Aerodynamic and Performance Analysis of Ground Spoilers on the Flying V

Abstract

Optimal design of a lift dumping assembly (LDA) has been found utilizing a gapped spoiler design that consists of two separate surfaces that are placed at 0.06b-0.17b and 0.28b-0.038b spanwise locations. The gapped design allows the cross flow amplified at the hingeline of the inboard spoiler to escape through the middle gap increasing the lift dumping per area efficiency of the design by 44% while only reducing lift dumping by 4.6% compared to the full spoiler span configuration. LDA spoilers reach a projection height of 8.7% local chord and the hingeline is placed at 80% local chord. With this combination of projection height and chordwise location, there are no occurrences of adverse lift phenomena. Other tested spoilers that are either smaller in chord length, deflection angle or placed such that it is submerged in the boundary layer have shown to increase the lift coefficient at angles of attack relevant to touchdown, 17 degrees. Control surfaces are integrated within the LDA given the spoilers do not heavily influence the authority of the control surfaces. The ground roll performance of the Flying without the LDA is already comparable to a B747-400 using spoilers. At the point of operation where ground roll is maximized, namely forward center of gravity and maximum landing weight, the Flying V can come to a stop from touchdown in 1300 m and 28.4. Introducing the LDA to the Flying V is less effective than introducing spoilers to a B747-400 as the Flying V does not have any lift from flaps that the LDA can spoil. Nonetheless at typical runway conditions LDA reduces the total ground roll by 95 m. The significance of dumping lift is amplified for adverse runway conditions as 130 m in wet runways and 500 m in icy conditions can be gained using the LDA. At 17 degrees touchdown angle of attack the LDA only uses the spoiler to create a slight nose down moment of -0.0069 to help derotate the aircraft. Furthermore the LDA can be directly deployed at touchdown to decrease the lift coefficient by 0.057 which is approximately equal to decreasing the angle of attack by 1.5 degrees on the clean aircraft reducing the possibility of a bounce-off. At braking attitude of -2.5 degrees angle of attack, control surfaces join the spoiler in lift dumping. In this case the LDA reduces the lift coefficient by 0.21 and increases the drag coefficient by 0.028.