richiemo
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Question About 744 Ailerons Locking

Fri Jan 29, 2010 3:47 am

Gang, I've heard two versions regarding the 744 ailerons. One says the outboard ailerons lock up once the aircraft reaches a higher speed, (with the aircraft then relying only on the inboard ones.) Another version says the outboard ailerons lock up once the flaps are fully retracted regardless of aircraft speed. Anyone know which version is true.
 
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jetmech
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RE: Question About 744 Ailerons Locking

Fri Jan 29, 2010 6:03 am

Quoting Richiemo (Thread starter):

I think the second one is true, but I do recall some pilots mentioning that there is an input based on speed as well. The outboard aileron lock-out actuator receives signals from the flaps, and locks out the control inputs to the outboard aileron PCU when the flaps are fully retracted.

According to this link, the 747 classic aileron lockout is based on flap position only, whereas the 744 aileron lockout is also based upon an airspeed signal.

http://www.pprune.org/archive/index.php/t-177401.html

Page two of the following document has a schematic of the overall system.

http://www.ntsb.gov/Recs/letters/1998/A98_6.pdf

Regards, JetMech

[Edited 2010-01-28 22:16:55]
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Transpac787
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RE: Question About 744 Ailerons Locking

Fri Jan 29, 2010 6:22 am

Both are true, in a sense.

Anytime the flaps are out of the "UP" detent, the outboard ailerons are unlocked. Also, anytime the airplane is slow the outboards are also unlocked. The exact speed is something really bizarre, like 234 KIAS or so. As always though, there are a few caveats to both of those rules, like on a speed-limited departure procedure (HKG is a good example) the 744 may need to leave Flaps 1 down for most of the DP. However, once the aircraft accelerates above 234 (or whatever it is), the outboard ailerons lock anyway, despite the flaps being out of the "UP" detent.
 
AA737-823
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RE: Question About 744 Ailerons Locking

Mon Feb 01, 2010 7:13 am

On the classic, it was a function of trailing edge flap position, as I recall.

I was, before fifteen seconds ago, unaware that the -400 had an airspeed input into the logic as well.

The 747-8 will have fly by wire ailerons, so I guess ALL of this stuff is about to change!
 
roseflyer
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RE: Question About 744 Ailerons Locking

Tue Feb 02, 2010 3:22 am



Quoting AA737-823 (Reply 3):

The 747-8 will have fly by wire ailerons, so I guess ALL of this stuff is about to change!

What? That's news to me if they changed it. Primary flight controls are still the same traditional system as far as I know.
If you have never designed an airplane part before, let the real designers do the work!
 
tdscanuck
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RE: Question About 744 Ailerons Locking

Tue Feb 02, 2010 5:02 pm



Quoting RoseFlyer (Reply 4):
What? That's news to me if they changed it. Primary flight controls are still the same traditional system as far as I know.

The ailerons have been FBW for some time; AvWeek was talking about it at least as far back as April 2008:
http://www.aviationweek.com/aw/gener...?channel=comm&id=news/OUT04118.xml

Tom.
 
workhorse
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RE: Question About 744 Ailerons Locking

Sun Jun 16, 2013 7:22 pm

Quoting Transpac787 (Reply 2):
Anytime the flaps are out of the "UP" detent, the outboard ailerons are unlocked. Also, anytime the airplane is slow the outboards are also unlocked. The exact speed is something really bizarre, like 234 KIAS or so.


Hello everybody, well, I know this thread is very old but since I'm allowed to write into it, I prefer doing that instead of starting a new one, hopefully the participants are still around or other people in the know...

Quoting Transpac787 (Reply 2):
As always though, there are a few caveats to both of those rules, like on a speed-limited departure procedure (HKG is a good example) the 744 may need to leave Flaps 1 down for most of the DP. However, once the aircraft accelerates above 234 (or whatever it is), the outboard ailerons lock anyway, despite the flaps being out of the "UP" detent.

How is that achieved exactly? Is there some button that says : "Ignore the flap setting, just follow the airspeed"?

And another question, how does this system behave in the case of loss of airspeed indications (a la AF447). Following the logic, the outboard flaps will be unlocked, but that's probably not what you want when flying Mach .88 at FL380... So, what to do in this case? Is there another button that says: "Ignore the airspeed, just follow flap settings"?
 
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Starlionblue
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RE: Question About 744 Ailerons Locking

Sun Jun 16, 2013 10:08 pm

Quoting workhorse (Reply 6):
How is that achieved exactly? Is there some button that says : "Ignore the flap setting, just follow the airspeed"?

Transparent to the pilots I would guess. The Air Data Computer figures out that the airspeed (EAS I would guess) is above a certain number and locks out the outboards.

[Edited 2013-06-16 15:11:34]
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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CCA
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RE: Question About 744 Ailerons Locking

Mon Jun 17, 2013 1:14 am

The O/B ailerons lock when the group A leading edge flaps are retracted AND the aircraft is above either 238kts or .53M

They unlock when the group A leading edge is not retracted (ie in transit still unlocks them) OR the speed is below 232kts or .51M

Simply put the Leading edge flaps control the lock and unlock unless the A/C is clean (flaps up) and flying slow (ie lightish weight eg 240T).

[Edited 2013-06-16 18:22:46]
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workhorse
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RE: Question About 744 Ailerons Locking

Mon Jun 17, 2013 8:25 pm

Quoting CCA (Reply 8):
The O/B ailerons lock when the group A leading edge flaps are retracted AND the aircraft is above either 238kts or .53M

They unlock when the group A leading edge is not retracted (ie in transit still unlocks them) OR the speed is below 232kts or .51M

Oh, thanks, that's very precise, just what I was looking for!

Now, as my second question says, what if, when you are in cruise at FL380 and Mach 0.88 and then suddenly the IAS drops to 0? The outboard ailerons will be unlocked, right? So, what to do?
 
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CCA
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RE: Question About 744 Ailerons Locking

Tue Jun 18, 2013 2:48 am

I doubt you'd care much about the aileron lockout and you'd be concentrating on the fact you had unreliable airspeed and follow the checklist.

By coincidence you would unknowingly be following the aileron lockout checklist which states avoid large and abrupt control wheel inputs.
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