-----Origi= nal Message-----
From: Rotary motors in = aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Jim Sower
Sent: Tuesday, September 23, 2003 6:20 = AM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: = Power on a cold day was Re: [FlyRotary] Re:Some turbo thoughts from a pro = ....

<... density change is proportional to the change in absolute temp, so 10F is about 2% ...>

True. But that 2% increase in power is ALL EXCESS THRUST (over and = above what it takes to hold exactly what you've got - say 90 kts and 1000 fpm climb). Two hp would be 66000 #'/min which with a 2000# airplane = produces 3300 fpm rate of climb - ABOVE what you started with !! Of course = not every spec of that extra power gets to the prop, but you can see how = what appears to be a modest power increase can produce results that are = apparently way out of proportion to change in power.
Just a theory .... Jim S.

Sorry; Jim. No cigar. = Wouldn’t it be wonderful. Except for drag and prop efficiency you’d = be close. Put those factors in and 2 hp will get you about 20 ft/min = more climb rate on a good day.

Al Gietzen wrote:

=

Rusty, the = rotary engine (for what ever reason) just LOOOVVVVVEEEESSS those cooler days. I = have had fuel flow of over 20 gph on take off when OAT was 28F. That calculates out to over 200HP, static RPM was 5800 rpm vice a nominal of = 5200 on a "normal" day. I've never said anything about it = because 1. Who would believe me 2. Who would believe me? and 3. Who = would believe me? Anytime the OAT is below 65F or so my static RPM increases about 200 rpm for ever 10F further temp = drop.

Ed;

The only problems with this is 1. I don’t believe it, 2. I don’t believe it; and 3, I find it hard to believe J.=

The air density change is proportional to the change in absolute temp, so = 10F is about 2%. Maybe 3 hp? Gee, we don’t really need = to turbo because the adiabatic temp drop with altitude will overcome the = loss of power due to altitude J. Could there be some other effect going on here? Fuel = density is also changing. How are you measuring fuel = flow.

One problem with hp inferred from fuel burn is that we know that the = rotary’s don’t burn all that fuel to make power. Fuel is burning = right on out into the exhaust pipe, and the amount of unburned fuel varies with a = lot of other factors.

Al

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Jim Sower
Crossville, TN; Chapter 5
Long-EZ N83RT, Velocity N4095T