Partial Engine Failure in a Piston Twin

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pelmet
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Partial Engine Failure in a Piston Twin

Post by pelmet »

A couple of videos have been posted to start other threads recently and it seems like a good idea.

https://hwcdn.libsyn.com/p/d/c/b/dcb208 ... 1e3a4d2c79

This one is about a Navajo that had some sort of a partial reduction in power and then was slow to respond. The engine seemed to be operating in a reasonable manner with a loss of 2" MP and no mention of vibration. The pilot decided to land at a nearby airport and forgot to lower the gear prior to landing.

There are various interesting subjects that come up in the podcast which can be discussed. One of them was what should be done with the engine that had a partial power loss.

Of course, each situation is different, so there is not going to be a single answer. One of my favourite portions of an answer is......"It depends".

But I have to say that based on the pilots description of his situation, I was leaning toward keeping the faulty engine running. That being said, he was light, had good weather, and in a fairly powerful twin that likely had reasonable single engine performance for a go-around if one was required.

Toward the end of the podcast, two very experienced pilots came on(at 32:50 and 41:15) to state that they would pretty much always shut down the engine. There can be advantages to this such as a situation where the faulty engine deteriorates as we saw with a King Air in Vancouver a few years ago, But a King Air has better single engine climb capabilities. What about for a light twin, what about at high density altitudes combined with poor weather. Some aircraft have landing gear that can't be retracted if the engine with the single engine-driven hydraulic pump stops operating. And I have personally gotten into situations in training where I got low and slow on final where significant power was required causing a lot of yaw which could be avoided if an engine running at 50% power or more is still operating smoothly.

So are those experienced guys are correct in general. Would you always shut down the engine not just for an obvious vibration that can't be resolved with troubleshooting/high oil temp-low oil pressure situation but for a smooth partial loss of power in a light twin with poor single engine performance.
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Eric Janson
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Re: Partial Engine Failure in a Piston Twin

Post by Eric Janson »

If the engine is developing power and all else is within limits leave it running - jmho.

The one engine failure I've had consisted of a momentary change of RPM on the right engine during climb followed by normal operation. Radial engined DC-3.

In cruise the oil temperature started to increase and pressure started to decrease on the right engine. The engine was kept running until the low oil pressure light came on then it was shut down. The last 50 miles was single engine and we were able to exit the runway and stop on the apron (2 left turns).

In this case we were able to use the engine to get us close to destination instead of returning to a remote mine site.
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pelmet
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Re: Partial Engine Failure in a Piston Twin

Post by pelmet »

Eric Janson wrote: Fri Sep 04, 2020 4:35 am If the engine is developing power and all else is within limits leave it running - jmho.

The one engine failure I've had consisted of a momentary change of RPM on the right engine during climb followed by normal operation. Radial engined DC-3.

In cruise the oil temperature started to increase and pressure started to decrease on the right engine. The engine was kept running until the low oil pressure light came on then it was shut down. The last 50 miles was single engine and we were able to exit the runway and stop on the apron (2 left turns).

In this case we were able to use the engine to get us close to destination instead of returning to a remote mine site.
Thanks Eric.

Appreciate the story. Some might say that the engine was left running more for convenience than safety if the mine site being remote was the only reason. On the other hand, if that remote strip was not a safe place to land with one engine inop it is a different story.

One thing that did cross my mind with the Navajo case was the chance that the other engine could fail. Highly unlikely with a turbine, pretty unlikely with a Navajo engine, more of a consideration on a DC-3, especially if a lot of power is required on the remaining engine.
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Blackdog0301
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Re: Partial Engine Failure in a Piston Twin

Post by Blackdog0301 »

I’ve encountered a partial power loss on a PT6 engine (about 50% power reduction) in flight, but we left the engine running as everything else was indicating normally. As long as you don’t suspect damage has/will occur. Some power is better than no power. Just my opinion.
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pelmet
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Re: Partial Engine Failure in a Piston Twin

Post by pelmet »

Blackdog0301 wrote: Tue Sep 08, 2020 1:24 pm I’ve encountered a partial power loss on a PT6 engine (about 50% power reduction) in flight, but we left the engine running as everything else was indicating normally. As long as you don’t suspect damage has/will occur. Some power is better than no power. Just my opinion.
Thanks,

I should add that idle power(which someone could correctly state is partial power) with the prop not feathered in a plane like that is dangerous for an approach due to the high drag as seen in this accident.......

https://reports.aviation-safety.net/199 ... PH-KSH.pdf

When I say partial power, I mean with positive thrust.
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anofly
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Re: Partial Engine Failure in a Piston Twin

Post by anofly »

if I had partial power, and no high oil temp , oil press ok, and it was not on fire,no visible oil/fuel leaks or shaking , i would leave it running.I would prefer fuel flows to be in line with approx power being produced, after all Its just an engine....
i might try alternate air, and or mess with mixture and or fuel source , and or pumps,and or mags, to see if can be "improved" LOL

If it was shaking like a wet dog, or oil temp took off high,along with low oil pressure, it is not long till things start making like the wet dog, so I would probably shut it down as soon as it started slight wet dog shakes.
might try a quick mag check, i have had an internal mag rotor drive gear fail and it made the engine rough(er?) as it kept firing the one spark plug, 6 times in a row, as the rotor was not turning. made things funny, that mag off made things happier
of course i would look around under the panel for leaking fuel and or oil.... most older twins had copper lines etc bringing that stuff into the panel gauges....
What else we got?
this answer is for a twin with no turbocharger... I have no navajo experience.
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Last edited by anofly on Wed Sep 09, 2020 5:10 am, edited 1 time in total.
planebored
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Re: Partial Engine Failure in a Piston Twin

Post by planebored »

If I was light, I'd shut it down and focus on flying they plane.

The last thing I'd want is the engine to make a bit of power and then fail completely in a critical phase of flight.

If I was very heavy depending on the phase of flight I'd keep it running until level and at a safe altitude. Then shut down and land single engine.
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trey kule
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Re: Partial Engine Failure in a Piston Twin

Post by trey kule »

I am recalling some long ago lessons, but IIRC, one of the concerns if a Navajo loses partial power , it could be a turbo charger failure. And than can lead, very very fast, to a burned through spar and possible fuel tank ignition.
I think Flight Safety recommended Shutting down the engine as a precautionary measure.

That being said, circumstances,particularily in the north, make it a sometimes difficult decision. If these is no sign of fire, other than that distracting glow through the little vents, and the temps and pressures are all good, and MP Hasnt dropped to outside pressure, I can understand the desire to just leave it run and monitor it.

Been 20 years plus since I flew a navajo so maybe that is faulty memory...as an aside I did experience a loss of power on a navajo once...just before the guages went wacky and it failed...cracked crankcase.
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Re: Partial Engine Failure in a Piston Twin

Post by digits_ »

trey kule wrote: Tue Sep 08, 2020 6:19 pm I am recalling some long ago lessons, but IIRC, one of the concerns if a Navajo loses partial power , it could be a turbo charger failure. And than can lead, very very fast, to a burned through spar and possible fuel tank ignition.
I think Flight Safety recommended Shutting down the engine as a precautionary measure.

That being said, circumstances,particularily in the north, make it a sometimes difficult decision. If these is no sign of fire, other than that distracting glow through the little vents, and the temps and pressures are all good, and MP Hasnt dropped to outside pressure, I can understand the desire to just leave it run and monitor it.

Been 20 years plus since I flew a navajo so maybe that is faulty memory...as an aside I did experience a loss of power on a navajo once...just before the guages went wacky and it failed...cracked crankcase.
If your turbo fails on a navajo, chances are you'll be burning through a lot of oil as well. You might be blowing it all overboard, depending on how the turbo failed.
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