Narrative:

As we descended through a scattered cloud deck at approximately 2;100 ft AGL both flight deck crewmembers noticed that a smell in the cabin air began. I would describe it as an 'oil or hydraulic fluid' smell. Upon landing the 'a' flight attendant called us on the cabin interphone. It was a very short taxi to the gate and by the time we were able to respond to the call from the cabin we were almost stopped at the gate. All 3 flight attendant's stated that during the last moments prior to landing the cabin air was overcome with a strong odor. Many passengers noticed the smell also; some were looking around in concern; trying to locate the source perhaps. After de-planing; two of the flight attendant's complained of moderate headaches. The headaches began to dissipate after a few minutes; but it took several hours for them to completely go away. Maintenance began to troubleshoot the problem which included running both engines separately at the gate and the air conditioning packs in various configurations. They also inspected the APU. Their conclusion was that the odor originated from the APU compartment; which they stated was over serviced. Note: the APU was not running at the time of the incident; and was started just prior to gate arrival on the taxi in. The airplane was about to be signed off and returned to service approximately 3 hours later. By this time I decided to talk to my crew about any concerns they may have. Every crewmember had reservations about flying the airplane at this point. (We were not satisfied with the APU as the origin of the odor theory). This was a moot point as it turned out because about that time our scheduling department decided that we were getting too close to being out of duty time and canceled the flight outbound. We ended up in an unscheduled ron. Maintenance performed something they called a 'cabin contamination check' that night which included changing the cabin hfpa filters. Part of the crew ferried the airplane the following morning with no incidents. I am not sure why it occurred; or why it occurred only when descending through approximately 2;100 AGL. My first officer was wondering if it may have something to do with the packs dealing with what was a large change in the outside air humidity and temperature; or if it had to do with the engine bleed source at that point. That is: the engines were at idle or nearly so when the demand on the packs increased causing the hp bleed source to become the main source. I understand that the airline industry is trying to come to grips with whether an engine oil additive (tcp) is the source of recent cabin air issues; and that there have been some crewmembers that have had some health issues (some rather severe) from cabin air incidents. Since the hfpa filter change seemed to help the problem perhaps they should be changed more frequently. If it is an issue with an engine oil additive I would question the industry's use of tcp.

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Original NASA ASRS Text

Title: An A319 crew detected a strong oil or hydraulic fluid smell descending for landing; so Maintenance removed the aircraft from service for a cabin contamination check and found the APU over serviced.

Narrative: As we descended through a scattered cloud deck at approximately 2;100 FT AGL both flight deck crewmembers noticed that a smell in the cabin air began. I would describe it as an 'oil or hydraulic fluid' smell. Upon landing the 'A' Flight Attendant called us on the cabin interphone. It was a very short taxi to the gate and by the time we were able to respond to the call from the cabin we were almost stopped at the gate. All 3 Flight Attendant's stated that during the last moments prior to landing the cabin air was overcome with a strong odor. Many passengers noticed the smell also; some were looking around in concern; trying to locate the source perhaps. After de-planing; two of the Flight Attendant's complained of moderate headaches. The headaches began to dissipate after a few minutes; but it took several hours for them to completely go away. Maintenance began to troubleshoot the problem which included running both engines separately at the gate and the air conditioning packs in various configurations. They also inspected the APU. Their conclusion was that the odor originated from the APU compartment; which they stated was over serviced. NOTE: the APU was not running at the time of the incident; and was started just prior to gate arrival on the taxi in. The airplane was about to be signed off and returned to service approximately 3 hours later. By this time I decided to talk to my crew about any concerns they may have. Every crewmember had reservations about flying the airplane at this point. (We were not satisfied with the APU as the origin of the odor theory). This was a moot point as it turned out because about that time our scheduling department decided that we were getting too close to being out of duty time and canceled the flight outbound. We ended up in an unscheduled RON. Maintenance performed something they called a 'cabin contamination check' that night which included changing the cabin HFPA filters. Part of the crew ferried the airplane the following morning with no incidents. I am not sure why it occurred; or why it occurred only when descending through approximately 2;100 AGL. My First Officer was wondering if it may have something to do with the packs dealing with what was a large change in the outside air humidity and temperature; or if it had to do with the engine bleed source at that point. That is: the engines were at idle or nearly so when the demand on the packs increased causing the HP bleed source to become the main source. I understand that the airline industry is trying to come to grips with whether an engine oil additive (TCP) is the source of recent cabin air issues; and that there have been some crewmembers that have had some health issues (some rather severe) from cabin air incidents. Since the HFPA filter change seemed to help the problem perhaps they should be changed more frequently. If it is an issue with an engine oil additive I would question the industry's use of TCP.

Data retrieved from NASA's ASRS site as of April 2012 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.