Background
The aircraft involved, an AVRO 146-RJ100 registered as HB-IXN, was operated by Swiss International Air Lines Ltd. on a scheduled passenger flight from Munich (EDDM) to Zurich (LSZH). The flight crew consisted of a commander and a copilot, both Swiss nationals holding Airline Transport Pilot Licences (ATPL). The aircraft had four Allied Signal LF507-1F engines.
During the days preceding the incident, the aircraft had been the subject of several maintenance reports related to unusual smells and smoke in the cockpit. On 16 April 2005, the crew of flight LX 725 reported a strong smell during descent. Maintenance inspections found no obvious cause. On 18 April 2005, the crew of flight LX 1026 reported oil smell and white fumes on approach to Düsseldorf; subsequent examination revealed oil coming from a temperature control valve and pack 1 was declared inoperative. After further maintenance, pack 1 was reactivated overnight without explicit documentation.
Incident Details
On 19 April 2005, the crew operated a flight from Zurich to Munich earlier in the day without any odour or haze issues. During the return flight (LX 1103), the approach and cruise were normal. At approximately 09:15 UTC, while descending through flight level 130, a pungent odour and haze appeared in the cockpit. The copilot began to feel unwell and immediately donned his oxygen mask. The commander remarked to the copilot, as recorded by the cockpit voice recorder, that the smell resembled oil and air conditioning smoke.
The commander requested landing priority from air traffic control, stating that there was an air conditioning smell in the cockpit and that the copilot was not feeling well. The controller offered radar vectors for runway 16 to shorten the approach path, but the crew declined as they had already prepared for runway 14. The commander did not wear his oxygen mask as he felt fine. The copilot removed his mask during the approach but re-donned it when breathing difficulties resumed, wearing it for the remainder of the flight.
During the final approach, the autopilot malfunctioned, as it had during the earlier flight to Munich, causing the commander to disengage it and land manually. The aircraft landed safely at 09:24 UTC and taxied to the stand, accompanied by firefighting vehicles. On arrival, the commander informed apron control that the smoke and haze had been caused by the air conditioning system and that the copilot had been affected. Passengers deplaned normally.
Aftermath
Post-incident inspection revealed oil deposits in pack 1 and high oil contamination in the bleed band area. Boroscope examination confirmed a No. 1 bearing leakage in engine 1, necessitating engine replacement. The ILS 2 receiver was also changed in response to the autopilot issues. The Swiss Federal Aircraft Accident Board determined that a serious incident had occurred.