Narrative:

Strong and apparently increasing smoke in cockpit and cabin immediately after takeoff. Emergency declared and clearance for downwind provided. Returned to runway of departure and landed. Fuel was dumped to reduce gross weight to minimum possible before landing. Crash fire rescue equipment crew inspected aircraft and declared 'no hot spots...all clear.' returned to gate. Callback conversation with reporter revealed the following information: the reporter was the captain on a B727-200 and he said that the flight crew had followed normal operating procedure and had closed the APU air bleeds and shut down the APU during taxi out. During takeoff they started to notice smoke coming through the air conditioning vents as they approached rotation speed. After lift-off the smoke intensified and they declared an emergency and requested to return to the airport. The tower controller cleared them to make a close-in pattern back to the same runway. The crew depressurized the aircraft and landed. After returning to the gate and deplaning the passenger, the maintenance technicians found that the flow multiplier was, apparently, the source of the smoke. The system is normally not operated or even in the pneumatic flow during flight and the reporter said that the air conditioning system was in the normal confign and the APU was shut down. He said that when he looked at the APU and the air conditioning and pressurization panels during the fuel dump procedure they looked normal except that the pressurization system had been shut off at this time to stop the smoke from continuing to enter the aircraft. After the flight the crew discussed the pre-smoke operation and everyone agreed that the operation was normal according to the captain. After maintenance finished their investigation and clearance of the aircraft back to operation the captain questioned their findings, but the technicians confirmed that the flow multiplier was the source. The reporter said that the technicians could not explain how the multiplier could have been active if the system had been isolated. The captain said that he flew the aircraft after maintenance was completed without the smoke recurring and he still does not know how the flow multiplier was able to operate during the original flight. He said that he has spoken to maintenance and the training department since this incident and, although it is still a mystery, it is now another incident that is used as a training aid in recurrent ground school.

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Original NASA ASRS Text

Title: AN ACR B727 FLC EXPERIENCED SMOKE IN THE CABIN AND FLT STATION AFTER TKOF. THEY RETURNED AND DURING THE POSTFLT MAINT INSPECTION THE TECHNICIANS DETERMINED THAT THE APU FLOW MULTIPLIER WAS THE SOURCE OF THE SMOKE.

Narrative: STRONG AND APPARENTLY INCREASING SMOKE IN COCKPIT AND CABIN IMMEDIATELY AFTER TKOF. EMER DECLARED AND CLRNC FOR DOWNWIND PROVIDED. RETURNED TO RWY OF DEP AND LANDED. FUEL WAS DUMPED TO REDUCE GROSS WT TO MINIMUM POSSIBLE BEFORE LNDG. CFR CREW INSPECTED ACFT AND DECLARED 'NO HOT SPOTS...ALL CLR.' RETURNED TO GATE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR WAS THE CAPT ON A B727-200 AND HE SAID THAT THE FLC HAD FOLLOWED NORMAL OPERATING PROC AND HAD CLOSED THE APU AIR BLEEDS AND SHUT DOWN THE APU DURING TAXI OUT. DURING TKOF THEY STARTED TO NOTICE SMOKE COMING THROUGH THE AIR CONDITIONING VENTS AS THEY APCHED ROTATION SPD. AFTER LIFT-OFF THE SMOKE INTENSIFIED AND THEY DECLARED AN EMER AND REQUESTED TO RETURN TO THE ARPT. THE TWR CTLR CLRED THEM TO MAKE A CLOSE-IN PATTERN BACK TO THE SAME RWY. THE CREW DEPRESSURIZED THE ACFT AND LANDED. AFTER RETURNING TO THE GATE AND DEPLANING THE PAX, THE MAINT TECHNICIANS FOUND THAT THE FLOW MULTIPLIER WAS, APPARENTLY, THE SOURCE OF THE SMOKE. THE SYS IS NORMALLY NOT OPERATED OR EVEN IN THE PNEUMATIC FLOW DURING FLT AND THE RPTR SAID THAT THE AIR CONDITIONING SYS WAS IN THE NORMAL CONFIGN AND THE APU WAS SHUT DOWN. HE SAID THAT WHEN HE LOOKED AT THE APU AND THE AIR CONDITIONING AND PRESSURIZATION PANELS DURING THE FUEL DUMP PROC THEY LOOKED NORMAL EXCEPT THAT THE PRESSURIZATION SYS HAD BEEN SHUT OFF AT THIS TIME TO STOP THE SMOKE FROM CONTINUING TO ENTER THE ACFT. AFTER THE FLT THE CREW DISCUSSED THE PRE-SMOKE OP AND EVERYONE AGREED THAT THE OP WAS NORMAL ACCORDING TO THE CAPT. AFTER MAINT FINISHED THEIR INVESTIGATION AND CLRNC OF THE ACFT BACK TO OP THE CAPT QUESTIONED THEIR FINDINGS, BUT THE TECHNICIANS CONFIRMED THAT THE FLOW MULTIPLIER WAS THE SOURCE. THE RPTR SAID THAT THE TECHNICIANS COULD NOT EXPLAIN HOW THE MULTIPLIER COULD HAVE BEEN ACTIVE IF THE SYS HAD BEEN ISOLATED. THE CAPT SAID THAT HE FLEW THE ACFT AFTER MAINT WAS COMPLETED WITHOUT THE SMOKE RECURRING AND HE STILL DOES NOT KNOW HOW THE FLOW MULTIPLIER WAS ABLE TO OPERATE DURING THE ORIGINAL FLT. HE SAID THAT HE HAS SPOKEN TO MAINT AND THE TRAINING DEPT SINCE THIS INCIDENT AND, ALTHOUGH IT IS STILL A MYSTERY, IT IS NOW ANOTHER INCIDENT THAT IS USED AS A TRAINING AID IN RECURRENT GND SCHOOL.

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.