The Delco Performance Management System

Abstract

i. I N T R O D U C T I O N Since the early nineteen-seventies, when the price of fuel went up so dramatically, airlines have been seeking methods of saving fuel. Climb, cruise and descent speeds were refined to give the most economical operation. Advisory systems came on the market, but these did little more than give crews information which could be obtained from operations manuals. Then equipment such as performance management systems (PMS) and flight management systems (FMS) was produced. The potential of these systems can be measured by the number of airlines who have purchased the equipment, and also by the fact that most of the new generation of aircraft are being built with PMS as part of the standard aeroplane.Since taking delivery of the first DC 10-30 in 1977, British Caledonian has studied various fuel-saving devices. It was stipulated that a suitable system for a long-range aircraft should satisfy two basic requirements:(1) it must be able to control the auto-throttle system;(2) as the majority of time is spent on the cruise, it must also be capable of saving fuel during this phase of the flight profile as well as saving fuel on the climb and descent.This paper describes the operation of the Delco PMS system and the results achieved. Principally, it highlights the importance of training. Without thorough training this equipment cannot realize its full potential. 2. DESCRIPTION OF THE E Q U I P M E N T . The Delco DC 10 PMS (Fig. i)consists of three line replaceable units: the control display unit (CDU) ; the computer unit (PMCU); the switching unit (swu). The PMS, in conjunction with the flight guidance system (FGS), controls pitch and thrust throughout the flight. This ensures maximum efficiency of fuel usage within the constraints of the flight plan, altitude clearance and aircraft performance limits.Without PMS, the auto-throttle system of the DC 10 is not as efficient as one would wish. First, the tolerances are very wide. Secondly, since the auto-throttle can only react to something that has already taken place, changes in speed due to atmospheric variations result in excessive movement of the throttles. In order to overcome this in the cruise, the response is damped to give a brief settling-down period prior to any throttle movement being made. This results in a tendency to cruise too fast. Furthermore, changes of speed due to changes of wind, pressure and temperature vary the drag of the aircraft, and this accentuates the power response necessary to restore the status quo. 413