What happened
On 29 January 2001, a TNT Airways British Aerospace BA 146-300, registration OO-TAS, was conducting a commercial cargo flight from Treviso to Liege. While cruising at FL 280, the flight crew detected an increasing electrical odor near the glare shield. Although no visible smoke was initially present, a haze developed within minutes.
In response to the developing situation, the commander initiated emergency smoke procedures and declared a mayday. The crew diverted the aircraft toward Geneva Airport. During the descent, the aircraft encountered icing conditions. The commander opted not to perform the full "electric smoke" checklist to avoid disabling the navigation systems, which would have complicated the approach in the icing conditions. The crew utilized oxygen masks, though they did not use smoke goggles. The aircraft landed at Geneva at 2/23 UTC following a straight-in ILS approach, and the crew evacuated the aircraft via the main door.
The investigation
Investigators examined the cockpit environment and the technical state of the navigation equipment. The investigation established that the crew experienced a strong electrical smell and haze, though they were unable to pinpoint the exact source of the fumes. The investigation also noted that communication between the flight crew and air traffic controllers was significantly hindered once the pilots donned their oxygen masks. Additionally, the investigation reviewed the decision-making process regarding the choice of diversion airport, noting that while Geneva was a viable option, closer alternatives like Strasbourg or Basle were available.
Findings
- The primary cause of the cockpit fumes was a faulty backlight inverter located within the Flat Panel Control Display Unit of the Universal navigation system.
- The crew's decision to divert to Geneva, while appropriate, involved a longer flight time than closer alternatives which might have been safer if the smoke had intensified.
- The use of oxygen masks without smoke goggles contributed to the crew experiencing aching eyes.
Safety action
Following the incident, the component manufacturer, Universal, issued a Service Bulletin (1117.XX-34-2699) which introduced an Inverter Circuitry Integrity Test to prevent similar failures.