Recently Douglas, in conjunction with Pratt & Whitney, formed an action team to address the dispatch reliability of MD-80 aircraft. The team focused specifically on hot starts, hung starts and slow engine acceleration. Several corrective actions have been proposed. They include installing the latest -15 fuel control unit, improved maintenance procedures, installing a new start bleed control valve, publishing All Operators Letters (AOL) from Pratt & Whitney and Douglas Product Support, and hosting an industry meeting to disseminate information. As part of that effort, this AOL provides flight crews with information regarding hot starts, hung starts and slow engine acceleration.

Some hot and hung starts may be prevented by strict adherence to the recommended start procedures in the Douglas FCOM. The following should be emphasized:

· Ensure maximum motoring speed is achieved before the fuel lever is mover to ON. Typical maximum motoring speed is 22 to 24 percent N2. This technique is especially important if the compressor is already warm from a previous operation.
 
· During quick turn-around, motor the engine to allow EGT to go below 100 degrees before the fuel lever is moved to ON.
 
· Allow engines to run at stabilized idle for a minimum of 5 minutes prior to shutdown.
 
· Observe the tail wind limits during start (20 knots maximum) to assure positive N1 rotation during start.
 
· Do not release the starter switch until 40 percent N2.
· Do not make bleed demands on an engine until it has achieved a stabilized idle.

Another area needing amplification is the rate of acceleration difference between engines. Factors which influence the acceleration rate are pilot technique, ambient conditions, bleed demands, bleed system configuration, variation in loading from pneumatics or hydraulics, and the fuel control idle trim setting.

An engine which exhibits noticeably slow acceleration with throttle advancement may indicate some abnormal condition. Normally, when throttles of properly trimmed engines are smoothly and simultaneously advanced to approximately 1.4 EPR, the engines should achieve a stable, spooled-up condition within three seconds of each other. Differences between engine acceleration rates greater than three seconds are not normal, and should be written up for appropriate maintenance action. These values are intended as guidelines, and are not operational limitations. Douglas suggests that flight crews advise maintenance of an observed discrepancy as soon as practical. Continue operation of the engine would then be at the discretion of maintenance, based on their analysis of all the information available. It should be noted that after achieving 1.4 EPR, both engines should accelerate equally to takeoff power.

Douglas does not plan an FCOM change, but operators may desire to add this information to their company manuals at their discretion.