Simviation Forums

When I get close to crusing altitude, I feather back the propeller RPM and lean the fuel mix.  

My questions are:

1. what is the real world reason for doing this?

2. How can you tell how much to lean the fuel mix (as in what gage to watch).  How far do you lean it?


Both are pushed back in for landing (I know that much).

Feathering the prop means the angle its at is changed, and fuel mixture needs to be altered the higher you get partly as the air is thinner and you'd run rich (and clogging up your spark plugs with unburn avgas and oil is a bad idea!).
The reason for this is to extend the range you can fly. On take-off or landing you want a fine pitch, and as you're at a lower altitude you'll need more fuel or else you start burning lean and can damage the engine.

Ozzy

How much do you want to lean or enrich the fuel mix, and what gage to you watch?

How far do you want to feather (I usually get the RPM to 20)

Jordonj:
Mixture and prop settings can be tricky to get; but once you figure it out it's easy.
1) Mixture. To control mixture; the gauge you read is the EGT; or 'Exhaust Gas Temperature'. This will tell you if your engine is running too lean (EGT gets hotter) or too rich (EGT gets cooler). But for FS purposes; it's far easier to just listen for it. Bring the mixture back just a wee bit every thousand feet of climb; keeping the engine sound strong. If it drops off; adjust mixture until it sounds strong again. It's a lot faster than using the EGT; the gauge takes a few seconds to move.
Basically; use the ear for climbing; then once you're in cruise; use the EGT for fine-tuning.
2) Prop setting. Most of the planes in the game with an adjustable propeller use a constant-speed prop.
It works kinda like a gear shift - when you need power; such as during takeoff, climb and landing (basically doing anything interesting with the bird); keep it fully fine - i.e. fuly forward. Without going into technical detail; this gives the engine maximum grunt to pull the plane forward. Once you're in cruise; set the prop to what it says in the checklist. If the checklist doesn't have that info (it will); try to adjust the prop so the prop RPM needle is around the bottom end of the green arc.
This is general only - your best bet is to look up the appropriate numbers in the manual and use them.
Cheers!

The lessons give a nice explanation.

Feathering ( like it has been said ) is just like gears.
On takeoff you need the most power ( or torque ) so you set the smallest angle possible, so that the engine can turn the prop with little effort.
The further you pull back the leavers, the more work the engine has to do, because the prop takes a larger 'bite' of air.
Of course when you are at cruise altitude, you will want the prop to create alot of thrust, while the engine uses as little fuel possible ( for economy ). So if you set the prop to take a large 'bite' of air, the rpm will decrease ( due to drag ) which in turn decreases the engine rpm.
Which is good  ;D .


Mixture:

The throttle controls the amount of air that can enter the engine.
The mixture controls the fuel.

So when you get higer-up, the air is less dense. Therefore you dont need be pumping in a large amount of fuel, since not all of it can burn ( due to the small amount of air ). So again its all for economy.

I hope that clears everything up  ;D.

Jordonj:

This is general only - your best bet is to look up the appropriate numbers in the manual and use them.
Cheers!

In the manual?

Do you mean the kneeboard (I don't remember documentation coming with my copy), or do you mean the learning center?

Any, as always, thanks for your responses.

In the manual?

Do you mean the kneeboard (I don't remember documentation coming with my copy), or do you mean the learning center?

Both. The "Learning Center" (Oy - nothing so ordinary as a 'manual' for microsoft, eh?) has all the required info for each aircraft; and rhe checklist part of the kneeboard contains similar info. As in a real flight; read everything before takeoff.
Enjoy!

The EGT and CHT gauges are a little slow and not too accurate. The best way to set mixture (in the sim) is to "peak" the fuel flow. Pull the mixture lean until the fuel flow peaks... if you keep leaning, it will drop back off again. You'll get the idea when you try it.

If you're leaning in a desperate attempt to save fuel while trying to figure out where you are, or where to land... pull the mixture lean until the engine starts to sputter.. and then richen, just a bit. In the real world.. that'll make the engine run on the hot side (fuel actually acts as a coolant before it ignites).

Prop RPM is like an infinitely-variable transmission. All the way in (max RPM) is like a low or passing/climbing/accelerating gear. Pulling the RPMs down is like shifting into a higher gear (or like over-drive in a car for cruising). It saves fuel and engine wear/tear. Pulled all the way out (min RPM) is "feathering" the prop.. or making it like a knife cutting edge first(if the engine has quit) (as opposed to trying to push it sideways) through the air. You need to do this when an engine fails.. The sim is so realistic, that feathering the prop actually increases your glide ratio (leaving a dead engine's prop unfeathered is like a speed-brake deployed).