X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 21 Oct 2012 09:56:38 -0400 Message-ID: X-Original-Return-Path: Received: from mail-vc0-f180.google.com ([209.85.220.180] verified) by logan.com (CommuniGate Pro SMTP 6.0c2) with ESMTPS id 5834984 for lml@lancaironline.net; Sat, 20 Oct 2012 21:56:25 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.220.180; envelope-from=fluffysheap@gmail.com Received: by mail-vc0-f180.google.com with SMTP id fl13so1541776vcb.25 for ; Sat, 20 Oct 2012 18:55:50 -0700 (PDT) MIME-Version: 1.0 Received: by 10.220.8.138 with SMTP id h10mr8120049vch.35.1350784550064; Sat, 20 Oct 2012 18:55:50 -0700 (PDT) Received: by 10.58.229.70 with HTTP; Sat, 20 Oct 2012 18:55:49 -0700 (PDT) In-Reply-To: References: X-Original-Date: Sat, 20 Oct 2012 19:55:49 -0600 X-Original-Message-ID: Subject: Re: [LML] Re: Leaning for High Density Altitude takeoff and any climb From: William Wilson X-Original-To: Lancair Mailing List Content-Type: multipart/alternative; boundary=bcaec54fb4144652d004cc8809c3 --bcaec54fb4144652d004cc8809c3 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable There's really only one rule of thumb, the rest is an explanation of why it is the way it is. EGT readings are only consistent at a particular power, so the advantage is that you can do it during runup rather than at full power. Otherwise you have to run up at 100% power, or fiddle with the mixture while taking off (EGT is also slow to react, so you won't even see the results of the adjustments right away). It wouldn't hurt anything to look at the EGT during takeoff and make a mixture adjustment to get it closer to reference if you have time, but I wouldn't consider it a necessity. You mostly just want to avoid taking off too close to peak or so rich that you lose a lot of power, it doesn't have to be exactly right. One other problem with the reference EGT method is that if you live at high altitude, you won't be able to get the reference numbers :) On Fri, Oct 19, 2012 at 10:07 AM, Colyn Case wrote= : > 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-compensate= d > 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. Th= e > 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 t= o > 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 tr= ue > 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 th= e > useful settings were leaner than the stop where the idle cutoff is suppos= ed > to be!) In that Arrow I just developed a sense of where the mixture need= ed > 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 a= t > 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 settin= g > 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 abou= t > 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. Eve= n > 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 whe= n > 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 wro= te: > >> 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 wo= uld >> 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 takeo= ff >> at Sedona=92s 5000=92 elevation. By the time I glanced at my engine gaug= es 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. Bott= om >> 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**** >> ** ** >> Adam,**** >> ** ** >> The Advanced Pilot Course teaches a procedure for takeoff and climb that >> really works well.**** >> ** ** >> 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 stand= ard >> 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 t= hat >> cylinder that you will lean to in the climb.**** >> ** ** >> 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 50= 0=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.**** >> ** ** >> 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.= * >> *** >> ** ** >> We have been flying with this procedure for 300 hours or so. Cyl. Head >> and Oil temps are not a problem, works as advertised. **** >> ** ** >> 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. **** >> ** ** >> Steve Colwell Legacy IO550N**** >> ** ** >> ** ** >> ** ** >> >> > > --bcaec54fb4144652d004cc8809c3 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable There's really only one rule of thumb, the rest is an explanation of wh= y it is the way it is.

EGT readings are only consistent at a particu= lar power, so the advantage is that you can do it during runup rather than = at full power.=A0 Otherwise you have to run up at 100% power, or fiddle wit= h the mixture while taking off (EGT is also slow to react, so you won't= even see the results of the adjustments right away).

It wouldn't hurt anything to look at the EGT during takeoff and mak= e a mixture adjustment to get it closer to reference if you have time, but = I wouldn't consider it a necessity.=A0 You mostly just want to avoid ta= king off too close to peak or so rich that you lose a lot of power, it does= n't have to be exactly right.

One other problem with the reference EGT method is that if you live at = high altitude, you won't be able to get the reference numbers :)
On Fri, Oct 19, 2012 at 10:07 AM, Colyn Case <colyncase@earthlink.n= et> wrote:
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 W= ilson wrote:

Correct high altitude operation varies based on wheth= er your engine is turbocharged or not.=A0 I live in Colorado, so I have lot= s of high density altitude experience.

Most turbocharged engines should be leaned for ground operations, but n= ot for takeoff/climb.=A0 Turbocharged engines usually have altitude-compens= ated mixture controls and should be full rich at high power regardless of a= ltitude.=A0 These engines also develop 90% to 100% power at all plausible t= akeoff altitudes.

Naturally aspirated engines are more complex.=A0 They should be leaned = for takeoff, but at most density altitudes, should not be leaned to peak.= =A0 The higher you are, the less enrichment is needed.=A0 Even in the hotte= st part of summer, 5000' is too low to take off at peak.=A0 One procedu= re is to lean to peak during runup (I usually use peak RPM, ignoring the EG= T), then enrich from there.=A0 How far to enrich depends somewhat on the pl= ane, but a rule of thumb I use is to enrich proportionally to the altitude,= relative to 10000'.=A0 At 10000' I would take off at peak, at sea = level full rich, and at 5000' halfway.=A0 At 7000', I would enrich = about 30% from peak.=A0 This is true altitude, not density altitude, and as= sumes 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 w= as so rich that most of the useful settings were leaner than the stop where= the idle cutoff is supposed to be!)=A0 In that Arrow I just developed a se= nse 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.=A0 The engine will not develop full power, and "full" = power at those altitudes is substantially less than actual full power.=A0 T= he 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 improper= ly configured).=A0 The famous Stinson accident on Youtube might not have oc= curred if the pilot had properly leaned the engine.

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

If you look at most = engine manuals, they will specify a power setting below which peak operatio= n is authorized.=A0 It is easy to see what your maximum power setting for a= given takeoff altitude is by looking at the manifold pressure gauge when t= he engine is off, and dividing it by 30.=A0 (To be fully accurate you would= also correct for temperature, which is worth a few percent).=A0 At most pl= ausible 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.=A0 At 10000' (s= uppose you flew to Leadville) you will develop a maximum of about 60-65% po= wer, which for many engines would mean taking off at peak would be acceptab= le.

Of course, in all cases, you need to enrich to keep CHTs acceptable.=A0= Even if the engine manufacturer authorizes peak operation at a given power= setting, cooling is another story.=A0 You might not have enough cooling ai= rflow in a climb, and the fact that the air temperature is well above stand= ard 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 w= hen at high altitudes.

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

Above about 12000', just about every non-turbo engine can run at pe= ak, as you will be at or below 60% power.=A0 Turbo engines should run LOP w= hen not climbing or in a very shallow climb, and should never run at peak.<= br>
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 e= ngine, things I would have done differently with my engine installation.

Colyn
=

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

= =93When departin= g Sedona a few weeks ago, I leaned the mixture for takeoff at Sedona=92s 50= 00=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 t= he temperatures came down within a minute or so. Bottom line: run ROP or LO= P but never at peak EGT. And yes, I=92ll be doing an oil analysis at my nex= t oil change. =93
= =A0
Adam,<= /u>
= =A0
The Advan= ced Pilot Course teaches a procedure for takeoff and climb that really work= s well.
= =A0
First, ma= ke sure your fuel flow is 30 gph on takeoff for a stock IO550N (typical Leg= acy engine) at a near sea level airport and close to a standard day.=A0 APC= says this is important for detonation suppression. Next, check the EGT of = the hottest cylinder about 500=92 agl.=A0 This is the temp on that cylinder= that you will lean to in the climb.
= =A0
Then, at = about 3000=92 density altitude (and all during the climb) keep leaning to m= aintain the EGT on the hottest cylinder you referenced at 500=92 on the tes= t day.=A0 (Ours is 1300 degrees)=A0 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.
= =A0
At cruise= above 8000=92 density altitude, level off, allow the plane to accelerate f= or a minute or so, reduce rpm to cruise and go lean of peak.<= /span>
= =A0
We have b= een flying with this procedure for 300 hours or so.=A0 Cyl. Head and Oil te= mps are not a problem, works as advertised. =A0
= =A0
A plug fo= r Advanced Pilot Course.=A0=A0= http://www.advancedpilot.com/=A0 I learned and understood more about en= gine operation in 2.5 days than I thought possible.=A0 They answer most que= stions before they are asked and explain the documentation to back up what = they are saying.=A0
= =A0
Steve Col= well=A0 Legacy=A0 IO550N
= =A0
= =A0
=A0<= /span>



--bcaec54fb4144652d004cc8809c3--