Return-Path: Sender: (Marvin Kaye) To: lml Date: Tue, 21 Oct 2003 20:19:14 -0400 Message-ID: X-Original-Return-Path: Received: from imo-m05.mx.aol.com ([64.12.136.8] verified) by logan.com (CommuniGate Pro SMTP 4.1.5) with ESMTP id 2645955 for lml@lancaironline.net; Tue, 21 Oct 2003 19:55:59 -0400 Received: from Sky2high@aol.com by imo-m05.mx.aol.com (mail_out_v36_r1.1.) id q.18e.215c71bf (16781) for ; Tue, 21 Oct 2003 19:55:55 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: <18e.215c71bf.2cc7218a@aol.com> X-Original-Date: Tue, 21 Oct 2003 19:55:54 EDT Subject: Re: [LML] Re: Horsepower Calculation X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1066780554" X-Mailer: 9.0 for Windows sub 1100 -------------------------------1066780554 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 10/21/2003 4:18:46 PM Central Daylight Time, marv@lancaironline.net writes: The formula is a little misleading in that it does not take in to consideration all of the variables necessary to calculate true %HP. It is a nice formula to use for general discussion. I would not recommend using it for setting fuel flows or for flight operations. > industry standard (verifable in any STC POH) is: (RPM/2700)*(MAP/29)=HP Joe, Actually, I made a small mistake, it should be: ((RPM/2700)*(MAP/29))*100=%HP as rated at sea level, standard conditions. This was the formula frequently used by aircraft manufacturers to develop their POH tables. It is close enough for fuel flows and flight operations. This formula has finally helped me manage my engine better - an engine of unknown horsepower because of "adjustments" - by reference to actions relevant to % horsepower. I carry just such a printed and plasticized excel spreadsheet with me at all times so I can get a "best estimate" of power. Using the Lycoming Engine manual and spending about 10 minutes carefully charting 25 squared for a 320-D, the chart came up with 80.6% power at 3000 feet pressure altitude (+ or - depending on the pen line width) where as the formula came up with 80%. Additionally, the notation from the engine manual says that there is a "...1% correction for each 10F variation from the standard temperature. The interesting part of the chart is that it shows a decrease in HP at lower altitudes if the standard temperature is used? BTW, my very effective induction ram air recovery is not considered in the engine manual nor are the high compression pistons. If you have a more useful method, please share it with us. Scott Krueger Sky2high@aol.com II-P N92EX IO320 Aurora, IL (KARR) -------------------------------1066780554 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

In a message dated 10/21/2003 4:18:46 PM Central Daylight Time, marv@la= ncaironline.net writes:

The formula is a little misleading in that it=20= does not take in to
consideration all of the variables necessary to calcu= late true %HP. It is a
nice formula to use for general discussion.&= nbsp; I would not recommend using it
for setting fuel flows or for flight= operations.

> industry standard (verifable in any STC POH) is: (R= PM/2700)*(MAP/29)=3DHP

Joe,

Actually, I made a small mistake, it should be:

((RPM/2700)*(MAP/29))*100=3D%HP as rated at sea level, standard conditi= ons.

This was the formula frequently used by aircraft manufacturers to devel= op their POH tables. It is close enough for fuel flows and flight oper= ations.

This formula has finally helped me manage my engine better - an en= gine of unknown horsepower because of "adjustments" - by reference to action= s relevant to % horsepower. I carry just such a printed and plasticize= d excel spreadsheet with me at all times so I can get a "best estimate" of p= ower.

Using the Lycoming Engine manual and spending about 10 minutes car= efully charting 25 squared for a 320-D, the chart came up with 80.6% power a= t 3000 feet pressure altitude (+ or - depending on the pen line width)=20= where as the formula came up with 80%. Additionally, the notation= from the engine manual says that there is a "...1% correction for each= 10F variation from the standard temperature. The interesting part of=20= the chart is that it shows a decrease in HP at lower altitudes if the s= tandard temperature is used? BTW, my very effective induction ram= air recovery is not considered in the engine manual nor are the high compre= ssion pistons.

If you have a more useful method, please share it with us.

Scott Krueger
Sky2high@aol.com
II-P N92EX IO320 Aurora, IL (KARR)

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