Mixture Control
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@BNI: If you want to stay happy as a Pistonpilot, learn and understand what the mixture knob does! I am very surprised you have training without intense teaching on how to manage fuel. Am I right, you have not gone through that part of the training were you scrub 15 traffic circles in 45 minutes?
Yes, it is indeed correct to point you to the POH, but it may be misleading as well. If you do training in an aircraft which was designed i.e. for 87 octane use and now fly on 100LL, the POH is not written for that and at latest, your FI should teach you what to do with the excess lead. If you drive an old 172 or 28 with TCM or Lycosaurus, you will get into trouble over time when not leaning on the ground -> thy collect lead on the sparks pretty quickly.
Yes, it is indeed correct to point you to the POH, but it may be misleading as well. If you do training in an aircraft which was designed i.e. for 87 octane use and now fly on 100LL, the POH is not written for that and at latest, your FI should teach you what to do with the excess lead. If you drive an old 172 or 28 with TCM or Lycosaurus, you will get into trouble over time when not leaning on the ground -> thy collect lead on the sparks pretty quickly.
Can you clarify what you mean by "scrub 15 traffic circles in 45 minutes"?
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A PPL is a license to learn, certainly on engine management.
Keep in mind that the POH is written by the engineers first, then modified to suit the marketing department, then the lawyers get their go. The message written by the engineers is very diluted or skewed.
Keep in mind that the POH is written by the engineers first, then modified to suit the marketing department, then the lawyers get their go. The message written by the engineers is very diluted or skewed.
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I am surprised no one has really talked about the fuel saving, we have pretty good engine instrumentation om our RV7 including fuel flow indication, leaning properly in the cruise brings the fuel flow down by over 10L/hour, so by leaning properly you are not only being kinder to your engine but saving considerably on fuel - even if I am hiring wet I would rather have that fuel in the tank than not!
Last edited by foxmoth; 3rd Jul 2017 at 22:52.
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If you are hiring from most clubs and use book figures you will amost certainly end up with less fuel than planned even with leaning, those figures are not done using a 20 year old aircraft with a 2.000 hour engine flown by an average club pilot! In fact as already pointed out in this thread many who hire club aircraft do NOT lean because they do not get the cost benefit of the fuel saving, which was the point of my post.
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Yes, it is indeed correct to point you to the POH, but it may be misleading as well. If you do training in an aircraft which was designed i.e. for 87 octane use and now fly on 100LL, the POH is not written for that and at latest, your FI should teach you what to do with the excess lead.
Here's how things should work in theory:
The aircraft, at some point in time, was manufactured and certified to run on a certain number of (then available) fuels. The POH should include any notes if there's anything specific for these fuels. If, after release of the POH, a new fuel becomes available, then the manufacturer should form an opinion as to whether and how that fuel can be used. If it can be used despite the original POH saying no, then the manufacturer should bring out a POH supplement. This is added to the original POH and legally becomes part of it. It should list all the consequences so the supplement will have the same structure as the original POH: Description, limitations, emergency procedures, normal procedures, weight and balance, ... Some of these sections can be empty: Switching from 87 to 100LL will not have any effect on W&B for instance.
If you have an aircraft whose original POH said "87 octane only", and you don't have any supplement that says "100LL is OK too", then flying it on 100LL is simply illegal and should not be done. Regardless of what the FI tells you.
But this is why it's so important to read the actual POH from the actual aircraft you're going to fly. That's the one which contains all the applicable supplements. A generic one off the internet somehow won't.
And now what happens in the real world: There are practices that deviate from both the POH and its supplements. Sometimes that's a good thing (*), sometimes it's based on OWTs, and sometimes they're downright dangerous. As in the example above: If your FI taught you specifically not to lean, and you take the aircraft out for a long cross-country basing your fuel consumption on book numbers, you're going to end up in a field. Or worse.
(*) As an example, EASA decided to do a wholesale certification of a large series of engines, both Lycoming and Continental, to run on mogas. They effectively circumvented the whole manufacturers POH supplement procedure and brought out their own STCs.
Last edited by BackPacker; 4th Jul 2017 at 10:27.
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My aircraft is an Emeraude built -59 I do not have a nice shiny POH to refer to.
I have been trying to find something on the net and have only come up with a generic engine management document for the C 90.
This document only says "lean above 5000ft" pretty much by revs/ear.
I run it on mogas and have had no problems for ten years.
I too was never taught to lean and have come to the conclusion that doing it by ear/trial and error is the only way that I can learn, or get someone to teach "his" version based on his experience.
People talking about damaging the engine by getting the procedure wrong is worrying to someone like me.
Fuel consumption I have discovered by trial and error has merely given me a set of figures based on fully rich. The flying budget tells me I should do better, reductions of 30% certainly seem attractive but not at the expense of a new engine if I screw it up.
Where does the likes of me go next, safely?
I have been trying to find something on the net and have only come up with a generic engine management document for the C 90.
This document only says "lean above 5000ft" pretty much by revs/ear.
I run it on mogas and have had no problems for ten years.
I too was never taught to lean and have come to the conclusion that doing it by ear/trial and error is the only way that I can learn, or get someone to teach "his" version based on his experience.
People talking about damaging the engine by getting the procedure wrong is worrying to someone like me.
Fuel consumption I have discovered by trial and error has merely given me a set of figures based on fully rich. The flying budget tells me I should do better, reductions of 30% certainly seem attractive but not at the expense of a new engine if I screw it up.
Where does the likes of me go next, safely?
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My suggestion is visit Pelican's Perch https://www.avweb.com/news/pelican/182146-1.html Articles 8, 18 and 19 are compulsory followed by 15 and 16 and any/all the rest John Deakin has written.
Please study Deakin's article No 8; "Go Ahead Abuse Your Engine." Your engine will burn cleaner, be healthier and not be damaged as some scaremongers might say.
Last edited by Chuck Notyeager; 4th Jul 2017 at 18:17. Reason: Added info
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Backpacker - that sounds interesting!
Your point about EASA issuing their own STC for Mogas has appeal. I run an O-360A4M in a 172. Previously, if I wanted Mogas I had to pay a Mr. Petersen in USA for an STC. Where would I find the EASA version, what cost, and do I need any mods?
Sorry to ask so much! Regards, CT.
Sorry to ask so much! Regards, CT.
Has an STC (US) ever been needed in the UK to use mogas? There was a CAA booklet, and an EASA document, listing the conditions for using filling station fuel in aircraft.
Now the CAA have washed their hands of any responsibility.
Now the CAA have washed their hands of any responsibility.
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I took the relevant section and saved it as .DOC
Last edited by Chuck Notyeager; 5th Jul 2017 at 06:46.
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My airplanes checklist tells you to lean on the ground immediately after starting - it says an inch (its a PA28-181).
In the air I lean at 2000ft and up - in my EGT I run hottest at around 1480 - it leaned all the way to get the peak then backed off/enriched (my airplane has a carb not injection so none of that lean of peak BS for me!) - when this is done at 8000ft+ the mixture is maybe 1/2" inch off the lean cut off position, v.scary.
In the air I lean at 2000ft and up - in my EGT I run hottest at around 1480 - it leaned all the way to get the peak then backed off/enriched (my airplane has a carb not injection so none of that lean of peak BS for me!) - when this is done at 8000ft+ the mixture is maybe 1/2" inch off the lean cut off position, v.scary.
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I also found a 240 page EASA document that debated everything about risks etc (due ethanol etc) and talking about how to mitigate. But it also contains copies of STCs that say I can use it. So with that and Chuck's info, I feel quite comfortable about legality of usage.
However, I'd prefer to stay with the aviation organisations that supply mogas (so it has the tighter specification), but airfields with pumps seem rare. Is there a current list of who has, and pricing?
Failing that, what fields do you know apart from Sywell? Thanks all! CT.
However, I'd prefer to stay with the aviation organisations that supply mogas (so it has the tighter specification), but airfields with pumps seem rare. Is there a current list of who has, and pricing?
Failing that, what fields do you know apart from Sywell? Thanks all! CT.
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My airplanes checklist tells you to lean on the ground immediately after starting - it says an inch (its a PA28-181).
In the air I lean at 2000ft and up - in my EGT I run hottest at around 1480 - it leaned all the way to get the peak then backed off/enriched (my airplane has a carb not injection so none of that lean of peak BS for me!) - when this is done at 8000ft+ the mixture is maybe 1/2" inch off the lean cut off position, v.scary.
In the air I lean at 2000ft and up - in my EGT I run hottest at around 1480 - it leaned all the way to get the peak then backed off/enriched (my airplane has a carb not injection so none of that lean of peak BS for me!) - when this is done at 8000ft+ the mixture is maybe 1/2" inch off the lean cut off position, v.scary.
At 8000' your mpg economy should be better than 2000' so as long as the engine runs smoothly, do not worry about the position of the red knob. After all, you are not at sea level.
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You can lean at any altitude. The absolute EGT number has no value except to determine peak, at what point it starts to fall. The hottest EGT is NOT the hottest exhaust valve temp. Think of EGT as a navigation instrument, you are at peak, before or past.
With a carb, you can try to lean slightly past peak and if not smooth, use a little carb heat to help fuel vapourisation. Please read John Deakin's articles. Once you understand you will not go back to the old way and do you engine and you bank account a favour at the same time.
With a carb, you can try to lean slightly past peak and if not smooth, use a little carb heat to help fuel vapourisation. Please read John Deakin's articles. Once you understand you will not go back to the old way and do you engine and you bank account a favour at the same time.
Crash one , not able to link in the O-200 manual , which also has C-90 stuff in .
Google it TCM O-200 overhaul manual . Lots of stuff in it inc. leaning procedures .
We lean appropriately an O-200 .
rgds condor .
Google it TCM O-200 overhaul manual . Lots of stuff in it inc. leaning procedures .
We lean appropriately an O-200 .
rgds condor .
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Operators manual for A&C engines and O 200.
Includes A65--C90 and O200.
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I said earlier that I've run the C90 for ten years on Mogas with no trouble.
True it's never missed a beat, but I have replaced both rear cylinders due to exhaust valve serious wear during that time. Noticed by a lack of power slowly creeping up over months.
One of them I could see daylight between the guide and stem!
Is this mechanical wear caused by hard carbon build up on the stem/guide?
What are the bad effects of running full rich all the time?
All the plugs are black, no sign of the brown that I would prefer.
True it's never missed a beat, but I have replaced both rear cylinders due to exhaust valve serious wear during that time. Noticed by a lack of power slowly creeping up over months.
One of them I could see daylight between the guide and stem!
Is this mechanical wear caused by hard carbon build up on the stem/guide?
What are the bad effects of running full rich all the time?
All the plugs are black, no sign of the brown that I would prefer.