On 12 December 2011, a Xian MA60 (PZ-MZG) being operated by Merpati Nusantara Airlines on a scheduled domestic passenger flight from Bima to Denpasar as MZ623 was climbing through 6000 feet in day Visual Meteorological Conditions (VMC) when a left engine fire warning occurred. Actual fire was confirmed and the engine was eventually shutdown and an air turnback to Bima accomplished without further event. Damage to the left engine from the effects of fire was externally visible.
The left engine cowling after flight showing cowling damage (Reproduced from the Official Report)
An Investigation was carried out by the Indonesian National Transportation Safety Committee (NTSC) - the Komite Nasional Keselamatan Transportasi (KNKT). Data from both the FDR and CVR were successfully downloaded and used to support the Investigation.
The 39 year-old Captain was found to have 4813 hours total flying experience including 1531 on type. Total flying experience for the First Officer was "not available" but he had 1088 hours flying experience on type. It was noted that pilot type conversion training had occurred in Xi'an (Captain) and Jakarta (First Officer) and in both cases had been conducted by instructors from the Aircraft Manufacturer aided by translators.
It was established that the Captain had been PF and that a Company Engineer had been travelling on the flight. In the climb passing 4000 feet, a Left DC GEN caution was annunciated but ceased following a reset. Passing 6000 feet, a transient engine fire warning occurred and three seconds later reoccurred and continued. The Investigation concluded from the CVR recording that "there was a confusion of both pilots to analyze the situation". After an initial discussion, the cabin crew was asked to get the Company engineer to come to the flight deck which he did and confirmed that a left engine fire was visible from the passenger cabin. Two minutes after the Fire Warning had occurred, both pilots "agreed" to shut down the engine. The PM then feathered the propeller and the PF decided to return to Bima. The PM then activated the first engine fire extinguisher shot prior to, 25 seconds later, shutting the left engine down. The Before Landing Checklist followed by the Engine Failure Checklist were then read. Between 4 and 5 minutes after the Fire Warning had begun the second extinguisher shot was activated but the fire warning remained active. The return to Bima was completed by a landing with the ARFF in attendance on the request of TWR after 22 minutes airborne. No explicit declaration of an emergency was made to ATC.
It was determined that a fuel leak had caused the fire. Inspection showed that the fire had begun in "the lower part of the cowling in front of the partition between hot and cold section of the engine" where the leaked fuel had accumulated and that the fire had then "moved upward crossing the frame bulkhead to the hot section". It was established from examination of FDR data from several previous flights that the same left engine fuel leak had been occurring and that on each occasion, the leak rate had been related to fuel flow, being at its maximum during take off and had then "reduced gradually during the climb stage and even ceased during the cruise". There was also evidence that there had been a gradual progressive increase in the leak which, it was considered, indicated that it was a leak which would typically be caused by mechanical loosening. The source of the leak was confirmed as being an "improperly tightened" fuel line fitting beneath the fuel flow transmitter for which the associated locking wire was still in place. This fitting was found to have originally been installed by the aircraft manufacturer.
The Investigation noted the failure of the crew to promptly execute the memory response to the fire warning and when it was carried out, the complete failure to follow the sequence prescribed in the QRH and the FCOM. The most significant effect of the latter was that the initial discharge of engine fire extinguisher was prior to engine shutdown and would therefore have been completely ineffective. It was also concluded that CRM had been poor and that "the coordination between the pilots during the emergency phase did not show the check - recheck philosophy" being followed. This latter was found to be partially in accordance with wording in the QRH which stated:
For checklist which contains memory items or memory and reference items combined together, PM should firstly verify each memory item has been completed, during verification, usually PM should read these checklist loudly, but PF does not need to respond except for items that are not in agreement with the checklist. But during verify the abnormal checklist about landing, PF must verify and answer checklist items.
The Investigation formally identified two Contributory Factors in respect of the occurrence as follows:
- The fire on the left engine was due to fuel leak on the fuel line fitting which was improperly tightened.
- The delay (in) pilot action had prolonged exposure to the risk (of) fire and jeopardised the safety of the flight.
Safety Action taken as a result of the occurrence was noted as including the following:
- Merpati Nusantara Airlines performed a one-time MA60 Fleet Inspection to check for any fuel leak from the PW127J engines or from the fuel flow transmitters.
- Xi'an Aircraft Industry issued Service Bulletins requiring Operators to:
- check the installation and connection of fuel and oil lines in the engine nacelle of all MA60 aircraft to eliminate the risk of loose connections caused by installation or environment and then check that the torque of all pipe connectors is as specified and no fuel leakage is found.
- perform a check of the required torque during the replacement of any engine fuel flow meter.
A total of 4 Safety Recommendations were made as a result of the Investigation as follows:
- that Merpati Nusantara Airlines should review the pilot training syllabus to ensure the standard (of) qualification.
- that Merpati Nusantara Airlines should emphasise Crew Resource Management (CRM) training to improve communication, role play and commandership.
- that the Xi’an Aircraft Manufacturer to review operational procedures to include check and recheck philosophy.
- that the Directorate General of Civil Aviation should review the policy for approving a training syllabus so as to ensure the standard (of) qualification.
The Final Report of the Investigation was published on 28 November 2014.