Scoot B789 near Singapore on Nov 26th 2016, engine shut down in flight

Last Update: October 31, 2017 / 16:20:54 GMT/Zulu time

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Incident Facts

Date of incident
Nov 26, 2016

Classification
Incident

Flight number
TZ-1

Aircraft Registration
9V-OJF

ICAO Type Designator
B789

A Scoot Boeing 787-900, registration 9V-OJF performing flight TZ-1 from Sydney,NS (Australia) to Singapore (Singapore), was descending towards Singapore when the right hand engine (Trent 1000) emitted sparks through the tailpipe. The crew shut the engine down and continued for a safe landing on Singapore's runway 02C.

A replacement Boeing 787-900 registration 9V-OJC performed the return flight TZ-2 and reached Sydney with a delay of 3.5 hours.

On Oct 31st 2017 Singapore's Transport Safety Investigation Bureau (TSIB) released their final report releasing following discussion of the incident:

2.1 IP compressor blade root cracks

2.1.1 One of the first stage IP compressor blade was missing and seven blades had cracks at the blade roots. It is probable that the first stage IP compressor blade that went missing also had a crack at its blade root.

2.1.2 The engine manufacturer looked into the possibilities of the cracks having been caused during the blade manufacturing process, by material defect, or by excessive stress at the blade roots, but could not find any related evidence.

2.1.3 The blade root cracks were probably a result of material fatigue. Once the crack was formed, the cyclical application of force in the engine environment then caused the failure of the blade root.

2.1.4 It is still unknown how the cracks at the IP compressor blade roots were initiated. The engine manufacturer is still conducting research to determine this. The cause of the LP vibration during the climb following take-off and during cruise cannot be determined. There is no evidence to suggest that the LP vibration was related to the cracks at the IP compressor blade roots.

2.2 Tower Controller action

2.2.1 The air traffic service provider had a standard operating procedure in place at the time of the incident whereby all departures and arrivals at a runway that had been assigned to an emergency aircraft (Runway 02C in this case) had to be suspended when the emergency aircraft was at 20NM from touchdown.

2.2.2 This procedure was a prudent one, to ensure that the emergency aircraft would have the exclusive use of the assigned runway. Otherwise, if a departing or arriving aircraft had an abnormal operation that made the runway not immediately useable (e.g. aborted take-off, aircraft parts fallen off), the emergency aircraft would have to go around and come in for another approach. This could mean additional risk for the emergency aircraft.

2.2.3 In this case, the Tower Controller made a decision to clear one aircraft to take off when the emergency aircraft was 5.5NM from touchdown. His consideration was that, should the emergency aircraft get stuck on the runway after landing, this aircraft, which was already taxiing for take-off on Runway 02C, would be delayed. The investigation team is of the opinion that granting a take-off clearance for this aircraft might not have been prudent, in view of paragraph 2.2.2.

The TSIB reported that the flight crew (captain, first officer, second officer) observed the vibration level of the right hand engine had increased to 4.0 units during the climb out of Sydney but reduced to 1.8 to 2.0 units after levelling off in cruise. As all engine parameters remained normal and the vibration level was within limits the crew decided to continue the flight. The aircraft climbed twice during the journey, during both climbs the right hand engine's vibration level increased, not exceeding limits however, and reduced again after levelling off. The crew continued to monitor the vibrations and engine parameters.

During the descent into Singapore the crew heard a loud bang and received indication the engine had shut down automatically, the TSIB annotated the automatic shutdown was initiated by detection of an overspeed of the Intermediate Pressure Turbine. The crew declared emergency with Singapore Air Traffic Control. A passenger reported seeing fire from the right hand engine, the second officer proceeded to the cabin to check the engine but could not observe any fire. ATC was advised about the observation and emergency services were requested on standby. The aircraft landed on Singapore's runway 02C, emergency services reported seeing no fire, and the aircraft taxied to the apron.

The TSIB reported:

Inspections by the ground maintenance personnel revealed the following
damage within the No. 2 engine:

(a) One blade from the first stage of the Intermediate Pressure (IP) compressor was missing;
(b) One variable inlet guide vane was missing;
(c) Some metal debris pieces were embedded in the interior of the engine; and
(d) The trailing edges of a number of fan blades were damaged.

The TSIB reported: "Detailed inspection of the No. 2 engine at the workshop revealed that, in addition to the missing blade, seven blades from the first stage of the IP compressor had each a crack of about 30.5mm on the front obtuse corner of the blade root and extending across the front face and along the top of the bedding flank."
Incident Facts

Date of incident
Nov 26, 2016

Classification
Incident

Flight number
TZ-1

Aircraft Registration
9V-OJF

ICAO Type Designator
B789

This article is published under license from Avherald.com. © of text by Avherald.com.
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