Steep-Descent Manoeuvre of Transport Aircraft


Journal of Aircraft book cover

A Filippone
Journal of Aircraft
Sep 2007

This paper solves the problem of steep descent of jet-powered transport aircraft. The cases considered involve a continuous descent approach. Steep descent is interpreted as a flight path with glide slope up to 5.5 degrees. Several requirements are discussed in detail; these include safety limits, stall control and noise emission. First, parametric analysis of the aerodynamic coefficients are shown to indicate where existing aerodynamic data would fail to achieve a steep descent. Second, flight trajectories are calculated as a two-value boundary value with constraints on the terminal descent rate, on the air speed, and the lift coefficient. The effects of landing weight, starting altitude, and a relax on the terminal constraint are simulated. Third, parametric changes in the aerodynamic polar and drag are proposed to accommodate changes required in the flight controls. Fourth, a noise model of the aircraft is presented, and calculations are performed at the reference flight paths to verify whether the overall sound pressure level at a reference point (FAR Part 36) is below the noise at the nominal flight path. The aircraft simulated is the Airbus A-310-200 with CF6-80C2 engines. It is concluded that: 1.) the highest descent angle for this aircraft is about 4 to 4.5 degrees; 2.) a steeper descent can be achieved with an increase in both the maximum lift and the zero-lift drag, with the condition that C_D/C_L^1.5 also increases; 3.) noise is reduced by up to 6dB, mostly due to the larger distance from the receiver; 4.) the maneuver time is reduced by up to 60 seconds.