Date: 201203
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: A319
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Turbine Engine
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Physiological - Other; Time Pressure
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; General Declared Emergency; General Maintenance Action
Contributing factors: Aircraft; Human Factors; Environment - Non Weather Related
Primary problem: Aircraft

Narrative: In the climb out the crew became aware of an oily smell in the cabin that did not dissipate but got stronger. Confirmed by the flight attendants and both pilots; we returned to the departure airport for landing and passenger removal. The pilots used our oxygen mask once the smell was identified and started the APU selecting it to supply the bleed air for the air conditioning packs to help vent the cabin while returning to land. After landing taxi to the gate to deplane passengers with out any injuries; smelled as if oil was being vaporized in the air that we were breathing.

Callback: The Reporter stated that he immediately started the APU so that its bleed air would supply the cabin and cut out the engine bleed air. He refused to ferry the aircraft to a maintenance base after finding out the borescope inspection located a bent compressor section blade which caused a slight shaft wobble allowing oil to enter the bleed system. The CFM 56 engine was ultimately changed.

Second narrative: Climbing through 8;000 we had a strong smell similar to diesel bus exhaust. We donned our oxygen masks and declared an emergency. We returned to the departure airport with an uneventful landing.

Second callback: The reporter stated that this is his third cabin contamination event in the past year and all three have smelled differently. One event was on the ground; the result of APU oil. The other events were in flight. His previous event was a dirty socks smell but this events smell was just like following a diesel bus. The pilots went on oxygen immediately. The flight attendants did not have oxygen. The two in-flight events that this reporter experienced have occurred as the engine thrust was being reduced. The current event occurred when the reporter selected vertical speed at 8;000 FT to round out a level off for a 10;000 FT climb constraint. The smell began just as power was reduced and then got stronger. The crew went to a Company physician after the flight but no immediate after effects were detected in the pilot crew; most probably because they were on oxygen immediately. The reporter did not know about flight attendant conditions. The following day he went to his personal physician and had blood drawn for a study being conducted by a university. The reporter talked with the Captain the following week and was told that he had flown this same aircraft several days later and discovered that an engine was changed after this event.

Synopsis: An A319 crew detected a diesel bus exhaust odor as thrust was reduced for a climb constraint so they went on oxygen immediately; declared an emergency and returned to the departure airport where a CFM56 bent compressor section blade was found which caused a slight shaft wobble.