X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 18 Aug 2011 14:23:57 -0400 Message-ID: X-Original-Return-Path: Received: from elasmtp-galgo.atl.sa.earthlink.net ([209.86.89.61] verified) by logan.com (CommuniGate Pro SMTP 5.4.1) with ESMTP id 5096492 for lml@lancaironline.net; Thu, 18 Aug 2011 14:21:10 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.61; envelope-from=liegner@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=DKOc2m0dLW5+4SR0rX6y8gdeACW/KGt8SjPGFXWdLZLcPFlu5nxYHevXn/+pRUTJ; h=Message-ID:Date:From:Reply-To:To:Subject:Mime-Version:Content-Transfer-Encoding:X-Mailer:Content-Type:X-ELNK-Trace:X-Originating-IP; Received: from [209.86.224.43] (helo=elwamui-norfolk.atl.sa.earthlink.net) by elasmtp-galgo.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1Qu7Cm-0007Ln-NX for lml@lancaironline.net; Thu, 18 Aug 2011 14:20:36 -0400 Received: from 24.229.41.52 by webmail.earthlink.net with HTTP; Thu, 18 Aug 2011 14:20:36 -0400 X-Original-Message-ID: <29547672.1313691636609.JavaMail.root@elwamui-norfolk.atl.sa.earthlink.net> X-Original-Date: Thu, 18 Aug 2011 14:20:36 -0400 (GMT-04:00) From: liegner@earthlink.net Reply-To: liegner@earthlink.net X-Original-To: lml@lancaironline.net Subject: RE: What are your numbers?? LIVP and LOP Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Mailer: EarthLink Zoo Mail 1.0 Content-Type: text/html; charset=UTF-8 X-ELNK-Trace: edc6c9c2805b57e3d780f4a490ca6956d5d4673fe7faad8619e70169d69a0cd9feddb3596dad2e9d350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 209.86.224.43

Lancair IVP Pilots:

We hav= e been recently reviewing LOP cruise numbers for the benefit of sharing wit= h outher LIVP drivers. Here's some numbers that have come out of the = discussion:

=09LOP Cruise: 28= " MAP 2300 RPM 14.0 GPH

=09LOP Cruise: 31= " MAP 2400 RPM 15.1 GPH

=09LOP Cruise: 34= " MAP 2500 RPM 18.0 GPH

One in= dividual 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= - full power - full rich" then "After this LOP at FL22, FL23 at 28 = inHG, 16.1 gph" which sounded interesting with outstanding speed number= s.

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

1.&nbs= p; Pressurization: When c= limbing at full power (38.5" MAP) or even 36" or 34" or (the original recom= mended 31" MAP), upon leveling off at the flight levels, if you reduce your= MAP, you will lower your cabin pressurization, perhaps somewhat significan= tly. If I were at 38.5" MAP (or even 34" MAP) during full power climb= to the flight levels, I would have 5.0+ psi cabin differential. If I= quickly reduced MAP to 31", and particularly to 28" MAP, the cabin altitud= e would quickly climb to >14,000' and the Duke's regulator would take se= veral 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 lower= MAP

2.&nbs= p; LOP Fuel Flow equals HP Outpu= t: We have previously recognized that LOP becomes a simple conversio= n of GPH to HP output. In a Nov 2010 LML post, we learned "Typical= ly, 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 seems to be= 14.6 to 14.75 HP/gph. Once LOP, the MAP is not important to the calc= ulation (only to control detonation). More MAP produces more compress= ive heat (both induction temperature, and cabin inlet temperature) which al= ters 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 av= ailable oxygen.

3.&nbs= p; Airspeed: My recent ex= ploration of these cruise numbers(above) revealed the following indicated a= irspeed at 8200 MSL, OAT 80*F:

=09LOP Cruise: 28= " MAP 2300 RPM 14.0 GPH....173 KIAS (206 HP, 59%)

=09LOP Cruise: 31= " MAP 2400 RPM 15.1 GPH....177 KIAS (222 HP, 63%)

=09LOP Cruise: 34= " MAP 2500 RPM 18.0 GPH....187 KIAS (265 HP, 76%)

Obviou= sly, 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% mo= re fuel, 3.3% faster). Note that these fuel flow (power settings abov= e) are VERY lean of peak (LOP), some 150-180*F LOP, and the engine is not t= hat happy. An extra tenth or two of a gallon lower (mixture), or a ch= ange in OAT as you transition across a front, will sometimes make an engine= cylinder cough...upsetting the delicate spouse sitting next to you.

4.&nbs= p; Adjust GPH, not MAP: I= f when in climb or upon 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 b= y adjusting fuel flow. If I climb at 34" MAP 2500 RPM 20 GPH (294 HP,= 84%) and then cruise at 34" 2500 RPM 18.0 GPH (265 HP, 76%), I do not expe= rience any cabin pressurization issues. If I roll back the RPM to&nbs= p; 34" MAP 2400 RPM and push back up the mixture to 18.0 GPH, I am less lea= n (the engine is happier), I have less internal friction (from the lower RP= M), and my HP output remains the same, and cabin pressure is static.

So I d= on't understand the allure of big reductions(or any reduction) in MAP after= establishing a satisfactory climb configuation...please explain the benefi= ts.

5.&nbs= p; Economy Mode vs Fast Mode: And regarding the economy mode of LOP at different power settings, we = see that 14.0 GPH yields 173 KIAS and 18.0 GPH yields 187 KIAS. (I wi= ll let your TAS be whatever based on altitude you chose, the same for both = fuel flows.) If I have 110 gals in my tanks, it seems that (in princi= ple) that 14.0 GPH (7.9 hrs at 173 kts) gets me 1360nm downrange. If = I use 18 GPH (6.1 hrs at 187 kts), I can go 1143 nm (just using simple calc= ulations); your mileage my vary (YMMV). 19% further, 30% longer fligh= t time, no potty break). While this economy mode vs get there fast mo= de is important, it seems like the missions and the fuel breaks usually com= e every 4.5 hours. With 110 gals, 19 gph seems a good blend of all cr= iteria, typically getting me 1100nm on a single tank (noting climb to fligh= t levels and TAS>>IAS).

This i= s a combination of shared experience and inquiry. Perhaps some piltot= s would like to contribute.

I have= taken the Engine course, do the BMP (big mixture pull) shortly after depar= ture (during climb), and typically keep my engine at 34" MAP 2500 RPM 19 GP= H throughout the entire flight. Opinions welcomed.

Jeff L=

LIVP i= n New Jersey