flyrotary@lancaironline.net Mailing List Archive

After re-reading your email, I think maybe you are thinking about the term 'best power' that we use in aircraft. That refers to a mixture setting with a given RPM. Power always goes up with RPM until the very end of the engine.

If you are using the IVO prop, remember that the flex in that prop throws a wrench into the mix.

Dave Leonard

On Thu, Aug 6, 2020 at 8:36 AM argoldman@aol.com <flyrotary@lancaironline.net> wrote:

Hy Guy,

It is possible that your initial blade angle is set too coarse.

With a CS or Variable pitch prop, one of the purposes is to enable max TO RPM at takeoff. One of the reasons that the RPM builds up after a few seconds is that after you achieve some forward motion the angle of attack to the blades changes enabling full RPM.

There is another possibility, again relating to the prop and that is that because of the pitch, the prop is actually stalling producing little lift (thrust) until forward motion changes the angle of attack and it unstalls. This is accompanied by a rather strange sound coming from the prop until it unstalls.

I had that problem with my dragonfly. (Midwest AE110R/ CS prop (airmaster) warp drive blades) Initially when I tried it on an early x-plane I thought that it was the program, however in real life it happened exactly as simulated. I solved that problem by slowly advancing the throttle.

-----Original Message-----
From: Stephen Izett stephen.izett@gmail.com <flyrotary@lancaironline.net>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Thu, Aug 6, 2020 9:58 am
Subject: [FlyRotary] Testing best rpm power setting

Hi guys

I’m wanting to inflight test for the best RPM for peak power of our 4 port Renesis with variable pitch prop (No constant speed control at present).

On Takeoff at Full Fine we hit 6900 after a few seconds and then rpm builds to 7400 by 500 feet and 110 KIAS

I’m wondering if we are well past the peak torque and would be better off at a lower rpm.

Am I right in thinking the following would use the aircraft as a Dyno to establish rpm for best power?

1. Set up level flight (auto pilot)

2. Maintain WOT and constant mixture (best power - say 0.9 Lambda - 13.2 AFR) via Wideband O2

3. Vary RPM in 200rpm increments for 2 minutes each setting between 5600 and 7200 by adjusting prop pitch

4. Note Fuel Flow and IAS (Logged on Dynon Skyview)

I’m thinking this would give me an indication of best RPM for highest power.

Our Inlet is just under 19” long, measured from the side face of the engine.

So I’m thinking peak torque may be around 6400 rpm.

Your insight would be appreciated.

Thanks

Steve Izett

Renesis 4 port RD1C (2.85:1) Inflight Adjustable Prop

--

Homepage: http://www.flyrotary.com/

Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html