Low-speed wind-tunnel tests of the longitudinal stability characteristics of some swept-wing quiet airbus configurations

Abstract

Measurements of lift, drag and pitching moment have been made on model configurations representing rear-engined layouts, with large nacelles so positioned that both wing and tailplane will make a contribution to noise shielding. Only round nacelles were used with a high-wing model but both round and flat types of nacelle were tested on a low-wing model. The investigation concentrated on the effects of the large lifting surfaces of the nacelles on the longitudinal stability and performance under the high-lift conditions appropriate to take-off and landing; the nacelles were not powered so the influence of the jet efflux was excluded. The results show that the influence of the nacelles on the downwash at the tailplane is such as to offset the lift losses and longitudinal stability changes incurred by adding the nacelles to models without tailplane; so that for the complete models the stability changes were small, and the effects on performance only became appreciable when the fiat nacelles were tilted several degrees nose down with a landing-flap setting. Included in the test programme were measurements of the distribution of total head at a hypothetical engine face inside the round nacelles for a number of model configurations and conditions.