What happened
On 4 January 2002, an Avro 146-RJ100, registration G-BXAS, was performing a scheduled passenger flight from London Gatwick to Amsterdam. Prior to the crew's arrival, the aircraft had undergone de-icing. Following standard operating procedures, the pilots utilized APU bleed air for cabin air conditioning during the initial stages of takeoff. Shortly after becoming airborne, the crew detected a pungent odor, reminiscent of de-icing fluid. As the smell intensified, the commander observed smoke appearing at the base of the left-hand 'A' windscreen panel. In response, the crew declared a MAYDAY and donned oxygen masks.
The smoke cleared rapidly, and the crew completed the necessary emergency checklists. After requesting radar vectors, the pilots returned to London Gatwick. Upon landing, no external fire or smoke was observed, and the 85 passengers and 6 crew members disembarked without injury.
Later that same morning, a second Avro 146-RJ100, registration G-BXAR, experienced a near-identical event. After being de-iced and taking off, the crew also encountered smoke and fumes in the flight deck, necessitating a return to Gatwick and the use of oxygen masks.
The investigation
Investigators examined the aircraft and found that the APU intake and the surrounding area of G-BXAS were heavily coated with de-icing fluid. This fluid had been drawn into the air conditioning system. The investigation determined that the airflow generated along the fuselage during the takeoff roll was responsible for carrying the fluid toward the APU intake. Similar findings were confirmed on G-BXAR, where de-icing fluid was also found around the APU intake and exhaust.
Findings
- The primary cause of the smoke and fumes was the ingestion of de-icing fluid into the APU intake.
- The movement of fluid toward the intake was caused by aerodynamic forces along the fuselage during the takeoff run.
- Both incidents occurred following the de-icing of the aircraft and the use of APU bleed air for cabin conditioning.