X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from wx-out-0506.google.com ([66.249.82.231] verified) by logan.com (CommuniGate Pro SMTP 5.2.0) with ESMTP id 2722931 for flyrotary@lancaironline.net; Sat, 09 Feb 2008 21:55:29 -0500 Received-SPF: pass receiver=logan.com; client-ip=66.249.82.231; envelope-from=msteitle@gmail.com Received: by wx-out-0506.google.com with SMTP id i27so3941323wxd.25 for ; Sat, 09 Feb 2008 18:54:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references; bh=xJXZOYhSyBsqlwGnVeaKMaFm+tV84Dd9RCJ45ftwTyE=; b=DidoBsX54BUauK1Alr3vq6B1hNBAcBEPsHdB6VYlxK5uux2otCv8y9IIObH5xQ+hQgB/C5ANiBNBmD7OXKFu8W9OCS0BSFfvTNkyzp71Z1iIdsCdGzo3giBAa7ZyRRVxiZ3+AvfTqm+PAORW860tJ4hM6SGUokQ8vgUpEeYKv5E= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references; b=j9jnaa7lJt277SMd3p065mKxjSTAgquESKdSFUbhlI1dkDZBqOHtZF+B37xJ8W5toTtJ2xyxsxDj30cmbt6HwxPuvWhP01qWJIrcstGqAkmO5elOF7Nu2lf87sG0MegVL3krL8HxwwF9R+qbBDVxC21V4Y7Z/zJON9L1fdGXT0w= Received: by 10.70.9.8 with SMTP id 8mr9358144wxi.27.1202612091409; Sat, 09 Feb 2008 18:54:51 -0800 (PST) Received: by 10.70.20.3 with HTTP; Sat, 9 Feb 2008 18:54:51 -0800 (PST) Message-ID: <5cf132c0802091854n5fa9ba61m24bf3a1209558c82@mail.gmail.com> Date: Sat, 9 Feb 2008 20:54:51 -0600 From: "Mark Steitle" To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] Fuel burn In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_15383_14970001.1202612091406" References: ------=_Part_15383_14970001.1202612091406 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Thanks, good data Al. I'm sure that some of the differences we're seeing ar= e due to altitude. So far, I've stayed fairly low (3000-5000'). I may try some higher altitude flight soon just to see how it changes my performance numbers. Another difference is that I have a M/T electric constant speed prop. I normally set it to 2150rpm for takeoff. This allows the engine to turn around 7000 rpm, which will account some for the higher fuel burn I'm seeing. My airport is at 520' msl, so there's a 1000' difference there fro= m your 1500' msl airport. Yes, she really accelerates down the runway. I'm usually airborne in about 900-1000'. Mark Loved the video!!! On Feb 9, 2008 1:24 PM, Al Gietzen wrote: > Let's see, I think it was Bob mentioned assuming .6 #/hp-hr (BSFC) for > fuel burn. Based on what I measured on the dyno on my 20B, that seems a = bit > high to me. My numbers ranged from 0.49 for lean cruise settings to 0.54= for WOT 5000 rpm, lambda of about > 0.93 (max power mixture). > > > > So-o-o . . , when I'm cruising at 7500' at 170 KTAS and 9.3 gph, I'll > assume a BSFC of about .5 which means a power of about 115 hp (mogas weig= hs > 6.18 #/gal). That's a believable number. > > > > When I'm taking off at WOT and about 5400 rpm I see about 19 gph. My dyn= o > hp curve shows about 230 sea level, standard day hp for that rpm. Adjust > that for 1500' elevation and using a BSFC of .54 says I should burn 18.7g= ph. That's very consistent. > > > > My dyno curve also says 270 hp @ 6200 rpm. Adjust that to 7500' (about > 80%) and varying the speed as the cube root of hp says if I get 170 KTAS = at > 115 hp, I should get 210 KTAS at WOT and 6200 rpm. Guess what =96 when I= did > that I saw 208 KTAS readout on my GRT EFIS. > > > > It all hangs together. (Don't forget that SAE rated hp is normalized to > sea level, 60F day.) > > > > These BSFC numbers should be fairly consistent with what a Lycoming could > get. The fact that I get better fuel economy than the Lyc powered > Velocitys suggests that I have a bit lower drag. > > > > This also suggests that the 20B on my Velocity doesn't ever have to reall= y > work very hard. > > > > Al > ------=_Part_15383_14970001.1202612091406 Content-Type: text/html; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Thanks, good data Al. I'm sure that some of the differences we're s= eeing are due to altitude.  So far, I've stayed fairly low (3000-5= 000').  I may try some higher altitude flight soon just to see how= it changes my performance numbers.  Another difference is that I have= a M/T electric constant speed prop.  I normally set it to 2150rpm for= takeoff.  This allows the engine to turn around 7000 rpm, which will = account some for the higher fuel burn I'm seeing.  My airport is a= t 520' msl, so there's a 1000' difference there from your 1500&= #39; msl airport.  Yes, she really accelerates down the runway. &= nbsp; I'm usually airborne in about 900-1000'. 

Mark
Loved the video!!!

On Feb 9, = 2008 1:24 PM, Al Gietzen <ALVentur= es@cox.net> wrote:

Let's see, I think it was Bob mentioned assuming .6 #/hp-hr (BSFC) for fuel burn.  Based on what I measured on the dyno on my 20B, that seems a bit high to me.  My numbe= rs ranged from 0.49 for lean cruise settings to 0.54 for WOT 5000 rpm, lambda = of about 0.93 (max power mixture).

 

So-o-o . . , when I'm cruising= at 7500' at 170 KTAS and 9.3 gph, I'll assume a BSFC of about .5 which means a power of about 115 hp (mogas weighs 6.18 #/gal).  That's a believable number.

 

When I'm taking off at WOT and about 5400 rpm I see about 19 gph.  My dyno hp curve shows about 230 s= ea level, standard day hp for that rpm.  Adjust that for 1500' elevation and usi= ng a BSFC of .54 says I should burn 18.7 gph.  That's very consistent.

 

My dyno curve also says 270 hp= @ 6200 rpm. Adjust that to 7500' (about 80%) and varying the speed as the cube root of hp says if I get 170 KTAS at 115 hp, I should get 210 KTAS at WOT a= nd 6200 rpm.  Guess what =96 when I did that I saw 208 KTAS readout on my GRT EFIS.

 

It all hangs together. (Don't forget that SAE rated hp is normalized to sea level, 60F day.)

 

These BSFC numbers should be f= airly consistent with what a Lycoming could get.  The fact that I get better fuel economy than the Lyc powered Velocitys suggests that I have a bit lower drag.

 

This also suggests that the 20= B on my Velocity doesn't ever have to really work very hard.

 

Al


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