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Climbing performance much worse than it should be


Corrigan

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According to the AJ SFI, https://drive.google.com/file/d/0B8bCDRcq9BVeY0gycWRrMXVIdTA/view (p. 64), I should be able to get to 10 km with full military power on a clean A/C with full fuel -275 kg at ISA, and it should take about 12 mins.

 

Not only can I not keep the climbing speed of v_i = 676 km/h at even close to that altitude; I can't get to even 10 km on dry power, no matter what I do.

 

Currently I'm doing 480 km/h indicated at 7.8 km altitude, and slowing down, in level flight.

Win10 x64 | SSDs | i5 2500K @ 4.4 GHz | 16 GB RAM | GTX 970 | TM Warthog HOTAS | Saitek pedals | TIR5

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These issues seem related so I'll continue here. I flew this climb with manual fuel regulation in ~12 minutes. The top speed at 10km also matches the chart on page 78.

 

ISA 15C 1013mbar set in the editor. Zone 3 takeoff to ~600 indicated, climbing with MIL trying to maintain 675 on the gauge until M0.9 intercept while adjusting the throttle to stay below EPR 2.2.

ISA_10km_MIL_ManualEPR2_2.rar

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These issues seem related so I'll continue here. I flew this climb with manual fuel regulation in ~12 minutes. The top speed at 10km also matches the chart on page 78.

 

ISA 15C 1013mbar set in the editor. Zone 3 takeoff to ~600 indicated, climbing with MIL trying to maintain 675 on the gauge until M0.9 intercept while adjusting the throttle to stay below EPR 2.2.

 

Cool! Fuel flow seems like a suspect, then? I don't know what the fuel regulator manual setting does, will read the SFI.

 

EDIT: Okay, so the fuel regulator to MAN means that the calculator which is normally used to decide how much fuel the engine gets is completely bypassed, and the fed fuel is instead simply proportional to the throttle setting. This is SFI, Del 1, Flik 9, sida 6.


Edited by Corrigan

Win10 x64 | SSDs | i5 2500K @ 4.4 GHz | 16 GB RAM | GTX 970 | TM Warthog HOTAS | Saitek pedals | TIR5

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That's my guess, I used the charts in AJS37, Del 2 Kap IV Sida 6/8 to try and match normal values during the climb.

 

To add to that, what got me thinking to begin with was people reporting fluctuating RPM at ground idle.

The idle RPM in game seems to decrease when the outside temperature increases, quite the opposite of what this shows.

 

lntGDgq.png?1

 

-40C in game gives me an idle of ~67%, at +40C it's fluctuating between 45-46%


Edited by Vladinsky
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You guys are doing seriously awesome work here. I'm as impressed by that as by the fact that the simulation is so accurate and detailed down to these subsystems in the engine and fuel feed system that you can actually do these tests in a meaningful way. You know the simulation is good when the real flight manual works better as documentation for the game than the game's manual does.

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You guys are doing seriously awesome work here. I'm as impressed by that as by the fact that the simulation is so accurate and detailed down to these subsystems in the engine and fuel feed system that you can actually do these tests in a meaningful way. You know the simulation is good when the real flight manual works better as documentation for the game than the game's manual does.

+1

 

Ideally, devs shouldn't even have to write the manual, they should throw the real manual at as and say "This is how you fly the plane!" :D

It seems the Viggen is pretty close.

 

Sorry for off topic.

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Climbing performance much worse than it should be

 

 

The idle RPM in game seems to decrease when the outside temperature increases, quite the opposite of what this shows.

 

 

lntGDgq.png?1

 

 

-40C in game gives me an idle of ~67%, at +40C it's fluctuating between 45-46%

 

 

So the engine rpm in sim has a flipped performance chart sort of? But even then 67% seems a bit high for -40.


Edited by outbaxx
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You guys are doing seriously awesome work here. I'm as impressed by that as by the fact that the simulation is so accurate and detailed down to these subsystems in the engine and fuel feed system that you can actually do these tests in a meaningful way. You know the simulation is good when the real flight manual works better as documentation for the game than the game's manual does.

 

I'm incredibly impressed by LNS, they've vastly exceeded my expectations, and they were pretty high to begin with.

Never thought I'd see a swedish plane in DCS.

 

So the engine rpm in sim has a flipped performance chart sort of?

 

I'm really not sure what it could be, at ISA sea level everything seems to be as it should. When you change the temperature or fly at altitude things start to deviate from the expected.

 

There's also the possibility that I've completely misinterpreted the charts. Fairly certain I haven't though.

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In automatic mode the engine's max RPM decreases greatly at high altitude, leading to a large loss of thrust. Bug is in the fuel control code.

Bug in the simulations fuel control code, or in the real planes aswell? Is it a thing to switch to manual in reality? (Or was it a thing )

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Bug in the simulations fuel control code, or in the real planes aswell? Is it a thing to switch to manual in reality? (Or was it a thing )

 

The climb performance matches reality pretty much perfectly when in manual mode. Manual mode is only used in emergencies in real life as far as I know.

DCS modules are built up to a spec, not down to a schedule.

 

In order to utilize a system to your advantage, you must know how it works.

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