Here is the path I recommend to willing pilots to learn about proper mixture management.
In order of cost:
1. read the Pelican’s Perch Engine columns by John Deakin. Nobody explained it better yet. free of charge.
2. Do the online APS course. A very good base that will pay back the investment. Cost 395 US$ plus a few hours of your time;
3. Take the APS live course. You get a free online course thrown in for free. Cost 995 US$ but you have to go to Oklahoma. We just had one three weeks ago in Kortrijk for 1290 US$ to cover cost of travel of the three teachers, sorry if you missed it. There is a lot more in the live course plus you get the interactive effect.
4. Take the APS Master Class 990US$, but only for those who have attended the Live Course.
It is not LOP versus ROP but how and when to ROP or LOP.
2 hours at FL95 on a very hot day in my case. Completely my fault for forgetting to lean at all. Also on board were an instructor (obviously not instructing) and the plane’s owner (obviously not worried about the fuel bill).
We only discovered the fouled plugs after the starter switch died and having to hand swing the O320, which wasn’t fun in Corsica in August. Finding a spark plug key wasn’t easy either, or hand starting the second time.
I lean now.
What happened?
A few of us flew a 180hp Lycoming in a Robin and put around 1200hrs on it over about 14years.
I’m very confident that 99.9 percent of that time was full rich.
Engine was still starting on 2nd turn from cold and probably 3rd from hot when we sold the aircraft. Power was good and the broker commented how smooth it flew.
Go figure?
Just saying……
At low level, sure. Most of UK GA training is done full rich. But they fly low, mostly at or below 2000ft. You can fly full rich to about 8000ft (on the IO540) and then is when you really start to lose power. It isn’t due to fouled plugs though; it is simply due to the wrong mixture. Some notes on engine management here. IME, the risk of fouled plugs does increase if you are too rich but it doesn’t happen universally.
Long story:
Pretty soon after my PPL we had a club trip to Propriano in Corsica. This was really good for me as it showed that longer flights, flight plans and water crossings aren’t all that difficult.
We stopped at Carpentras for fuel and to file flightplans (Cannes was expensive even back then) and I flew the leg to St Tropez and along the VFR routes to Ajaccio then along the coast to Propriano. Fully rich the whole way.
We had a really good long weekend staying in tents and with hire cars to visit the island, plenty of Pietra (chestnut beer) at lunch and seafood at night. Walking around the marinas after dinner is an eye-opener: I thought flying was expensive, but some of the yachts… Bonifacio is really worth a visit, and we also went to a couple of villages up in the hills that are apparently nests of Corsican separatists (I think I was being wound up). Took a couple of girls for a local flight around the island, which was a bit of good PR for GA. Just a swim in the sea and an enforced rest on the beach was very relaxing.
I can’t remember exactly why we didn’t get avgas on landing at Propriano (I think they were just being awkward), but when we wanted to leave they’d just had a fuel delivery and we couldn’t wait for it to settle, so decided to go to Calvi for fuel. This is when I found the starter wasn’t working. I thought at the time I’d broken it, and felt pretty guilty, but it turned out back home that the spring behind the starter button stuck or fallen out or something silly like that. We had to start the engine by swinging the propeller, very stressful for me just watching with hands on mixture and throttle, and very hot for the bloke doing all the work in 35 degree heat. After a very long time we got it started, and found on the magneto check that the engine ran very rough, so we taxied back, stopped the engine, and walked around the deserted apron and car park trying to find someone with a toolkit. Luckily there was a helicopter pilot who had just dropped by to check something, and he lent us the spark plug key from his Robinson and we cleaned the spark plugs. Profuse thanks to this kind man, and we started all over again with the hand-starting, now probably 40 degrees on the concrete, but easier with clean plugs.
Arrived at Calvi, which wasn’t very friendly – each aircraft had to park in a painted square, and some officials drove over to shout at us when we walked outside the squares. Things got quite heated. We were stressed with our engine problems, and the other pilots were getting fed up because we were slowing them down. Once we’d fueled we then had to go through the whole hand-start procedure again: the O320 is hard work to turn. We did the return flight in one go as we just about had enough fuel (~30 minutes on landing) and couldn’t face restarting the engine yet another time.
I don’t know at what point of the flight the fouling took place, but I always lean now, even at lower altitudes and on the ground. In this current hot weather the mixture control is quite far back. In the south of France also on a hot day I once lost patience leaning, pulled a bit too sharply, and it suddenly went very quiet, but the engine restarted instantly I pushed the mixture back in.
Lycoming have an SB on the plug fouling issue………. may be its worth a read ?
Thanks A_and_C, just found and read it. Everything makes sense, but not sure I agree with running up to 1800rpm before shutdown (but not sufficiently qualified to argue about it)
Where is this SB?
The high rpm is mainly for turbo cooling before shutdown, AFAIK.
I also think (see post #11) that the spark plug condition depends more on what the engine was doing in the last few minutes than in the general flying before – other than the amount of lead deposits which I think take a lot longer to accumulate.
