A-319 flight crew reported a ground return to gate due to caustic odor throughout the aircraft while...

Attributes
ACN	1723300
Time
Date	202001
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	A319
Operating Under FAR Part	Part 121
Flight Phase	Taxi
Flight Plan	IFR
Person 1
Function	Pilot Not Flying Captain
Qualification	Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 115 Flight Crew Total 15000 Flight Crew Type 1595
Person 2
Function	First Officer Pilot Flying
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor

Narrative:

After pushback from gate in ZZZ we taxied to runway xx and were caught up in a lot of ground traffic congestion from a thunderstorm that had prevented take offs and landings. While sitting on the taxiway in line for our delayed takeoff; we noticed a smell that we had noted after engine start and initial taxi was becoming more irritating and slightly caustic to us. We called the flight attendants to see if they noticed the smell and initially they did not but later as they walked the cabin closer to the cockpit noticed the smell also. We made a write up in the logbook and broke the mrd (maintenance release document). We then called maintenance control and talked to the airframe controller who said to return to the gate for further investigation by maintenance and turn off bleeds and packs. We told the tower that we needed to return to the gate and he began to move aircraft as able to allow us to proceed back to the gate. We donned oxygen masks as a precaution and taxied back to the gate without incident. At block in; maintenance met us and we filled out a form for maintenance to help identify the source of the sour smell. I also notified the duty manager as per the fom. There was no ensuing discussion with the duty manager regarding the odor from an unknown source; only discussion regarding crew legality.

Original NASA ASRS Text

Title: A-319 flight crew reported a ground return to gate due to caustic odor throughout the aircraft while waiting in line for takeoff.

Narrative: After pushback from gate in ZZZ we taxied to runway XX and were caught up in a lot of ground traffic congestion from a thunderstorm that had prevented take offs and landings. While sitting on the taxiway in line for our delayed takeoff; we noticed a smell that we had noted after engine start and initial taxi was becoming more irritating and slightly caustic to us. We called the flight attendants to see if they noticed the smell and initially they did not but later as they walked the cabin closer to the cockpit noticed the smell also. We made a write up in the logbook and broke the MRD (Maintenance Release Document). We then called Maintenance Control and talked to the Airframe Controller who said to return to the gate for further investigation by Maintenance and turn off bleeds and packs. We told the Tower that we needed to return to the gate and he began to move aircraft as able to allow us to proceed back to the gate. We donned oxygen masks as a precaution and taxied back to the gate without incident. At block in; Maintenance met us and we filled out a form for Maintenance to help identify the source of the sour smell. I also notified the Duty Manager as per the FOM. There was no ensuing discussion with the Duty Manager regarding the odor from an unknown source; only discussion regarding crew legality.

Data retrieved from NASA's ASRS site 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.