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Subject: Re: [FlyRotary] On the step
References: <list-5644116@logan.com>
From: Tracy <rwstracy@gmail.com>
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Date: Mon, 9 Jul 2012 12:22:33 -0600
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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The effect you mentioned is true but whether it is significant or not will d=
epend on the shape of your HP curve which depends in turn on the design of i=
ntake, exhaust, etc.  Torque curve is probably pretty flat around 6200 so no=
t too likely to be a big factor.

But more significantly, was that 150 IAS, TAS, or GPS?   Were you at WOT?  I=
've forgotten what the AC type was so don't know how to judge the results fr=
om just this figure.

Tracy

Sent from my iPad

On Jul 9, 2012, at 10:42 AM, bktrub@aol.com wrote:

> I commented on here recently about how I took a cross- country flight to W=
alla Walla from Everett, Wa recently and was only seeing 140-150 mph cruise a=
t 11,500 feet. It got me to thinking- I was getting about 6200 rpm on the en=
gine which is 2175 at the prop. So, I'm a little overpropped/ underpowered.
> =20
> So, there's the old chestnut about how you can get a few more knots from a=
n airplane in cruise if you go a little above your cruise altitude and then d=
escend to your cruise altitude, thereby getting "on the step" . Some pilots s=
wear by this, others dismiss it. I have a theory- if I climb to a cruise alt=
itude and stay at full throttle while doing so, I will only get the engine t=
o run up to a certain RPM and therefore a certain hp will be achieved, and n=
o more and so the airplane will settle into an equilibrium at a certain spee=
d- say at whatever hp/speed - 140 mph at 6200 rpm- lt's say x hp.
> =20
> Now, If I were to descend to my cruise altitude in a shallow dive, I will b=
e acheiving a higher rpm and hence horsepower, say 6800 rpm and horsepower w=
ill be x + 9%x for a hp of 109% of the hp achieved at 6200 rpm, so I should b=
e able to achieve and maintain a higher cruise  speed if I descend to my cru=
ising altitude. ( I picked 9% arbitrarily for the sake of argument) .
> =20
> Anyone want to shoot me down on this one?
> =20
> This is just an theory, If I want to go faster first I have to clean up my=
 drag. My cooling scoop is effective, but obviously draggy. And It needs a f=
lap on it. That's a project for this winter.
> =20
> Brian Trubee

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<html><head></head><body bgcolor="#FFFFFF"><div>The effect you mentioned is true but whether it is significant or not will depend on the shape of your HP curve which depends in turn on the design of intake, exhaust, etc. &nbsp;Torque curve is probably pretty flat around 6200 so not too likely to be a big factor.</div><div><br></div><div>But more significantly, was that 150 IAS, TAS, or GPS? &nbsp; Were you at WOT? &nbsp;I've forgotten what the AC type was so don't know how to judge the results from just this figure.</div><div><br></div><div>Tracy<br><br>Sent from my iPad</div><div><br>On Jul 9, 2012, at 10:42 AM, <a href="mailto:bktrub@aol.com">bktrub@aol.com</a> wrote:<br><br></div><div></div><blockquote type="cite"><div><font color="black" size="2" face="arial">
<div><font style="BACKGROUND-COLOR: transparent" face="Arial, Helvetica, sans-serif">I commented on here recently about how I took a cross- country flight to Walla Walla from Everett, Wa recently and was only seeing 140-150 mph cruise at 11,500 feet. It got me to thinking- I was getting about 6200 rpm on the engine which is 2175 at the prop. So, I'm a little overpropped/ underpowered. </font></div>


<div>&nbsp;</div>


<div>So, there's the old chestnut about how you can get a few more knots from an airplane in cruise if you go a little above your cruise altitude and then descend to your cruise altitude, thereby getting "on the step" . Some pilots swear by this, others dismiss it. I have a theory- if I climb to a cruise altitude and stay at full throttle while doing so, I will only get the engine to run up to a certain RPM and therefore a certain hp will be achieved, and no more and so the airplane will settle into an equilibrium at a certain speed- say at whatever hp/speed - 140 mph at 6200 rpm- lt's say x hp. </div>


<div>&nbsp;</div>


<div>Now, If I were to descend to my cruise altitude in a shallow dive, I will be acheiving a higher rpm and hence horsepower, say 6800 rpm and horsepower will be x + 9%x for a hp of 109% of the hp achieved at 6200 rpm, so I should be able to achieve and maintain a higher cruise&nbsp; speed if I descend to my cruising altitude. ( I picked 9% arbitrarily for the sake of argument) .</div>


<div>&nbsp;</div>


<div>Anyone want to shoot me down on this one?</div>


<div>&nbsp;</div>


<div>This is just an theory, If I want to go faster first I have to clean up my drag. My cooling scoop is effective, but obviously draggy. And It needs a flap on it. That's a project for this winter. </div>


<div>&nbsp;</div>


<div>Brian Trubee</div>
</font></div></blockquote></body></html>
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