Lift, and pitching moment measurements on an EC 1240 tailplane elevator at high speeds with elevator gap sealed

Abstract

Previous measurements at high speeds made in the 12-in. Circular High Speed Tunnel of the lift, drag and pitching moment for an aerofoil with elevator have now been repeated for lift and moment with the gap between aerofoil and elevator sealed. It was found previously that there was no serious loss of control until a Mach number of M = 0.75 to 0.78 was reached and this result has now been found to hold good for the 'gap sealed' condition. Above M = 0.78 the control falls rapidly, reaching one half its low-speed value at about M = 0.81. This result holds good whether the gap is sealed o rnot. With the gap unsealed, a2 was practically independent of Mach number at a value 3.0 from M = 0.45 to 0.73 ; with the gap sealed the value of a2 approximated to the value 3.6/~/(1 - M2), following the Glauert formula, over the range M = 0.4 to 0.7. The effect of sealing the gap is to increase a2 by 40 per cent. at M = 0.4 and 60 per cent. at M = 0.7.