Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Question About 744 Ailerons Locking  
User currently offlineRichiemo From United States of America, joined Jul 2008, 222 posts, RR: 0
Posted (4 years 8 months 3 weeks 6 days 9 hours ago) and read 6706 times:

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.

10 replies: All unread, jump to last
 
User currently offlineJetMech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 1, posted (4 years 8 months 3 weeks 6 days 7 hours ago) and read 6596 times:

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]


JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineTranspac787 From United States of America, joined Jul 2007, 3214 posts, RR: 13
Reply 2, posted (4 years 8 months 3 weeks 6 days 7 hours ago) and read 6572 times:

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.


User currently offlineAA737-823 From United States of America, joined Mar 2000, 5873 posts, RR: 11
Reply 3, posted (4 years 8 months 3 weeks 3 days 6 hours ago) and read 6119 times:

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!


User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9666 posts, RR: 52
Reply 4, posted (4 years 8 months 3 weeks 2 days 10 hours ago) and read 6014 times:



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!
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 5, posted (4 years 8 months 3 weeks 1 day 20 hours ago) and read 5889 times:



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.


User currently offlineworkhorse From France, joined Jul 2005, 219 posts, RR: 0
Reply 6, posted (1 year 4 months 1 week 18 hours ago) and read 2438 times:

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"?


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17068 posts, RR: 66
Reply 7, posted (1 year 4 months 1 week 15 hours ago) and read 2345 times:

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."
User currently offlineCCA From Hong Kong, joined Oct 2002, 838 posts, RR: 14
Reply 8, posted (1 year 4 months 1 week 12 hours ago) and read 2268 times:

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]


C152 G115 TB10 CAP10 SR-22 Be76 PA-34 NDN-1T C500 A330-300 A340-300 -600 B747-200F -200SF -400 -400F -400BCF -400ERF -8F
User currently offlineworkhorse From France, joined Jul 2005, 219 posts, RR: 0
Reply 9, posted (1 year 4 months 6 days 17 hours ago) and read 2061 times:

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?


User currently offlineCCA From Hong Kong, joined Oct 2002, 838 posts, RR: 14
Reply 10, posted (1 year 4 months 6 days 10 hours ago) and read 1985 times:

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.



C152 G115 TB10 CAP10 SR-22 Be76 PA-34 NDN-1T C500 A330-300 A340-300 -600 B747-200F -200SF -400 -400F -400BCF -400ERF -8F
Top Of Page
Forum Index

Reply To This Topic Question About 744 Ailerons Locking
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Question About Aircraft Generators posted Wed Nov 25 2009 23:07:34 by N612ua
A Little Question About Engine posted Tue Sep 15 2009 01:15:10 by Alphafloor
Quick Question About The Taxi Stage Of Flight. posted Fri Jul 31 2009 02:11:44 by Tesko
Question About Being An Airline Dispatcher posted Sun Jun 28 2009 14:02:16 by N612ua
Technical Question About Cockpit In General posted Mon May 25 2009 10:40:50 by Flaps30
Question About 727 Nose posted Wed May 20 2009 19:32:18 by DreamsUnited
Question About A320 Series Wing posted Tue May 19 2009 19:20:41 by Teo747
Question About SQC7334 ORD-DFW 09MAY09 posted Sat May 9 2009 20:59:03 by DescendVia
Question About The Thrust Reverse posted Wed May 6 2009 20:10:24 by Vietsky
Question About Diversions. posted Sun Apr 19 2009 12:32:18 by Braniff747SP

Sponsor Message:
Printer friendly format