DIRECT law).

 

That means:

To get the Airbus in DIRECT law you MUST set some ABnormal conditions:

-either switch off some computers (FAC1/2) and lower the gear

-or switch off all ADIRS (and loose the PFD/ND)

 

I read also that If you switch off ALL FAC/ELAC/SEC computers you pass in

MECHANICAL backup law, which is used only in the case of temporary

loss of all electricty. You can not land in this law ("crash in a semi controlled fashion...")

So you must try to get back at least in Direct law before landing.

.

And then it's also no FUN to fly in DIRECT mode as you said above

"she handles like a 3 legged bull in direct law". :rolleyes:

 

And once more: those are just THEORETHICAL considerations to better understand

the Airbus systems. I know very well that in practice there will NEVER be the need

to pass voluntarily in DIRECT law.

 

Guy

Guy, are you running a secret new method of double posting? http://forum.avsim.net/topic/395794-what-is-fly-by-wire/page__st__50#entry2561924

Guy, are you running a secret new method of double posting? http://forum.avsim.n...50#entry2561924

 

No secret. Simply didn't remember that I had posted this already in the morning !

My excuses for the double post !

 

Guy

:lol: Ok, I was just wondering. You had my puzzled with that one. I first thought of an error in the Matrix.

@ WarpD

 

The way I understand it, Flight Envelope Protection - because that's what we are talking about in this thread - can save lives, and has done so:

 

The Hudson river Airbus A320 ditching would not have been successful (aka zero fatalities) if the crew were not backed up by the plane's Flight Envelope Protection that constantly, automatically, and without adding workload to the crew:

 

a. kept the plane level (no roll)

b. kept the plane (by gradually but continuously pitching up a bit) just barely above stall speed

 

These enabled the aircraft to come in contact with the water with:

 

1. Not too much downward speed element that would probably have cut the fuselage in two (cross-section of the "cut" somewhere around the back where its gets narrower -> most probably just behind the rear pressure bulkhead)

 

2. The least possible forward speed element

 

3. Give it a proper angle to allow the water to "lessen" the contact and absorb a big portion of the kinetic energy (due to the forward element of the speed)

 

Conclusion:

 

In any comparable (in size and weight) aircraft, without Flight Envelope Protection, some people (if not everybody) would have died at that incident.

 

 

 

PS: I'm not a pilot, just a civil engineer (specialized in transportation). That means, that I know (and can employ) common sense and common logic when I see it, and I can conclude 2 from 1+1.

(it also means that I know a few things about stresses, loads, etc.).

So when I see a revelant documentary (the equivalent air-crash investigation) with scientific evidence that gives me a and b, I can then conclude 1, 2 and 3.

 

I am also not a a really excited user.

 

And as a passenger, I will fly with anything from Airbus, with Boeings 7x7 (3<=x<=8).

 

I only avoid anything from McDonnell Douglas (except MD-11), and all former eastern block planes (Tupolev, Illushin, Yakovlev).

 

(for Embraers, Bombardiers and ATRs, I have not formed an opinion)