Losing an engine in cruise

Recently, a Delta flight made minor headlines when an engine failed during cruise, and the flight was forced to divert to Phoenix. The mainstream media and much of the flying public seem to think that such an event is met with a rising crescendo of music and heroes saving the day, followed by a commercial break.

In the real world, this is rarely the case, especially in a jet.

The reality is that losing an engine in cruise is just not that big of a deal in an airliner, be it a turboprop or a jet. The design criteria are such that, on takeoff, the airplane has a reserve of 100 percent power; that is, it can lose an engine during the takeoff roll and still safely continue the takeoff while clearing all obstacles in the departure path. It will then be able to return and land. It stands to reason that shutting down an engine in cruise is less of a problem.

A spontaneous engine failure with a turbine engine in cruise is truly rare. More common is a need to shut down an engine as a precaution. The crew might get a message saying that a bleed air system has developed a leak, or vibration is exceeding allowable tolerances, or oil pressure is declining. In a jet, the crew will work the shutdown through the checklist, and it is possible that nobody on board would even know about it–though they may feel a bit of a yaw. On a turboprop, it will be unmistakable, as the airplane will not only yaw, but the passengers on the affected side will see the propeller stop propelling; that’s pretty hard to hide.

I’ve only had to shut down an engine once in my career, and because it was a turboprop, the captain decided we should brief the flight attendant and make an announcement to the passengers first. That became my job. Afterward, we shut the engine down and continued to our destination, which was also the closest, most suitable airport. I’ve also been on one airplane as a passenger when the crew had to shut the engine down. In the cabin, we never knew it as it was so smooth, until the captain came on the public address system and told us what had happened.

The obvious question is what about altitude? It is clearly no big deal when over flat terrain. In the mountains, it is a different story. The crew will have available the information needed to determine the single-engine ceiling for the day based on weight, temperature, and altitude. If terrain is an issue, the flight planning process should have already taken that into account by choosing a route that allows the crew to descend to its new maximum altitude while turning away from the terrain or joining a safer airway before leveling off. Each airframe manufacturer and each airline may do things slightly differently, but the goal is the same: put the crew in the safest possible position to make a safe emergency single-engine landing.

Cue the music…—By Chip Wright

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