Return-Path: Received: from mail.theofficenet.com ([65.166.240.5] verified) by logan.com (CommuniGate Pro SMTP 4.2) with SMTP id 375040 for flyrotary@lancaironline.net; Mon, 23 Aug 2004 10:59:33 -0400 Received-SPF: none receiver=logan.com; client-ip=65.166.240.5; envelope-from=jackoford@theofficenet.com Received: (qmail 1896 invoked from network); 23 Aug 2004 14:52:31 -0000 Received: from ip-66-45-192-201.nw-tel.com (HELO jack) (66.45.192.201) by mail.theofficenet.com with SMTP; 23 Aug 2004 14:52:31 -0000 Message-ID: <002c01c48921$b7a05280$c9c02d42@jack> From: "Jack Ford" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Compressor maps Date: Mon, 23 Aug 2004 07:58:56 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0029_01C488E7.0A425A00" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 This is a multi-part message in MIME format. ------=_NextPart_000_0029_01C488E7.0A425A00 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable David The "dry adiabatic lapse rate for air" is 5 1/2 deg. F per thousand = feet; The normal lapse rate for "average" air is 2 deg. C or 3.6 deg. F. = "Normal" jibes with your POH information. This from Kershner's "The Student Pilot's Flight Manual", 1979. Jack Ford ----- Original Message -----=20 From: David Staten=20 To: Rotary motors in aircraft=20 Sent: Monday, August 23, 2004 7:16 AM Subject: [FlyRotary] Re: Compressor maps John... first thing I can see is that I want to say PSI declines at a = rate of 0.5 PSI/1000 ft ballpark, so ambient pressure at 10k ft should = be 9.7 (14.7-(10*0.5)) on a standard day. Using that ROUGH estimate, 5 = PSI ambient is more like 20k feet. (and probably higher than that, given = the error in most "rules of thumb".. The lapse rate for Inches Mercury = is 1 per 1000 ft, which is what they drilled into our heads in flight = training.=20 =20 The second one I am NOT sure of at all, but looking at your = spreadsheet and formula's... the sea level data seems workable, but the = conversion factor you are using in box B20 appears to be the conversion = factor for standard condition air (59*F and 29.92" / 14.7 psi)... = Digging out some books and webpages, it appears that standard conditions = at 10K feet include a temp of 23*F/-5*C and an estimated pressure of = 9.7 psi/19.7" for a density value of 0.0543 lb/CF =20 I used the calculator at http://www.stealth316.com/2-air-fuel-flow.htm for these density = calcs, and I couldnt remember the lapse rate for temps, so I dug the = standard temp value out of a performance chart in a POH. =20 I hope this helps Dave Staten John Slade wrote: Let's see if I understand this. To help me read the map, I made a tiny spreadsheet (attached) to = show lbs/min at various rpm=20 This tells me I have 23lb/min at 6000. So... At SL and MAP 50 I have a PR of (30+20)/30 =3D 50/30 =3D 1.66 So on the map I read up from 23 till I hit 1.66 on the y axis and = see that I'm on the bottom of the island.=20 Now go to 10000ft and set the MAP at, say 40. My PS is now = (10+30)/10 =3D 40/10 =3D 4.0 which is off the scale. :( Looking at the (compressor) MAP again I see that my max PR at 23lb = is about 1.8, so working backwards my max MAP at 6000 ft is 18 if I want = to stay on the island. To get into higher PR's I need more rpm. I'd = need 9000+ rpm to reach the top of the island where the available PR is = about 2.5. Doesn't sound right. Where did I go wrong? Comments? -------------------------------------------------------------------------= --- Homepage: http://www.flyrotary.com/ Archive: http://lancaironline.net/lists/flyrotary/List.html =20 >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_0029_01C488E7.0A425A00 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
David
The "dry adiabatic lapse rate for air" = is 5 1/2=20 deg. F per thousand feet; The normal lapse rate for "average" air is 2 = deg. C or=20 3.6 deg. F. "Normal" jibes with your POH information.
This from Kershner's "The Student = Pilot's Flight=20 Manual", 1979.
Jack Ford
 
----- Original Message -----
From:=20 David=20 Staten
Sent: Monday, August 23, 2004 = 7:16=20 AM
Subject: [FlyRotary] Re: = Compressor=20 maps

John... first thing I can see is that I want to say PSI = declines at a rate of 0.5 PSI/1000 ft ballpark, so ambient pressure at = 10k ft=20 should be 9.7 (14.7-(10*0.5)) on a standard day. Using that ROUGH = estimate, 5=20 PSI ambient is more like 20k feet. (and probably higher than that, = given the=20 error in most "rules of thumb".. The lapse rate for Inches Mercury is = 1 per=20 1000 ft, which is what they drilled into our heads in flight training. =
 
The second one I am NOT sure of at all, but looking at = your=20 spreadsheet and formula's... the sea level data seems workable, but = the=20 conversion factor you are using  in box B20 appears to be the = conversion=20 factor for standard condition air (59*F and 29.92" / 14.7 psi)... = Digging out=20 some books and webpages, it appears that standard conditions at 10K = feet=20 include a temp of 23*F/-5*C and an estimated pressure of  9.7 = psi/19.7"=20 for a density value of 0.0543 lb/CF
 
I used the calculator = at
 http://www.stealth= 316.com/2-air-fuel-flow.htm=20 for these density calcs, and I couldnt remember the lapse rate for = temps, so I=20 dug the standard temp value out of a performance chart in a=20 POH.
 
I hope this helps
Dave Staten

John Slade=20 wrote:
Let's see if I understand this.
To=20 help me read the map, I made a tiny spreadsheet (attached) to show = lbs/min=20 at various rpm
This tells me I have 23lb/min at 6000. = So...
At SL and MAP 50 I have a PR of (30+20)/30 =3D = 50/30 =3D=20 1.66
So on the map I = read up from=20 23 till I hit 1.66 = on the y=20 axis and see that I'm on the bottom of the island. =
 
Now go to 10000ft and set the MAP at, say 40. My PS is=20 now (10+30)/10 =3D 40/10 =3D 4.0 which is off the scale.=20 :(
 
Looking at the (compressor) MAP again I see that my max PR = at 23lb is=20 about 1.8, so working backwards my max MAP at 6000 ft is 18 if I = want to=20 stay on the island.  To get into higher PR's I need more rpm. = I'd=20 need 9000+ rpm to reach the top of the island where = the available=20 PR is about 2.5.
 
Doesn't sound right. Where did I go = wrong?
 
Comments?
 
 
 
 

  
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