Prop surging

[ArizonaAero]

OK I'm beating myself over the head to figure this one out. At takeoff RPM with the prop control full forward, the prop gov starts routing oil to the hub and increasing pitch thereby decreasing RPM by 200 - 250 RPM.

Have had the governor looked at twice by the prop shop, built a governor braket from the gov to the control cable so there was no movement in the rigging and still cant figure this out. Any ideas?
Charlie

[Kahuna]

Can you confirm you are only surging with the prop fwd?
No surging at other RPM settings?

[174Bob&Nancy]

What governor and prop combo do you have,there has been a problem in the past with the hartzell and the mt governor surging,sent my governor back and had it updated and no more problem.

[174Bob&Nancy]

Forgot to mention that as the oil temp got warmer the problem got worse,first flight of the day was usually good then things went downhill from there.

[scard]

What ignition are you using?

[Kahuna]

Has it always surged?

Usually its the govenor, or air.
Here is a good list of items to check.

[CNEJR]

with my MT Gov. & Hartzell. Sent MT back for mod & it cleared up.

[L.Adamson]

Originally Posted by CNEJR

with my MT Gov. & Hartzell. Sent MT back for mod & it cleared up.

Early German made governors sold under the name MT (circa 2003) didn't have this problem. They were the replacement that Van's sold after the Woodwards. I have one of these, and no problems. Later versions by a different supplier/design did have the potential surge problem.

L.Adamson -- RV6A

[Andy Hill]

Charlie...

Just to check, have you set the Prop Static RPM up correctly? i.e. the fine pitch stop.

The book has you set the governor to above 2700 RPM, and then ensure the RPM will not exceed 2700 whilst stationary*. Over a few RV-8 Hartzell/MT Gov combinations, it seems to me any surging is reduced / eliminated by this. Unless performance is absolutely critical, I would suggest setting the static RPM to 2600 or so - this ensures even with a headwind, the RPM stabilises and lets the governor "catch up".

Hope of some use / interest...

Andy (Hill)
RV-8 G-HILZ

* In fact, static running an RV-7/8 frightens me, and I tend to do a short accel run, record "static RPM", and correct it over the 1st few flights.

[Flybuddy2]

Had similar scenario years back on a Mooney. Drove me nuts. Turned out to be a loose fitting on the governor (the line was tight but the fitting was just a hair loose). It caused a very small leak but it apparently let in air. Once I found and tightened, the surging went away.