This bulletin provides information informing flight crews of temporary recommended procedures for inadvertent inflight deployment of the spoilers.
Service experience has show when extending flaps to 25 or 30, a spoiler may extend. Pilot reports and flight data recorder information indicate spoiler extension is evident by uncommanded airplane roll, and by the requirement to maintain control wheel displacement for a sustained period to counteract the roll. Pilots have also reported spoiler extension is accompanied by the SPOILERS EICAS advisory message and the SPOILERS light on the overhead panel. Spoiler extension may occur with the speedbrakes lever in the DOWN or ARMED detent. Reports and flight recorder data indicate that retracting the flaps to 20 allows the extended spoiler to retract.
Spoiler panels are held in the down position by hydraulic pressure in the spoiler panel hydraulic actuator. Leaking hydraulic actuator seals may cause a pressure drop in the actuator, allowing air loads at flaps 25 and 30 to lift the spoiler panel up. There are no mechanical means to lock spoiler panels in the down position. Extension of flaps early in the approach will provide added time for recognition and action.
If, upon selection of flaps 25 or 30, the SPOILERS EICAS message is observed, uncommanded airplane roll is encountered or sustained control wheel displacement is required, immediately retract flaps to 20 and use flaps 20 and Vref 20 for landing. Select the Ground Proximity Flap Override Switch to OVRD.
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 757-27A0105.