A MD80's APU leaked oil onto the ramp during preflight because the oil cap was loose. The right air conditioning pack inlet apparently picked some of the oil up causing cabin smoke and fumes after takeoff. An emergency was declared and the aircraft was returned to the departure airport.
Synopsis
A MD80's APU leaked oil onto the ramp during preflight because the oil cap was loose. The right air conditioning pack inlet apparently picked some of the oil up causing cabin smoke and fumes after takeoff. An emergency was declared and the aircraft was returned to the departure airport.
Narrative
Just after takeoff the Flight Attendants called and said they saw and smelled smoke in the cabin. They reported that it had a maple syrup odor. We briefly smelled the same thing and then the odor went away. I talked to the Flight Attendants on the interphone while the Captain flew the airplane and talked to ATC. We accomplished the QRH procedure for Air Conditioning Smoke/Fumes while coordinating with ATC to return to land. Prior to our gate departure; our APU had shut down. The Mechanic who responded said that the oil filler cap was loose and allowed oil to leak out and eventually trigger an automatic shutdown. He has reserviced the oil and secured the cap. There was a large puddle under the APU and as we pushed back airport service people were beginning the clean up. We surmised that oil being drawn into the air conditioning pack inlet was the most likely cause of the smoke and fumes. In retrospect; more oil getting into the right pack inlet duct than the left would have explained the greater amount of smoke in the cabin than in the cockpit. The odor we briefly smelled may have even come through the vents in the cockpit door. All other engine and systems indications were normal. During the vectors back to the field; the Captain checked with the Flight Attendants and they said there was less smoke and smell than before but some was still present. The Captain answered ATC's questions about souls on board and fuel. We accomplished the mechanical checklist for a normal landing. I called operations on base leg to let them know we would need a gate and to get them to pass the word to Dispatch that we were returning for smoke and fumes. We landed normally and cleared the runway where the Airport Rescue and Fire Fighting vehicles looked our aircraft over. Aircraft weight was only 116;000 pounds and the Captain used only light braking to stop the aircraft. The Airport Rescue and Fire Fighting Commander's radio was hard to understand (scratchy with a little feedback) but Rescue 19 was able to relay his calls clearly. They said the aircraft was clean and said we could taxi to the gate. We taxied and shutdown uneventfully. The Captain and the Gate Agent decided to deplane the passengers. The Flight Attendants reported symptoms including light headedness and dizziness due to the amount of smoke and exposure time. Their Supervisor took them to medical for further assessment. The mechanics who met us agreed with the oil in the inlet duct theory and said the fix was a lengthy one at the hangar. The Captain made requested phone calls for requested details to ATC and Dispatch. Soon we got word from tracking that our segment was cancelled. All agencies were prompt and helpful.
Second reporter narrative
After we landed as the Airport Rescue and Fire Fighting trucks were looking over the aircraft I asked the First Officer if we technically declared an emergency; even though I was asked all the 'declared emergency' questions on base leg and was told Airport Rescue and Fire Fighting trucks were waiting for us. It appears an emergency wasn't declared; even though it appeared it was by the questions I was asked in the traffic pattern. We did complete the air conditioning smoke and fumes procedure on base leg and completed all of the appropriate checklists. In short; our intention was to get the plane on the ground first before this turned into a serious emergency and run the air conditioning smoke and fumes procedure in case things got worse later. This entire flight was traffic pattern only.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.