SA Airlink RJ85 near Johannesburg on Nov 8th 2017, uncontained engine failure takes out two engines

Last Update: April 11, 2019 / 19:57:45 GMT/Zulu time

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Incident Facts

Date of incident
Nov 8, 2017

Classification
Accident

Airline
SA Airline

Flight number
4L-8103

Aircraft Registration
ZS-ASW

ICAO Type Designator
RJ85

A SA Airline Avro RJ-85, registration ZS-ASW performing flight 4L-8103/SA-8103 from Harare (Zimbabwe) to Johannesburg (South Africa) with 34 passengers and 4 crew, was enroute nearing the top of descent towards Johannesburg when the #2 engine (LF507, inboard left hand) suffered an uncontained failure ejecting parts of the hot section and turbine towards the #1 engine (outboard left hand) causing the engine to fail, too. The aircraft continued to Johannesburg, was vectored for an approach to runway 21R (runways 03 were active) while other aircraft were pulled off the approaches to runways 03 and landed without further incident, vacated onto taxiway L and taxied to the apron followed by the emergency services awaiting the aircraft.

The airline reported all passengers remained uninjured and wrote: "While en route one of the four engines suffered an uncontained failure which then caused damage to its adjacent engine. Upon assessing the damage and status of the aircraft, the crew elected to continue to Johannesburg where it landed safely under the power of its remaining two engines. At no point was the safety of the passengers or crew in jeopardy. Airlink has notified the South African Civil Aviation Authority, which will launch an investigation into the event in order to determine its likely cause. Airlink will provide whatever technical assistance is requested by the SACAA."

The SACAA released their final report concluding the probable cause of the accident was:

The cause of the no2 engine uncontained failure was attributed to the LP turbine retaining nut becoming dislodged resulting on the fourth-stage turbine rotor disk disengaged from the LP turbine shaft. The fourth-stage turbine rotor disc compromised the turbine casing and turbine debris from the no. 2 engine struck the no. 1 engine, causing an un-commanded shutdown and leading to a catastrophic failure of both port-side engines.

Contributory factors

- The incorrect application of torque settings; or improper installation due to a possible mis-stacking of the over-speed ring during maintenance

The SACAA reported:

According to the flight crew, at approximately 1738Z during cruise phase at a height of 34 000 ft (FL340) within South African airspace (over UTULI area), a loud bang was heard on the flight deck and subsequent right yaw experienced. The crew observed an immediate visual indication on the cockpit engines instruments that engines no. 1 and 2 had experienced catastrophic failure. According to the flight recordings, the no. 1 engine failed first. This was due to damage to the full authority digital electronic control (FADEC) box, which had been struck by the turbine blades debris from engine no.2.

Following the incident, the crew declared a MAYDAY call due to the instant failure of the two engines on the port wing, and immediately followed emergency operating procedures. Search and rescue was activated and the dispatch team put on hold. A DETRESFA signal was sent at approximately 1757Z. According to the CVR recordings, the crew requested cabin crew advice the passengers and further take control of the situation in the cabin. Airforce base Makhado (FALM) was put on standby in case the crew decided to divert there. According to the pilot’s report, contact was made with the operator’s maintenance control centre (MCC) to report and discuss the situation. A decision was then made by the crew following considered assessment of the situation to continue with the flight to the destination (for a distance of approximately 240 Nm).

Upon broadcasting their intention to fly to FAOR, they were then requested to change to a dedicated radio frequency (132.15 MHz) at 1810Z. The crew were offered runway 21R, which they accepted, and were handed over to Approach on 124.5 MHz at 1828Z. Prior to landing the cabin crew was heard advising the passengers and preparing them for the emergency landing procedures. The aircraft landed uneventfully on runway 21R at 1839Z and DETRESFA was cancelled.

The SACAA analysed: "The investigation revealed that the fourth-stage turbine rotor disc dislodged from its assembly LP shaft due to a retaining nut that backed off over time during operation. The retaining nut might have backed off due to improper installation caused by one of over-speed ring mis-stacking, improper torque application or a missing lock cup washer. However, it is likely that the lock cup washer was lost due to engine thrust during the incident sequence, as the washer is light in weight."
Incident Facts

Date of incident
Nov 8, 2017

Classification
Accident

Airline
SA Airline

Flight number
4L-8103

Aircraft Registration
ZS-ASW

ICAO Type Designator
RJ85

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