Endurance of KA-50?

[AlphaOneSix]

Would be nice to have someone like AlphaSixOne comment on this.

 

Ha! I mean...thanks??

 

Just got off the plane and back in A-stan, so my mind isn't functioning on all cylinders yet. One bit of trivia about the EPR gauge that you can mess with is this:

 

The outer (yellow) markers are air pressure readings from the combustion chamber. The numbers on the left and right are the combustion chamber pressures for each engine measured in kg per sq cm. In a nutshell, the faster the compressor (N1) turns, the higher the pressure.

 

The inner (red) markers are, as you already know, engine condition markers, which tell you what condition your engine is currently operating in (i.e. Cruise, Nominal, Takeoff). The red markers are affected by outside air temperature and outside air pressure. The red marker doesn't correlate to the number scale on the gauge in any direct way.

 

So on hot, high altitude days, the red markers will be in a different position compared to operation on a cool, sea level day. Also, the red marker will move as you fly through changing atmospheric conditions.

[AlphaOneSix]

The Russian flight manual states it in better detail that the gauge is in fact T3 = gas temperature before turbine.

 

Indeed! I just happen to have a picture...

[Griffin]

Thanks for the quick answer! FlankerOne did the test at standard atmospheric conditions at sea level so that shouldn't affect it really. I assume he was flying forward though and the table assumes "H=0, V=0" which is altitide and speed zero? Would that affect the readings so much? If it does, we would need to strap the helicopter down somehow to test it because by the time you stabilize the EGT at a certain reading you would be quite high already.

 

What do you think? By the way, is the engine cutout picture your own or can we find it online? Can't check Google yet.

[AlphaOneSix]

we would need to strap the helicopter down somehow to test it because by the time you stabilize the EGT at a certain reading you would be quite high already.

 

What do you think? By the way, is the engine cutout picture your own or can we find it online? Can't check Google yet.

 

One way to test engines under load without leaving the ground is to put full fuel, plus 4 full ferry tanks. That will give you the heaviest configuration. Then either run one engine at a time or use the individual throttles to keep one in IDLE with the other at AUTO.

 

As far as the cutaway pics go, I can't remember where I saw them online, but I had to email the guy directly for the hi-res copies. I can probably host them myself shortly, he didn't seem to mind.

[Griffin]

Good idea! Didn't think of that. The earliest I can test is weekend because I'll reinstall the whole system onto an SSD.

 

I would appreciate if you host them but it's no big deal of it's trouble. I'm studying jet engines at home so I'm finding this thread and further information very interesting.

[flanker0ne]

OK but operatively, if it is normal to have such a difference between the values ​​of EPR and temperature, which value should I follow for:

Do not damage the engine, even slightly like flying at Max Cont over 60 min.

Getting a fuel consumption of reference.

Edited February 27, 2013 by flanker0ne

[Griffin]

flankerOne; could you test the engines the way A16 described? I doubt it will make any difference but at least it would be verified. I can test it on weekend the earliest.

[AlphaOneSix]

In my world, whether it is correct or not, we basically ignore the EPR gauge and use N1 and EGT for determining power conditions. This means that I have very little real world experience with EPR readings and why they might be incorrect. As soon as I get settled somewhere I'll take a crack at it in-game, unless someone beats me to it.

[flanker0ne]

flankerOne; could you test the engines the way A16 described? I doubt it will make any difference but at least it would be verified. I can test it on weekend the earliest.

 

ONLY ONE ENGINE RUNNING TEST

 

1 st Cruise: EGT 815°C correspond to N_gg 93,9 +- 0,5 %.

Ok but the EPR index should be at K

 

Max Continous: EGT 845°C correspond to N_gg 95,0 +- 0,5 %.

Ok but the EPR index should be at H

 

Take Off: EGT 920°C correspond to N_gg 97,7 +- 0,5 %.

Ok but the EPR index should be at B, almost

 

As you can see the results are the same as the previous test.

 

If I remember right AlphaOneSix already answered at my question about engine.

What I realized is that the engine management is a little bit more complicated than mach some index with other, and EPR gauge is useful for transition situation where the pilot need a quick reference for setting power, relegating EGT for long term situation as long Climb or Cruise.

I'm right? More or less?

Edited February 27, 2013 by flanker0ne

[AlphaOneSix]

Well, you don't have to be perfectly even with the top of the K to be at the limit of cruise. Remember that by the manual, You reach the top end of Cruise 1 when your EGT reaches a certain temp, or your N1 reaches a certain RPM, whichever occurs first, it never mentions the EPR gauge. Same goes for the other condition indications.

 

Also, I think the EPR gauge is a bit of a "perfect world" gauge (just my opinion). That is to say, if your engine was in perfect running order, it would match the lines. As an example, using your first image in Cruise power... The red marker indicates that your engines may put out up to roughly 7.7 kf/cm2, but in fact your engine in the example is only putting out roughly 6.9 kg/cm2. Maybe it needs an engine cleaning, maybe it's a bit old and the compressor is getting a bit of wear and can't put out as much pressure for a given RPM...etc. ED had a lot of real world data to build a realistic representation of the engines, but the odds of the real world data being perfect (i.e. the chances of them actually seeing how a "perfect" engine performs) is very slim indeed. Besides, I don't think such a "perfect" engine exists except on paper or in theory, but the EPR gauge has to use something as a baseline...best to use a "perfect" case or else it may indicate a power condition of Nominal even if EGT and N1 say you're still in Cruise 1, for example.

 

Sorry for rambling, hope something I said makes sense. If it helps, I have never seen the lines match up in any of the Mi-17s that I fly on, either...they are always well below, even lower than these in-game examples. Maybe we just have crappy engines.

[flanker0ne]

Looking at the chart taken from the manual BS2, are given five characteristic points.

Instead if we look at the table of the TV3-117VMA engine, ignoring the point of idle, are four characteristic points.

The point in excess reported by ED corresponds to the combination [1473kW / 0.32 SFC / 893°C / 96,6%] and I do not understand where this point comes from.

It would seem an auxiliary point to break the graph bringing it closer to reality or to the model used to reproduce the curve of the engine.

But if we translate all the characteristic points of one position to the right, I mean by deleting the point Cruise1 and making the Max Cont the new point of Cruise and the "Unknow Auxiliary Point " the new point of Max Cont, then the EPR returns to express a behavior adherent to its function.

 

I try to suggest that this shift towards higher values the cause of the idle speed too high to be able to carry simulated autorotations, forcing us to shut down both engines?

Edited March 1, 2013 by flanker0ne

[Griffin]

Very interesting guys. Don't be afraid of rambling A16. You bring invaluable real life information which can calm our perfect engine model assumptions. :)

 

I don't know if I understood you correctly flankerOne and I don't know if some devs have checked the values already. The idle power and autorotation has been in discussion in the past. Maybe some dev checked it already or not?

 

If someone of the developers could quickly tell us if it's all correct after past checks, we could stop beating the dead horse? If you could give us a quick info, we could spread the word in the future if the question arises again.

[flanker0ne]

I will never stop thanking A16 for its timely and continuous support always full of information from the real world.

 

Very interesting guys. Don't be afraid of rambling A16. You bring invaluable real life information which can calm our perfect engine model assumptions. :)

 

I don't know if I understood you correctly flankerOne and I don't know if some devs have checked the values already. The idle power and autorotation has been in discussion in the past. Maybe some dev checked it already or not?

 

The problem of idle too high is still present and manifests itself in two ways (at least for me :chair:):

1. In simulated autorotations but it is a "Problem No-Problem".
   I mean, why make a simulated autorotation (as a percentage closer to real Emergency) when I can always recreate the situation of real emergency switching off both engines?
    
   
2. In the test of EEG the helicopter almost takes off , if not deliberately weighed more than 11000kg or tested with one engine running at time.

 

In addition i found in the .lua Jungla these usefull data:

power_take_off	=	1618,
power_max	=	1618,
power_WEP	=	1618,
power_TH_k = 
[1] = {0,-230.8,2245.6},
[2] = {0,-230.8,2245.6},
[3] ={0,-325.4,2628.9},
[4] ={0,-235.6,1931.9},
SFC_k = 	{2.045e-007,	-0.0006328,	0.803},
	power_RPM_k = 	{-0.08639,	0.24277,	0.84175},
	power_RPM_min	=	9.1384,

 

From the SFC_k I have extrapolated the Law/Curve for the SFC.

Edited March 1, 2013 by flanker0ne

[AlphaOneSix]

I've uploaded the TV3-117 cutaway photos:

 

http://wish.halo5.net/~darrell/tv3-117/

[Griffin]

Excellent pictures, thank you! What is that flexible shaft from the power turbine to the AGB?

Edited March 2, 2013 by Griffin

[AlphaOneSix]

N2 flex shaft. It is how the fuel control on the engine knows the N2 RPM (and thereby rotor RPM).

[flanker0ne]

Thank you for the invaluable information that you get us

[DieHard]

Find some very useful information to share with you, hardcore helicopter pilot simmer as I am.

 

 

The graphic on the Black Shark 2 manual is not very readable so is not helpful enough to become a flight tool.

But the data reported on it are accurate, as the original russian TB3-117VMA document show.

 

I usually just take a set of Vikhrs and one pair fuel tanks. Before I add the fuel tanks I fill my main tanks 3/4 full. This gives me lots of time on station for search and destroy. But in hot weather, my hover climb rate really stinks even with the Altitude Hold button not on.

 

I fly by feel. I have CH Products controllers and though they are not Force-Feedback, I swear I still can feel the heaviness, etc., especially at high speed runs at around 300 km/h when doing turns, with my eyes and brain. I can actually feel the approaching limit of---oops! I now slow down to 250 km/h turning unless I have to be evasive.

 

So far, flying Shark a year, my best outing to date is 4 sorties out and back with the same helicopter in World on the 104th's server. I am slowly getting better.

[DieHard]

I've uploaded the TV3-117 cutaway photos:

 

http://wish.halo5.net/~darrell/tv3-117/

 

Nice!

 

I once worked at Chromalloy in Orangeburg, NY making parts for commercial and some military jets and overhaul/rebuilding of compressor fans. The coatings they apply to those blade inserts is dangerous stuff to work with having to deal with the harsh environment the jet engines operate in.

 

You appear to be a military copter aviator.

 

Do you guys do scheduled maintenance and R&R on in-service aircraft before stuff wears out or breaks? I mean, replace with new parts or rebuilt parts on a schedule whether in fact it really needs to be replaced, yet. The better industrial, non-military, production lines operate this way to lessen down time.

[AlphaOneSix]

You appear to be a military copter aviator.

 

Do you guys do scheduled maintenance and R&R on in-service aircraft before stuff wears out or breaks? I mean, replace with new parts or rebuilt parts on a schedule whether in fact it really needs to be replaced, yet. The better industrial, non-military, production lines operate this way to lessen down time.

 

I'm not military anymore. My employer contracts out to the U.S. State Department, so we do government work, but my company is strictly civilian.

 

Assuming you're familiar with FAA regulations, we are a part 91 operator.

 

We perform inspections and replace parts on an overhaul schedule as recommended by the manufacturer. If a part is working perfectly fine, but the book says replace it at X hours for overhaul, we replace it at X hours.

[DieHard]

Yes, that is smart.

 

From a metallurgical point of view, internal stresses could be there before they fail.

 

Thanks for the reply.