madog From Australia, joined Nov 2000, 87 posts, RR: 0 Posted (1 year 3 months 6 days 5 hours ago) and read 3857 times:
During final approach, I've noticed that in all of the 777s that I've flown in the past several years that the outer ailerons deflect upwards. It may be a stupid question, but why is that? I though the outer ailerons were supposed to give better handling when the aircraft is at low speeds i.e take off and approach. when it is deflected upwards does it suppose to give some kind of special handling quality????
Chimborazo From United Kingdom, joined Sep 2011, 64 posts, RR: 0 Reply 1, posted (1 year 3 months 5 days 23 hours ago) and read 3661 times:
I'm by no means an expert on the 777 flight controls but I should imagine each time you were landing in a cross-wind so a little aileron was being used. I presume you couldn't see out the other side and that the other aileron was down a little?
Roseflyer From United States of America, joined Feb 2004, 8740 posts, RR: 52 Reply 2, posted (1 year 3 months 5 days 19 hours ago) and read 3538 times:
I am not sure what you are seeing. What you are saying that you see is actually opposite of what the airplane does. When the flaps are deployed, the outboard aileron droops 8 degrees trailing edge down. The droop is automatic. The only way that they would not droop is if the airplane is approaching above recommended speed which results in the droop being removed so that the airplane will pitch up and slow down.
You could be seeing the autopilot reacting to a cross wind, but that wouldn't result in a continuous upward position of the aileron.
If you have never designed an airplane part before, let the real designers do the work!
CM From , joined Dec 1969, posts, RR: Reply 4, posted (1 year 3 months 5 days ago) and read 3237 times:
Quoting CXB77L (Reply 3): I think this might be what the OP is referring to:
I believe what you are seeing in these photos are evidence of roll command, and the opposite wing would not look the same. This is particularly true for the top photo, as the flaps are already at a high setting, which causes the ailerons on both sides to droop - this is true for all 777 models.
DocLightning From United States of America, joined Nov 2005, 16819 posts, RR: 57 Reply 6, posted (1 year 3 months 4 days 15 hours ago) and read 3099 times:
Quoting Roseflyer (Reply 2): You could be seeing the autopilot reacting to a cross wind, but that wouldn't result in a continuous upward position of the aileron.
Because the flight path is still coordinated (not in a slip or skid condition) all the way down final. The only time it gets uncoordinated in a crosswind is when the crab is taken out with the rudder, and this part requires opposite aileron.
madog From Australia, joined Nov 2000, 87 posts, RR: 0 Reply 8, posted (1 year 3 months 4 days 1 hour ago) and read 2966 times:
I know that the outer ailerons are designed to droop down as a function of flap setting. during my last three landings sitting on either side if the 777-300ER in the last month I have seen the same thing happening. at full flaps the outer alerion deflect upwards, although it does move a bit what I saw was that it never went into downwards position during the last two flap settings. I Will take a video the next time I fly in a few eeks time to show what I exactly mean.
OldAeroGuy From United States of America, joined Dec 2004, 3206 posts, RR: 66 Reply 9, posted (1 year 3 months 3 days 2 hours ago) and read 2716 times:
Quoting CM (Reply 4): This is particularly true for the top photo, as the flaps are already at a high setting, which causes the ailerons on both sides to droop - this is true for all 777 models.
The outboard ailerons droop at takeoff flap settings for the 777. At landing flap settings, they are not drooped.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
mandala499 From Indonesia, joined Aug 2001, 6180 posts, RR: 74 Reply 10, posted (1 year 3 months 3 days ago) and read 2688 times:
Quoting CM (Reply 4): I believe what you are seeing in these photos are evidence of roll command
By that deflection, the roll spoilers should be playing a bit. If there is a little play in the roll spoilers, then it should be a roll command.
I've seen this on the 320, on final approach, both ailerons deflect upwards slightly. I can't remember seeing that on the 777 but then, I could be wrong!
When losing situational awareness, pray Cumulus Granitus isn't nearby !
Because an upward aileron (assuming the other side isn't up as well) imparts a roll moment to the airplane. To make a turn in an airplane, you turn the controls in the desired direction until you get the angle of bank you want, then return them to center (in reality, you have to fiddle a little bit due to various aerodynamic factors, but you're not holding nearly as much control pressure once you've established a bank as you do in order to establish that bank).
In a steady crosswind, you'd see a deflection of the ailerons as the crab angle was established, then they would return to center until it was time to take out the crab again just prior to touchdown.
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