Narrative:

We were descending using VNAV and LNAV; with the left autopilot engaged; from approximately 20000 ft to cross beano at 11000 ft and 250 KTS. Our speed was about 315 KTS. We were slightly above the descent profile; so the captain selected half or less than half flight spoilers. The drag on the aircraft felt unusual and the autopilot commanded a left turn to maintain wings level. The captain took control as the autopilot disengaged automatically. He maintained left aileron to keep the wings level and slowed the aircraft to 250 KTS. We had a spoilers light on the overhead panel and on the upper EICAS screen. The captain re-selected 50% spoilers and the asymmetry disappeared. He put the spoiler handle full forward (fully retracted) and the spoilers retracted symmetrically. We referenced the QRH; flight controls; but it did not apply. The captain flew the rest of the descent and approach with the autopilot off. We chose runway 08 as it's longer than runway 10. We did not arm the auto spoilers for landing but they did deploy properly when we went to reverse. At the gate; we talked to dispatch via phone to get them up to speed on the situation. San juan maintenance checked the spoiler computer and the autopilot computers. They told us the left autopilot indicated a fault.

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Original NASA ASRS Text

Title: B757 flight crew experienced asymmetrical spoilers during descent. When speed brake handle is stowed right spoiler panel remains up. Second attempt causes left spoiler to extend and both spoilers to retract when stowed.

Narrative: We were descending using VNAV and LNAV; with the left autopilot engaged; from approximately 20000 FT to cross BEANO at 11000 FT and 250 KTS. Our speed was about 315 KTS. We were slightly above the descent profile; so the Captain selected half or less than half flight spoilers. The drag on the aircraft felt unusual and the autopilot commanded a left turn to maintain wings level. The Captain took control as the autopilot disengaged automatically. He maintained left aileron to keep the wings level and slowed the aircraft to 250 KTS. We had a spoilers light on the overhead panel and on the upper EICAS screen. The Captain re-selected 50% spoilers and the asymmetry disappeared. He put the spoiler handle full forward (fully retracted) and the spoilers retracted symmetrically. We referenced the QRH; flight controls; but it did not apply. The Captain flew the rest of the descent and approach with the autopilot off. We chose Runway 08 as it's longer than Runway 10. We did not arm the auto spoilers for landing but they did deploy properly when we went to reverse. At the gate; we talked to Dispatch via phone to get them up to speed on the situation. San Juan Maintenance checked the spoiler computer and the autopilot computers. They told us the left autopilot indicated a fault.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.