The disintegrating airplane engine
Although no longer in the news, just about two weeks ago the headlines on most of the news channels began with the hair-raising story of engine parts falling from the sky. It happened on a United flight that had just taken off from Denver for Hawaii. It appears one of the engines had disintegrated raining its parts on a swath of residential neighborhood near the airport. Some of these were rather large pieces of metal which hurled down at high speeds and could have caused loss of lives and major damage to the properties where they fell. Fortunately, that did not happen – no one got killed or injured and there were no major damages to the neighborhood residences. The plane made a quick turn around and safely landed back at Denver with no injuries to passengers or crew. United simply rebooked the passengers on another flight. End of story on a good note. Not much of interest to the news media anymore who quickly moved on to the next big sensational story.
So, was it just a matter of luck that even after what looked like a catastrophic engine failure there were no casualties, and everyone safely made it back to Terra Firma? Hardly. Allow me to elaborate, but first let me show you this video from that flight. Just click on the link below:
So, what do you see? Yes, the engine has lost a bunch of parts and you can actually see the innards of it. What else? Well, even in that disintegrated and severely damaged stage, the engine is still running with the flame in the combustion chamber still going strong! Scary yes, but to an aircraft engine designer like myself it was a remarkable sight. It was the validation of our FAA mandated requirements that we design aero-engines to withstand catastrophic failures such as these and not completely disintegrate allowing the airplane to be safely brought back to ground. While we don’t yet know the exact cause of this failure, preliminary reports indicate the large fan that you see in the front of airplane engines might have lost a blade which ejected out as a high-speed projectile, taking part of the fan casing and the cowling that surrounds it. These were the large parts that were discovered in one of the neighborhood houses. The majority of the engine had managed to mostly stay intact.
Now, as a retired Pratt & Whitney engineer I would have liked to say “of course it would stay intact -it is a P&W engine”. But that would not be true. You see, in order for aero-engines to be certified to the extremely rigorous and stringent FAA requirements, they have to be able to withstand all kind of mechanical and environmental catastrophes. To demonstrate and prove that it indeed would, we have to carry out thousands of hours of testing where all type of foreign objects such as ice, hale, and birds of different sizes – it used to be real but now made of clay, are thrown at the engine while it is running. And even under the barrage of these foreign objects the engine must keep working and producing thrust albeit at somewhat lower levels.
The final series of these foreign object tests include what is called the “Fan Blade Off Test” in which one of the blades is intentionally released from its hub while the engine is operating at full power. The requirement is for it to keep running without disintegrating and remaining mostly intact.
The United flight appears to have demonstrated this in spades in a real-life situation.
So, next time you board a flight just know that the engineers at Pratt & Whitney and yes at other engine companies as well have got your back and their engine will keep on ticking even while taking a catastrophic licking.