X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fmailhost02.isp.att.net ([204.127.217.102] verified) by logan.com (CommuniGate Pro SMTP 5.4.6) with ESMTP id 5644370 for flyrotary@lancaironline.net; Mon, 09 Jul 2012 15:02:47 -0400 Received-SPF: none receiver=logan.com; client-ip=204.127.217.102; envelope-from=bbradburry@bellsouth.net Received: from desktop (adsl-98-85-107-198.mco.bellsouth.net[98.85.107.198]) by isp.att.net (frfwmhc02) with SMTP id <20120709190210H0200sofage>; Mon, 9 Jul 2012 19:02:10 +0000 X-Originating-IP: [98.85.107.198] From: "Bill Bradburry" To: "'Rotary motors in aircraft'" References: In-Reply-To: Subject: RE: [FlyRotary] On the step Date: Mon, 9 Jul 2012 15:02:11 -0400 Message-ID: <38479E90BE45498FBE9DAF5F1FAF6B6A@Desktop> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0009_01CD5DE3.D1D79BA0" X-Mailer: Microsoft Office Outlook 11 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6002.18463 Thread-Index: Ac1d8e7jipdMgFD1TbeGLc8lhbA7ngAEPsLA This is a multi-part message in MIME format. ------=_NextPart_000_0009_01CD5DE3.D1D79BA0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Brian, Getting "on the step" might get you at your terminal velocity/hp/rpm equilibrium sooner, but no matter when, at some time it will all level out at the equilibrium point. You might be able to dive and pick up 9% more, but it will not hold and will eventually bleed off the same point no matter how you got there. It seems true that you can judge the rotary hp by its rpm, but in the case of the shallow dive, you are actually reducing the load on the prop and the engine uses the hp not needed to pull the plane to increase the prop rpm. When the load from the plane comes back, when you level out, the rpm will drop back because the hp is now being used to pull the plane as before. If this didn't work this way, you could carry a plane with a 3 hp lawnmower engine up to 30K feet and drop it out and the engine would be producing 10,000 hp by the time it got down to sea level!! It would then level out and maintain mach 2!!! :>) My next door hangar neighbor has an RV-7 with a 200HP fixed pitch prop and he is pretty consistently running 150 knots of true airspeed at 8K feet. You could probably use him as a guide for performance on your plane. At 8K feet he is at close to 75% power. Say 150 HP. B2 _____ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of bktrub@aol.com Sent: Monday, July 09, 2012 12:43 PM To: Rotary motors in aircraft Subject: [FlyRotary] On the step 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. 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. 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 speed if I descend to my cruising altitude. ( I picked 9% arbitrarily for the sake of argument) . Anyone want to shoot me down on this one? 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. Brian Trubee ------=_NextPart_000_0009_01CD5DE3.D1D79BA0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Brian,

 

Getting “on the step” = might get you at your terminal velocity/hp/rpm equilibrium sooner, but no = matter when, at some time it will all level out at the equilibrium point.  = You might be able to dive and pick up 9% more, but it will not hold and will = eventually bleed off the same point no matter how you got = there.

 

It seems true that you can judge = the rotary hp by its rpm, but in the case of the shallow dive, you are = actually reducing the load on the prop and the engine uses the hp not needed to = pull the plane to increase the prop rpm.  When the load from the plane comes = back, when you level out, the rpm will drop back because the hp is now being = used to pull the plane as before.  If this didn’t work this way, you = could carry a plane with a 3 hp lawnmower engine up to 30K feet and drop it = out and the engine would be producing 10,000 hp by the time it got down to sea level!!  It would then level out and maintain mach 2!!!  = :>)

 

My next door hangar neighbor has an = RV-7 with a 200HP fixed pitch prop and he is pretty consistently running 150 = knots of true airspeed at 8K feet.  You could probably use him as a guide = for performance on your plane.  At 8K feet he is at close to 75% = power.  Say 150 HP.

 

B2

 

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of bktrub@aol.com
Sent: Monday, July 09, = 2012 12:43 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] On = the step

 

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. =

 

=

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.

 

=

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  speed if I descend to my cruising altitude. ( I picked 9% arbitrarily for the sake of argument) .

 

=

Anyone want to shoot me down on = this one?

 

=

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.

 

=

Brian = Trubee

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