Narrative:

While climbing out at approximately 16000 ft the flight crew felt and heard a vibration at the front portion of the aircraft. As speed increased the noise became louder. Airspeed was decreased slightly and noise seemed to decrease. Maintenance control was contacted via radio and after some discussion they requested we return to ZZZ. Our location was approximately 135 mi east of ZZZ when we started our return. The cause suspected at this point was the external power panel may have been left open by the pushback crew. We were given an amended release by dispatch to return to ZZZ. Overweight landing as well as gusty winds in ZZZ was discussed by captain and first officer. Dispatch was consulted; also. Flight crew elected to declare an emergency so fire equipment would be available during landing. Dispatch was also advised of this. Aircraft requested lower altitude early in order to burn as much fuel off as possible. Landing weight was approximately 156600 pounds with winds approximately 190 degrees/14 KTS gusting to 21 KTS. Flap blowback was a major concern during approach since reference speeds were very high. Aircraft was landed without incident. Inspected by the fire department and then taxied to gate. Maintenance write-ups were the original noise as well as an overweight landing with a sink rate upon touchdown of less than 200 FPM. Maintenance confirmed external power panel door was indeed left open and damaged slightly.

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Original NASA ASRS Text

Title: EXTERNAL PWR DOOR WAS LEFT OPEN ON A B737; CREATING A VIBRATION THAT INCREASED WITH INCREASING AIRSPEED. FLT RETURNED TO DEP ARPT.

Narrative: WHILE CLBING OUT AT APPROX 16000 FT THE FLT CREW FELT AND HEARD A VIBRATION AT THE FRONT PORTION OF THE ACFT. AS SPD INCREASED THE NOISE BECAME LOUDER. AIRSPD WAS DECREASED SLIGHTLY AND NOISE SEEMED TO DECREASE. MAINT CTL WAS CONTACTED VIA RADIO AND AFTER SOME DISCUSSION THEY REQUESTED WE RETURN TO ZZZ. OUR LOCATION WAS APPROX 135 MI E OF ZZZ WHEN WE STARTED OUR RETURN. THE CAUSE SUSPECTED AT THIS POINT WAS THE EXTERNAL PWR PANEL MAY HAVE BEEN LEFT OPEN BY THE PUSHBACK CREW. WE WERE GIVEN AN AMENDED RELEASE BY DISPATCH TO RETURN TO ZZZ. OVERWT LNDG AS WELL AS GUSTY WINDS IN ZZZ WAS DISCUSSED BY CAPT AND FO. DISPATCH WAS CONSULTED; ALSO. FLT CREW ELECTED TO DECLARE AN EMER SO FIRE EQUIP WOULD BE AVAILABLE DURING LNDG. DISPATCH WAS ALSO ADVISED OF THIS. ACFT REQUESTED LOWER ALT EARLY IN ORDER TO BURN AS MUCH FUEL OFF AS POSSIBLE. LNDG WT WAS APPROX 156600 LBS WITH WINDS APPROX 190 DEGS/14 KTS GUSTING TO 21 KTS. FLAP BLOWBACK WAS A MAJOR CONCERN DURING APCH SINCE REF SPDS WERE VERY HIGH. ACFT WAS LANDED WITHOUT INCIDENT. INSPECTED BY THE FIRE DEPT AND THEN TAXIED TO GATE. MAINT WRITE-UPS WERE THE ORIGINAL NOISE AS WELL AS AN OVERWT LNDG WITH A SINK RATE UPON TOUCHDOWN OF LESS THAN 200 FPM. MAINT CONFIRMED EXTERNAL PWR PANEL DOOR WAS INDEED LEFT OPEN AND DAMAGED SLIGHTLY.

Data retrieved from NASA's ASRS site as of May 2009 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.