Narrative:

While in cruise flight we noticed an acrid odor followed by thin smoke in the cockpit. We went on O2 and investigated while initiating a turn to the nearest airport. We had no ECAM messages or fire warnings. We checked with the flight attendants to see if there were any signs of smoke; fire or odors in the cabin. They said there were none but at about the same time we all began to hear a loud grinding; vibrating; growling sound seemingly below us. I informed the flight attendants we were diverting to the nearest suitable airport. The lack of smoke and fumes in the cabin lead us to rule out a cabin fire or an air conditioning problem. We saw no unusual engine indications and the APU was not in use. We therefore believed that the most likely source of the odor was avionics smoke. We ran the first page of the avionics smoke checklist and the smoke began to dissipate. We continued to our diversion airport; made an uneventful landing; and had the fire dept inspect the aircraft. Finding no signs of fire they cleared us to taxi to the gate. Maintenance later determined that the cause of the smoke and fumes was a failed avionics extract fan. I recommend adding to the smoke/fire section of the aom emergency procedures a checklist titled 'smoke and fumes of unknown origin' or possibly the incorporation of similar language into the 'smoke and fumes elimination' checklist.

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Original NASA ASRS Text

Title: An A319 flight crew diverted to the nearest suitable airport when an acrid odor and smoke entered the cockpit from a failing avionics cooling fan.

Narrative: While in cruise flight we noticed an acrid odor followed by thin smoke in the cockpit. We went on O2 and investigated while initiating a turn to the nearest airport. We had no ECAM messages or fire warnings. We checked with the Flight Attendants to see if there were any signs of smoke; fire or odors in the cabin. They said there were none but at about the same time we all began to hear a loud grinding; vibrating; growling sound seemingly below us. I informed the flight attendants we were diverting to the nearest suitable airport. The lack of smoke and fumes in the cabin lead us to rule out a cabin fire or an air conditioning problem. We saw no unusual engine indications and the APU was not in use. We therefore believed that the most likely source of the odor was avionics smoke. We ran the first page of the avionics smoke checklist and the smoke began to dissipate. We continued to our diversion airport; made an uneventful landing; and had the fire dept inspect the aircraft. Finding no signs of fire they cleared us to taxi to the gate. Maintenance later determined that the cause of the smoke and fumes was a failed avionics extract fan. I recommend adding to the Smoke/Fire section of the AOM emergency procedures a checklist titled 'Smoke and fumes of unknown origin' or possibly the incorporation of similar language into the 'Smoke and fumes elimination' checklist.

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.