Runaway Prop

[Rob58]

Had an attention getting experience today. Climbing out some 20 minutes after takeoff the left engine prop on my Commander started running away. RPM surging up and down by over 800 RPM with no warning. This event was not preceded by any power change or other pilot action. Prop control had absolutely no effect on RPM during this episode. This went on for about 90 seconds. Was about to shut down the engine when everything settled down just as suddenly as it started. Now I am left trying to figure out what happened. Logically this has something to do with the governor (overhauled about 350 hours ago), but I want to understand the root cause of this kind of event. Run away propellers is something you hear about but it’s not something you want to experience. I’m hoping the POA collective can shed some light on how this happens. TIA.

 

[Tom Hurley]

Do you by any chance have an engine monitor that records parameters? I would look back at the oil pressure during the anomaly. Years ago, I had the same thing happen when the line from the proper governor to the hub failed.

 

[Stewartb]

Check your screen/filter and your suction screen for metal.

 

[Let'sgoflying!]

Yes, Rob when my prop ranaway, metal in filter, engine parameter recordings showed oil P loss; but no metal in governor screen.
Good luck.

 

[Bell206]

Logically this has something to do with the governor (overhauled about 350 hours ago), but I want to understand the root cause of this kind of event.

Any root cause answer will depend on the type of props you have installed. But in general, multi-engine props and single props have different failure routes when governing oil is lost. Multi tend to feather and singles tend to overspeed. Also need to address the overspeed and see if you meet the inspection range. While its not mandated on a Part 91 aircraft its highly recommended you look into those requirements. And at 90 seconds of duration I believe you are in that range. Lycoming has an SB that addresses this.

 

[Magman]

Generally the Gov Gasket has a screen built in as well.

Perhaps the screen packed with crud which would account for runaway

Then the gasket/ screen ruptures and operation returns but with

contaminated oil!


C-54 ( from -1 POH) Runaway Prop

Mixture - ICO

Throttle- wide open


If you cannot control it carefully observe the prop and

when it appears ready to separate from the Shaft roll the

aircraft and attempt to throw it over the fuselage!!


Sounded like another “ shark repellant “ deal.

 

[Rob58]

Thanks for the feedback... I will report further as I inspect oil filter and take other action.