Event Details

Title:Uncontained engine failure, Boeing 747-121, October 23, 1995
Micro summary:This Boeing 747-121 experienced an uncontained engine failure on takeoff.
Event Time:1995-10-23 at 0350 EDT
File Name:1995-10-23-US.pdf
Publishing Agency:National Transportation Safety Board (NTSB)
Publishing Country:USA
Report number:MIA96FA013
Site of event:Miami, FL
Departure:Miami International Airport, Miami, Florida, USA
Destination:Piarco Intl,T Airport, Port-Of-Spain, Trinidad
Airplane Type(s):Boeing 747-121
Flight Phase:Takeoff
Operator(s):Tower Air
Type of flight:Cargo
Serious Injuries:0
Other Injuries:0
Executive Summary:

NTSB short summary:

failure of the No. 4 engine fifth stage turbine hub due to a cyclic stress rupture for undetermined reasons, which resulted in an uncontained failure of the engine.

NTSB synopsis:

The flight had an uncontained failure of the No. 4 engine during the takeoff roll. The takeoff was rejected and the aircraft stopped on the remaining runway. Airport emergency personnel extinguished a fire that erupted in the engine after failure. Examination of the aircraft showed the engine, pylon, right wing, flaps, and aileron, right horizontal stabilizer, and fuselage sustained damage from engine debris released during failure of the engine. Examination of the engine indicated the low pressure turbine fifth stage hub had ruptured. About 180 degrees of the hub rim had separated along with the blade attachment slots and blades. The hub ruptured from an area of a well oxidized, intergranular fracture that originated at a tierod hole. There was no apparent defect observed along the edge of the tierod hole that would cause a crack to initiate and propagate to critical length.

NTSB factual narrative text:

On October 23, 1995, about 0350 eastern daylight time, a Boeing 747-121, N613FF, registered to and operated by Tower Air, Inc., as flight 803, a 14 CFR Part 121 international cargo flight from Miami, Florida, to Port of Spain, Trinidad, sustained substantial damage when the No. 4 engine had an uncontained failure during takeoff from Miami. Visual meteorological conditions prevailed at the time and an instrument flight rules flight plan was filed. The airline transport-rated captain, first officer, flight engineer, and two extra crewmembers were not injured. The flight was originating at the time of the accident.

The captain stated the first officer was performing the takeoff on runway 9L. Takeoff engine thrust was set at 1.42 EPR. All engines operated normally and the aircraft accelerated normally with no unusual vibration felt. Upon reaching the V 1 speed, they heard a loud bang and observed a flash on the right side of the aircraft. The aircraft veered slightly to the right. He, the captain, took control and rejected the takeoff. The flight engineer reported an engine failure. The aircraft was stopped on the runway about 1,000 feet from the departure end. The ATC local controller reported that the No. 4 engine was on fire. They performed the engine fire procedures and fired the engine fire bottles for the No. 4 engine. Airport emergency equipment arrived and extinguished the fire.

Readout of the digital flight data recorder (DFDR) from N613FF was performed by Jeremy Akel, Aerospace Engineer, NTSB, Washington, D.C. The data shows engine power was set at 1.42 EPR on all engines and the aircraft accelerated. Upon reaching an indicated airspeed of 155 knots the No. 4 engine EPR dropped to .98. Upon reaching 162 knots the EPR on the remaining engines decreases to about 1.0 and the aircraft begins to decelerate. (See the Aerospace Engineer Memorandum.)

Postaccident examination of the aircraft by NTSB personnel showed an uncontained failure occurred in the turbine area of the No. 4 engine. The engine, engine cowling, engine pylon, right wing, aileron, and flaps, fuselage, and right horizontal stabilizer sustained damage from debris released during engine failure. A 5 x 7 inch triangular shaped hole was cut into the right side of the fuselage, just aft of station 2,000 and 6 feet above the main cabin floor. A rib and longeron were severed behind the hole and the pressurized area of the airplane was compromised.

Teardown examination of the No. 4 engine showed the low pressure turbine fifth stage turbine hub was missing about a 180 degree continuous arc of the rim, which includes the blade attachment slots. Five pieces of the rim were found on or to the side of runway 9L. The No. 5 hub was found to have ruptured from an area of a well oxidized, intergranular fracture that originated at a tierod hole. There was no apparent defect observed along the edge of the tierod hole that would cause a crack to initiate and propagate to a critical length. (See the Powerplant Group Chairman Factual Report and Metallurgist's Factual Report.)
Learning Keywords:Operations - Bang, pop, crack, sizzle!
Systems - Engine - Uncontained Engine Failure
Consequence - Damage - Airframe or fuselage


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