Lufthansa B735 near Zurich on Apr 12th 2015, odour in cockpit

Last Update: June 22, 2018 / 20:32:29 GMT/Zulu time

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Photo of Lufthansa D-ABJB, Boeing 737-500 — Lufthansa D-ABJB, Boeing 737-500 (Photo credit: airlines470 / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Apr 12, 2015

Classification
Incident

Airline
Lufthansa

Departure
Geneva, Switzerland

Destination
Frankfurt/Main, Germany

Aircraft Registration
D-ABJB

Aircraft Type
Boeing 737-500

ICAO Type Designator
B735

A Lufthansa Boeing 737-500, registration D-ABJB performing ferry flight LH-9921 from Geneva (Switzerland) to Frankfurt/Main (Germany) with 2 crew, was climbing out of Geneva when the crew stopped the climb at FL240 reporting an unusual odour in the cockpit and decided to divert to Zurich, where the aircraft landed safely on runway 14 about 20 minutes later.

Lufthansa confirmed the crew decided to divert to Zurich due to an unknown odour in the cockpit. The cause of the odour is being investigated.

On Apr 7th 2015 the aircraft had arrived in Geneva as flight LH-1216 maintaining routine communication, the return flight LH-1217 was cancelled however. The aircraft remained on the ground in Geneva until Apr 12th.

On Jun 22nd 2018 Switzerland's SUST released their final summary report in German reporting that the crew observed the odour of evaporated engine oil but believed this was just residue after the right hand engine had been replaced the previous night. The odour however persisted, the crew donned their oxygen masks and began to work the related checklists while in cruise flight and decided to divert to Zurich. The aircraft landed, the crew opened both cockpit windows but kept their oxygen masks on until after arrival at the stand.

A medical check of the crew showed no danger to the health of the pilots.

At the stand fresh oil was found underneath the right hand engine as well as at the underside of the right hand engine cowl. The oil was cleaned, an engine run with both engines was performed which did not reproduce the odour. Following another engine run simulating a regular flight without any odour the SUST cleared the aircraft to return to Frankfurt. In Frankfurt maintenance made further tests and were able to reproduce the odour, the air cycle machine #1 (left hand) was identified as the most likely source of the odour. A bearing and seal was found defective.

The SUST analysed that the oil deposits below the right hand engine appear to be unrelated to the odour event. It is likely that the odour indeed originated from the defective air cycle machine #1. The SUST analysed that although the odour from the air cycle machine itself does not yet constitute a serious failure, the following needs to observed nonetheless:

- oil fumes being inhaled have a negative impact on health of passengers and crew
- oil fumes can reduce visibility in cockpit and complicate cockpit work. Donned oxygen masks can negatively affect crew communication.

The SUST therefore raises the question whether the inspection intervals for the relevant parts of the air cycle machine need to be re-defined to permit detection of deterioration of such parts also on older air conditioning systems.