videns
Posts: 132
Joined: Thu Mar 18, 2004 3:28 pm

Flight Surface Authority

Sun Oct 03, 2004 2:33 pm

What are the speeds at which flight surfaces start having an effect on an aircraft?
eg: when an airplane is taxiing, none of the flight surfaces have any effect on what the airplane does...
Any flight surface/aircraft combination info appreciated...
Travel? Why would i travel if I can watch it on TV?
 
Woodreau
Posts: 1331
Joined: Mon Sep 24, 2001 6:44 am

RE: Flight Surface Authority

Sun Oct 03, 2004 3:57 pm

I think it depends on the airfoil design.

There are gliders when sitting on the ground, hooked up for aerotow, the ailerons are fully effective and can be used to keep it upright when a good 5-10kt breeze blows across wings.

Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
 
wilco737
Posts: 7275
Joined: Sun Jun 20, 2004 12:21 am

RE: Flight Surface Authority

Sun Oct 03, 2004 7:18 pm

hi Videns,

during take off roll u use the rudder pedals to keep the aircraft on the centerline. This happens because the nose wheel is connected to the rudder pedals and you have a steering angle of about 3.5° in each direction! At about 60-80 kts the rudder on the tail is effective that you can hold the aircraft on the centerline only with the aerodynamic forces of the rudder! So, you can say at about 60-80 kts the filght controls become effective...

WILCO737
 
FredT
Posts: 2166
Joined: Thu Feb 07, 2002 9:51 pm

RE: Flight Surface Authority

Mon Oct 04, 2004 3:35 am

They don't become effective at one defined airspeed. They are effective in proportion to the dynamic pressure, which is proportional to the airspeed squared. At a very small airspeed, they are effective but perhaps not effective enough to control the aircraft, depending on what you do. At twice that airspeed, they are four times as effective... which might just be enough.

It is like asking "at which temperature does cold water turn into warm water". There's no answer as it all depends on what you are trying to use it for!

Regards,
Fred
I thought I was doing good trying to avoid those airport hotels... and look at me now.

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