Narrative:

On flight xyz from bfi to tol, on takeoff (first officer flying) when gear was selected up, there was a loud bang (sounded like an explosion) and very loud wind noise, also vibration under first officer's seat. I thought that we had a tire blow up or a nose gear door break loose. Notified ATC and advised them of the problem, declared an emergency. They asked us if we could maintain VFR and 1500 ft MSL. We said yes, and they vectored us downwind back to bfi. We requested them for fuel dumping instructions, and they cleared us to go ahead and dump, which was done mostly over water between 1500-1800 ft down to landing weight. After all checklists were completed, ATC vectored us back to final for runway 13R bfi. The reason for the altitude at 1500-1800 ft was due to the low ceiling and the IFR arrs at sea airport. I took over from the first officer and made a normal landing at bfi. After landing and inspection of the aircraft, found nothing wrong. Callback conversation with reporter revealed the following information: the reporter stated the aircraft was a DC8-71 cargoliner. The reporter said the noise heard was a loud bang accompanied with wind noise and vibration under the first officer's floor. The reporter stated it was first thought the nose tires exploded due to the loud bang or the nose gear door or doors broke off. The reporter said the aircraft was inspected at bfi for 3 hours with nothing found. The reporter stated the aircraft was flown uneventfully to the air carrier's maintenance base, reinspected and again nothing was discovered. The reporter stated the aircraft has been operated daily with no subsequent reports. The reporter said 2 possible explanations were ice ingestion in the pack system and nose shock strut malfunction, but neither could not be proved.

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Original NASA ASRS Text

Title: A DC8-71 CARGOLINER ON TKOF WHEN THE LNDG GEAR WAS SELECTED UP THE ACFT EXPERIENCED A LOUD BANG, WIND NOISE AND VIBRATION UNDER THE FO'S FLOOR. DECLARED EMER, DUMPED FUEL AND RETURNED TO THE FIELD.

Narrative: ON FLT XYZ FROM BFI TO TOL, ON TKOF (FO FLYING) WHEN GEAR WAS SELECTED UP, THERE WAS A LOUD BANG (SOUNDED LIKE AN EXPLOSION) AND VERY LOUD WIND NOISE, ALSO VIBRATION UNDER FO'S SEAT. I THOUGHT THAT WE HAD A TIRE BLOW UP OR A NOSE GEAR DOOR BREAK LOOSE. NOTIFIED ATC AND ADVISED THEM OF THE PROB, DECLARED AN EMER. THEY ASKED US IF WE COULD MAINTAIN VFR AND 1500 FT MSL. WE SAID YES, AND THEY VECTORED US DOWNWIND BACK TO BFI. WE REQUESTED THEM FOR FUEL DUMPING INSTRUCTIONS, AND THEY CLRED US TO GO AHEAD AND DUMP, WHICH WAS DONE MOSTLY OVER WATER BTWN 1500-1800 FT DOWN TO LNDG WT. AFTER ALL CHKLISTS WERE COMPLETED, ATC VECTORED US BACK TO FINAL FOR RWY 13R BFI. THE REASON FOR THE ALT AT 1500-1800 FT WAS DUE TO THE LOW CEILING AND THE IFR ARRS AT SEA ARPT. I TOOK OVER FROM THE FO AND MADE A NORMAL LNDG AT BFI. AFTER LNDG AND INSPECTION OF THE ACFT, FOUND NOTHING WRONG. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS A DC8-71 CARGOLINER. THE RPTR SAID THE NOISE HEARD WAS A LOUD BANG ACCOMPANIED WITH WIND NOISE AND VIBRATION UNDER THE FO'S FLOOR. THE RPTR STATED IT WAS FIRST THOUGHT THE NOSE TIRES EXPLODED DUE TO THE LOUD BANG OR THE NOSE GEAR DOOR OR DOORS BROKE OFF. THE RPTR SAID THE ACFT WAS INSPECTED AT BFI FOR 3 HRS WITH NOTHING FOUND. THE RPTR STATED THE ACFT WAS FLOWN UNEVENTFULLY TO THE ACR'S MAINT BASE, REINSPECTED AND AGAIN NOTHING WAS DISCOVERED. THE RPTR STATED THE ACFT HAS BEEN OPERATED DAILY WITH NO SUBSEQUENT RPTS. THE RPTR SAID 2 POSSIBLE EXPLANATIONS WERE ICE INGESTION IN THE PACK SYS AND NOSE SHOCK STRUT MALFUNCTION, BUT NEITHER COULD NOT BE PROVED.

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.