B737-800 flight crew was dispatched with engine anti-ice valve stuck in the open position per MEL 30-3B. However; maintenance failed to deactivate high stage bleed valve as required by MEL. Cowl anti-ice light illuminates after takeoff and crew returned to departure airport for over weight landing.
Synopsis
B737-800 flight crew was dispatched with engine anti-ice valve stuck in the open position per MEL 30-3B. However; maintenance failed to deactivate high stage bleed valve as required by MEL. Cowl anti-ice light illuminates after takeoff and crew returned to departure airport for over weight landing.
Narrative
Before departure; we had a #1 engine anti-ice valve stuck in the open position. Maintenance then deferred this item per 30-3B of the MEL; which specifies that the associated high stage bleed valve must also be locked closed. I assumed it was done since the Mechanic balanced our write-up by saying that the maintenance procedure per MEL item 30-3B had been complied with; but did not specify also deactivating the high stage bleed valve. After takeoff; the amber #1 'Cowl Anti-ice' light illuminated. The QRH checklist was completed; and the light extinguished with a reduction of the #1 thrust lever. Being unable to continue I elected to return. Although we were approximately 5000 LBS over max landing weight; I decided to land immediately due to concern over the bleed overpressure event with the valve; thunderstorm activity in the terminal area; and the difficulty in burning fuel down due to the reduced power on the one engine. We declared an emergency with approach for the overweight landing.
Second reporter narrative
Prior to departure we wrote up the left engine anti-ice valve stuck open and maintenance performed their procedure and signed it off. After takeoff; the #1 anti-ice cowl valve illuminated amber. The QRH told us it was a bleed over pressure and the only way to extinguish the light was to reduce power on #1 engine. We elected to land overweight and declare an emergency because of the bleed overpressure and the rain showers in the area.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.