Message-ID: <407352EF.2080506@netdoor.com>
Date: Tue, 06 Apr 2004 20:01:35 -0500
From: Charlie & Tupper England <cengland@netdoor.com>
Reply-To: cengland@netdoor.com
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: : Percent Power, Throttle position, & RD-1C performance
References: <list-3147648@logan.com>
In-Reply-To: <list-3147648@logan.com>
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OK, how about a 'real world' cruise power fuel burn? My 160hp fixed=20
pitch Lyc powered -4 burned ~9.2-9.5 gph of avgas at ~190-195 statute=20
mph. What are you burning down around 190 mph (allowing a little wiggle=20
room for 'work in progress' aerodynamics of your plane)?

Tracy Crook wrote:

> Took closer note of throttle position on todays flight. At 2000 ft the =

> throttle was only about 1/3 open (position of throttle quadrant, but=20
> it closely mirrors butterfly position) at economy cruise setting which =

> was 6.0 GPH. This is about 42% power, 82 HP according to the EM2 which =

> is fairly close but not perfectly calibrated yet. The same power=20
> setting with the -B drive would bave been a bit further open.
> I did a quick check of MAP at 1000 ft at full throttle and found I was =

> not getting any drop at 150 MPH and had .5" boost at 220 MPH (ram air=20
> recovery I assume). I did not get around to checking it in slow climb=20
> which would more accurately compare to what you would see on a dyno.
> Finally got some reasonably calm air to do performance comparisons of=20
> -C drive vs -B drive. Without the prop blade cuffs it looks like the=20
> break even point is at 203 MPH. Above that -C burned more fuel than=20
> the -B. After installation of the cuffs, the break even point was off=20
> the scale! i.e., above top speed with -B drive. I had a good data=20
> point on the -B drive while burning 17 GPH (209 mph during SUN 100=20
> race). At the same speed, the C drive was burning 15.8 gph. This was=20
> better than I had hoped for.
> Tracy
>
>     Thanks, Tracy. I was hoping there would be someone out there
>     flying with the same TB diameters.
>
>     Like most things, TB diameter is a tradeoff. My conclusion from
>     the dyno data is that 44mm per rotor (1 =BE) is a bit small as the
>     MAP is dropping off over 5000 RPM. But if you want to idle at
>     1500, and have a decent transition from there to 3000; 1 =BE is
>     good. For a 2.85 to redrive, I=92d want to increase that flow area
>     by 30% or so =96 to about 2=94 dia for each rotor.
>
>     My data may not be representative because of restricted flow to
>     the TB. The =91airbox=92 size is restricted by the cowl, and may ha=
ve
>     restricted the flow a bit. In hindsight, it would have been smart
>     (and easy) to make a run with the airbox off and see what
>     difference it made.
>
>     Al
>