Flight tests on a falcon with spoiler lateral control

Abstract

As part of a general investigation of tile use of spoilers for lateral control, flight tests were required on a Falcon with retractable circular-arc spoilers. In the first stage of the flight tests pilots' impressions and criticisms of response and stick feel were recorded and used as a basis for improving the,control. These tests were made at various speeds, flaps up and flaps down. In the second stage, after improving the control, flight tests were made with full-span flap in operation and landings were made with flap fully down. Finally, some measurements were made of time to bank at various speeds with-out flap and with flap fully down. By reducing the area of the top surface of the spoiler to a minimum and constructing it in the form of a cylindrical arc concentric with its hinge, a spoiler has been produced with zero aerodynamic hinge moment and no tendency to suck out of the wing surface. Provided that the inertia of the spoiler and the friction and backlash in the control circuit are reduced to a small amount pilots do not appear to find the resulting stick feel objectidnable after a little experience. The spoiler provides good response at cruising speeds and rapid though less even response at high speed. At low speed without flaps the response is poor. With a full-span split flap giving a CL MAX of 2.25 it is very good. For an aircraft fitted with full-span split flap, this type of spoiler appears to offer a satisfactory form of lateral control. There is no evidence of any time lag in response with these spoilers. Response for small control movements is not good at any speed, but at high speed the contrast between the initial stage of comparatively slow response and the succeeding stage of rapid response appears to become more marked, with the result, that when the control is applied in a normal manner the main response does not occur until the stick has been displaced somewhat. This effect is sometimes mistaken for time lag.