Ual747 From , joined Dec 1969, posts, RR:
Reply 3, posted (11 years 8 months 3 weeks 6 days 8 hours ago) and read 7007 times:
From what I understand, as the plane reaches a certain speed, the ones with inboard and outboard ailerons, the outboard ailerons lock into position and the plane is completely controlled by the inboard ailerons. The flapping motion you see on approach is the inboard ailerons reacting to the manuevers the pilot is making with the stick. If you look closely, at slower speeds, the outboard and inboard ailerons work together.
Anyway, think about it...balance a pencil or a rod on the top of your finger, it takes more energy to tilt the rod to the left or right if the pressure is being applied closely to the finger the rod is balanced on. Now, move your finger one end of the rod, either left or right, and you will find it takes less energy to tilt the rod. It's all about leverage. When the plane is at cruising speed, using the inboard ailerons gives the pilot a less-sensitive, smoother banking methods.
However, inboard and outboard ailerons are not on all aircraft. In the Boeing line, the 727, 747, 767, and 777 all have inboard and outboard ailerons. (Not sure about the 707). The DC-10, and MD-11 have both as does the L-1011. AFAIK, NONE of the airbus products have inboard ailerons except for the A300/310 you show in your picture.
Hope you can understand what I wrote. It's hard to explain, and it's late, so I'm sure I made absolutely no sense whatsoever.
Klaus From Germany, joined Jul 2001, 21652 posts, RR: 53
Reply 5, posted (11 years 8 months 3 weeks 6 days 1 hour ago) and read 6915 times:
Ual747: AFAIK, NONE of the airbus products have inboard ailerons except for the A300/310 you show in your picture.
The FBW models don´t need it. Sidestick deflection has no direct connection to the position of the control surfaces (except in "direct law" on the ground or in an emergency). Instead, it requests a certain acceleration in the indicated direction which is simply satisfied by a smaller deflection of the outboard ailerons at high speed.
The 777 which basically emulates a conventional mechanical control setup with its FBW system still does have separate high and low-speed ailerons as far as I know.
AJ: Interestingly the A300-600R as pictured does not use outboard ailerons at all, same with the A310.
They should be operational at lower speeds. Maybe you just didn´t happen to recognize any major deflection after takeoff or during approach.
ChallengerDan From Canada, joined Sep 2003, 173 posts, RR: 0
Reply 7, posted (11 years 8 months 3 weeks 4 days 22 hours ago) and read 6781 times:
Actually, I think the manufacturers were more concerned about wing twisting moment caused by outboard ailerons than smoothness and sensitiveness for the pilots. That explains why a319 and up don't have them. The software keeps the twisting moment within acceptable levels. That rod analogy is good, only you got it backwards: it's not the load needed to input the movement to the rod that they are concerned with, it's the load the rod actually has to withstand. Don't want to get too technical on this, but a low speed aileron makes it possible to keep the structure near the wing tip lighter. On the airbus, the software does that job by keeping aileron movement to a minimum. no idea why Boeing didn't do samething with 777 since it is fly by wire too... maybe it has something to do with the way the back-up or emegency system works...
if your flight goes MX in YUL, I might be called to fix it!
Pilotaydin From Turkey, joined Sep 2004, 2561 posts, RR: 48
Reply 10, posted (11 years 8 months 3 weeks 4 days 18 hours ago) and read 6691 times:
hey guys, i have an old united 744 manual given to me by a captain when i was in school. I read the chapter on flight controls and it said there is an automatic switching between the inboard and outboard use at 235 KIAS.
I dont know where that manual is now, so i can't contribute anymore
nice to be new to this forum!
The only time there is too much fuel onboard, is when you're on fire!