Take off rpm

Roger Lee wrote:

You can flatten a prop pitch to a point it looses efficiency.

Prop pitch can become inefficient with too much or too little pitch.

Roger,

I can’t dispute your claim. I’m just citing the Rotax 912 OM chart that links horsepower to RPM. According to Rotax data, my 912UL won’t make maximum horsepower at any rpm below 5,800.

5800 is fine, but the prop pitch can be flattened more and it has limits to over and under pitching. Flatten the blade completely and see what happens. Had one guy that turned the blade pitch the wrong way and his plane went backward on the ground.

No different than the engine. The engine won't  work well at 7K rpm and you can't  maintain level flight at 1800 rpm. There are upper and lower limits for everything on your plane or Mfg's wouldn't  have specs to follow and have to test everything.

C'mon, you saw that in THOSE MAGNIFICENT MEN IN THEIR FLYING MACHINES. You can't fool me. ?

Jim, it has been a month since I flew.

According to my notes on 6/24/23, the blade pitch was set at 10*, and the level flight WOT yielded 5,720 rpm. I did not note the rpm for TO run and climb, I just noted that climb was good. My questionable memory tells me that the TO & CO rpm were around 5,000 or less. If my memory is correct and the remembered rpm is so low that the engine would be damaged, then I would prefer to have the TO/CO rpm closer to 5,200. If that is changed, then the WOT rpm will also increase.

This prop might be set just fine. I can't test it because things are down for installing the dual throttle kit. When I can test things, I will try to return to this discussion and report what I find.

For entertainment purposes, the IAS on 6/24/23 was 85-90 mph (rough summer air). I have tried testing the ASI with a home-grown anemometer, but have yet to get that to work. This 701 has slats removed and vortex generators installed.

Wizard, just want to point out that for some reason, replies or comments or whatever they are come up sort of out of order on my MacBook. It sort of looks like someone posted an answer right before I asked a question. In other words, the information that I was seeking was in the comment just preceding my question. The only difference it makes is that it might look argumentative.

I will go to the link you gave and read it a couple of times.

I went back and read your previous replies a couple of times and I think had I noted the rpm during TO and initial climb, I would find that the prop setting I have now is fine. I did not note that at the time because I was thinking only of the WOT limit of 5,800.

BTW, the 85-90 IAS I mentioned in another reply was at 5,500rpm - I understand METO. I normally cruise at 5,000-5100rpm.