SriLankan, Civil Aviation Authority in dogfight over new aircraft's safety issue

National carrier defends its Maintenance Dept, says engine defect a global issue; but regulator has questions over airline's safety management practices

SriLankan Airlines this week mounted an impassioned defence of its Maintenance Department, blaming January’s in-flight shutdown ( IFSD) of an engine on UL898 to Bangkok on “a global issue that has occurred on identical engines fitted to aircraft of other airlines”.

But the Civil Aviation Authority of Sri Lanka ( CAASL)-- the industry regulator--also hit back strongly, questioning why the aircraft was dispatched by SriLankan management for commercial flights “with known defects in its engines, without proper investigation for identification of causal factor and necessary rectification”.

“We observed that the airline had merely followed certain written procedures in the manuals without giving weighted attention to the sound maintenance practices that shall be applied based on sound Safety Management Principles which advocate proactive and predictive approach for identification of hazardous conditions with a view to eliminating possible risks, rather than being reactive which entails adverse ramifications,” said H M Nimalsiri, Director General of Civil Aviation (DGCA), in written comments to the Sunday Times.

This newspaper exclusively reported last week that SriLankan Airlines lost certification to operate its new A320neo and A321neo aircraft for more than an hour outside the range of airports suitable for emergency landings after its Maintenance Department released one of the planes (registration 4R-ANE) for use despite having detected debris in the oil monitoring system of an engine.

As a result, the A321neo aircraft flying as UL 898 to Hong Kong on January 21, 2018, was forced to shut down the engine in question and divert to Bangkok on a single engine. After an investigation, the Civil Aviation Authority of Sri Lanka (CAASL) immediately withdrew certification granted to the airline “to conduct A320/321 aircraft on ETOPs [Extendedrange Twin- engine Operational Performance Standards] with 90 minutes diversion time”.

The CAASL said at the time that it did not find any cogent reason for the company’s Maintenance Department to have released the A321neo aircraft for service after detecting debris in the oil monitoring system of one engine ( which has direct impact on flight safety) “without analysing the debris and taking appropriate preventive/corrective measures”, in a letter to SriLankan.

Without ETOPS approval, a flight must always be within 60 minutes of an emergency or diversion airport. With certification, however, it may fly longer–in the case of the A320-321neos, at least 90 minutes– outside the range of a suitable landing area.

The IFSD of a CFM LEAP 1A engine on aircraft 4R-ANE “can in no way be attributed to a lapse on the part of the maintenance staff ”, the airline claimed, in a written response. Attributing the event to a manufacture design failure, it insisted, “No serious lapses in procedures or working practices of Maintenance Department have been identified.”

The company said the relevant department had an impeccable track record with multiple national aviation authority approvals for maintenance of third party aircraft. “The initial investigations carried out by the engine manufacturer CFM International (CFMI) confirmed that the in-flight shutdown on 4R-ANE was due to an internal bearing failure,” it continued.

The manufacturing defect could be attributed to a number of cases, it said, including (but not limited to) material failures, workmanship, manufacturing processes, improper tooling, quality escapes during assembly and damage during transportation, etc.

Four such failures (IFSDs) have been reported worldwide on aircraft of various airlines and CFMI is currently investigating the root cause, SriLankan said: “CFMI continues to remotely monitor all aircraft operating the LEAP 1A engine using condition monitoring technology and will alert operators regarding any future issues.”

The company also said it was in active discussions with the CAASL with regard to the restoration of its ETOPS certification for aircraft fitted with the LEAP 1A engines.

The regulator countered, however, that “after detecting the engines to have developed a serious problem requiring shutting down engine in-flight, as a responsible civil aviation regulators, CAASL cannot just allow the airline to continue”.

“It has accordingly taken immediate action to withdraw the 90 minutes ETOPS approval and also commenced conducting detailed investigation to find out causal factor(s),” Mr Nimalsiri asserted. “During this process the entire episode behind the incident would be dissected for detailed analysis of system errors/deficiencies with a view to rectifying aiming at enhanced flight safety.”

SriLankan also said in its statement that the airframe manufacturer Airbus Industrie has calculated that the in-flight shutdown rate of the A320neo/ CFM LEAP 1A (including the last SriLankan Airlines event) to be 0.008/1000EH. It said this is well below the IFSD rate target of 0.0225/1000EH for ETOPS 180 minutes as defined by the European Aviation Safety Agency (EASA).

Responding to this technical point, the DGCA asserted that the statistics only help one understand “the probability of occurrence of something in the absence of real time evidence about the possibility of its happening”.

“Of course, in granting ETOPS with 90 minutes diversion time, CAASL based its decision on world fleet statistics,” he said. “However, our assumptions were proven to be wrong with SriLankan Airline’s own experience.”

The 4R-ANE aircraft began operations on December 20, 2017, and had performed only 202 flight cycles and 595 flight hours when IFSD occurred on January 20, 2018. “In relation to SriLankan Airline’s own experience, it is much higher than the IFSD ratio,” he pointed out.