Investigation of the dynamic response of aircraft to microburst (JAWS) wind shear

A derivation of the governing equations of aircraft motion in variable wind field results in additional wind shear terms appearing in the force equations. Computer simulations of B727 type aircraft flying (landing and taking off) through the microburst (JAWS) wind shear data have been carried out and are in good agreement with those of the NASA/ Ames B727 piloted simulator.

The critical penetration heights through the center of the microburst are determined by computing the aircraft trajectory deviations from the intended flight path at the ILS Category II decision height window. It is found that the higher the magnitude of the wind gradient terms, the more influence they have on the aircraft performance, especially on sideslip angle, angle of attack, and rolling moment. However, the maximum magnitude of the wind gradients in JAWS August 5, 1982, microburst data is about 0.03 s^{-1. The wind shear effects on three generic types of aircraft, a three-engine passenger airliner (PA), a twin-engine STOL (STOL), and an executive jet (EJ), are also investigated in this study. In the simulation of the aircraft flying through a microburst center along the intended path AB at a height of 820 feet, the maximum trajectory deviations from the glide slope are 350 feet, 200 feet, and 100 feet for the PA, EJ, and STOL type airplanes, respectively. Large jet aircraft experience greater difficulty in flight through a microburst wind shear field than smaller aircraft.}

It is recommended that a turbulence model to supplement the JAWS wind field be developed, and the flight simulator computer programs be updated to incorporate the additional wind shear terms into the equations of vehicle motion. Finally, the influence of time variations of the JAWS wind shear on the aircraft performance is investigated.