Engine startup randomness

[colmbo]

I wasn't aware that diesel engines can also have such problems.

How can you have a vapor lock when your already flying? I thought if that engine is already started vapor lock would not happen.

One would think.

Vapor lock is the only thing we could come up with as a reason it quit.  Low power during descent, engine started surging and fuel pressure fluctuating.  Boost pump to high, mixture richer, switched tanks all no help -- big surge and engine  quit. Down to 5000 AGL so didn't spend much time playing with it for restart, just flew the pattern and landed.  Explained to the boss what happened (he had been operating this specific airplane (as well as other 200 series Cessnas) for over 20 years and knew it very well).  Engine driven and electric fuel pumps working fine, clean fuel, plenty of fuel.  After 10 minutes or so I started it up no problems, a couple high speed taxiis using takeoff power then a short test flight - all without any issues.

[Babalonian]

It'd be nice if the engines didn't always start on the first turn.  Making it so sometimes takes 2 or 3 or even 5 attempts to get your engine started would add a bit of realism to the game.  Also I find it completely ridiculous to fight someone in 2 consecutive flights and have them cut their engines no less than 10 times, and have it instantly start back up.  The E key is used as a crutch when in reality it should be throttle control.  If the engine didn't always start right back up, maybe it'd force people to learn other aspects of the game besides Shift-+ and HO... i mean go.

But we have the pattented AH perfect-mixture/primo-prime/instant-preoiler system, guarenteed to be just right and instantaneous each time you flip on the mags.


OK, but seriously, if they do this, then next we'll have to impliment marshallers just to let us know if we're wet or dry prime just to alleviate subscriber smashed-monitor rates.

[MachFly]

One would think.

Vapor lock is the only thing we could come up with as a reason it quit.  Low power during descent, engine started surging and fuel pressure fluctuating.  Boost pump to high, mixture richer, switched tanks all no help -- big surge and engine  quit. Down to 5000 AGL so didn't spend much time playing with it for restart, just flew the pattern and landed.  Explained to the boss what happened (he had been operating this specific airplane (as well as other 200 series Cessnas) for over 20 years and knew it very well).  Engine driven and electric fuel pumps working fine, clean fuel, plenty of fuel.  After 10 minutes or so I started it up no problems, a couple high speed taxiis using takeoff power then a short test flight - all without any issues.

Interesting.

I don't understand how you can have a vapor lock if your engine is already running. Don't get me worn I believe what your saying, I'm just trying to figure out what mechanically needs to happen in order to get a vapor lock.
If the engine is already running than the fuel pumps are running so what ever vapor might develop in the fuel lines would go to the engine right away, so it would not have time to develop a large bauble that would stop the engine. I am wrong?

[icepac]

Fuel boils at a pretty low temperature.

You don't need a "large bubble" since many small ones are enough to lean the engine beyond the ability to fire.

[hitech]

Interesting.

I don't understand how you can have a vapor lock if your engine is already running. Don't get me worn I believe what your saying, I'm just trying to figure out what mechanically needs to happen in order to get a vapor lock.
If the engine is already running than the fuel pumps are running so what ever vapor might develop in the fuel lines would go to the engine right away, so it would not have time to develop a large bauble that would stop the engine. I am wrong?

I have had it multiple times taxing with a hot engine. Had to flip the boost pump on to keep the engine running.

HiTech

[colmbo]

Interesting.

That's flying.

I don't understand how you can have a vapor lock if your engine is already running. Don't get me worn I believe what your saying, I'm just trying to figure out what mechanically needs to happen in order to get a vapor lock.
If the engine is already running than the fuel pumps are running so what ever vapor might develop in the fuel lines would go to the engine right away, so it would not have time to develop a large bauble that would stop the engine. I am wrong?

And I was descending with lots of what should have been cooling air flowing around the injector lines.

I trust what the boss said.  He had operated that particular airplane for around 11,000 hours and was on the 5th or 6th engine in it.  He has been working on airplanes since the '50s (Marine Corp working on Corsairs and Skyraiders) and had a very large knowledge bank to draw from.  Things aren't always as the "common knowledge" would lead you to believe.

[MachFly]

And I was descending with lots of what should have been cooling air flowing around the injector lines.

I trust what the boss said.  He had operated that particular airplane for around 11,000 hours and was on the 5th or 6th engine in it.  He has been working on airplanes since the '50s (Marine Corp working on Corsairs and Skyraiders) and had a very large knowledge bank to draw from.  Things aren't always as the "common knowledge" would lead you to believe.

I don't doubt that you trust him and that he is correct. I'm trying to figure out how it's physically possible.

I have had it multiple times taxing with a hot engine. Had to flip the boost pump on to keep the engine running.

HiTech

I'm having hard time understand why that would happen.
Could you explain why that happens?



Thanks

[MachFly]

Fuel boils at a pretty low temperature.

You don't need a "large bubble" since many small ones are enough to lean the engine beyond the ability to fire.

In that case it would be happening all the time. Since it doesn't than it must not be the case.

[B4Buster]

A bit off topic...

I knew of an instructor who used to simulate engine outs with his students by leaning the mixture until the engine cut out. One time, him and his student were practicing landing in a field. At about 500', the instructor put the mixture back to full rich to start a climbout, but the engine didn't come back to life. They made a real forced landing in the field. Instructor and student were unhurt.

[Puma44]

I'm sure it was in every WWII fighter manual and flight class too --  "If you overshoot your target, shut off your engine... it'll help you slow down faster."

Do you have documentation that states that?  Or, are you making the "statement" in an attempt to support your idea?  Using "flying" skills will help you slow down faster.  

By the way, shut down the engine in flight is not an ACM maneuver.  It, however, demonstrates extremely poor judgement as a pilot.

A bit off topic...

I knew of an instructor who used to simulate engine outs with his students by leaning the mixture until the engine cut out. One time, him and his student were practicing landing in a field. At about 500', the instructor put the mixture back to full rich to start a climbout, but the engine didn't come back to life. They made a real forced landing in the field. Instructor and student were unhurt.

A perfect example why you don't play games with your normally operating engine and the only time you shut it down is after landing, parked in the chocks.

[Krusty]

Uh.... Puma? It was sarcasm...

[colmbo]

I don't doubt that you trust him and that he is correct. I'm trying to figure out how it's physically possible.


I'm having hard time understand why that would happen.
Could you explain why that happens?

Vapor lock occurs when fuel in the injection lines vaporizes.  For that to happen you have to have some heat -- vapor locks most commonly occur on a hot day after the engine is shut down.  The lack of cooling air moving thru the cowl allows the fuel lines to heat up, fuel boils/vaporizes and voila!  it won't start when you finish lunch.

In Hitech's case the engine is hot, he's on the ground taxiing so little to no cooling air and at idle you're moving very little fuel through the lines.  It doesn't take much to disrupt the correct fuel/air mixture.

[Krusty]

In AH there are 'features' in the game that make restarting your engine a no-penalty thing in both GV's and Airplanes...  I'm simply saying either correct the 'feature' or make it so your desperation move is just that... and you damn well better hope your engine starts back up.

You're trying to solve a problem that isn't a problem. Probably all of 1-2 people in this game (player base in the 10,000's no doubt) toggle engine in fights. Some do it because they don't have a good throttle on their stick, and they say it's how they chop throttle. Better than full power 100% of the time, right?

You're really taking off on this idea that toggling the engine off is breaking the game somehow... but it's not. It really isn't. You want to model in human error, well howabout the pilot scrambling to get into the cockpit forgot his maps? No clipboard for you! How about an armorer screwed up and the first cannon round out of your guns plugs the barrel and the next one starts a chain reaction that blows your wing off, through no fault of your own. Whether you want complex engine management or not, that's another topic. But random failures? HTC doesn't do that, and for good reason.

You've suggested a punitive measure against folks that are not to blame. It does nothing to help and only annoys people trying to fly and fight. I would suggest turning your problem-solving juices to the larger problems we have in-game.

[Puma44]

Uh.... Puma? It was sarcasm...

Uh......Krusty?  Relax and don't fall off your perch.

[icepac]

In that case it would be happening all the time. Since it doesn't than it must not be the case.

Basic physics dude.

I deal with vapor lock issues when designing engine management systems.

My daily driver car's engine is known to vapor lock so nissan equipped it with a blower that blows across the injectors for 15 minutes after you switch the car off.

Later nissan turbo Zs were equipped with "dual feed injectors" that had top and side inlets which allowed the fuel pushed past the regulator to flow through the injectors which cooled them rather than just the rails before them.....which left them hot.

These cars operate with 35 psi fuel pressure at idle and still boil the fuel.

Imagine how much less heat you need to boil fuel at atmospheric pressure.