X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 18 Aug 2011 17:06:54 -0400 Message-ID: X-Original-Return-Path: Received: from imr-db02.mx.aol.com ([205.188.91.96] verified) by logan.com (CommuniGate Pro SMTP 5.4.1) with ESMTP id 5096548 for lml@lancaironline.net; Thu, 18 Aug 2011 15:06:12 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.91.96; envelope-from=vtailjeff@aol.com Received: from mtaomg-mb06.r1000.mx.aol.com (mtaomg-mb06.r1000.mx.aol.com [172.29.41.77]) by imr-db02.mx.aol.com (8.14.1/8.14.1) with ESMTP id p7IJ5Qxb029027 for ; Thu, 18 Aug 2011 15:05:26 -0400 Received: from core-mnb005a.r1000.mail.aol.com (core-mnb005.r1000.mail.aol.com [172.29.106.145]) by mtaomg-mb06.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id 6F01EE00009B for ; Thu, 18 Aug 2011 15:05:26 -0400 (EDT) References: X-Original-To: lml@lancaironline.net Subject: Re: [LML] Re: What are your numbers?? LIVP and LOP X-AOL-IP: 75.33.127.82 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: vtailjeff@aol.com X-MB-Message-Type: User Content-Type: multipart/alternative; boundary="--------MB_8CE2BF0CE673D9D_1950_7984D_webmail-m034.sysops.aol.com" X-Mailer: AOL Webmail 34047-STANDARD Received: from 75.33.127.82 by webmail-m034.sysops.aol.com (64.12.101.217) with HTTP (WebMailUI); Thu, 18 Aug 2011 15:04:36 -0400 X-Original-Message-Id: <8CE2BF0CE569404-1950-25688@webmail-m034.sysops.aol.com> X-Originating-IP: [75.33.127.82] X-Original-Date: Thu, 18 Aug 2011 15:05:26 -0400 (EDT) x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:345999392:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d294d4e4d62764098 This is a multi-part message in MIME format. ----------MB_8CE2BF0CE673D9D_1950_7984D_webmail-m034.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="us-ascii" you probably have a leaky cabin If I quickly reduced MAP to 31", and particularly to 28" MAP, the cabin alt= itude would quickly climb to >14,000' and the Duke's regulator would take s= everal minutes to equilibrate. And even then, it might not be able to rest= ore 5.0 psi differential (at 28" MAP). So, all this talk of lower MAP -----Original Message----- From: liegner To: lml Sent: Thu, Aug 18, 2011 1:24 pm Subject: [LML] Re: What are your numbers?? LIVP and LOP Lancair IVP Pilots: We have been recently reviewing LOP cruise numbers for the benefit of shari= ng with outher LIVP drivers. Here's some numbers that have come out of the= discussion: LOP Cruise: 28" MAP 2300 RPM 14.0 GPH LOP Cruise: 31" MAP 2400 RPM 15.1 GPH LOP Cruise: 34" MAP 2500 RPM 18.0 GPH One individual offered: "Climb - full power - full rich" (I assume this is = 38.5" MAP, 2700 RPM, 43 GPH ROP, 350 HP), then "Level off at FL22, FL23 - f= ull power - full rich" then "After this LOP at FL22, FL23 at 28 inHG, 16.1 = gph" which sounded interesting with outstanding speed numbers. I have some questions for the group of more (than me) informed pilots. 1. Pressurization: When climbing at full power (38.5" MAP) or even 36" or = 34" or (the original recommended 31" MAP), upon leveling off at the flight = levels, if you reduce your MAP, you will lower your cabin pressurization, p= erhaps somewhat significantly. If I were at 38.5" MAP (or even 34" MAP) du= ring full power climb to the flight levels, I would have 5.0+ psi cabin dif= ferential. If I quickly reduced MAP to 31", and particularly to 28" MAP, t= he cabin altitude would quickly climb to >14,000' and the Duke's regulator = would take several minutes to equilibrate. And even then, it might not be = able to restore 5.0 psi differential (at 28" MAP). So, all this talk of lo= wer MAP 2. LOP Fuel Flow equals HP Output: We have previously recognized that LOP = becomes a simple conversion of GPH to HP output. In a Nov 2010 LML post, w= e learned "Typically, the 8.5:1 compression ration engines use 14.9 hp/gph = while the 7.5:1 CR engines use 13.7 hp/gph." In my TSIO-550E, the ratio se= ems to be 14.6 to 14.75 HP/gph. Once LOP, the MAP is not important to the = calculation (only to control detonation). More MAP produces more compressi= ve heat (both induction temperature, and cabin inlet temperature) which alt= ers performance and where one is on the LOP side of the curve, but not the = HP output, as every bit of fuel vapor is being consumed by an excess of ava= ilable oxygen. 3. Airspeed: My recent exploration of these cruise numbers(above) revealed= the following indicated airspeed at 8200 MSL, OAT 80*F: LOP Cruise: 28" MAP 2300 RPM 14.0 GPH....173 KIAS (206 HP, 59%) LOP Cruise: 31" MAP 2400 RPM 15.1 GPH....177 KIAS (222 HP, 63%) LOP Cruise: 34" MAP 2500 RPM 18.0 GPH....187 KIAS (265 HP, 76%) Obviously, the more fuel you provide LOP, the faster you go. An example of= this is 31" MAP, 2400 RPM, 15.6 GPH (229 HP, 65%) gave me 183 KIAS (3.3% m= ore fuel, 3.3% faster). Note that these fuel flow (power settings above) a= re VERY lean of peak (LOP), some 150-180*F LOP, and the engine is not that = happy. An extra tenth or two of a gallon lower (mixture), or a change in O= AT as you transition across a front, will sometimes make an engine cylinder= cough...upsetting the delicate spouse sitting next to you. 4. Adjust GPH, not MAP: If when in climb or upon reaching cruise, if I mov= e quickly to LOP (with the big mixture pull), I can control HP output at a = fixed prop speed and MAP by adjusting fuel flow. If I climb at 34" MAP 250= 0 RPM 20 GPH (294 HP, 84%) and then cruise at 34" 2500 RPM 18.0 GPH (265 HP= , 76%), I do not experience any cabin pressurization issues. If I roll bac= k the RPM to 34" MAP 2400 RPM and push back up the mixture to 18.0 GPH, I = am less lean (the engine is happier), I have less internal friction (from t= he lower RPM), and my HP output remains the same, and cabin pressure is sta= tic. So I don't understand the allure of big reductions(or any reduction) in MAP= after establishing a satisfactory climb configuation...please explain the = benefits. 5. Economy Mode vs Fast Mode: And regarding the economy mode of LOP at dif= ferent power settings, we see that 14.0 GPH yields 173 KIAS and 18.0 GPH yi= elds 187 KIAS. (I will let your TAS be whatever based on altitude you chos= e, the same for both fuel flows.) If I have 110 gals in my tanks, it seems= that (in principle) that 14.0 GPH (7.9 hrs at 173 kts) gets me 1360nm down= range. If I use 18 GPH (6.1 hrs at 187 kts), I can go 1143 nm (just using = simple calculations); your mileage my vary (YMMV). 19% further, 30% longer= flight time, no potty break). While this economy mode vs get there fast m= ode is important, it seems like the missions and the fuel breaks usually co= me every 4.5 hours. With 110 gals, 19 gph seems a good blend of all criter= ia, typically getting me 1100nm on a single tank (noting climb to flight le= vels and TAS>>IAS). This is a combination of shared experience and inquiry. Perhaps some pilto= ts would like to contribute. I have taken the Engine course, do the BMP (big mixture pull) shortly after= departure (during climb), and typically keep my engine at 34" MAP 2500 RPM= 19 GPH throughout the entire flight. Opinions welcomed. Jeff L LIVP in New Jersey -- For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html ----------MB_8CE2BF0CE673D9D_1950_7984D_webmail-m034.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="us-ascii" you probably have a leaky c= abin
If I q= uickly reduced MAP to 31", and particularly to 28" MAP, the cabin altitude = would quickly climb to >14,000' and the Duke's regulator would take seve= ral minutes to equilibrate.  And even then, it might not be able to re= store 5.0 psi differential (at 28" MAP).  So, all this talk of lower M= AP




= -----Original Message-----
From: liegner <liegner@earthlink.net>
To: lml <lml@lancaironline.net>
Sent: Thu, Aug 18, 2011 1:24 pm
Subject: [LML] Re: What are your numbers?? LIVP and LOP

Lancair IVP Pilots:

We have been recently revi= ewing LOP cruise numbers for the benefit of sharing with outher LIVP driver= s.  Here's some numbers that have come out of the discussion:

LOP Cruise: 28" MAP 2300 RPM 14.0 GPH<= /div>
LOP Cruise: 31" MAP 2400 RPM 15.1 GPH<= /div>
LOP Cruise: 34" MAP 2500 RPM 18.0 GPH<= /div>

One individual offered: "<= I>Climb - full power - full rich" (I assume this is 38.5" MAP, 2700 RPM= , 43 GPH ROP, 350 HP), then "Level off at FL22, FL23 - full power - full= rich" then "After this LOP at FL22, FL23 at 28 inHG, 16.1 gph" = which sounded interesting with outstanding speed numbers.

I have some questions for = the group of more (than me) informed pilots.

1.  Pressurization: When climbing at full powe= r (38.5" MAP) or even 36" or 34" or (the original recommended 31" MAP), upo= n leveling off at the flight levels, if you reduce your MAP, you will lower= your cabin pressurization, perhaps somewhat significantly.  If I were= at 38.5" MAP (or even 34" MAP) during full power climb to the flight level= s, I would have 5.0+ psi cabin differential.  If I quickly reduced MAP= to 31", and particularly to 28" MAP, the cabin altitude would quickly clim= b to >14,000' and the Duke's regulator would take several minutes to equ= ilibrate.  And even then, it might not be able to restore 5.0 psi diff= erential (at 28" MAP).  So, all this talk of lower MAP

2.  LOP Fuel Flow equals HP Output: We have pr= eviously recognized that LOP becomes a simple conversion of GPH to HP outpu= t.  In a Nov 2010 LML post, we learned "Typically, the 8.5:1 compre= ssion ration engines use 14.9 hp/gph while the 7.5:1 CR engines use 13.7 hp= /gph."  In my TSIO-550E, the ratio seems to be 14.6 to 14.75 HP/gp= h.  Once LOP, the MAP is not important to the calculation (only to con= trol detonation).  More MAP produces more compressive heat (both induc= tion temperature, and cabin inlet temperature) which alters performance and= where one is on the LOP side of the curve, but not the HP output, as every= bit of fuel vapor is being consumed by an excess of available oxygen.

3.  Airspeed: My recent exploration of these c= ruise numbers(above) revealed the following indicated airspeed at 8200 MSL,= OAT 80*F:
LOP Cruise: 28" MAP 2300 RPM 14.0 GPH.= ...173 KIAS (206 HP, 59%)
LOP Cruise: 31" MAP 2400 RPM 15.1 GPH.= ...177 KIAS (222 HP, 63%)
LOP Cruise: 34" MAP 2500 RPM 18.0 GPH.= ...187 KIAS (265 HP, 76%)
Obviously, the more fuel y= ou provide LOP, the faster you go.  An example of this is 31" MAP, 240= 0 RPM, 15.6 GPH (229 HP, 65%) gave me 183 KIAS (3.3% more fuel, 3.3% faster= ).  Note that these fuel flow (power settings above) are VERY lean of = peak (LOP), some 150-180*F LOP, and the engine is not that happy.  An = extra tenth or two of a gallon lower (mixture), or a change in OAT as you t= ransition across a front, will sometimes make an engine cylinder cough...up= setting the delicate spouse sitting next to you.

4.  Adjust GPH, not MAP: If when in climb or u= pon reaching cruise, if I move quickly to LOP (with the big mixture pull), = I can control HP output at a fixed prop speed and MAP by adjusting fuel flo= w.  If I climb at 34" MAP 2500 RPM 20 GPH (294 HP, 84%) and then cruis= e at 34" 2500 RPM 18.0 GPH (265 HP, 76%), I do not experience any cabin pre= ssurization issues.  If I roll back the RPM to  34" MAP 2400 RPM = and push back up the mixture to 18.0 GPH, I am less lean (the engine is hap= pier), I have less internal friction (from the lower RPM), and my HP output= remains the same, and cabin pressure is static.

So I don't understand the = allure of big reductions(or any reduction) in MAP after establishing a sati= sfactory climb configuation...please explain the benefits.

5.  Economy Mode vs Fast Mode: And regarding t= he economy mode of LOP at different power settings, we see that 14.0 GPH yi= elds 173 KIAS and 18.0 GPH yields 187 KIAS.  (I will let your TAS be w= hatever based on altitude you chose, the same for both fuel flows.)  I= f I have 110 gals in my tanks, it seems that (in principle) that 14.0 GPH (= 7.9 hrs at 173 kts) gets me 1360nm downrange.  If I use 18 GPH (6.1 hr= s at 187 kts), I can go 1143 nm (just using simple calculations); your mile= age my vary (YMMV).  19% further, 30% longer flight time, no potty bre= ak).  While this economy mode vs get there fast mode is important, it = seems like the missions and the fuel breaks usually come every 4.5 hours.&n= bsp; With 110 gals, 19 gph seems a good blend of all criteria, typically ge= tting me 1100nm on a single tank (noting climb to flight levels and TAS>= >IAS).

This is a combination of s= hared experience and inquiry.  Perhaps some piltots would like to cont= ribute.

I have taken the Engine co= urse, do the BMP (big mixture pull) shortly after departure (during climb),= and typically keep my engine at 34" MAP 2500 RPM 19 GPH throughout the ent= ire flight.  Opinions welcomed.

Jeff L
LIVP in New Jersey



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