What happened
On June 8, 2012, a Cessna 525A Citation CJ2, registration PH-JNE, was performing a positioning flight from Rotterdam The Hague Airport (EHRD) to Amsterdam Airport Schiphol. Shortly after departing from runway 24, the crew noticed an unusual odor in the cockpit, which quickly developed into a visible mist-like smoke.
The crew immediately implemented emergency memory items, including the use of oxygen masks. They requested permission from air traffic control to perform a return to the airport via a right-hand circuit. While the crew did not issue a formal distress call, air traffic controllers treated the event as an emergency and positioned airport fire services near the parking stands. After landing, the aircraft taxied to a parking position near a Boeing 737, where the fire brigade inspected the aircraft and found no evidence of an actual fire.
The investigation
The investigation focused on the technical cause of the smoke and the crew's emergency response. Because the aircraft was not equipped with flight data or cockpit voice recorders, investigators relied on crew interviews.
Technical inspections of the air conditioning and bleed air systems revealed significant residues of white soap within both systems. Investigators traced the source back to routine maintenance performed two days prior, which involved washing the engine compressors. The investigation established that the maintenance procedures for the bleed air system were not strictly followed during the cleaning process.
Findings
- Improper maintenance procedure: During the compressor washing two days earlier, the bleed air system was connected to the engines while they were running. This allowed water and cleaning fluid to enter the bleed air system.
- Evaporation of residues: During the takeoff on June 8, the high temperatures of the bleed air system caused the trapped cleaning fluid to evaporate, creating the odor and smoke observed in the cockpit.
- Communication difficulties: The use of oxygen masks, combined with the crew's failure to switch off their active microphones, caused severe interference in both inter-cockpit and air traffic control communications due to the loud sound of breathing.
- Operational risks: The decision to taxi the aircraft to a parking stand near other aircraft, rather than stopping on the runway, presented a potential risk to third parties and other aircraft.
Safety action
- The airline has since integrated the lessons learned from this incident into its Crew Resource Management (CRM) training, specifically addressing the challenges of communicating while using oxygen masks.
- The investigation highlighted the need for improved training regarding the use of oxygen masks and the importance of using standard emergency terminology (such as 'Pan-Pan' or 'Mayday') to ensure clear communication with air traffic control.