An A320 with an inoperative APU developed a dirty socks odor after a cross bleed engine start; so the aircraft returned to the gate where it was removed from service. Captain suggested that adding air quality monitor devices would help.
Synopsis
An A320 with an inoperative APU developed a dirty socks odor after a cross bleed engine start; so the aircraft returned to the gate where it was removed from service. Captain suggested that adding air quality monitor devices would help.
Narrative
The APU was on the MEL. We started engine #1 at the gate with an air-start machine. We pushed back and cross-bleed started the 2nd engine. As we began the taxi; while still on the ramp; the 'A' Flight Attendant called us and said there was a bad odor in the cabin and many passengers were complaining. I told her it was probably due to the air start and or cross-bleed start and it would probably clear up. I told here to call me back in about 5 minutes and tell me if it was any better. She called back about 5 minutes later and said it was no better; perhaps worse. We called Ground Control and asked them if we could pull into the cargo ramp; and we did. I turned the airplane into the wind; so as to eliminate any engine exhaust from blowing back into the airplane. I bumped the power up slightly (25% N1) above idle to help with the air flow. I selected 'HI' flow for our packs and we sat there for a few more minutes to see if it got better. I sent the First Officer back to see what he thought. He came back a few minutes later and said he certainly smelled it and it smelled like a faint electrical smell to him. Passengers and flight attendants reported it as a burning plastic or musty smell. I too; thought it smelled musty. After a few minutes; we all decided it wouldn't be a good idea to fly this airplane. We returned to the gate and I radioed for a Customer Service and Maintenance Supervisor to meet the airplane. They did and all agreed there was a bad; unidentifiable odor in the airplane. One female passenger complained of burning eyes. We transferred to another airplane and completed our flight.How about an air quality monitor in the cabin? This is costing the airlines millions and; in some cases; causing harm to crew members and passengers. Most of these odor problems are probably nothing; but how do we know? We have to keep safety in mind. If there's any doubt; we don't go! There are lots of odors on an airplane. Most of which are probably harmless. We have carbon monoxide detectors in our homes. Can't we get something to monitor the air in our cabins? It would probably benefit the airlines to do this; we would probably have a lot less 'Toxic Fume' incidents if the crew knew that what they smelled wasn't going to harm them!
NASA callback
The reporter stated that he included the various smell descriptions as his crew reported them to him; but when he actually went to the cabin himself after returning to the gate he would describe the smell as 'dirty socks.' Thirteen passengers plus the entire crew acknowledged the smell. Several years ago he experienced the same smell and the entire crew had headaches after flying two short legs with the same aircraft before finally refusing to fly it further. The next day he was assigned that same aircraft at a different station and nothing had changed; so the aircraft 'dirty socks' odor was not being treated seriously at that time. After this event; the reporter was told that mechanics are told to service the APU one half quart below full to preclude oil migration into the air conditioning system.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.