Indigo A20N at Mumbai on Jan 21st 2017, rejected takeoff due to engine failure

Last Update: March 14, 2019 / 23:15:17 GMT/Zulu time

Bookmark this article

Incident Facts

Date of incident
Jan 21, 2017

Classification
Incident

Cause
Rejected takeoff due to engine failure

Airline
Indigo Airlines

Flight number
6E-248

Departure
Mumbai, India

Destination
Delhi, India

Aircraft Registration
VT-ITF

Aircraft Type
Airbus A320-200N

ICAO Type Designator
A20N

An Indigo Airbus A320-200N, registration VT-ITF performing flight 6E-248 from Mumbai to Delhi (India) with 165 passengers and 6 crew, was accelerating for takeoff from Mumbai's runway 27 when the right hand engine (PW1127) emitted a loud bang and sparks prompting the crew to reject takeoff at low speed. The aircraft vacated the runway about 1000 meters/3300 feet down the runway and returned to the apron.

A replacement Airbus A320-200 registration VT-ITD reached Delhi with a delay of 2.5 hours.

On Mar 11th 2019 India's DGCA released their final report concluding the probable cause of the incident was:

The stud (bolt) in the combustion chamber got liberated during engine operation which travelled through the HPT and LPT and ultimately impacted and damaged the rd s-t age LPT blades resulting in engine stall.

The OEM disposition permitting an inspection interval of 375 hours after detecting a partially attached stud in the combustion chamber, is a contributory factor for the incident.

The DGCA reported engines were accelerating for takeoff from Mumbai's runway 27, the thrust levers were advanced into the Flex detent. About 3 seconds later the left hand engine reduced from 80% to 37% N1 and the engine stall warning activated. The crew rejected takeoff at 73 KIAS. The aircraft returned to the apron, where passengers disembarked normally.

The left hand engine sustained damage including the liberation of fan blade parts.

The DGCA analysed:

The neo engines were inducted into service by M/s Indigo Airlines in March 2016.

However, ever since their induction, a number of component failures on the engines have been reported primarily:

1. No. 3 bearing compartmental seal
2. Chip detector in accessory gearbox
3. Erosion in combustion chamber
4. Detection of cracks/lift offs in the inner and outer liner of combustion chamber

On the advice of the manufacturer P&W, the borescopic inspection were being carried out at shorter intervals to detect the failure on ground before it occurs during a flight.

A number of borescopic inspections were carried out on the engine to detect any abnormality and the engine (P770139) was kept in service based on the dispositions given by the OEM to M/s Indigo Airlines.

During the fourth borescopic inspection on 9th January 2017, the operator had reported that 'Stud appears partially attached to segment'. The OEM had given a disposition stating that any cracking that causes partial detachment or exposure of stud is permitted for inspection interval of 375 hours.

During investigation, the combustor floatwall segments displayed coating thermal distress throughout including localized areas of parent material loss. There was a burn through hole at the 12:30 position on the combustion chamber outer liner and floatwall segment where a stud is typically located. The stud was missing and was not found during investigation.

Investigation also revealed that the HPT blades and vanes were noticed to have impact damage and coating loss. All LPT 3rd stage blades were fractured above platform and within 50% of span. The likely sequence of events is that the combustor stud, nut, and washer liberated as one piece, which was ingested into the gas path of the engine and travelled through the HPT and LPT impacting and damaging the blades and vanes as it went through, and ultimately impacting and liberating the 3rd stage LPT blades.

Component bench testing of the LPT 3rd blade shows the mass of the stud, nut and washer would result in significant damage to the leading edge of the 3rd stage which would reduce the fatigue capability of the blades leading to blade fracture which is consistent in this instant case.