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NTSB: American Airlines Engine Failure Attributable to Fatigue

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NTSB: American Airlines Engine Failure Attributable to Fatigue

NTSB: American Airlines Engine Failure Attributable to Fatigue
November 04
12:12 2016

MIAMI — The National Transportation Safety Board (NTSB) issued an Investigative Update of American Airlines flight AA383, which caught fire on runway 28R at Chicago O’Hare International Airport after aborting its take-off.

The report states that the right engine number 2 stage high pressure turbine (HPT) disk failed and fractured into at least four pieces. A large disk fragment landed in an UPS warehouse located about 2,920 feet (890m) from the aircraft.

Recovered stage 2 HPT disk pieces (Credits: NTSB)

Recovered stage 2 HPT disk pieces (Credits: NTSB)

According to the NTSB, the incident occurred while the Boeing 767-300ER, powered by two GE CF6-80 engines, was accelerating for takeoff through 128 Knots-Indicated Air Speed (KIAS) with the engines set at takeoff power thrust setting. Two seconds after the failure, the power levers were retarded at 134 KIAS and brake pressures began to increase as autobrakes activated and speedbrakes automatically extended.

The aircraft came to a full stop about 25 seconds later 9,225 feet (2,811m) past the runway threshold, with a fire below its right wing fed by a pool of leaked fuel. 161 passengers and nine crew were evacuated, with 20 passengers and one flight attendant reporting non-critical injuries.

The NTSB also informed that the stage two HPT disk of the right engine failed and fractured into at least four pieces. The 90% of the disk was collected and sent to Washington D.C. for further examination.

 Fatigue crack location on a disk fracture surface. (Credits: NTSB)

Fatigue crack location on a disk fracture surface. (Credits: NTSB)

Preliminary results so far show one of the fractures showed indications of fatigue cracking initiated at an internal inclusion near the forward side of the hub’s inner bore. Ongoing metallurgical examinations of the disk will focus on detailed characterization of the inclusion and the fracture surfaces, the NTSB said.

The aircraft involved in the incident (N345AN • MSN 33084 • LN 906) was built in 2003, and is among American’s youngest 767-300s. At the moment of the incident, the aircraft had logged 8,120 cycles and 50,632 flight hours.

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Roberto Leiro

Roberto Leiro

Airline and Aviation Writer, with a Fascination for Languages and History, Translator, Incurable Planespotter and Aviation Enthusiast.

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12 Comments

  1. TC
    TC November 04, 23:09

    Last time I checked the 767-300 ER dues not have a auto speed brake feature on takeoff.
    At least the ones I fly do not.

    You might want to fact check the article on the AA 767 at ORD otherwise good synopsis of a tragedy averted by swift thinking on the part of the AA flight crew.

  2. John MacLeod
    John MacLeod November 06, 19:43

    The article mentions “The aircraft logged 8,120 cycles and 50,000 miles”. What are cycles?

  3. Ravee Kurian
    Ravee Kurian November 07, 23:58

    And airframe cycles have little to do with the hours that a particular engine has operated. Engines typically have a separate maintenance record from the airframe and a separate record of hours operated. Not sure why they have provide the age and cycles of the airframe. It will have little relevance to why there has been a metal fatigue failure within that particular engine.

  4. Jake
    Jake November 08, 00:34

    Auto SPD brake after at least reverse idle position is selected during the RTO.

  5. Arthur Alan Wolk
    Arthur Alan Wolk November 11, 08:23

    I litigated United 232, the DC-10 with the exploding No. 2 CF-6 engine.
    That was caused by a titanium inclusion in a turbine disk which had been reported triple melted and was not. It is most disturbing to me after all these years (1989 Sioux City) that the very same problem caused a near tragedy in a B-767. I thought after years of litigation we had put that behind us but like most things I have seen in aviation safety, it’s only swept under the rug until the next accident. The lack of containment, once again, confirms that the standards for the nacelle containment rings are antiquated and ineffective and need to be changed. Good job by the crew, bad job by NDT from manufacture to last inspection of that “blisk”. I predict NTSB will shrug its shoulders and the FAA will have another cup of coffee. Nothing will get corrected. Arthur Alan Wolk

    • cu4hwgs
      cu4hwgs November 11, 11:44

      That is disturbing. What would have been the likely outcome if the failure had occurred after the plane had left the ground and was beyond the runway? Would the remaining engine have had enough power to keep the plane airborne during takeoff?

      • John Rogers
        John Rogers November 11, 18:48

        Airplanes are not certified if they can not maintain flight on a single engine (2 engine Airplane)

  6. Bob Cyborski
    Bob Cyborski November 11, 10:07

    It really bothers me that the NTSB and FAA would swep tis under the rug. Do people have to die before they act responsibly? All the disks on all these planes should be checked now for metal fatigue regardless of impact on the airlines revenue stream and passenger inconvenience. I as a passenger would rather be safe than sorry.

  7. Andre Malo
    Andre Malo November 11, 10:25

    First, an engine cycle is a speed variation from stop to TO speed. Partial cycles exist for idle-TO things like flight idle to TO performed during a go around.

    As engineer working for P&WC I was involved in the testing and development of the APU engine installed in the tail of the 747 400 model. Because the APU was installed under the elevator that is a big fuel tank on this model and under a web of hydraulic flight control line Boeing did not want to accept any statically base reliability concerning the possibility of a HP disk fracture leading to an uncontained event. To met Boeing a 45 lb containment ring had to be installed in this small engine and in addition explosion test had to be performed where a cut disk had to be run to max speed and exploded. After few test we manage to have the cut dimension perfect to cause explosion at the max speed and few more test to have the containment disk design to contain the triple disk (worst energy case) to absorb the 5.5 millions pound force and keep everything contained. You should have seen the mess inside the engine . Boeing was ready to accept a 45lb penalty in the tail for this case however for main engine I assume that the weight would be lot higher and the decision to requested such containment ring is balance by risk evaluation that are very complex and approved by the approval authority.

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