I'm sat here sunning myself in Corfu doing NOWT (that's NOTHING to those that don't know NOWT) apart from giving my IPad a lot of work. I was looking at AVWEB and tripped over the pelican's Perch articles published there. I've read these some years ago, anyway, I read them again and I have to say that whether you buy into Lean of Peak operation or not these articles a definitely worth reading (or re-reading). Pick some from the list that takes your fancy but I particularly found #63 onwards about "where to set your engine" very interesting even second time around. Here's the link:
https://www.avweb.com/features/avweb-classics/pelicans-perch/pelicans-perch-index/
Ian
Nobody has done more to drag GA into the 21st century than the legendary John Deakin.
Some of his recommendations may not be applicable to your aircraft, and some of them you may not want to use for other reasons, but every one of his articles is worth reading because you will take something home from it.
Brilliant, thanks for posting that list STOLman. I'll bookmark now, while I remember. I've read a couple of JD's articles and they're excellent.
This is one of my favourites: Throw Away That Stupid Checklist
Yep, just throw it away...
There is one thing in his articles that confuses me. He agitates against decreasing power after take off claiming the engines have some mixture enhancement feature at full throttle and therefore any power reduction will lead to leaner mixture. Is this really the case? Which engines does it apply to and how does the feature work?
I really like Deakin's articles as well. His approach is to consider accepted practices and ask "why?" which I think in aviation is a good approach - whether you are dealing with maintenance, instructors or fellow pilots.
There is one thing in his articles that confuses me. He agitates against decreasing power after take off claiming the engines have some mixture enhancement feature at full throttle and therefore any power reduction will lead to leaner mixture. Is this really the case? Which engines does it apply to and how does the feature work?
It's not a specific "feature" but the effect is the same. The Lyco/Conti engines are thermal-dissipation limited i.e. they cannot deliver full rated HP while running at best-economy (peak EGT or close to), so at high power settings, and especially in low cooling airflows (e.g. during climb) they need to be run very rich. The fuel servos / carbs are adjusted for something like 150F ROP with all three levers fully forward, which achieves this.
If you reduce the throttle opening, you are going away from this.
However it may be an interesting discussion whether simply reducing the throttle actually leans the mixture. I doubt it does. But it will reduce the climb performance and make it difficult to maintain a decent airflow.
However it may be an interesting discussion whether simply reducing the throttle actually leans the mixture. I doubt it does. But it will reduce the climb performance and make it difficult to maintain a decent airflow.
Actually the mechanism like power valve (thanks achimha!) clearly does it. Do for instance Continental O-200 or Lycoming O-360 have this? How does it work with injected engines?
That was my question. I don't think fuel servos have an explicit mechanism that does that. Carburettors have all kinds of weird things...
I agree that these articles are most pertinent to operators of large fuel injected engines such as my IO550 Conti but there are loads of little gems for everyone in there. He does mention carburettor engines but not much. And, before a lot of this makes sense you need GAMI injectors and at least an EDM 700. Here are a few of the little gems I made a note of:
Don't bother cycling the prop on a constant speed prop on run up. Just look for red line RPM as you start your roll full throttle.
LOP for HP multiply fuel flow in GPH by 14.9. This does not work ROP. 14.9 is the figure for 8.5 compression ratio.
1250 - 1320 EGT on take off should be correct. If higher the max fuel flow is too low. Have it reset.
Outside the Red Box
At 65% power, use richer than 100 ROP, or leaner than peak EGT.
At 70%, use richer than 125ºF ROP, or leaner than 25ºF LOP.
At 75%, use richer than 180ºF ROP, or leaner than 40ºF LOP.
At 80%, use richer than 200ºF ROP, or leaner than 60ºF LOP.
This last one is particularly relevant to me as I had to have a top end overhaul at 350 hours, albeit Conti paid for the parts and the work, not the removal and refitting:
Unfortunately, we need to separate all the "flat" (horizontally opposed) engines into two groups. One group is all TCM engines manufactured since about 1991, and the other group is "all others."
Something changed in TCM engines in about 1991. I cannot tell you for sure what it was. It may have been the "choke," it may have been a change in the machining processes. It may have been changing to a different method of installing valves. TCM essentially threw away all the old machinery that had served so well (if inefficiently), and installed all-new, modern machinery. They had a strike that resulted in management assembling engines for a time, and they lost a lot of their senior engineering talent. But one thing seems clear: It's a very, very rare TCM engine that lasts more than about 400 to 700 hours without major cylinder work, if the cylinders were made since 1991.
Mostly interesting and often controversial.
Ian
