Static thrust rpm

[tbienz]

Today I re-installed my newly overhauled 210cm MT prop.
At the request of my IA, I warmed up the engine, then tried mid-range rpm prop pitch changes. All seemed fine, no leaks.
Then he asked for full power: only made 2300rpm
I had never tried this before. The plane made 2700 during the takeoff and climb-out, pre overhaul, but I never tested max static rpm. I told my IA that I could go take off and check RPM. He said even if it makes 2700rpm during the roll & climb, if it’s only 2300 static, then the low pitch stops need adjustment.
Thoughts? We will check tach calibration with a laser strobe.

 

[Snowbirdxx]

Thomas, that happens all the time. No big deal.

Remove Spinner
Remove Safety wire of the large front spinner jam nuts.
Use two 32mm wrenches to open the front jam nut. Do not turn the rear nut while opening the jam.
Now turn the rear nut one turn clockwise.
Tighten the front jamnut and safety wire preliminary.
Remove the two small fairings behind the propblades. If you run the engine with them on, you will need new ones.
Do a static run. If happy with static RPM Safterty wire the jamnuts finally, otherwise adjust.
Do not set static RPM over 2650, otherwise the governor will have to kick in to avoid overspeed if throttle is advanced fast.
Install bladefairings and spinner, go fly! Enjoy your Husky.

Be careful TomD

 

[tbienz]

Thanks Tom. I have adjusted that nut before and even made a special thin box wrench to hold the rear nut while working the front one. Cowling and spinner are still off so access is easy.
I guess my main questions are:
1) at my altitude of 7300ft, should I expect my engine to put out enough power to get 2650 (or is it kind of like a carburetor and the prop low pitch stop just needs to be adjusted for altitude so that at my reduced power output, it still makes the rpm target)?
2) is it expected (normal) that a prop that just came out of overhaul and was set to whatever factory pitch stops are called out in the maintenance manual, that its static run is so far off the expected target?

From what you write (“that happens all the time”) I’m assuming the answer to question #2 is yes, it’s common.
For #1, if we set the low pitch stop to allow my 180hp engine (which up here is really only a 140hp engine) to make 2650 static, and the I fly down to sea level, I assume the governor takes care of the resultant over speed risk?

 

[Snowbirdxx]

MT usually sets the low pitch stop to 2400 for noise. If you set it for 2650 at your altitude the only issue you would get at Sea level is a bit overspeed if you advance the throttle very very agressive. If you want to avoid that ,set it to a tad under 2600 at your altitude.

 

[tbienz]

Will do. Thanks very much for the advice.

 

[Flying Dave]

I’ve always wondered if the typical 2700 rpm limit is an engine design limitation or more for noise and propeller efficiency.

 

[tbienz]

I took care of it as Tom suggested and adjusted until static was at 2650. I have not flown it yet as I need to have everything signed off before doing so. In case anyone else does this, the only alteration is that you must turn nut counterclockwise to increase rpm. 100rpm per quarter turn.
interestingly, the director of the prop overhaul shop recommended I leave the prop where they set it during overhaul (that the remaining rpm above 2300 would be acquired during the takeoff roll which is “normal.”) MT service manual that came with the propeller is well written and very detailed.
Last thing I’ll do before flight (and wiring nut) is to compare indicated on panel to an optical tach. My Husky has supposedly always been louder than others (I’ve heard this from several people) so I wonder if the prop is spinning faster than I think.

 

[Larson]

I had the exact problem after my overhaul (210cm MT).
I believe they set the low pitch stop for the 200hp engine not 180hp ??

Did the exact same as suggested- all went well!

 

[Ak Kurt]

I took care of it as Tom suggested and adjusted until static was at 2650. I have not flown it yet as I need to have everything signed off before doing so. In case anyone else does this, the only alteration is that you must turn nut counterclockwise to increase rpm. 100rpm per quarter turn.
interestingly, the director of the prop overhaul shop recommended I leave the prop where they set it during overhaul (that the remaining rpm above 2300 would be acquired during the takeoff roll which is “normal.”) MT service manual that came with the propeller is well written and very detailed.
Last thing I’ll do before flight (and wiring nut) is to compare indicated on panel to an optical tach. My Husky has supposedly always been louder than others (I’ve heard this from several people) so I wonder if the prop is spinning faster than I think

Thomas, what static did you get before the overhaul?

Kurt

 

[tbienz]

Kurt, I can’t say I ever ran it up to max without moving (until after overhaul).
When I bought the prop 12ya the installer set the rpm for 2700. First annual after installation the A&P doing the inspection said MT sent only the European STC (2500) so he dialed it back to 2500.
I adjusted it back to where it had been and contacted MT in Germany who contacted Flight Resource here and got the updated STC for the US for my plane (which it was supposed to have to begin with).
The plane always went to 2700 during takeoff.
About a year ago, my analog tach failed. I ordered a new one and had them set the Hobbs to match. Nothing else changed but the new tach showed 2775-2800 or so during takeoff. Thus my interest in the optical tach.

 

[Ksmith]

Thomas, thinking back to when you added the MT to 2TQ, as I remember you got a 210cm, no longer available in Europe due to the additional noise with the prop tips going supersonic. I believe the only available prop now is 205cm, does this sound right?

 

[ChipBeck]

I’ve always wondered if the typical 2700 rpm limit is an engine design limitation or more for noise and propeller efficiency.

Dave,

The engine is fine spinning way faster than 2700 RPM and would make more power too. The limit is propeller tip speed which is approaching supersonic (depending upon blade length) at 2750-2800 RPM. Once the tips go Mach 1 two things happen. They are far less efficient and they make an ear splitting racket. Two examples are a Pitts Special S1-S with its fixed pitch prop in a dive at full throttle where RPM may exceed 3300. Sounds like a continuous whip crack. And an AT-6 on its take off roll with the propeller tips making twice as much noise as the engine.

Chip

 

[tbienz]

Optical tach did not work. So nothing further to report on my end.
And Kerry, yes, mine is a 210cm. I don’t know if they are still made, but I think the 205 may have replaced it.

 

[Flying Dave]

Dave,

The engine is fine spinning way faster than 2700 RPM and would make more power too. The limit is propeller tip speed which is approaching supersonic (depending upon blade length) at 2750-2800 RPM. Once the tips go Mach 1 two things happen. They are far less efficient and they make an ear splitting racket. Two examples are a Pitts Special S1-S with its fixed pitch prop in a dive at full throttle where RPM may exceed 3300. Sounds like a continuous whip crack. And an AT-6 on its take off roll with the propeller tips making twice as much noise as the engine.

Chip

That is what I assumed. Thanks.

 

[harry harper]

Optical tach did not work. So nothing further to report on my end.
And Kerry, yes, mine is a 210cm. I don’t know if they are still made, but I think the 205 may have replaced it.

They still make replacement 210 blades. At least as of late last fall. Mine came from the factory.

 

[Ak Kurt]

Just overhauled my 2 blade MT ultra due to calendar time. 2,700 RPM exactly static.

Kurt

 

[Flying Dave]

Mind sharing the cost and turnaround time?

 

[Ak Kurt]

About $5,200 and 3 weeks for a MT Ultra, Tiffin Aire. I changed the color of the tips and spinner so it came to close to $6,000 due to the extra paint work of spinner.

My brothers Hartzell was around $7,500 and 6 weeks if I remember correctly, it had to be sent back to Hartzell.

Kurt

 

[Flying Dave]

Thanks Kurt!