Partial Power Failure

Yes, you may have more options with a partial power loss instead of complete engine failure, but don’t get fancy.

Joseph E. (Jeb) Burnside

Wednesday, October 16, 2024 at 06:01 AM ET

Verified

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Key Takeaways:

Partial engine failures are dynamic and can be more dangerous than total failures by fostering a false sense of security and potentially worsening unpredictably.
In single-engine aircraft, prioritize troubleshooting, establishing best glide speed, declaring an emergency, and utilizing altitude to plan a controlled, circling descent to a suitable runway.
For multi-engine aircraft, it's often safer to secure and feather a partially failed engine promptly—before start locks engage at low RPM—rather than attempting to nurse it, to avoid increased drag and further risks.
Regardless of aircraft type, maintain maximum altitude as long as possible to preserve options, and generally avoid go-arounds with a sick engine due to critically compromised performance.

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The one time I suffered an engine failure, it was partial, not total. One cylinder’s intake valve spontaneously disassembled itself—a neat trick for a one-piece component—leaving the other five jugs to continue merrily along, albeit with some major vibration and a distinct power loss. I had plenty of altitude and enough engine power to reach a nearby 9000-foot-long runway after a couple of 360-degree turns to lose altitude. (Pro tip: Keep as much altitude as you can as long as you can until descending for the runway in such a situation.) The airplane was even able to taxi off the runway and to the ramp under its own power. Regardless, we were done flying that day.

Of course, one pilot’s partial power failure is another’s partial failure. In this instance, pieces of the former valve spread throughout the intake system and into a balance tube, and acted as a flapper valve, interfering with the airflow to the cylinders on that side of the engine. It was kind of like the old joke about a car’s turn signal. “Yeah, it’s on; Wait, no it isn’t. Okay, now it’s back on again….”