Preliminary Study of the Use of an Autothrottle to Improve The Throttles-Only Control Characteristics of a Twin Jet Transport Aircraft With Aft-Mounted Engines

摘要

In the case of total flight control system failure, engine thrust may be the only way to control an airplane. There is a large class of transport jet airplanes with the twin engines mounted on the aft fuselage. The techniques for controlling these airplanes with engine thrust (Throttles-Only Control (TOC) has been briefly studied. Because the engine thrust line is either at or above the vertical center of gravity for these aircraft, they require different techniques from the underslung engines configuration for TOC. The MD-90 is a relatively recent version of this class of aircraft, with high-bypass turbofan engines, a digital flight management system and a digital autopilot and autothrottle. A very brief first look at TOC in an MD-90 high-fidelity level D simulator in 1995 showed promising results. Therefore, a further study using a desktop simulation has been conducted to determine the TOC characteristics of the MD-90 and to investigate and develop methods for control sufficient for survivable runway landing. One promising method is to use the speed-hold autothrottle to stabilize and control the flightpath. Tests were flown for a no-flaps configuration at a speed of 200 and 220 kts, Flaps 15 at 155 kts, and Flaps 30 at 137 kts in this brief look at the concept.