Comair B738 near Lanseria on Jul 8th 2019, engine shut down in flight

Last Update: August 4, 2020 / 19:54:03 GMT/Zulu time

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Photo of Comair ZS-ZWE, Boeing 737-800 — Comair ZS-ZWE, Boeing 737-800 (Photo credit: Asylumkid / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Jul 8, 2019

Classification
Incident

Cause
Engine shut down in flight

Airline
Comair

Flight number
MN-494

Departure
Cape Town, South Africa

Destination
Lanseria, South Africa

Aircraft Registration
ZS-ZWE

Aircraft Type
Boeing 737-800

ICAO Type Designator
B738

A Comair Boeing 737-800, registration ZS-ZWE performing flight MN-494 from Cape Town to Lanseria (South Africa) with 182 passengers and 6 crew, was enroute at FL330 and about to reach the top of descent into Lanseria when the crew observed a left engine (CFM56) low oil quantity indication and detected the oil quantity had received to 17%. Following the detection the crew requested an early descent to FL210 and consulted with dispatch, who instructed the flight crew to monitor the oil quantity and if the oil depletes prior to reaching Lanseria divert to Johannesburg if possible. The crew initiated the descent towards Lanseria, during the descent the oil quantity reduced to 0% prompting the crew to shut the engine down. The crew diverted the aircraft to Johannesburg for a safe landing on runway 21L.

A post flight inspection revealed engine oil on the inside of the engine cowlings, the starter drain/fill magnetic plug housing was found loose inside the engine cowlings.

South Africa's CAA (SACAA) rated the occurrence and incident and opened an investigation releasing a preliminary report. The SACAA stated: "On board the aircraft was a crew of 6 and 194 passengers (188 souls) on board." (Editorial note: I have trouble with that math! 188 souls including 6 crew means 182 passengers, not 194 according to mathematics, maximum seat capacity in single class configuration is 189 people).

The SACAA reported the aircraft had suffered a starter failure of the left engine the previous day while preparing for departure from George (South Africa). The only Licensed Aircraft Maintenance Engineer (LAME) available to perform the necessary repairs at George was permanently based at Capetown but was in George on relief duty for the local LAME. He phoned the base in Johannesburg to find out whether a replacement starter was available and was told, no starter unit was available in storage, however, a starter unit was available on a serviceable engine currently in the work shop at Johannesburg. The starter was dismounted and shipped to George arriving in George about 4 hours after the starter failure.

The LAME attented to a number of aircraft while waiting for the starter, then began to dismount the defective starter, noticed the part number of the dismantled starter and the replacement were different and consulted with maintenance in Johannesburg whether those were interchangeable, which was affirmed. The LAME had to attend to another two aircraft landing in and departing George while replacing the starter. After finishing the assembly of the replacement starter the aircraft ZS-ZWE was released for its next flights. ZS-ZWE departed to Cape Town about 6 hours after the starter failure but suffered the occurrence the following day. First indications of oil quantity reduction occurred in flight during the occurrence flight.

The SACAA stated that the Aircraft Maintenance Manual (AMM) required the starter drain/fill magnetic plug required to be torqued at a a specific torque, subsequently a safety wire should be attached. The relevant computer software system showing the applicable AMM was not available to the LAME however. The LAME thus did not torque the magnetic plug at the required torque nor did he apply the safety wire. The SACAA wrote: "The engine oil leak was due to a magnetic plug that loosened during operation as it was not torqued and secured with a safety locking wire as per the applicable AMM procedures."

On Aug 4th 2020 SACAA released their final report concluding the probable causes of the incident were:

Probable Cause

The starter oil drain/fill magnetic plug separated during a flight from FACT to FALA as it was not locked after maintenance which was undertaken the previous day. This resulted in the oil leaking from the engine number 1 through the starter oil drain/fill port.

Contributory Factors:

The AME, when performing a starter change, relied on the information he was given by the base station in FACT, and not the AMM.

The AME was overwhelmed with work on 7 July 2019 due to extra maintenance required on the defected engine number 1 starter.