Narrative:

At approximately PM45 local time my crew and I boarded an aircraft which we had been swapped into for our last leg of the night--a flight of about 1 hour 20 mins. In accordance with far's and company regulations, I performed a thorough preflight, which included an inspection of the landing gear wheel wells. In order to inspect the wheel wells a door over the first officer's head must be opened, a t-handle pulled to release the gear doors, and the overhead door closed again. The prestart checklist includes checking that this overhead door is closed, which I did visually at the appropriate time. Our flight was cleared for takeoff at next hour + 10 mins, and after the copilot's call of 'positive rate of climb,' I called for the gear up. When the first officer selected gear up we got an indication of 3 green 'down and locked' lights and 3 red 'gear unsafe' lights. This indicated that the gear was actually still down and locked though the gear switched disagreed with the gear position. At a safe altitude (approximately 1500' AGL) I had the first officer check the emergency checklist for the appropriate procedure. There was none. We attempted to recycle the gear and got a safe indication with the gear switch down, unsafe when up. We left the switch in the down position. I had the first officer notify the company, F/a and ATC of our situation, and advise them that we would return to bwi to have maintenance check the aircraft. We landed west/O incident. On the ground the mechanic checked the alternate release door and found it partially ajar. This relieved all hydraulic pressure to the gear and prevented its retraction. The door was closed, we took off again and continued to our destination west/O further problems. This type of incident was addressed in the ground school for the aircraft, though it was not demonstrated in my training or that of the first officer. Contributing to the incident may have been an aircraft swap at night during a relatively short (50 min) turnaround time, which was also the dinner break for the crew. Either the first officer or I should have thought of the release door as the culprit, though our departure from bwi at one of its busiest times left me preoccupied with flying and the first officer busy handling frequent vectors, handoffs and altitude changes.

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Original NASA ASRS Text

Title: A DESIGN FUNCTION THAT WAS NOT UNDERSTOOD ON PREFLT AND TKOF INTERFERES WITH THE GEAR RETRACTION ON TKOF.

Narrative: AT APPROX PM45 LCL TIME MY CREW AND I BOARDED AN ACFT WHICH WE HAD BEEN SWAPPED INTO FOR OUR LAST LEG OF THE NIGHT--A FLT OF ABOUT 1 HR 20 MINS. IN ACCORDANCE WITH FAR'S AND COMPANY REGS, I PERFORMED A THOROUGH PREFLT, WHICH INCLUDED AN INSPECTION OF THE LNDG GEAR WHEEL WELLS. IN ORDER TO INSPECT THE WHEEL WELLS A DOOR OVER THE F/O'S HEAD MUST BE OPENED, A T-HANDLE PULLED TO RELEASE THE GEAR DOORS, AND THE OVERHEAD DOOR CLOSED AGAIN. THE PRESTART CHKLIST INCLUDES CHKING THAT THIS OVERHEAD DOOR IS CLOSED, WHICH I DID VISUALLY AT THE APPROPRIATE TIME. OUR FLT WAS CLRED FOR TKOF AT NEXT HR + 10 MINS, AND AFTER THE COPLT'S CALL OF 'POSITIVE RATE OF CLB,' I CALLED FOR THE GEAR UP. WHEN THE F/O SELECTED GEAR UP WE GOT AN INDICATION OF 3 GREEN 'DOWN AND LOCKED' LIGHTS AND 3 RED 'GEAR UNSAFE' LIGHTS. THIS INDICATED THAT THE GEAR WAS ACTUALLY STILL DOWN AND LOCKED THOUGH THE GEAR SWITCHED DISAGREED WITH THE GEAR POS. AT A SAFE ALT (APPROX 1500' AGL) I HAD THE F/O CHK THE EMER CHKLIST FOR THE APPROPRIATE PROC. THERE WAS NONE. WE ATTEMPTED TO RECYCLE THE GEAR AND GOT A SAFE INDICATION WITH THE GEAR SWITCH DOWN, UNSAFE WHEN UP. WE LEFT THE SWITCH IN THE DOWN POS. I HAD THE F/O NOTIFY THE COMPANY, F/A AND ATC OF OUR SITUATION, AND ADVISE THEM THAT WE WOULD RETURN TO BWI TO HAVE MAINT CHK THE ACFT. WE LANDED W/O INCIDENT. ON THE GND THE MECH CHKED THE ALTERNATE RELEASE DOOR AND FOUND IT PARTIALLY AJAR. THIS RELIEVED ALL HYD PRESSURE TO THE GEAR AND PREVENTED ITS RETRACTION. THE DOOR WAS CLOSED, WE TOOK OFF AGAIN AND CONTINUED TO OUR DEST W/O FURTHER PROBS. THIS TYPE OF INCIDENT WAS ADDRESSED IN THE GND SCHOOL FOR THE ACFT, THOUGH IT WAS NOT DEMONSTRATED IN MY TRNING OR THAT OF THE F/O. CONTRIBUTING TO THE INCIDENT MAY HAVE BEEN AN ACFT SWAP AT NIGHT DURING A RELATIVELY SHORT (50 MIN) TURNAROUND TIME, WHICH WAS ALSO THE DINNER BREAK FOR THE CREW. EITHER THE F/O OR I SHOULD HAVE THOUGHT OF THE RELEASE DOOR AS THE CULPRIT, THOUGH OUR DEP FROM BWI AT ONE OF ITS BUSIEST TIMES LEFT ME PREOCCUPIED WITH FLYING AND THE F/O BUSY HANDLING FREQUENT VECTORS, HDOFS AND ALT CHANGES.

Data retrieved from NASA's ASRS site as of July 2007 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.