X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 21 Aug 2011 14:09:47 -0400 Message-ID: X-Original-Return-Path: Received: from elasmtp-spurfowl.atl.sa.earthlink.net ([209.86.89.66] verified) by logan.com (CommuniGate Pro SMTP 5.4.1) with ESMTP id 5097751 for lml@lancaironline.net; Fri, 19 Aug 2011 14:58:33 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.66; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=nItit4/2W/XP/e+CHMBi8OkmVbtHBIaAxeuyI2wUPji4ha4Pdd/LPJJl1VYRm6kf; h=Received:From:Mime-Version:Content-Type:Subject:Date:In-Reply-To:To:References:Message-Id:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [64.223.110.60] (helo=[192.168.1.24]) by elasmtp-spurfowl.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1QuUGV-0000xV-JD for lml@lancaironline.net; Fri, 19 Aug 2011 14:57:59 -0400 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: multipart/alternative; boundary=Apple-Mail-684-465630512 Subject: Re: [LML] Re: What are your numbers?? LIVP and LOP X-Original-Date: Fri, 19 Aug 2011 14:57:59 -0400 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: <8B1342B7-128F-4FD1-83CE-B901F3138B65@earthlink.net> X-Mailer: Apple Mail (2.1084) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da94032a67c37206f06b58dc343e0c3081693350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 64.223.110.60 --Apple-Mail-684-465630512 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii Jeff, When you back off the MAP you will have less flow through the cabin. = That means the outflow valve has to close down somewhat. If you have it set to "change altitude" really slowly what you are = really doing is limiting the speed of the motor that changes the outflow = valve opening. You might be happier with that set higher. What is your TIT at 34"/2500/19gph? On Aug 18, 2011, at 2:23 PM, liegner@earthlink.net wrote: > Lancair IVP Pilots: >=20 > We have been recently reviewing LOP cruise numbers for the benefit of = sharing with outher LIVP drivers. Here's some numbers that have come = out of the discussion: >=20 > 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 >=20 > 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 - full power - full rich" then "After this LOP at FL22, FL23 = at 28 inHG, 16.1 gph" which sounded interesting with outstanding speed = numbers. >=20 > I have some questions for the group of more (than me) informed pilots. >=20 > 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, perhaps somewhat significantly. 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 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 lower MAP >=20 > 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, we 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 seems 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 compressive heat (both induction 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. >=20 > 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% 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 transition across a front, will = sometimes make an engine cylinder cough...upsetting the delicate spouse = sitting next to you. >=20 > 4. Adjust GPH, not MAP: If 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 by 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 experience any cabin pressurization = 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 happier), I have = less internal friction (from the lower RPM), and my HP output remains = the same, and cabin pressure is static. >=20 > 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. >=20 > 5. 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 will 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 principle) 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 calculations); your mileage my vary = (YMMV). 19% further, 30% longer flight time, no potty break). 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. With 110 = gals, 19 gph seems a good blend of all criteria, typically getting me = 1100nm on a single tank (noting climb to flight levels and TAS>>IAS). >=20 > This is a combination of shared experience and inquiry. Perhaps some = piltots would like to contribute. >=20 > 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. >=20 > Jeff L > LIVP in New Jersey >=20 >=20 >=20 > -- > For archives and unsub = http://mail.lancaironline.net:81/lists/lml/List.html --Apple-Mail-684-465630512 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii Jeff,

When you back off the MAP = you will have less flow through the cabin.  That means the outflow = valve has to close down somewhat.
If you have it set to = "change altitude" really slowly what you are really doing is limiting = the speed of the motor that changes the outflow valve = opening.
You might be happier with that set = higher.

What is your TIT at = 34"/2500/19gph?

On Aug 18, 2011, at 2:23 PM, liegner@earthlink.net = wrote:


We = have been recently reviewing LOP cruise numbers for the benefit of = sharing 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 - 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.

 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, perhaps = somewhat significantly.  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 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 lower = MAP

 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, we 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 seems 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 compressive heat (both induction 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 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% 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 transition across a front, will sometimes make an = engine cylinder cough...upsetting the delicate spouse sitting next to = you.

 Adjust GPH, not MAP: = If 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 by 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 experience any cabin pressurization 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 happier), 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 satisfactory climb configuation...please explain = the benefits.

 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 will 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 principle) 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 calculations); your mileage my vary = (YMMV).  19% further, 30% longer flight time, no potty = break).  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.  With 110 gals, 19 gph seems a good blend of all = criteria, typically getting me 1100nm on a single tank (noting climb to = flight levels and TAS>>IAS).

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.

LIVP in New Jersey


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