Operating in cold climates

[AlphaOneSix]

IRL there is a warmup phase for the APU after startup and a mimimum APU cooldown period between engine starts (as well as before APU shutdown), which is about 1 minute, IIRC . Also the engines must not be taken out of idle before eng oil temp is above 30°C(?) and gearbox oil temp above -5°C(?), so as not to risk to reduce service life or damage the engines. In DCS, however, this does not cause any ramifications. Same thing with takeoff power, time limit is 6 mins (?, i'm sure A16 is gonna correct me on these values :)) and time limit for max cont is 1 hour (again, not sure on the numbers). In DCS, you will not notice any engine degradation below the governed maximum power setting.

 

I don't think the APU cooldowns are mentioned in the manual, but they are as follows:

 

Allow one minute between the start of the APU and the first engine start to allow the APU to stabilize. Allow one minute between air bleeds (engine starts) to allow the APU to cool slightly.

 

The timing would go like this:

 

Start APU.

Wait one minute (measured from the time the APU ON light comes on to the time you press the engine start button for the first engine).

Start the first engine.

Wait one minute (measured from the time the START VALVE* light goes out to the time you press the engine start button for the second engine).

Start the second engine.

 

*As long as the "START VALVE" light is on, that means that air is being bled from the APU and is being forced through the starter on the engine. This causes your APU EGT to increase. The wait time between engine starts is to allow the APU to cool down a bit.

 

Minimum engine oil temperature before advancing the throttles to AUTO is 30 degrees. So you may have to wait a minute or two after the second engine start for the oil in the second engine to get up to 30 degrees (by this time it's pretty much guaranteed that the first engine you started will already be warmed up).

 

If you do not adhere to these limits, there is no consequence as far as I know. You can start the whole aircraft in about a minute and a half if you are good at flipping switches. However, the times between starts are good times to be doing other things, like setting up your systems and letting the INU get started.

 

The time limits for the different engine power regimes can safely be ignored, because the only consequence of exceeding them is a reduction in the time before the engine needs to be overhauled. Since this is a flight/combat simulator, and not a maintenance simulator, you can safely assume that your engines are being replaced as necessary.

 

If interested, and for the sake of completeness, the time limits are as follows:

 

IDLE throttle setting: 20 minutes (before advancing the engines to AUTO)

Cruise (below the "K" on the Engine Power Indicator): Unlimited

Nominal/Max Continuous (Above the top of the "K" but below the top of the "H" on the Engine Power Indicator): 60 minutes

Takeoff power (Above the top of the "H" but below the top of the "B" on the Engine Power Indicator): 6 minutes under normal conditions, up to 30 minutes in emergency conditions, and up to 90 minutes if the other engine is inoperative.

 

If you run the engine near the max of one of the above time limits, it must be operated at Cruise power or below (below the "K" on the Engine Power Indicator) for 5 minutes before entering one of the higher power settings again.

 

Note that above 2500 meters of altitude, the Engine Power Indicator is no longer the primary indicator of the power setting of the engines. Above 2500 meters, your power setting (Cruise, Nominal, Takeoff) should be determined by your engine EGT or N1, whichever puts you into a higher power setting. This is not at all simulated in the game, as far as I can tell, since it requires the use of PPCs (Performance Planning Charts) which don't come with the game. (Personally, I use the charts for the Mi-17, which has nearly identical engines, the only difference being that the Takeoff power setting has more power and you can spend more time in the Takeoff power regime under emergency and OEI (one engine inoperative) conditions.

[ARM505]

20 minutes at idle?!? Did you mean 2? I hope so....I feel bad for my virtual engines when I don't allow the correct times - just force of habit. Thanks for the info though, very informative as always.

[sobek]

I don't think the APU cooldowns are mentioned in the manual, but they are as follows:

 

I know, i just remembered you telling us :)

 

Seems at least i was spot on with the times :pilotfly:

[AlphaOneSix]

20 minutes at idle?!? Did you mean 2? I hope so....I feel bad for my virtual engines when I don't allow the correct times - just force of habit. Thanks for the info though, very informative as always.

 

No, it's 20. In other words, do not leave the engines in IDLE for more than 20 minutes before advancing the throttles to AUTO.

[sobek]

No, it's 20. In other words, do not leave the engines in IDLE for more than 20 minutes before advancing the throttles to AUTO.

 

What's the problem with idle? Does the oil overheat?

[AlphaOneSix]

Yep. At lower RPMs, the oil pump is slower, so it doesn't move as much oil to the coolers. Also, since the cooler fan is attached to the main gearbox, the coolers are less efficient at the low rotor speed that you'll have at idle.

 

I have not tried this in the game, though, so it may not be modeled.

[sobek]

Yep. At lower RPMs, the oil pump is slower, so it doesn't move as much oil to the coolers. Also, since the cooler fan is attached to the main gearbox, the coolers are less efficient at the low rotor speed that you'll have at idle.

 

I have not tried this in the game, though, so it may not be modeled.

 

According to Yo-Yo, the heat transfer model is quite sophisticated (i asked about it some time ago), so it might very well work. E. g. when you move to idle after a long period of full auto, the oil heats up very rapidly and gets hotter when you turn the engines off. Would be interesting though, if overheating the oil causes any consequences (in the game).

[StrongHarm]

If you turn your deicing systems on in warm weather, can they overheat like in real life or is that not coded into the sim?

[AlphaOneSix]

Yes, this is true for most electrically-heated de-ice units, such as the blades. Normally, it would be fine to turn on the engine anti-ice, even in warm weather, but on the Ka-50, turning on the engine anti-ice also turns on the electrical de-ice units for the dust protectors, so that;s a no-go as well.

 

You can turn on pitot heat in warm weather (which is normal to prevent moisture from entering the pitot lines), that won't cause a problem...but the pitot heaters are not modeled in the game.

[slug88]

You can turn on pitot heat in warm weather (which is normal to prevent moisture from entering the pitot lines), that won't cause a problem...but the pitot heaters are not modeled in the game.

 

Are you sure about that? I recall reading that pitot icing is modelled and that you'll lose IAS and baro alt readings if you don't turn the heaters on in cold weather.

 

Edit: This post by Yo-yo seems to suggest that pitot icing is indeed modelled. I would think this implies that the pitot heaters are also modelled.

 

http://forums.eagle.ru/showpost.php?p=503737&postcount=378

Edited January 26, 2010 by slug88

[AlphaOneSix]

Well there you go. I thought I remembered it being mentioned that it was not modeled. Maybe that was sometime during the beta and it just wasn't modeled at that time, or maybe I'm completely wrong. Good to know it is indeed modeled now, though.

[sharkforce]

a few hundred HP lost is nothing compared to the HP lost from the drop in air density as altitude is increased, at 10000m for example the air density ratio is only .337, .337 *2200 = 741 available HP glhf with that much power. near the ceiling at 5km, the power available is ~ .6* 2200 = 1320 HP.

Edited January 26, 2010 by sharkforce

[Frederf]

I've never managed to get the pitot heat test lights/switches to do anything meaningful. How are those suppose to work again?

 

Back with the old C-172 you'd turn it on for a few seconds and then go and feel if it was warm during the walkaround. More than once I left it on too long and burned the bejebus out of my hand though.

[StrongHarm]

Yes, this is true for most electrically-heated de-ice units, such as the blades. Normally, it would be fine to turn on the engine anti-ice, even in warm weather, but on the Ka-50, turning on the engine anti-ice also turns on the electrical de-ice units for the dust protectors, so that;s a no-go as well.

 

You can turn on pitot heat in warm weather (which is normal to prevent moisture from entering the pitot lines), that won't cause a problem...but the pitot heaters are not modeled in the game.

 

So if it's possible to damage the aircraft by misusing the deicing system, what are the thresholds or safe operating temps? Is there a basic rule of thumb for activation of deicing systems? I couldn't find any data in the manual.

[AlphaOneSix]

a few hundred HP lost is nothing compared to the HP lost from the drop in air density as altitude is increased, at 10000m for example the air density ratio is only .337, .337 *2200 = 741 available HP glhf with that much power. near the ceiling at 5km, the power available is ~ .6* 2200 = 1320 HP.

 

The power available does not drop off in a straight line as you're suggesting. At lower altitudes, the engines will produce their maximum power well below their maximum RPM. As the altitude increases and the air density decreases, the engine still produces it's maximum power, but the RPM required to generate that power also increases. Eventually, you will hit an air density where the maximum RPM of the engine produces exactly the maximum power, and once above that, you will see the power available start to drop off.

[AlphaOneSix]

So if it's possible to damage the aircraft by misusing the deicing system, what are the thresholds or safe operating temps? Is there a basic rule of thumb for activation of deicing systems? I couldn't find any data in the manual.

 

I don't know that the game models damage to the aircraft by turning on de-icing systems if it's too warm. In real life, the max temp. for continuous operation of the de-icing systems is +5C. From +5C to something like +15C, you can run it for up to two minutes for testing. From +15C to +25C you can run it for one minute for testing. It is prohibited to turn on the de-icing systems above +25C. Those are the numbers for the Mi-17 and I'd be very surprised if it was any different for the Ka-50, although it could be different.

 

All we need now is a working OAT (outside air temperature) gauge and we'll be set!

[Bucic]

For now you have to get some sniper math skills ;)

 

In metric system it's about 0.5 deg C temperature drop for every 100m altitude increase.

For quick calculation

t=t0-(alt/100*0.5) -> t=t0-alt/200

So for example if the temp. at sea level is t0=20 deg C then the temperature at 3000m is t=20-3000/200=5 [deg C]

 

To simplify even more - air temperature:

reaches 0 deg C, when you are at alt=/t0*200/ e.g. with temp at sea level t0=20 deg you'll hit 0 deg at alt=4000m

decreases by 2*t0 when at alt=/t0*400/ obviously e.g. with temp at sea level t0=20 deg you'll hit -20 deg at alt=8000m

 

where /x/=abs(x) and t0 is the temperature at sea level you check in the briefing.

 

Com on, it's so much fun without the OAT gauge ;)

[Martillo1]

I tested it at -50 ºC and the gearbox takes a loooong time to warm. Any indications about the procedure at that temperature? What about the throttle levers?

[sharkforce]

The power available does not drop off in a straight line as you're suggesting. At lower altitudes, the engines will produce their maximum power well below their maximum RPM. As the altitude increases and the air density decreases, the engine still produces it's maximum power, but the RPM required to generate that power also increases. Eventually, you will hit an air density where the maximum RPM of the engine produces exactly the maximum power, and once above that, you will see the power available start to drop off.

thankyou for correcting me, i was just using my over-simplifed knowledge of turbojet engines. :p

 

any idea what altitude max RPM and max power meet?

could you produce > max power if you used higher rpm's than normal at sea level

Edited January 26, 2010 by sharkforce

[AlphaOneSix]

any idea what altitude max RPM and max power meet?

could you produce > max power if you used higher rpm's than normal at sea level

 

Don't know about the altitude off the top of my head, but I can look at some engine charts and hopefully find the air pressure (in millimeter of mercury) where power and RPM meet.

 

You can't get higher than max power at sea level because at that altitude the power will be limited by the EGT limiter (limited to 990C).

 

You should notice that if you pull enough power to get into EGT limiting (RH/LH POWER SET LIMIT light) at sea level, your engine RPMs should be lower than if you did the same thing at high altitude.

[AlphaOneSix]

I tested it at -50 ºC and the gearbox takes a loooong time to warm. Any indications about the procedure at that temperature? What about the throttle levers?

 

There is actually a minimum temperature for the oils in the engines and gearboxes below which they require heating from an external source before starting. It depends on the type of oil used, but it typically around -30C. If below that temp., you must heat the gearboxes with some kind of heater (helps to be in a hangar at this point, but we've also been known to use ducting to blow warm air onto the gearboxes).

 

For the engines, here are the specific procedures for extreme cold:

 

*If the compressor rotor blades are frozen to the stationary components or icing is detected on the engine components, heat the engine with hot air at a temperature rot exceeding 80°C using ground heaters for the purpose of delivering hot air into the engine gas flow duct. After heating make sure that the rotors rotate easily and are free from ice.

*If in winter the engine oil temperature is minus 30-40°C before start it is necessary to perform 2 engine crankings, with 3 minutes intervals between them.

*In order to ensure reliable start of the engines in winter at ambient temperatures of -5°C or below after a prolonged parking period (for 24 h or more) it is necessary to crank the engines before start.

 

Cranking the engines is similar to starting them, but you don't put any fuel into the engines. The start switch on the start panel is defaulted to "START" but can also be switched to "CRANK" or "FALSE START". A false start is like a crank but fuel gets injected into the engine, but is not ignited.

 

Here are a few more cold-related procedures to follow once the engine are started, but before advancing the throttles to AUTO:

 

Powerplant warm-up. Test of flight controls and hydraulic system

(1) Warm up the powerplant at idle power with the collective pitch control lever at the lower stop, the throttle control twist grip turned fully to the left, the engines throttle levers latched in the neutral position. (*Note, this is the Mi-17, for the Ka-50 it means leave the throttle levers in the IDLE position.)

(2) In the course of the powerplant warming up monitor the powerplant instruments which readings should be within the limits indicated in Section 2.

In all cases the warming up period should be not less than 1 min.

(3) It is allowed to accelerate the engines from idle up to higher power ratings after the engine outlet oil temperature reaches +30°C and the main gearbox oil temperature reaches at least -15°C.

(4) In the course of the engines warming up switch on the command radio.

(5) Test the flight controls and the hydraulic systems at idle power following the procedure below:

(a) Alternately move the control stick and pedals to make sure that the controls move smoothly, without jerks and jamming.

(b) At ambient temperature below 30°C apply the control stick in small increments to ensure pumping of the АМГ-10 hy-draulic fluid through the system for the purpose of its warm-ing up.

[Martillo1]

Thanks Alpha :)

[AlphaOneSix]

any idea what altitude max RPM and max power meet?

could you produce > max power if you used higher rpm's than normal at sea level

 

I found the chart I was looking for. It's for a TV3-117VM engine, not the TV3-117VMA that the Ka-50 uses, but the only difference is that the takeoff and emergency power bands are increased by 200hp each. That is, for the takeoff band (regime), it's 2200hp instead of the 2000hp as shown in the chart. So the curves are the same, they are just shifted upwards slightly for the takeoff and emergency power bands. The nominal and cruise bands are the same.

 

As you can see, the ideal altitude that allows the most power to be generated (in takeoff mode) is actually around 1,750 meters (assuming a standard temperature and pressure day).

 

For those that don't read Russian, the vertical scale is horsepower, the horizontal scale is altitude in kilometers, and the lines from top to bottom are: emergency (contingency) regime, takeoff regime, nominal (max continuous) regime, and cruise regime. Note that the engine governors will prevent you from exceeding takeoff power unless one of the engines is inoperative.

 

Don't forget to shift the takeoff and contingency regimes up an extra 200hp for the VMA engines.

 

Edited January 28, 2010 by AlphaOneSix

[renders]

have the same problem and i think it's related to vents icing

[ParrotOne]

I turn on all the heat related switches:

 

Pitot static port and AoA Sensors heat switch: LALT+LSHIFT+S

Pitot ram air and clock heat switch: LCTRL+LSHIFT+S

Rotor de-icing system switch: LALT+LCTRL+LSHIFT+S

Engines de-icing systems switch: LALT+I

 

As part of takeoff routine.

 

Don't forget the INU heater: I + RShift + RAlt. It's on the rear panel next to 'INU on'.

 

Wow, this thread is pretty old, isn't it? Should have checked the date.

Edited March 3, 2011 by ParrotOne