Questions about fuel

[Check Six 2]

I've always flown Over Flanders Fields using Auto Mixture "On" because I didn't know the answers to these questions. Can anyone help me out here?

 

I have a few newbie, uninformed questions to ask about fuel. If you can't answer all of the queries comprehensively, I'd appreciate your reply to single questions I pose here.

 

Firstly, I would like to know about fuel mixture. I understand that any particular engine "prefers" or runs better with a certain percentage of atomised fuel and air mixture.

 

Do you require a "richer" mixture [is that the correct term?] (ie more fuel than usual) to start the engine, and then gradually decrease the fuel percentage as the engine warms up (similar to a "choke" in a modern engine... And the term "choke" - is the fuel/air mixture altered by decreasing the air (choking), and not increasing the fuel, and if so, why the heavier fuel smell when starting under choke on winter mornings, and problems of "flooding")?

 

At sea level, your percentage of fuel to air is higher I would suppose. As you gain altitude, the air gets thinner, do you then feed the engine MORE fuel to compensate for this, or LESS to keep the percentage of fuel to air roughly the same? When you start to return to earth, do you need to constantly adjust the mixture again, and if so, do you add or subtract fuel from the formula to keep the engine running smoothly to compensate for the higher percentage of oxygen?

 

If you enyered in combat, and jinked and manoeuvred to either get on your opponent's six, or to prevent him getting on your six, do you need to adjust the mixture any further to gain more power (assuming for example that the combat stays at the same altitude, so that losing several hundred feet doesn't enter into the formula)?

 

I guess all this adjusting was by feel, and that there were no "Fuel/Air Ratio" gauges in the cockpit, but did they have any fuel gauges to assist (even just an "Empty/Full" guage, or did this take the form of some sort of clear gravity tube visible from the cockpit)? If this method was employed, how did inversion during combat affect the gauge? I suppose a few aircraft had a spare tank, and that when their main tank ran out, and they were forced to switch on the reserve tank, that warned the pilot to get his craft home quickly.

 

How was the problem of flying inverted solved? I understand carburettors have floats in them that are forced to obey the laws of gravity (as all things do), and that fuel injection solved this problem, but was it available in WW1? (Interestingly enough, this was an evasion tactic used by the Luftwaffe in WW2. As Spitfires and Hurricanes had carburettors and Messerschmitts had fuel injected Mercedes engines, the evading Luftwaffe pilot simply nosed down abruptly; if the RAF pilot attempted to follow the manoeuvre, his engine would cough and splutter due to the carburettors starving. They developed the counter manoeuvre of inverting their aircraft, and pulling back on the stick to follow the Luftwaffe pilot. This also took a second or so, and enabled the Luftwaffe pilot a small window of escape. But how were they able to fly inverted with carburettors?).

 

And lastly, which of these mixture problems and carburettion problems were "solved" by inline engines, and which were only present in rotaries?

 

A long, complicated question, and I apologise for my ignorance, but these questions would help me to understand the problems faced by a scout pilot who was forced to manage his engine as well as try absolutely everything to escape being shot out of the sky by an opponent. I would appreciate any help any of you people could give me.

[Duce Lewis 3]

Good questions Check6!

 

As Al says, mixture is only altitude (not temperature) sensitive

OFF simulates this very well

Start rich and gradually lean as you climb

If you lean it too much she'll stutter or stall but quickly reversing the richness and she'll refire on her own

 

Yes, if you're dogfighting and lose altitude she'll stall at some point

But eventually you'll learn to be mindful of that

 

Weather seems to have an effect too

Storms bring lower barometric pressure so it seems leaner mixtures are required

 

I read about the Spitfire carburater issues in "Fly for your Life" by R S Tuck ...good book!

He said the "boffins" developed a floatless carburater to solve this

How this worked? I don't know

 

There are two options for Mixture Control in OFF

Number Keys that control by 10% increments ...IIRC

or your can create an Axis Command to a Rotary or Slide Control

I have a Thumb Slider on my Throttle that works well

 

HTH,

[Winston DoRight 3]

Do you require a "richer" mixture [is that the correct term?] (ie more fuel than usual) to start the engine, and then gradually decrease the fuel percentage as the engine warms up (similar to a "choke" in a modern engine... And the term "choke" - is the fuel/air mixture altered by decreasing the air (choking), and not increasing the fuel, and if so, why the heavier fuel smell when starting under choke on winter mornings, and problems of "flooding")?

As you press your START button in all CFS3 expansions the mixture is automatically set at full rich, as it should be for proper engine startup. No mixture adjusting is necessary as the temperature of the engine changes.

 

At sea level, your percentage of fuel to air is higher I would suppose. As you gain altitude, the air gets thinner, do you then feed the engine MORE fuel to compensate for this, or LESS to keep the percentage of fuel to air roughly the same? When you start to return to earth, do you need to constantly adjust the mixture again, and if so, do you add or subtract fuel from the formula to keep the engine running smoothly to compensate for the higher percentage of oxygen?

As altitude increases you must LEAN your mixture. If you don't you cannot get full power. As you decend you must richen or the engine may starve and die. This is modeled quite well in CFS3

 

If you enyered in combat, and jinked and manoeuvred to either get on your opponent's six, or to prevent him getting on your six, do you need to adjust the mixture any further to gain more power (assuming for example that the combat stays at the same altitude, so that losing several hundred feet doesn't enter into the formula)?

No, small changes in altitude can be ignored when combat give you other things to do. But if your opponent dives for the deck, you better richen your mixture as you follow or your engine will cut out on you when you need it the most!

 

I guess all this adjusting was by feel, and that there were no "Fuel/Air Ratio" gauges in the cockpit, but did they have any fuel gauges to assist (even just an "Empty/Full" guage, or did this take the form of some sort of clear gravity tube visible from the cockpit)? If this method was employed, how did inversion during combat affect the gauge? I suppose a few aircraft had a spare tank, and that when their main tank ran out, and they were forced to switch on the reserve tank, that warned the pilot to get his craft home quickly.

The SOUND your engine makes as you lean/richen the mixture is the key here. Try this test: After starting your engine, gradually lean the mixture until the engine begins to loose rpm (sputter). Going much farther will shut down the engine. When your engine just begins to sputter, richen the mixture by just a few presses. You are now at optimal mixture for the current altitude (verify this with tachometer if equipped). As you climb you can lean it even more, just remember to richen it as you decend.

 

How was the problem of flying inverted solved? I understand carburettors have floats in them that are forced to obey the laws of gravity (as all things do), and that fuel injection solved this problem, but was it available in WW1? (Interestingly enough, this was an evasion tactic used by the Luftwaffe in WW2. As Spitfires and Hurricanes had carburettors and Messerschmitts had fuel injected Mercedes engines, the evading Luftwaffe pilot simply nosed down abruptly; if the RAF pilot attempted to follow the manoeuvre, his engine would cough and splutter due to the carburettors starving. They developed the counter manoeuvre of inverting their aircraft, and pulling back on the stick to follow the Luftwaffe pilot. This also took a second or so, and enabled the Luftwaffe pilot a small window of escape. But how were they able to fly inverted with carburettors?).

 

And lastly, which of these mixture problems and carburettion problems were "solved" by inline engines, and which were only present in rotaries?

Flying inverted problems were not solved in WW1 with inline carburated engines although by wars end several aircraft had automatic mixture control devices. Positive "G" had to be maintained when upside down to keep the fuel flowing. Inverted maneuvers were brief, with positive G's and performed infrequenty by inexperience pilots. A good example; In the new "The Red Baron" movie, while flying an Albatros, Richtofen needed to get the attention of his flight members. He abruptly nosed over his Alby and it coughed and backfired loudly when the negative G's momentarily interrupted the flow of fuel.

 

A long, complicated question, and I apologise for my ignorance, but these questions would help me to understand the problems faced by a scout pilot who was forced to manage his engine as well as try absolutely everything to escape being shot out of the sky by an opponent. I would appreciate any help any of you people could give me.

After awhile managing your mixture will become a sixth sense. You'll do it automatically and without really thinking especially if you have an "axis" or a programmable rotary knob on your controller(s) to assign to the mixture to replace the keyboard strokes.