While the investigation is still in the very early stages, the National Transportation Safety Board has provided an update that sheds a bit more light on the failure of the Boeing 777’s Pratt & Whitney PW4000-series engine that led to a grounding of all so equipped models. Among the observations was the fact that the engine appeared to continue “burning” after the fuel had been shut off and the twin fire-suppression systems had been activated.
According to the NTSB, “Initial examination of the right engine fire damage found it was primarily contained to the engine’s accessory components, thrust reverser skin, and composite honeycomb structure of the inboard and outboard thrust reversers. The spar valve, which stops fuel flow to the engine when the fire switch is pulled in the cockpit, was found closed—there was no evidence of a fuel-fed fire.” The NTSB said that the engine accessories “showed multiple broken fuel, oil, and hydraulic lines and the gearbox was fractured.”
In addition, the NTSB said that “According to FDR data and flight crew interviews, about 4 minutes after takeoff, the airplane was climbing through an altitude of about 12,500 feet msl with an airspeed of about 280 knots. The flight crew indicated they advanced power at that time to minimize time in expected turbulence during their climb up to their assigned altitude of flight level 230. Immediately after the throttles were advanced a loud bang was recorded on the CVR. FDR data indicate the engine made an uncommanded shutdown and the engine fire warning activated shortly after.”
Additional early examinations revealed: “Initial examination of the right engine fan revealed the spinner and spinner cap were in place and appeared undamaged. All fan blade roots were in place in the fan hub, two blades were fractured. One fan blade was fractured 7.5 inches above the base at the trailing edge. The fracture surface was consistent with fatigue. The second fractured blade exhibited indications of overload failure, consistent with secondary damage.” The blade that failed at the hub had accumulated just fewer than 3,000 cycles since the last inspection. After the Denver incident, the FAA published an emergency AD to require inspections of the first-stage fan before further flight.
I’m sure people thought I was the worst person to sit next o on a flight, because I was always reading books on accident reports. I was on a Delta flight out of Atlanta reading one of my books During the take off roll. I was sitting in the rear of an old DC-9 (this was back in the early 90s) when the was a loud bang and the aircraft aborted the take off. A terrified woman sitting next to me looked over at me. I calmly said it was no big deal, just a compressor stall. We will likely try to take off again.
The captain came on and announced just what I had told the lady, and we taxied back for another go… no problems the rest of the way to Miami.
“Pay no attention to that fire in the engine, for that is not from fuel!”…said the NTSB, the Oz of all things aerial, from behind the curtain of aviation accident investigation. I feel so safe now that fire is more OK when it is not produced by fuel. Now we will have to wait for another year to hear the NTSB opine about what their findings will be about the tangle of cut wires, hyd/oil lines, and missing cowlings that resulted from a fan blade fracturing.
Obviously you have never been involved first hand with an accident investigation of this kind. I am at a loss as to your thinking. The report is only confirming that the fuel shutoff valves functioned as advertised and therefore fuel could be ruled out as the cause of the fire. It did not imply that fire of any kind is okay.
The fire was not fuel? So what!
Assuming the engine had been properly secured, a fuel-fed fire would have had much wider implications. I read no fuel-fed fire as the engine was properly secured and that fuel and hydraulics once shut off did not make their way past shut off valves etc. The general public and probably not just a few pilots among them may have concluded from the photo that fuel was still pouring in to the engine.