Prop overspeed

decathlon737 · #1 01-19-2009, 12:26 PM

I have new PCU5000x governor and new Hartzell BA prop on Lycoming IO 360 A1B 200 hp angle valve engine. I usually warm oil to 120 degrees before first takeoff of the day and cycle prop 3-4 times. Problem is first takeoff of the day the prop wants to overspeed 100-150 rpm's. Usually first takeoff I have to pull rpm's back with governor. It works fine after the initial takeoff. Is this a prop stop problem or governor problem? Suggestions are appreciated. Mahlon?

flyeyes · #2 01-19-2009, 03:45 PM

I had this exact symptom, and it was related to a tach issue.

Specifically, a wonky power supply in the tach would drift as it warmed up, skewing the readings. After repair, the "first takeoff overspeed" went away.

I checked the readings inflight with one of the optical tachs.

decathlon737 · #3 01-19-2009, 06:41 PM

Thanks for the input but I have a mechanical tach. Could a mechanical tach be reading erroneous?

mannanj · #4 01-19-2009, 06:53 PM

Quote:

Originally Posted by decathlon737

Thanks for the input but I have a mechanical tach. Could a mechanical tach be reading erroneous?

Bill:

I have an electronic tach checker, the one that you point at the prop and it reads the rpm's. If you want to check your tach come on over.

Dan at Sensenich Propellers in Gainseville, GA. is No. one in my book for Propeller/Govener work in this part of the Universe. Good guy and is RV friendly. They do Prop balancing too.

770-519-4999

David-aviator · #5 01-19-2009, 07:40 PM

Could it be that the fine pitch stop is set at too shallow a blade angle?

The hydraulic system may be a bit slow on the first take off to catch the rpm as it surges up to it.

decathlon737 · #6 01-19-2009, 08:09 PM

David, this was kinda my thoughts, Mannan, I had Dan in mind and I guess I'll be contacting him. Thanks for the input.

kiwipete · #7 01-20-2009, 03:06 AM

Mahlon

Basically as the engine rpm rapidly increases on throttle opening at takeoff the governor isn't quick enough to respond
I had the same thing until I set the fine pitch stops as per the hartzell manual.
This is something everyone seems to overlook. But it's a safety issue as if you have a governor fault you may have diffcultly getting the prop back under control.

Hartzell manual - Chapter 4 Testing + trouble shooting - Max rpm (Static)
Low pitch Stop Adjustment

It took me about 4 attemps to set this as the stops were way too fine as set by the factory.

Peter

Kevin Horton · #8 01-20-2009, 04:54 AM

The low pitch stop on my Hartzell was also set way too fine, as delivered from the factory.

Andy Hill · #9 01-20-2009, 01:06 PM

We had this "issue too" until the error of our ways was pointed out

It is not that Hartzell have "set the stop too fine" - they have no idea of what HP engine the prop is going to be attached to

and are quite clear in their manual you need to setup the "static RPM" via the FP stop.

But as above

Quote:

This is something everyone seems to overlook

which you seem to have, we did, and countless others

Andy & Ellie Hill
RV-8 G-HILZ