Mahan B743 at Tehran on Oct 15th 2015, uncontained engine failure

Last Update: November 8, 2017 / 18:02:45 GMT/Zulu time

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Incident Facts

Date of incident
Oct 15, 2015

Classification
Accident

Airline
Mahan Air

Flight number
W5-1095

Departure
Tehran Mehrabad, Iran

Destination
Bandar Abbas, Iran

Aircraft Registration
EP-MNE

Aircraft Type
Boeing 747-300

ICAO Type Designator
B743

A Mahan Airlines Boeing 747-300, registration EP-MNE performing flight W5-1095 from Tehran Mehrabad to Bandar Abbas (Iran) with 422 passengers and 19 crew, was climbing out of Tehran's runway 29R when a part of the inboard right hand engine (CF6, engine #3) separated from the engine, penetrated the engine pylon and impacted the fuselage of the aircraft while the low pressure turbine and exhaust duct section of the engine separated and fell down onto the ground. The crew stopped the climb, secured engine #3, received a low oil pressure and quantity indication for the outboard right hand engine (#4) and shut the engine down, too. The aircraft returned to Tehran Mehrabad Airport's runway 29L for a safe landing on two engines about 15 minutes after departure. There were no injuries, the aircraft received substantial damage.

The airline confirmed a part separated from the engine and hit the fuselage due to a mechanical malfunction. The aircraft returned to Mehrabad.

A replacement Airbus A300-600 registration EP-MNI as flight W5-1095 and an Airbus A310-300 registration EP-MMP as flight W5-4541 delivered the passengers to Bandar Abbas with a delay of approximately 4.5 hours.

Iran's CAO released their final report concluding the probable causes of the accident were:

IRI CAO Aircraft Accident Investigation Board determines the probable cause of this accident was the operator’s fault to modify the ENG# 3 with AD requirement, and ineffective action for N1 Vibration which caused uncontained engine failure.

The contributing factors:

- In sufficient operator maintenance & engineering performance

- Lack of effective monitoring in operators line maintenance

- Lack of support for engine parts and mandatory information from the manufacturer

- Lack of effective monitoring in Mahan air concerning operation, training and technical divisions.

The CAO reported the aircraft was climbing through 7500 feet out of Tehran when the #3 engine failed, some components of the engine detached and impacted engine #4 as well as other aircraft structure. Hydraulic systems #1, #3 and #4 failed as result of the ejected parts hitting other aircraft structure. Despite the engine vibrations the captain (61, ATPL, 24,500 hours total, 360 hours on type), pilot flying for the sector, took control of the aircraft and returned the aircraft to Tehran. The first officer (53, ATPL, 3,783 hours total, 639 hours on type) was pilot monitoring, both were assisted by a flight engineer trainer and a flight engineer trainee.

The CAO wrote: "The aircraft substantially damaged and it was out of Structural Repair Manual (SRM)."

Parts of the engine fell down to the ground damaging livestock on the ground.

The CAO wrote with respect to the related airworthiness directives:

The Federal Aviation Administration (FAA) issued Airworthiness Directive AD 2012-02-07 mandating inspections with guidance of related GE service bulletins which was concerning to LPT rotor stage 3 disks of this type of engine. This AD require inspections of high-pressure turbine (HPT) and LPT rotors, engine checks, and vibration surveys. According to this AD, a new lower life limit for the LPT rotor stage 3 disks is necessary. Due to some problems the operator did not implement this AD on the engine. It can be considered as the main cause of engine failure and accident.

The CAO complained that the aircraft landed within 17 minutes after the engine failure, however, the captain forgot to pull the circuit breaker for the cockpit voice recorder (30 minutes capacity) which therefore was overwritten.

The CAO analysed that 8 similiar occurrences had been recorded since 2008. The engine manufacturer analysed those occurrences and found a common root cause which resulted in the release of the airworthiness directive (already mentioned above). For EP-MNE the CAO wrote: "The main problem which led to engine failure was vibration as a result of unbalance engine HPT module, which caused crack propagation in ENG.#3 LPT."

The CAO analysed that following the engine failure about 3 minutes after becoming airborne all engine parameters for engine #3 dropped to zero, fuel flow and N1 of engine #4 also dropped to zero with the other engine #4 parameters remaining normal indicating the engine continued to operate. The ground/air parameter on the flight data recorder was also inconsistent 20 minutes after departure suggesting the wiring harness or position sensors were damaged.

The CAO analysed that engines #1, #2 and #4 showed vibration levels at 0.4 units after takeoff while engine #3 showed 2.3 units following departure.

The CAO analysed that following the failures of engine #3 and #4 as well as the hydraulic failures of systems #1, #3 and #4 the crew did not declare emergency but requested to maintain 8000 feet and enter a holding. The crew tried to restart #4 while heading towards the holding but failed to do so, and thus decided to proceed for landing immediately. The CAO analysed:

These technical tasks should be reviewed and done by the cockpit crew accordingly. It made a large pressure work on the pilots with required suitable times and their accuracy might save the aircraft and people on board.

1- Declaring emergency and related coordination
2- Two Engine INOP check list
3- Two HYD systems INOP
4- Two generators INOP
5- Fuel Leak Procedure
6- Nose & Body gear steering INOP( RWY occupation, Tow track Coordination)
7- T/E flap extension
8- One pack air-condition operation

These tasks should be declared by non-flying pilot, then accomplished by pilot& confirmed. All actions were supervised by both available flight engineers in the cockpit. Also they should take decision to return nearest aerodrome.

The hydraulic system description of B747 should be observed to determine the severity of the accident and analyze the operation of the systems.

...

As the pilot has not initiated to retract 10 Deg. Flaps , therefore , there was an opportunity to maintain aircraft stability with access to outboard control surfaces empowering by No;2 Hydraulic System .
But PITCH & ROLL angle were not in their order condition and made inconvenience for passengers during these critical condition.

After leading the aircraft to the holding area, crew tried to restart the engine #4 but it was not successful. The pilot of aircraft decided to make landing in Tehran.

The pilots tried to use 1(A) autopilot system but due to HYD#3 failure, they could not active autopilot system however they did not try on autopilot 2(B).

Finally the aircraft has landed on RWY 29L of Mehrabad International Airport successfully and stopped on the Runway. The pilot has requested towing car for vacating the runway due to lack of nose gear steering system caused by HYD #1 system failure.
Incident Facts

Date of incident
Oct 15, 2015

Classification
Accident

Airline
Mahan Air

Flight number
W5-1095

Departure
Tehran Mehrabad, Iran

Destination
Bandar Abbas, Iran

Aircraft Registration
EP-MNE

Aircraft Type
Boeing 747-300

ICAO Type Designator
B743

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