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D6-27370-866-EGP B-28 Page 1 of 4
CoversFile HighlightReduced Engine Respo nse TimesEGP-28
Flight Crew Operations Manual Bulletin
for
Egyptair
Number: EGP-28 R1
IssueDate: January 9, 2015
Subject: Reduced Engine Response Times
Reason: This bulletin informs 737NG flight crews of slow engine acceleration
following thrust reduction at cruise altitude due to a recent EEC
software update. The bulletin provides suggested techniques to help
prevent excessive airspeed loss.
This bulletin has been revised to provide CFMI Service Bulletin
information for EEC software version 7.B.W.
THE FOLLOWING PROCEDURE AND/OR INFORMATION IS EFFECTIVE UPON RECEIPT
Background Information
Boeing has received pilot reports of slow engine acceleration at high altitudes
(above FL300) which have resulted in airspeed losses as high as 20 to 30 knots.
These reports indicate the events have occurred after thrust is reduced and
immediately re-applied. When an airplane experiences an abrupt airspeed
increase at high altitude, as might be experienced when encountering a mountain
wave, the engine will decelerate to a lower N1 and take longer to accelerate back
to full or normal power than is desired.
Analysis of these reports indicates that this is related to the Electronic Engine
Control (EEC) software revisions 7.B.U1 and 7.B.V2. Revision 7.B.U1 reduced
the engine deceleration and acceleration rates for specific thrust lever transients
at high altitude. Revision 7.B.V2 returned the deceleration rate back to normal
but retained the reduced acceleration rate. Both versions of the EEC software
reduce engine acceleration rate if the throttles are in idle for less than 60 seconds.
Slowing the acceleration rate of a heat soaked engine improves engine
operability (stall margin) characteristics.
The Boeing Company
Seattle, Washington 98124-2207
Information in this bulletin is recommended by The Boeing Company, but may not be FAA approved
at the time of writing. In the event of conflict with the FAA approved Airplane Flight Manual
(AFM), the AFM shall supersede. The Boeing Company regards the information or procedures
described herein as having a direct or indirect bearing on the safe operation of this model airplane.
September 24, 2015
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