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8 Aug 2019 - Preliminary report issued into oil loss and IFSD of 737-800 ZS-ZWE at Tambo on 8 Jul 2019

On 8 Jul 2019, B737-800, ZS-ZWE (40854/5518) operated by Kulula from FACT to FALA suffered a loss of oil in the #1 engine leading to an in-flight shutdown (IFSD). The aircraft diverted to FAOR and was landed safely by the crew.

The preliminary report found that 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.

The interview with the AME revealed that he did not use the applicable AMM due to unavailability on the used available computer software system. Also on completion of the starter installation, the AME did not torque and secure the magnetic plug with a safe locking wire.

SIgnificant extracts from the report are given below.

 

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The drain/fill magnetic plug and the starter without locking wires

History of the Flight

A Comair Limited aircraft operated by Kulula with flight number CAW494 was in a flight to Lanseria Aerodrome (FALA) from Cape Town international Aerodrome (FACT) on 8 July 2019. On board the aircraft was a crew of 6 and 194 passengers (188 souls) on board. According to the PIC reporting, 10 nautical miles (Nm) prior to initiating a descend, the crew noticed a number 1 engine low oil quantity indication warning caption reading 17%. Following the warning, the crew followed requirements of the emergency check list and contact FALA air traffic control (ATC) requested an early descend from 33000 feet (ft) or flight level (FL) 330 to FL210, and they stated the emergency situation. He further stated that, they contacted the maintenance control centre (MCC) to request further technical assistance. The MCC advised the crew to continue with route to FALA and monitor the aircraft engine oil quantity until it run to 0% on which they can commence with an engine shutdown.

The MCC also requested that the crew divert to OR Tambo International Aerodrome (FAOR) in case the number 1 engine oil quantity run to 0% prior to reaching FALA and if it was permissible for the flight. The crew proceeded to FALA and kept consistent monitoring of the aircraft engine oil quantity indication that did not stop reducing. Upon reaching FALA when the aircraft was overhead the engine low oil quantity indication reached 0% and the crew requested a go around and diverted to FAOR and permission was granted. An inflight engine shutdown procedure was carried out by the crew and the number 1 engine was shutdown. The aircraft proceeded to FAOR and requested a further descend to FL110 and was handed to RADAR monitoring procedure. On approach for FAOR emergency landing procedure were carried out by the crew and the airport emergency fire and rescue (AEFRS) were put on standby. The aircraft landed safe on Runway 21L and was escorted to the apron by the AEFRS.

No injuries were sustained by any of the aircraft occupants and the aircraft had no damages. The aircraft damages were limited to the starter.

The aircraft incident occurred in flight during day light meteorological condition at position south of FAPS FAR75 at a distance 30Nm from FALA.

Engine number 1

A preliminary review of maintenance records was conducted in relation to the reported incident, a review of specific engine maintenance record revealed the following: According to the available maintenance records, on the 07 July 2019, a starter change was conducted at George airport following an aircraft starter failure for number 1 engine during departure preparation following a push back. The aircraft proceeded with flight to FACT following a sign off by a qualified technician on site on the same day of installation on 07 July 2019. On 8 July 2019 the engine experienced oil loss during flight which led to an inflight engine shutdown followed by the aircraft diverting to FAOR were it landed safe.

D-FDR

Recordings According to the D-FDR downloaded information analysis the following was revealed

  • The first indication of a reduced in number 1 engine oil quantity was at 11:11:25, with 12.8 units recording. The previous recording was at 11:07:53 which indicated 06min 24seconds earlier with 13.3 units of oil quantity recorded.
  • The N1 engine oil quantity continued to drop at a constant rate during the cruise up to 3 units remaining at 11:54:01. Then the N1 engine oil quantity began to drop slower rate of 1 unit during a descent approximately 12:10:29.
  • The oil quantity dropped to 0 during a go around at approximately 12:14:37 over FALA. Following this the N1 engine fuel flow was reduced to 0 at approximately 12:17:32 which was 02minutes and 55seconds after the oil quantity was reached 0 units indication in the cockpit display.
  • The N1 oil pressure dropped to 0 at approximately 12:18:12 which was 40seconds following fuel flow shutdown.
  • The N1 engine oil drained from 13.3 units to 0units in a period of approximately 1hr 6min and 44sec (From 11:07:53to 12:14:37).

Tests and Research

According to the SAAT during the post incident inspection oil was found on the inside of the engine cowlings. Also the starter drain/fill magnetic plug housing was found loos inside the cowlings.

During the installation of the starter, the AME did not follow the requirements of the 737600/700/800/900 AMM CML D633A101-CML Rev69-15 June 2019 which required the use of an adopter or alternatively to use gravity feed for oil servicing.

Also the AME did not fallow the 737-600/700/800/900 AMM CML D633A101-CML Rev69-15 June 2019 which requires that the starter drain/fill plug to be torqued to 7.3-4.52Nm or 65.0-40.0 in-lb and be safety wired.

Preliminary Findings

  • The PIC was issued with an air transport pilot licence (ATPL) on 12 December 2018 with an expiry date of 31 December 2019. His last skills test was carried out on 23 March 2019.
  • The PIC was issued with a medical certificate on 26 March 2019 with an expiry date of 31 March 2020.
  • The FO was issued with an air transport pilot licence (ATPL) on 23 January 2019 with an expiry date of 3 April 2020. His last skills test was carried out on 23 January 2019.
  • The FO was issued with a medical certificate on 22 August 2018 with an expiry date of 31 August 2019.
  • The AME was issued with a AME licence on 26 July 2018 with an expiry date of 02 October 2020.
  • The interview with the AME revealed that he did not use the applicable AMM due to unavailability on the used available computer software system. Also on completion of the starter installation, the AME did not torque and secure the magnetic plug with a safe locking wire.
  • 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.
  • The aircraft was initially issued with Certificate of Airworthiness (C of A) on 18 August 2015 with an expiry date of 17 August 2019. The Certificate of Registration (C of R) was issued on 19 August 2015.
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