X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 19 Oct 2012 12:07:49 -0400 Message-ID: X-Original-Return-Path: Received: from elasmtp-scoter.atl.sa.earthlink.net ([209.86.89.67] verified) by logan.com (CommuniGate Pro SMTP 6.0c2) with ESMTP id 5832794 for lml@lancaironline.net; Fri, 19 Oct 2012 09:06:50 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.67; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=A4IH0eM5XtQ/9ItRvsTNYKdO8xBnY87o9OD/Gl28iCmrgG5gQ8BUKQyiWkQ1GZzZ; 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 [64.222.105.48] (helo=[192.168.1.24]) by elasmtp-scoter.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1TPCHC-0002fp-Ri for lml@lancaironline.net; Fri, 19 Oct 2012 09:06:11 -0400 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: multipart/alternative; boundary=Apple-Mail-206-830104150 Subject: Re: [LML] Re: Leaning for High Density Altitude takeoff and any climb X-Original-Date: Fri, 19 Oct 2012 09:06:15 -0400 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: X-Mailer: Apple Mail (2.1084) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da9403eb39a037565353be15c5e318431e686350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 64.222.105.48 --Apple-Mail-206-830104150 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 Why would all those rules of thumb be more reliable than the 0 MSL = referenced EGT method Steve describes below? On Oct 19, 2012, at 8:28 AM, William Wilson wrote: Correct high altitude operation varies based on whether your engine is = turbocharged or not. I live in Colorado, so I have lots of high density = altitude experience. Most turbocharged engines should be leaned for ground operations, but = not for takeoff/climb. Turbocharged engines usually have = altitude-compensated mixture controls and should be full rich at high = power regardless of altitude. These engines also develop 90% to 100% = power at all plausible takeoff altitudes. Naturally aspirated engines are more complex. They should be leaned for = takeoff, but at most density altitudes, should not be leaned to peak. = The higher you are, the less enrichment is needed. Even in the hottest = part of summer, 5000' is too low to take off at peak. One procedure is = to lean to peak during runup (I usually use peak RPM, ignoring the EGT), = then enrich from there. How far to enrich depends somewhat on the = plane, but a rule of thumb I use is to enrich proportionally to the = altitude, relative to 10000'. At 10000' I would take off at peak, at = sea level full rich, and at 5000' halfway. At 7000', I would enrich = about 30% from peak. This is true altitude, not density altitude, and = assumes the mixture range is not excessively rich (many planes have = mixtures that are way too rich - the Piper Arrow I used to rent had a = mixture that was so rich that most of the useful settings were leaner = than the stop where the idle cutoff is supposed to be!) In that Arrow I = just developed a sense of where the mixture needed to be for typical = situations. Taking off at high altitude too rich is not much better than taking off = too lean. The engine will not develop full power, and "full" power at = those altitudes is substantially less than actual full power. The tree = at the end of the runway is no better for your engine than running too = hot (but most Lancairs have enough power to take off even when = improperly configured). The famous Stinson accident on Youtube might = not have occurred if the pilot had properly leaned the engine. The prop responds faster than the EGT gauge and at lower power, so = setting mixture based on the RPM is usually easier. If you look at most engine manuals, they will specify a power setting = below which peak operation is authorized. It is easy to see what your = maximum power setting for a given takeoff altitude is by looking at the = manifold pressure gauge when the engine is off, and dividing it by 30. = (To be fully accurate you would also correct for temperature, which is = worth a few percent). At most plausible takeoff altitudes, the 1" per = 1000' rule will apply, so at 5000' you can expect 25" of MP, so your = engine will develop about 80-83% of maximum power - too much to takeoff = at peak. At 10000' (suppose you flew to Leadville) you will develop a = maximum of about 60-65% power, which for many engines would mean taking = off at peak would be acceptable. Of course, in all cases, you need to enrich to keep CHTs acceptable. = Even if the engine manufacturer authorizes peak operation at a given = power setting, cooling is another story. You might not have enough = cooling airflow in a climb, and the fact that the air temperature is = well above standard means it doesn't cool as effectively (another way to = look at it is the lower density air has less ability to conduct the heat = away). Finally, remember that (in terms of IAS) Vy is lower and Vx is higher = when at high altitudes. The "reference EGT" method is also good, but requires more attention as = you have to monitor your EGT during takeoff. Above about 12000', just about every non-turbo engine can run at peak, = as you will be at or below 60% power. Turbo engines should run LOP when = not climbing or in a very shallow climb, and should never run at peak. On Thu, Oct 18, 2012 at 12:01 PM, Colyn Case = wrote: I'll second the APS (Advanced Pilot Seminars) recommendation. I went to learn LOP but came out with a lot of other information = including: how easy it is to destroy a turbo-charged engine, things I = would have done differently with my engine installation. Colyn On Oct 18, 2012, at 12:41 PM, Steve Colwell wrote: =93When departing Sedona a few weeks ago, I leaned the mixture for = takeoff at Sedona=92s 5000=92 elevation. By the time I glanced at my = engine gauges 60 seconds after takeoff, the CHTs were 460deg! I went to = full rich and reduced power and the temperatures came down within a = minute or so. Bottom line: run ROP or LOP but never at peak EGT. And = yes, I=92ll be doing an oil analysis at my next oil change. =93 =20 Adam, =20 The Advanced Pilot Course teaches a procedure for takeoff and climb that = really works well. =20 First, make sure your fuel flow is 30 gph on takeoff for a stock IO550N = (typical Legacy engine) at a near sea level airport and close to a = standard day. APC says this is important for detonation suppression. = Next, check the EGT of the hottest cylinder about 500=92 agl. This is = the temp on that cylinder that you will lean to in the climb. =20 Then, at about 3000=92 density altitude (and all during the climb) keep = leaning to maintain the EGT on the hottest cylinder you referenced at = 500=92 on the test day. (Ours is 1300 degrees) The ref. EGT will = provide a comfortable detonation margin, maintain good power, keep plugs = clean and save fuel all the way up to cruising altitude. =20 At cruise above 8000=92 density altitude, level off, allow the plane to = accelerate for a minute or so, reduce rpm to cruise and go lean of peak. =20 We have been flying with this procedure for 300 hours or so. Cyl. Head = and Oil temps are not a problem, works as advertised. =20 =20 A plug for Advanced Pilot Course. http://www.advancedpilot.com/ I = learned and understood more about engine operation in 2.5 days than I = thought possible. They answer most questions before they are asked and = explain the documentation to back up what they are saying.=20 =20 Steve Colwell Legacy IO550N =20 =20 =20 --Apple-Mail-206-830104150 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 Why = would all those rules of thumb be more reliable than the 0 MSL = referenced EGT method Steve describes below?

On Oct = 19, 2012, at 8:28 AM, William Wilson wrote:

Correct high altitude operation = varies based on whether your engine is turbocharged or not.  I live = in Colorado, so I have lots of high density altitude = experience.

Most turbocharged engines should be leaned for ground = operations, but not for takeoff/climb.  Turbocharged engines = usually have altitude-compensated mixture controls and should be full = rich at high power regardless of altitude.  These engines also = develop 90% to 100% power at all plausible takeoff altitudes.

Naturally aspirated engines are more complex.  They should be = leaned for takeoff, but at most density altitudes, should not be leaned = to peak.  The higher you are, the less enrichment is needed.  = Even in the hottest part of summer, 5000' is too low to take off at = peak.  One procedure is to lean to peak during runup (I usually use = peak RPM, ignoring the EGT), then enrich from there.  How far to = enrich depends somewhat on the plane, but a rule of thumb I use is to = enrich proportionally to the altitude, relative to 10000'.  At = 10000' I would take off at peak, at sea level full rich, and at 5000' = halfway.  At 7000', I would enrich about 30% from peak.  This = is true altitude, not density altitude, and assumes the mixture range is = not excessively rich (many planes have mixtures that are way too rich - = the Piper Arrow I used to rent had a mixture that was so rich that most = of the useful settings were leaner than the stop where the idle cutoff = is supposed to be!)  In that Arrow I just developed a sense of = where the mixture needed to be for typical situations.

Taking off at high altitude too rich is not much better than taking = off too lean.  The engine will not develop full power, and "full" = power at those altitudes is substantially less than actual full = power.  The tree at the end of the runway is no better for your = engine than running too hot (but most Lancairs have enough power to take = off even when improperly configured).  The famous Stinson accident = on Youtube might not have occurred if the pilot had properly leaned the = engine.

The prop responds faster than the EGT gauge and at lower power, so = setting mixture based on the RPM is usually easier.

If you look = at most engine manuals, they will specify a power setting below which = peak operation is authorized.  It is easy to see what your maximum = power setting for a given takeoff altitude is by looking at the manifold = pressure gauge when the engine is off, and dividing it by 30.  (To = be fully accurate you would also correct for temperature, which is worth = a few percent).  At most plausible takeoff altitudes, the 1" per = 1000' rule will apply, so at 5000' you can expect 25" of MP, so your = engine will develop about 80-83% of maximum power - too much to takeoff = at peak.  At 10000' (suppose you flew to Leadville) you will = develop a maximum of about 60-65% power, which for many engines would = mean taking off at peak would be acceptable.

Of course, in all cases, you need to enrich to keep CHTs = acceptable.  Even if the engine manufacturer authorizes peak = operation at a given power setting, cooling is another story.  You = might not have enough cooling airflow in a climb, and the fact that the = air temperature is well above standard means it doesn't cool as = effectively (another way to look at it is the lower density air has less = ability to conduct the heat away).

Finally, remember that (in terms of IAS) Vy is lower and Vx is = higher when at high altitudes.

The "reference EGT" method is also = good, but requires more attention as you have to monitor your EGT during = takeoff.

Above about 12000', just about every non-turbo engine can run at = peak, as you will be at or below 60% power.  Turbo engines should = run LOP when not climbing or in a very shallow climb, and should never = run at peak.

On Thu, Oct 18, 2012 at 12:01 PM, Colyn = Case <colyncase@earthlink.net> = wrote:
I'll second the APS (Advanced Pilot = Seminars) recommendation.
I went to learn LOP but came out with a = lot of other information including: how easy it is to destroy a = turbo-charged engine, things I would have done differently with my = engine installation.

Colyn

On Oct 18, 2012, at 12:41 PM, Steve = Colwell wrote:

=93When departing = Sedona a few weeks ago, I leaned the mixture for takeoff at Sedona=92s = 5000=92 elevation. By the time I glanced at my engine gauges 60 seconds = after takeoff, the CHTs were 460deg! I went to full rich and reduced = power and the temperatures came down within a minute or so. Bottom line: = run ROP or LOP but never at peak EGT. And yes, I=92ll be doing an oil = analysis at my next oil change. =93
&n= bsp;
Adam,<= /u>
&n= bsp;
The = Advanced Pilot Course teaches a procedure for takeoff and climb that = really works well.
&n= bsp;
First, = make sure your fuel flow is 30 gph on takeoff for a stock IO550N = (typical Legacy engine) at a near sea level airport and close to a = standard day.  APC says this is important for detonation = suppression. Next, check the EGT of the hottest cylinder about 500=92 = agl.  This is the temp on that cylinder that you will lean to in = the climb.
&n= bsp;
Then, = at about 3000=92 density altitude (and all during the climb) keep = leaning to maintain the EGT on the hottest cylinder you referenced at = 500=92 on the test day.  (Ours is 1300 degrees)  The ref. EGT = will provide a comfortable detonation margin, maintain good power, keep = plugs clean and save fuel all the way up to cruising = altitude.
&n= bsp;
At = cruise above 8000=92 density altitude, level off, allow the plane to = accelerate for a minute or so, reduce rpm to cruise and go lean of = peak.
&n= bsp;
We have = been flying with this procedure for 300 hours or so.  Cyl. Head and = Oil temps are not a problem, works as advertised. =  
&n= bsp;
A plug = for Advanced Pilot Course.  http://www.advancedpilot.com/  I learned and = understood more about engine operation in 2.5 days than I thought = possible.  They answer most questions before they are asked and = explain the documentation to back up what they are = saying. 
&n= bsp;
Steve = Colwell  Legacy  IO550N
&n= bsp;
&n= bsp;
 
=


= --Apple-Mail-206-830104150--