This bulletin provides information informing flight crews of temporary recommended procedures for descent planning.
Recent test cell and inflight testing have revealed a potential for engine surges following rapid, re-application of full power after several minutes operation at minimum idle. Further, ground and flight testing have shown no occurrence of this anomaly when inflight engine idle is limited to approach idle. This condition has not been reported by any operator as an in-service problem.
When Boeing Service Bulletin 767-73-0033 is incorporated, the engine fuel control system limits the inflight idle to approach idle, This change affects the FMC descent forecast which must be modified by the crew prior to descent. There is no impact on takeoff or landing performance and a small change in trip fuel.
Boeing Service Bulletin 767-73-0041 enables returning to inflight idle settings.
To assist in forecasting an accurate descent path in-flight, 30 minutes, or not less than 50 miles, prior to top of descent, the flight crew should enter on the Descent Forecast Page on the FMC, a TAI/ON altitude equal to the top of descent altitude until Boeing Service Bulletin 767-73-0041 is incorporated.
This Operations Manual Bulletin will be canceled after Boeing is notified that all affected airplanes in the operators fleet have been modified by Boeing Service Bulletin 767-73-0041.