Takeoff engine trouble

[Charly_Owl]

Hullo folks!

 

First, I got to thank you guys for the help you've given me with landing. It really, really helped.

 

But now, I'm stumbling on another weird issue I don't understand.

 

When I'm taking off in summer or spring in sunny/cloudy conditions, I can take off no problem.

 

However, in winter and fall settings, when I throttle up for takeoff, something weird happens. When I hit about 40 inches manifold pressure and I'm accelerating (and all temperatures and rpm settings are fine, I think), my engine coughs (as if it was running out of fuel) and spools down in a matter of about 10 secondes. Prop generates no more thrust and I can't liftoff at all. It's not like a violent engine seizure with the "KLANK"... it's as if I was running out of fuel.

 

I just can't put my finger on where this problem originated from. Any ideas

 

N.B. I always do a cold start.

[NoJoe]

It could be that the engine temp isn't yet high enough for it to run well? There's a little placard in the cockpit by the pilot's right elbow that lists engine limits, including minimum coolant and oil temperatures for takeoff. That might explain the coughing engine.

 

--NoJoe

[ff4life4]

I would check your oil pressure gauge, when your engine is warmed up, the pressure wont go past redline when you give it throttle. I haven't had any of the symptoms you have when doing cold weather takeoffs.

 

Only other tip I have is I slowly advance the throttle. I have noticed if you ram it forward she doesn't like that sometimes and will begin to knock.

 

EDIT: Also, I know this sounds dumb but check which tank you have the fuel selector on. If I load out with heavy ordinance, I cannot take a full fuel load. The way DCS works is it fill the main tanks (left and right) first, than after that it will fill the center fuselage tank. I have had time where there is a tiny amount of fuel in the center tank and it runs out on or directly after the take off. The coughing sound generally happens when you run out of gas

Edited October 2, 2013 by ff4life4

[xcom]

If its in cold weather, you would need to move the carborator air flow control to hot air, you don't want that cold air going through the carborator at takeoff, your ignition would be lost.

[Mike Busutil]

you don't want that cold air going through the carborator at takeoff, your ignition would be lost.

 

 

What....

[sobek]

If its in cold weather, you would need to move the carborator air flow control to hot air, you don't want that cold air going through the carborator at takeoff, your ignition would be lost.

 

Your ignition won't go anywhere. 50°C up or down don't matter much when the plasma in the spark gap has in excess of a few thousand degrees. Fuel evaporation is a problem at startup, but the carb heat system won't help with that, it is only used to cure carb ice problems.

[xcom]

OK, thanks for the explanation, I always figured that the engine was stalling because of the cold air going into an already very cold engine, usually when I set the hot air would fix the issue, maybe it was a coincidence.

[Scrim]

Speaking of cold temperatures, is it actually possible to start the engine during, well, Stalingrad grade cold? Just tried it at -50, and the starter keeps burning out. I know -50 is much, but I recall trying at -20 and getting largely the same result, so what should I keep in mind when starting in cold temperatures?

Edited October 2, 2013 by Scrim

[msalama]

You'll need to use oil dilution in subzero temperatures.

[Merlin-27]

You'll need to use oil dilution in subzero temperatures.

 

This. From what I understand it is modeled in DCS to allow you to dilute the cold sluggish oil right before cranking. In RL the pilot would have to dilute the oil right before shutdown in preparation for a super cold start. I recall reading about fires being built under the noses of German aircraft during their time spent in Russia.

[352ndRJ]

Carb heat on the left side behind the trims. Check your carb heat gauge as well. You could be getting carb ice.

 

HOT AIR CONTROL LEVER. The Hot Air Control lever has two positions: NORMAL and HOT AIR. When set to NORMAL, the hot air door is closed and either ram air or unrammed filtered air enters the carburetor, depending on the Ram Air Control lever setting. When set to HOT AIR, the hot air door is open and warm air from the engine compartment enters the carburetor. Note, the warm air door is spring-loaded and will open automatically in case of icing or other foreign object obstruction due to the suction on the carburetor.

Edited October 2, 2013 by 352ndRJ

[sobek]

Carb icing is not yet modelled.

[ff4life4]

Carb icing is not yet modelled.

 

Well that explains how I did a flight at 40k feet one time with the carb temp gauge reading -50c. I was wondering why nothing went wrong, btw carb heat was on too.

[Charly_Owl]

Thanks guys for the quick response. Diluting the oil did the trick. I held it for approx. 6-8 seconds, and the engine didn't fail.

 

I'm curious about why you need to dilute the oil with gasoline when it's cold...

Edited October 3, 2013 by Charly_Owl

[Merlin-27]

Thanks guys for the quick response. Diluting the oil did the trick. I held it for approx. 6-8 secondes, and the engine didn't fail.

 

I'm curious about why you need to dilute the oil with gasoline when it's cold...

 

If you mix the oil with gas you increase the viscosity which helps get things moving on a very cold start.

[Echo38]

Isn't that a decrease rather than an increase?

[Merlin-27]

Isn't that a decrease rather than an increase?

 

Ah yes. I guess I misunderstood the term. Since it is a measure of resistance... high viscosity is "thicker"

Edited October 3, 2013 by Merlin-27

[ff4life4]

Thanks guys for the quick response. Diluting the oil did the trick. I held it for approx. 6-8 secondes, and the engine didn't fail.

 

I'm curious about why you need to dilute the oil with gasoline when it's cold...

 

Interesting, because the manual says that the oil dilution can be used for up to 2 minutes. Im surprised 8 seconds would affect it.

 

 

I usually let the stang warm up for several min or so when its cold weather. Ill start up and grab food/drink, or have a bathroom break.. because once you take off there is no way you can step away from the controls for any length of time before becoming a bomb

Edited October 3, 2013 by ff4life4

[Charly_Owl]

Interesting, because the manual says that the oil dilution can be used for up to 2 minutes. Im surprised 8 seconds would affect it.

 

 

I usually let the stang warm up for several min or so when its cold weather. Ill start up and grab food/drink, or have a bathroom break.. because once you take off there is no way you can step away from the controls for any length of time before becoming a bomb

 

Well, I re-did the test, held Oil Dilution button for 10 seconds, started the engine, got to the runway, held Oil Dilution for 10 seconds, attempted to take off, and then just as I was about to throttle up, my engine died. I guess I was just lucky when I did the first test. Darnation.

 

I... I just don't understand. How much time, and when should that button be held in winter conditions? I read the manual and it says that the oil dilution button should be used AFTER flight. What about when you're starting a flight? And how much time should that button be pressed? 2 minutes, you say? The DCS manual is very vague about taking off during winter...

[ff4life4]

Charly,

 

The oil dilution adds gasoline into the oil to make it thinner for starting (edit:the gasoline will eventually burn off when the engine is running). When oil gets cold it is very thinck and doesn't flow easily. I notice this when my engine is cold in my pickup in the winter, I can see my oil pressure gauge skyrocket when I floor it on a cold engine.

 

My suggestion would be to try the oil dilution for 30 seconds before starting, then start and let it warm up for 5 minutes. You will know the engine and oil is warm when the oil pressure gauge doesn't go above redline when you give it throttle. Its the small gauge on the left directly under the oil temperature.

 

Try that and see if that works.

 

Edit: Also just out of curiosity use the left fuel tank, as thats the one I always use when taking off

Edited October 3, 2013 by ff4life4

[alfredo_laredo]

Check the tank selector is on the Left Side.. always take off on the left fuel tank

Check Theres Fuel on the tank

Keep the Electric Fuel Pump On! During all flight.

 

About Oil Dilution...

If Your Oil temp are above 40, the Oil is not an issue on your takeoff.

 

By the way,

 

--oil dilution doesnt work If Your engine is off.

--Oil Dilution Doesnt Work when Oil Temp is Really Hot.. Because the Fuel will evaporate.

If you plan to re-start your engines in a below 0° situation.. dilute the oil before engine shutdown for a few minutes...

--If you start in cold situation you can use Oil Dilute before your Run Up checklist to bring down your Oil Pressure

Edited October 3, 2013 by alfredo_laredo

[ff4life4]

Thanks for clarifying, I never knew the oil dilution didn't work when engine wasn't running. I guess my longish warm up times were enough to heat the oil