What happened
On 25 August 2020, an Airbus A319-1ER, registration G-EZDD, was performing a commercial passenger flight during its descent to Gatwick Airport. While passing through 6,000 ft, the flight crew detected a strong odor, described as a "wet sock" smell, emanating from the cockpit air conditioning ducts. Simultaneously, cabin crew notified the flight deck of an acrid smell within the passenger cabin.
As a precautionary measure, the pilots donned their oxygen masks and continued the approach. The aircraft landed without further incident, involving 64 passengers and 6 crew. Following the landing, the crew sought medical evaluations at a local hospital due to symptoms including chest tightness and tingling in the fingertips. No injuries were reported long-term.
The investigation
The investigation examined the aircraft's maintenance history, revealing that the aircraft had been subject to three separate "Smell in Aircraft Reports" (SIAR) in the three weeks prior to this event. Previous maintenance efforts had addressed leaks from the Auxiliary Power Unit (APU) drain mast, oil cooler, and an APU gearbox plug.
During the post-incident diagnosis, engineers identified additional oil leaks from various Line Replaceable Units (LRUs) on the APU. Although the APU was eventually replaced, the odor persisted, leading technicians to identify oil contamination within the environmental air conditioning system (ECS). To rectify this, nine components within the No 2 ECS were replaced.
Findings
- The primary cause of the odor was the presence of oil within the aircraft's No 2 ECS system.
- The contamination likely originated from oil leaking from one or more LRUs associated with the APU.
- The investigation noted that the lack of standardized medical protocols for assessing crew following fumes events could impact the collection of evidence in future incidents.