RPM FOR DAKOTA

daviddillehay · February 18

After a long idle for avionics install, my 81 Dakota does not want to exceed 2350 rpm but as usual has plenty of power. Any ideas?

Dave Dillehay

N8442A

planewrench · February 18

First of all what does the POH say take off RPM should be? Carl

daviddillehay · February 19

THE POH does not give a takeoff RPM. The O540J35D engine only says 2400 RPM max. Are there any Dakota owners that can add their experience?

Dave Dillehay

N8442A

planewrench · February 19

Dave that is the take off RPM. Do you have a digital tac or a standard tac?

Carl

daviddillehay · February 19

WE have both and they seem accurate.

Dave

planewrench · February 20

Ideally you should be hitting the 2400 static before you do anything you need to make sure there's no slop in the prop control system and that you're hitting the stop on the governor and you have a cushion on the prop control on the quadrant. If you're hitting 2400 on the takeoff roll you're actually doing pretty good. Verify no play in the system then your mechanic can adj the gov. .

Nice to have a digital system to verify mechanical tach.

Carl

daviddillehay · February 21

Finally the answer. Prop governor was going out and completely failed with broken pump shaft. Whew...just more money! Now if the Dual Mag (D-3000) is fixed!

Dave Dillehay

N8442A

griff390 · February 22

https://piperowner.org/talk/discussion/comment/1447372#Comment_1447372

Dave;

Glad you found the issue, thanks for the follow-up post!

planewrench · February 22

I hope it didn't cause any issues. But the only indication you had was a 50 RPM drop?. Carl

planewrench · February 22

How many hours on the engine / Governor?

daviddillehay · February 22

1850 SMOH…I THINK THE 50 RPM DROP WAS SHOWING THE GOVERNOR WAS STUCK AND ABOUT TO FAIL.

DAVE DILLEHAY

N8442A

planewrench · February 22

Very interesting don't see this very often. Thanks Carl

griff390 · February 23

https://piperowner.org/talk/discussion/comment/1447376#Comment_1447376

Dave:

During your run-up, did the prop cycle properly, or is that when you determined that something wasn't right?

Follow-up: did it ultimately fail on the ground or while you were in the air?

daviddillehay · February 24

it completely failed during warm up.

Dave

griff390 · February 24

https://piperowner.org/talk/discussion/comment/1447388#Comment_1447388

Good that it failed while you were still on the ground!

daviddillehay · March 1

It gets worse. Close examination of the prop governor showed lots of metal specs, followed by Oil Filter exam confirmed. Any suggestions for an O 540 J3A5D overhaul?

Dave Dillehay

DAKOTA N8442A

griff390 · March 2

https://piperowner.org/talk/discussion/comment/1447402#Comment_1447402

Dave;

That's not good. Sorry to hear.

If I recall, you're not nearby, but I can highly recommend Poplar Grove Airmotive in IL. I've also heard good things about Penn Yan Aero, but have no experience with them. I'm sure there are good rebuilders near you. Post where you are located here on the forum. Someone will know a good rebuilder nearby.

You may want to consider a factory overhaul or rebuild (they are not the same). A factory engine will be more expensive, but there are advantages:

It's generally a fixed price
A factory rebuilt engine is a zero time engine and comes with a brand new logbook.
All A/D's are complied with and are included in the price.

When I was in your spot, I went with the factory zero time engine. Back then, the difference between a field rebuild and a zero time was only about $1,000 (I know current prices are nowhere near that). Bonus was the factory rebuilt engine came with roller cam and lifters. To this day, the engine is still very smooth and makes good power.

RPM FOR DAKOTA

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