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Operations Manual Bulletin
for
International Lease Finance Corp.
The Boeing Company Seattle, Washington 98124-2207
Number: ILF2-33(R2)
Date: April 1, 1999
Document Effectivity: D6-30151-425
Subject: UNCOMMANDED AUTOPILOT ENGAGEMENT, FLIGHT MODE CHANGES, AND IAS/MACH WINDOW SPEED CHANGES
Reason: To advise flight crews of the possibility of uncommanded autopilot engagement, flight mode changes, and IAS/Mach Window speed changes, and provide recommended temporary instructions for these situations. Revised for administrative purposes.
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.
THE FOLLOWING PROCEDURE AND/OR INFORMATION IS EFFECTIVE UPON RECEIPT
Background Information
UNCOMMANDED AUTOPILOT ENGAGEMENT AND FLIGHT MODE CHANGES
Boeing has received reports from operators of uncommanded autopilot engagement and flight mode changes. The reports document at least one rejected takeoff and one undesired heading change. Engineering investigation has determined these anomalies are caused by faulty MCP push-button switches installed during production or subsequent component repair. Intermittent switch malfunction can cause this anomaly without pilot action. The normal means for disengaging the autopilot, Autopilot Disengage Switches and the Autopilot Disengage Bar, are unaffected by this anomaly and operate normally.
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Operations Manual Bulletin No. ILF2-33(R2), Dated April 1, 1999 (continued)
UNCOMMANDED IAS/MACH WINDOW SELECTED SPEED CHANGES Boeing has also received reports from operators of unexpected transition from selected speed to 0.84 Mach upon multiple channel autopilot engagement during automatic approach, and upon autopilot disengagement. Under these conditions, the selected IAS/MACH Window speed changes to 0.84 Mach, requiring pilot intervention to regain airspeed control. Investigation has determined these anomalies occur only with older flight control computers (FCC S241T100-133 and earlier).
Operating Instructions
This bulletin does not apply to airplanes modified by SB 747-22A2214. UNCOMMANDED AUTOPILOT ENGAGEMENT
Flight crews should closely monitor PFD flight mode annunciations for autopilot status, and be prepared to respond to uncommanded autopilot engagement during critical phases of flight, including takeoff. Uncommanded autopilot engagement can be corrected by disengaging the autopilot.
UNCOMMANDED FLIGHT MODE CHANGES Flight crews should closely monitor PFD flight mode annunciations for autothrottle, roll, and pitch status, and be prepared to respond to uncommanded mode changes during critical phases of flight, including takeoff. Uncommanded flight mode changes can be corrected by selecting the desired mode on theMCP.
UNCOMMANDED IAS/MACH WINDOW SPEED CHANGES
Flight crews should closely monitor command speed on the PFD and be prepared to respond to uncommanded changes to 0.84 Mach under the following conditions:
1.
multiple channel autopilot engagement during automatic approach
2.
autopilot disengagement.
If the command speed changes to 0.84 Mach under either condition; disconnect the autothrottle, push the IAS/MACH Select Switch to change the IAS/MACH Window display to IAS, then set desired speed in the IAS/MACH Window. After resetting speed, the autothrottle may be reconnected.
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