It also depends on the engine. The IO-550 I can lean a long way before it goes rough. Leaning to rough and richening a bit I’d still be somewhere in LOP territory.
The problem with that is that you might just end up more or less at 50 ROP, which will be hard on the engine and run the CHT way up a few moments after lifting off.
Therefore, I prefer the method using known fuel flow values. There Cirrus has a small table in the POH for that which is also printed on the RH side dashboard. If you don’t have such for your aircraft, then, I agree with the other, just work one out yourself using 150-200ROP in a climb.
Of course, the fuel flow method only works if you have a (working) fuel floelw gauge.
When I was doing a long trip in the US in a C182, I just leaned it till it went rough then enriched a bit. That will get it close enough without having to wait for the temperature gauge to settle.
The valley in Samedan is so big that you can easily fly circles in a SEP. It’s only the jets that play Russian roulette in dodgy weather and as a result the SEP pilots get punished.
The strange thing is that the jet pilots are not really punished at all! Cat B/C aircraft pilots can just fly there without any kind of checkout if the weather is CAVOK, while cat A pilots always need a local checkout (or mountain rating).
I don’t consider Samedan to be particularly difficult at all, I was there in a C172M in summer with 3 adults, i.e. very marginal performance and it was no problem at all.
I looked at the online briefing for Samedan and I agree that from a SEP perspective it doesn’t look more difficult than any other airfield in the alps. You have to be careful with your performance calculations, of course. I wouldn’t hesitate the least in going there.
If it is LSZS in Switzerland with very high terrain around and a rising valley in the west take great care. Those are the moments all the expenses for a turbo pay of in one single flight…
The valley in Samedan is so big that you can easily fly circles in a SEP. It’s only the jets that play Russian roulette in dodgy weather and as a result the SEP pilots get punished. I don’t consider Samedan to be particularly difficult at all, I was there in a C172M in summer with 3 adults, i.e. very marginal performance and it was no problem at all.
Obviously not. But the MP would increase. Or maybe not
The MP will not change significantly if you lean. Usually you can only feel the additonal power. At the moment you lean properly engine rpm will increase a bit until the governor adapts the prop and the engine will run much softer.
Where do you want to land this summer? If it is one of the Franch altiports I would not worry too much because at takeoff not much power is needed as you go downhill. If it is LSZS in Switzerland with very high terrain around and a rising valley in the west take great care. Those are the moments all the expenses for a turbo pay of in one single flight…
Shorrick_Mk2 wrote:
A constant speed prop won’t change RPM when you lean it, will it?
Obviously not. But the MP would increase. Or maybe not. I’ve never had to lean before takeoff with a VP prop.
Typical sea level (ISA) takeoff EGT on my TB20 is about 1330F, so setting that will give you about 150F ROP which will be good enough.
A constant speed prop won’t change RPM when you lean it, will it?
Lucius wrote:
I haven’t had to take off from a density altitude between 6000 and 9000 feet. But it may happen this summer. I was wondering how to lean to 125 degree ROP on the ground prior to take off.
Should you really lean by temperature in this situation and not to max rpm/MP?
