Max Takeoff RPM

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blsewardjr
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Max Takeoff RPM

Post by blsewardjr »

My DA40-180 with about 600 hours on the engine was showing only 2600-2610 on takeoff and climb out. During last month's annual I had the mechanic look at it. He was able to get it up to 2620-30 but that was it. The AFM (Section 4A.3.7) has a warning that says take off RPM should be 2680 +/- 20 so a minimum value would be 2660. The mechanic seemed at a loss as to why it wasn't showing and/or developing the full RPM. Any ideas? What do you guys normally see? Thanks. Bernie
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Re: Max Takeoff RPM

Post by astaib »

Hi Bernie,

Mine has 2680 at full throttle while take off and initial climb.

Did your mechanic touch the governor settings?

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Re: Max Takeoff RPM

Post by DaveS1900 »

Did your mechanic do the 500 hour mag rebuild?

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Re: Max Takeoff RPM

Post by blsewardjr »

No, the mag was rebuilt by a shop. My mechanic did do the Slick SB on the other mag.
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Re: Max Takeoff RPM

Post by blsewardjr »

I believe he worked on the governor. Whatever it was he turned it up to max.
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Re: Max Takeoff RPM

Post by CFIDave »

The IO-360 puts out 180 hp at 2700 RPM, but IIRC only 160 hp at 2500. So being able to generate only 2600 RPM on takeoff may rob you of about 10 hp.

I would suggest the issue is likely to be a faulty or misadjusted prop governor.
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Re: Max Takeoff RPM

Post by Rich »

CFIDave wrote:
Thu Apr 18, 2019 1:44 pm
The IO-360 puts out 180 hp at 2700 RPM, but IIRC only 160 hp at 2500. So being able to generate only 2600 RPM on takeoff may rob you of about 10 hp.

I would suggest the issue is likely to be a faulty or misadjusted prop governor.
Mine had a similar, though not as severe, deal early on where it would only get to 2660. We flew it like that for a couple of years. I had a local shop that had the proper certifications and equipment check the governor out and it was operating correctly. We put it back on the plane - same behavior. So we "re-clocked" it. Here's what that means:

The arm that the prop cable connects to is limited in its travel. It attaches to a shaft in the governor that the arm rotates via a spline and clamp mechanism. We removed the arm, moved it one tooth on the spline so that the shaft rotated more to the high-RPM side at all placements of the arm. Problem solved.

I would recommend you do what we did. Get the governor checked out by a proper shop. If that doesn't clear it up, then make the arm-spline adjustment we did.
Last edited by Rich on Thu Apr 18, 2019 2:41 pm, edited 1 time in total.
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Re: Max Takeoff RPM

Post by blsewardjr »

Rich - Thanks! I will have that done. Bernie
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Re: Max Takeoff RPM

Post by Thomas »

Just adjust the detent of the governor, I did the installation of the governor myself after overhaul and had to do it, with the VM1000 (steam gauge) the RPM is blanked out above 2700... but you have then (almost) 180 HP at full PWR, depending of the atmospheric condition of course. (I do have a A/P Licence - its legal :) )
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Re: Max Takeoff RPM

Post by Rich »

Thomas wrote:
Thu Apr 18, 2019 7:54 pm
Just adjust the detent of the governor, I did the installation of the governor myself after overhaul and had to do it, with the VM1000 (steam gauge) the RPM is blanked out above 2700... but you have then (almost) 180 HP at full PWR, depending of the atmospheric condition of course. (I do have a A/P Licence - its legal :) )
We found the detents alone on my Woodward governor didn't allow enough travel. Hence we had to "re-clock" the lever arm on the shaft.
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