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ASN Wikibase Occurrence # 212561
Last updated: 21 November 2021
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Time:11:30 LT
Type:Silhouette image of generic B735 model; specific model in this crash may look slightly different
Boeing 737-530
Registration: D-ABJB
MSN: 25271/2117
Fatalities:Fatalities: 0 / Occupants: 2
Other fatalities:0
Aircraft damage: None
Location:near Genève -   Switzerland
Phase: En route
Departure airport:Genève-Cointrin Airport (GVA/LSGG)
Destination airport:Frankfurt International Airport (FRA/EDDF)
Investigating agency: STSB Switzerland
The crew of the Boeing 737-500, registration D-ABJB, took off from Geneva at 11:28 LT for a ferry flight to Frankfurt. The flight number was DLH 9921. Other than the two pilots, there were no other persons on board. Shortly after takeoff, the pilots noticed a strong smell of engine oil fumes. At first, they thought that the smell was simply from oil residue from the replacement of the right hand engine of D-ABJB, carried out the day before. However, it did not dissipate so that at 11:31 the pilots put on their oxygen masks.
At 11:39, when they had reached flight level 240, the crew put the aircraft into horizontal flight and began conducting emergency checks using the corresponding "Smoke, Fire and Fumes" checklist. In accordance with this checklist, some electrical consumers have been triggered. In addition, it prescribes the diversion of the aircraft to the nearest and most appropriate airport while continuing checks: "divert to the nearest suitable airport while continuing the procedure". The crew therefore decided to divert the plane to Zurich airport. At 11:45, the pilots informed the air traffic control of the nature of the problem, and then declared a situation of distress and requested to be diverted to Zurich Airport (LSZH). The aircraft was still at flight level 240, approximately 3 nautical miles west of the omni-directional beacon Willisau VHF (WIL) VOR. It was at this moment that air traffic control authorized the pilots to initiate the descent, and then to Zurich airport by means of brief instructions.
The aircraft landed at 11:58 on runway 14 at Zurich Airport. The firefighters were already present at the runway edge at the time of landing. The crew taxied the aircraft to his parking space without any assistance. The pilots then opened the windows from their cockpit while keeping their oxygen masks on. The smell was still perceptible after that the turbojet engines were shut down and the pilots removed their masks.

It is probable that the odour perceived in the cockpit was due to defects in the level of the air cycle machine 1 which is supplied with compressed air by the left engine.
Experience has shown that a few drops of oil in the air conditioning system are sufficient to cause the formation of vapours and their emission into the cockpit and the cabin. The fact that Lufthansa Technik was able to reproduce this smell in Frankfurt, which had not been possible a few hours earlier in Zurich, is surprising in view of the in-depth tests carried out there. The oil marks on the ground and on the lower part of the right engine nacelle appear to be due to the engine replacement, carried out the day before, and not related to the perceived odour in the cockpit.



Accident investigation:
Investigating agency: STSB Switzerland
Status: Investigation completed
Duration: 3 years and 2 months
Download report: Final report


Photo of D-ABJB courtesy

Geneva - International (LSGG / GVA)
11 August 2015; (c) Freek Blokzijl

Revision history:

23-Jun-2018 12:56 harro Added

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