If you are running LOP and using carby heat to do so. What happens if you get some situation whereby you start to get carb ice?
Do you want to think about that again? To get carby ice you need....
Previously I was too afraid to operate these engines differently to what I had been taught
Unfortunately, often what we are taught is not consistent with the engine operators manual. Go to Essco or wherever and buy a copy of the engine operators manual for the 421 engines. Most of the time that is consistent with what the Advanced Pilot Seminars teach. If you want to learn more, enrol in one of Jaba's courses.
The geared turbocharged Continental 520's require a lot more caution and you may find that you have trouble maintaining pressurisation at the power levels used for LOP operation. John Deakins has a couple of articles specifically on turbocharged engines. Go to Avweb and find them. Print them and read them more than once.
Note: By some freak of luck, TCM have a pdf copy of the engine operators manual for the GTSIO 520 D fitted to the 421.
see here:
http://www.tcmlink.com/pdf2/maintena...044/x30044.pdf
There are a few things to note:
1. TCM recommend climb at 75% power full rich. Your climb will be a different thing than the average BO because instead of climbing to 4-6,000 ft you're probably climbing to 20,000 ft or more (hopefully at Carson speed). Cooling deteriorates and becomes more critical as the air becomes thinner / dryer so inlet charge cooling from rich operation becomes more important. Especially since Australia is typically 15 - 20 degC above ISA temperatures.
2. There is a strong chance that a LAME somewhere has screwed up your fuel pump settings. Its tedious to set properly and many don't bother or think they know better and can do it by "feel". The engine operators manual shows a maximum fuel flow for 75% power. Check your fuel flows against that. Our aircraft is too rich, so I lean in the climb to achieve the Continental figure.
3. The Continental instructions are based on TIT, not EGT. On a turbocharged engine they can be quite different. Do not apply the APS / Deakin teaching to TIT. You need to fit an engine monitor to follow their teaching.
4. There is a lot of data, but not presented in a user friendly manner. You'll need to do some unit conversions to make sense of it all. Get out a pencil and change the charts.
5. The Continental manual defers to the Cessna POH for cruise leaning instructions. The Cessna POH seems to be saying to lean to a fuel flow derived from a fuel computer. However it also suggests leaning to peak EGT below 65% power. Deakins et. al. will cry that this is inside one of their red boxes. However, you need to know where the temperature is measured first and the Cessna POH doesn't say. If it is in fact a turbo charger inlet temperature (TIT) rather than an EGT (near the exhaust valve) then Cessna may be correct.
6. In my (limited) experience with pressurised aircraft, you might find that it doesn't maintain the cabin altitude at the flight levels that give best efficiency at 65% power. There are more gains from optimal altitudes than optimal leaning. Someone will correct me if I'm wrong, but I don't believe APS advocate LOP above 65% power.