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

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Key Takeaways:

Partial engine failures are dynamic and deceptive, requiring pilots to immediately troubleshoot, establish best glide speed, and prioritize getting to a suitable runway.
For single-engine aircraft, maintain altitude until over the chosen airport, then execute a circling descent, delaying gear and flaps until the runway is assured, as the engine's condition can worsen.
In multi-engine aircraft, it's often safer to secure (shut down and feather) the ailing engine early to prevent further issues and ensure the propeller can be feathered before start locks engage.
General best practices include staying at altitude as long as possible to maximize options and avoiding go-arounds during partial power emergencies due to significant risks; accepting a runway overrun may be a safer alternative.

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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….”