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Old 5th Nov 2009, 10:26
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Hogg


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Join Date: Oct 1997
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perfectly normal

This takeoff seems perfectly normal at what may have been a max xwind (wet) windspeed.Roll spoilers are interconnected with the ailerons, so as to perform in harmony with them. In many aircraft roll spoilers deploy as a function of airspeed.
The reason roll spoilers are often required on high-speed aircraft is because they operate across such great speed ranges — such planes must resolve high-speed aerodynamics with the slow flight required for safe takeoffs and landings. Planes fly fastest with small, thin wings and high wing loading. Safe take-offs and landings, on the other hand, require high-camber, high-lift wings, with low wing loading. In essence, two different airplanes are required: one that can go fast, and one that can get everybody off the ground in less than ten miles of runway!
This challenge is resolved through extensive use of big flaps and leading edge devices (LEDs) which effectively convert the wing from a high-speed shape to a low-speed, takeoff-and-landing shape. The problem is that in order to make wing size (and drag) small for optimum cruise speeds, the flaps must extend across as much of the wingspan as possible for adequate low-speed effectiveness. With all those flaps installed, there’s little room left on the wing for ailerons. Small ailerons may be fine for high speed cruise, but they’re often too small for adequate roll response at low airspeeds, like when taking off and landing. One solution to this problem is to put multiple ailerons on each wing, separately activated as a function of airspeed. The other solution is to install roll spoilers to help the ailerons. (The Boeing 767 utilizes roll spoilers AND two ailerons per wing — the outboard ones are locked above 240 kts).
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