Sun Way IL76 at Karachi on Nov 28th 2010, engine fire

Last Update: March 8, 2017 / 17:13:47 GMT/Zulu time

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Incident Facts

Date of incident
Nov 28, 2010

Classification
Crash

Cause
Engine fire

Aircraft Type
Ilyushin Il-76

ICAO Type Designator
IL76

On Mar 8th 2017 Pakistan's Safety Investigation Board (SIB) released their final report concluding the probable cause of the crash were:

The cause of the occurrence was uncontained failure of the 2nd stage disk of LP compressor of Engine # 4 due to fatigue fracture which resulted in in-flight fire and damage to adjacent areas of right wing / flaps to an extent that flight could not be sustained.

- The use of mishap engine beyond its manufacturer’s assigned life without assessment and life enhancement by the manufacturer was the cause of its uncontained fatigue failure.

The SIB reported the aircraft departed Karachi with a takeoff mass of 197 tons including 74 tons of fuel and 30.5 tons of cargo, humanitarian aids (tents). The CG was at 30% MAC.

The captain (57, ATPL, 7,272 flight hours total, 5,502 hours on type) was assisted by a first officer (46, CPL, 2,220 hours total, unknown hours on type) and a navigator (49, Navigators License, 6,350 hours total, 4,800 hours on type).

The aircraft departed Karachi's runway 25L at 20:48Z, reached 460 feet AGL then descended again and disappeared from radar. No emergency message or information about the status on board was received by ATC. The aircraft impacted ground at N24.8942 E67.1068 about 2nm from the runway end at a heading of 070 degrees. All 6 crew and 2 support engineers on board of the aircraft as well as 3 people on the ground were killed in the crash, the aircraft as well as a number of houses under construction were destroyed.

Fragments of the #4 engine low pressure compressor were found 1900 meters (1.03nm) from the runway end, the #4 engine low pressure compressor second stage disk (error in the graphics provided) was found 2400 meters (1.3nm) past the runway end, both showed no signs of fire damage.

The SIB complained that they did not receive the complete log books of the aircraft, only a number of pages from the log books were provided.

The SIB reported that the aircraft had received a certificate of airworthiness by Georgia's Ministry of Regional Development and Infrastructure valid until May 15th 2011.

However, Ilyushin had limited the service life of the airframe to 20 years which expired on May 29th 2004.

The last periodic maintenance was conducted in Osh (Kyrgyzstan) on Nov 13th 2010.

Engine #4 had been manufactured on Dec 30th 1980 and had undergone three overhauls since. The initial useful life of the engine had been defined as 6500 flight hours and 3375 flight cycles, the engine had accumulated (since new) 6,055 flight hours and 2877 flight cycles, since last overhaul 1,209 flight hours in 451 flight cycles.

Engine #4 was also service limited by calendar on Oct 26th 2011.

Engine #4 has been removed from service in 2004 following the expiry of its initial service life. The SIB wrote referencing the engine manufacturer NPO Saturn:

The engine was put out of service on 1st May, 2004 after completion of its assigned life. The engine had completed 1638 / 6485 hours 501 / 2929 cycles at the time it was put out of service.

- NPO Saturn did not have any information about operation, maintenance and prolongation between-overhaul hours / cycle’s life or calendar service life after 1st May, 2004.

- The section 6.2 of the engine log book (resource, service life) had entries of betweenoverhaul life extended up to 26th October, 2010 and 26th October, 2011 referring “Technical Condition Reports” dated 20th May, 2010 and 19th July, 2010 respectively. However, “Technical Condition Reports”, NPO Saturn telegrams and records of log book section 12.2 were not made available by the operator.

- According to the information provided by the operator as on 13th November, 2010 this engine had between-overhaul remaining life of 444 hours / 496 cycles and its calendar service life were expiring on 20th October, 2011. The operator however, could not provide “Technical Condition Report” and NPO Saturn telegrams in support of service life extensions.

- Based on the available evidence it was established that at the time of the crash this engine (S No. 0304404011876) was being operated beyond the service life established by NPO Saturn.

The SIB analysed that on previous flights the crew had difficulties starting engine #4 and needed to shut the engine down again using the emergency stop valve, probably due to a hung start. Subsequently the air bleed for Inlet Guide Vane heating was opened for the restart of the engine. The SIB analysed that the cause of the abnormal starts most likely was wear of blades reducing the compressor efficiency.

The SIB analysed that for engine start for the accident flight engines #1, #2 and #3 were started, the crew opened the air bleed for inlet guide vane heading and started engine #4 without issue.

The aircraft commenced the takeoff run at 20:43:05Z, the crew rotated the aircraft for takeoff at 20:43:53Z at 274 kph (148 KIAS). The gear was retracted. At 20:44:27Z the aircraft was climbing through 90 meters/295 feet at 320 kph (173 KIAS), the crew just made a transmission but interrupted the transmission probably by a critical situation on board. Radio contact was lost afterwards.

At 20:44:30.5Z the high pressure rpm of the #4 engine suddenly ran down, a fire #4 engine indication as well as a fire indication on board occurred, the aircraft climbed through 100 meters/330 feet at 325kph (175 KIAS) about 2000 meters past the runway end. The other three engines continued to run normally on takeoff power. The aircraft banked to the right at about 8 to 9 degrees/second, ailerons and spoilers were deflected on maximum angles to compensate for the right hand roll, at the same time the crew applied left rudder pressure (-9 degrees of rudder position), the right hand roll stopped reaching a maximum of 14.7 degrees and reduced. Thrust lever engine #4 was reduced to idle, the engine was shut down using the emergency stop valve 11 seconds after the engine failure.

After 20:44:39Z the aircraft continued to roll right despite full left deflections of ailerons and spoilers and reached 32 degrees of right bank within the next 4 seconds. The climb stopped at 140 meters/460 feet AGL and the aircraft began to descend again, due the bank angle the radio altitude continued to increase. By 20:44:51Z the aircraft had reached 71 degrees of right bank and impacted ground at 20:44:53z.

The SIB reported that the fragment of the 2nd stage low pressure compressor disk was lost in the cause of the investigation, the failure analysis of the #4 engine was thus conducted based on the photographs that were made after recovery of the fragment (see below).

A fatigue crack had developed in the 2nd stage disk starting from the extreme edges of the hole of the disk, which is meant for installing the bushing for pin of compressor blades. There had been previous such failure scenarios as result of fretting corrosion in the holes for installing the bushings. This type of failure had been discovered in 1992 and remedial measures were mandated via 4 bulletins. All aircraft operating in the Russian federation were accordingly modified. However, due to the lack of documentation provided it could not be determined, whether the accident engine had undergone that modification.

The SIB analysed that a single engine failure could not have caused a scenario in which it was impossible to counter the yaw/roll tendency with the flight controls. Mathematic modelling showed however, that the accident aircraft's additional roll tendency might have been caused by damage to the flaps located right above and behind the engine causing the loss of lift on parts of the right hand wing. The effect observed on the accident aircraft could be produced by loss of 20% of the flaps.
Incident Facts

Date of incident
Nov 28, 2010

Classification
Crash

Cause
Engine fire

Aircraft Type
Ilyushin Il-76

ICAO Type Designator
IL76

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