[WIP]Engine model discrepancies

RPM and FTIT discrepancies

enigne limitations for the GE-129 are:

[TABLE]Max RPM at MIL/AB = 108%

Max FTIT at MIL/AB = 980 [/TABLE]

In DCS, [Please note of possible bug: there is a difference between MIL (throttle against detent gate) and AB (throttle past the detent)].

[TABLE]MAX RPM at MIL = 100%

MAX FTIT at MIL = 880

MAX RPM at AB = 101%

MAX FTIT at AB = 901 (at mach 2.0, I reach 940)

[/TABLE]

Nozzle position discrepancies:

Furthermore, at FULL AB the noz position should be between 40% and 70%, in DCS it sits at maximum ~38% in FULL AB at sea level, except at mach 2.0, which is at about 50% open.

DEC discrepancies:

According to the same document, the engine increases IDLE rpm at high altitute in order to maintain ECS bleed air and avoid engine instability. This results in a higher IDLE and consequently, fatser throttle response.

Not only that, but above Mach 1.4, the engine IDLE is near MIL power, meaning that moving the throttle to IDLE above mach 1.4 will result in ~ 100% RPM.

For both instances above, the DCS model doesn't behave correctly, with the engine reaching an idel of ~70% regardless of altitude and mach number.

All of the above tested on a standard temperature and pressure day.

EDIT: track attached.

RPM and FTIT discrepancies

enigne limitations for the GE-129 are:

 

 

[TABLE]Max RPM at MIL/AB = 108%

 

Max FTIT at MIL/AB = 980 [/TABLE]

 

In DCS, [Please note of possible bug: there is a difference between MIL (throttle against detent gate) and AB (throttle past the detent)].

 

[TABLE]MAX RPM at MIL = 100%

 

MAX FTIT at MIL = 880

 

 

MAX RPM at AB = 101%

 

MAX FTIT at AB = 901 (at mach 2.0, I reach 940)

[/TABLE]

 

Nozzle position discrepancies:

Furthermore, at FULL AB the noz position should be between 40% and 70%, in DCS it sits at maximum ~38% in FULL AB at sea level, except at mach 2.0, which is at about 50% open.

DEC discrepancies:

According to the same document, the engine increases IDLE rpm at high altitute in order to maintain ECS bleed air and avoid engine instability. This results in a higher IDLE and consequently, fatser throttle response.

 

Not only that, but above Mach 1.4, the engine IDLE is near MIL power, meaning that moving the throttle to IDLE above mach 1.4 will result in ~ 100% RPM.

 

For both instances above, the DCS model doesn't behave correctly, with the engine reaching an idel of ~70% regardless of altitude and mach number.

 

 

All of the above tested on a standard temperature and pressure day.

Sent from my Xiaomi MI8

RPM and FTIT discrepancies

enigne limitations for the GE-129 are:

 

 

[TABLE]Max RPM at MIL/AB = 108%

 

Max FTIT at MIL/AB = 980 [/TABLE]

 

In DCS, [Please note of possible bug: there is a difference between MIL (throttle against detent gate) and AB (throttle past the detent)].

 

[TABLE]MAX RPM at MIL = 100%

 

MAX FTIT at MIL = 880

 

 

MAX RPM at AB = 101%

 

MAX FTIT at AB = 901 (at mach 2.0, I reach 940)

[/TABLE]

 

Nozzle position discrepancies:

Furthermore, at FULL AB the noz position should be between 40% and 70%, in DCS it sits at maximum ~38% in FULL AB at sea level, except at mach 2.0, which is at about 50% open.

DEC discrepancies:

According to the same document, the engine increases IDLE rpm at high altitute in order to maintain ECS bleed air and avoid engine instability. This results in a higher IDLE and consequently, fatser throttle response.

 

Not only that, but above Mach 1.4, the engine IDLE is near MIL power, meaning that moving the throttle to IDLE above mach 1.4 will result in ~ 100% RPM.

 

For both instances above, the DCS model doesn't behave correctly, with the engine reaching an idel of ~70% regardless of altitude and mach number.

 

 

All of the above tested on a standard temperature and pressure day.

 

EDIT: track attached.

I just wanna clarify that the Engine limits are hard limits: So the stated 108% (+/- 1%) and 980 degrees (+/-10 degrees) are realtime limits. When a pilot is in AB or full military power he expects the engine to meet those limits. If the engine does not the pilot will go home and the engine is written up.

The engine is still being tuned, known issues with AB and fuel consumption as well.

Question NineLine, and feel free to say you can't discuss it..

Is it simply a data error in that the engine is producing the appropriate thrust but it's not being displayed correctly on the gauges and readouts...or is the engine actually both underperforming and thus showing a displayed limit that is lower?

As I understand it, where the AB kicks in and how it acts is not 100% correct, as far as the guages I am sorry, not 100% sure if the guages are reading correctly or not. I don't have a ton of details other than things are still being tuned.

fair enough!

If it is okay, I would like to add to this as it may be related? but I was fully loaded, with 2 tanks, 2 gbu-12's and 2 mk-82's and a120's, aim-9x's. The jet seemed VERY sluggish, and my max rpm was around 89 % even in afterburner. I reloaded the mission and the same thing occured, even with an empty jet. Not sure if I am missing something during startup, or what, but it doesn't seem quite right lol. I also confirmed that my throttle maxes out in the axis control settings, and in the pit I can see the throttle moving all the way to the end of it's rotation. Sorry if I should have started a new thread on this..

If it is okay, I would like to add to this as it may be related? but I was fully loaded, with 2 tanks, 2 gbu-12's and 2 mk-82's and a120's, aim-9x's. The jet seemed VERY sluggish, and my max rpm was around 89 % even in afterburner. I reloaded the mission and the same thing occured, even with an empty jet. Not sure if I am missing something during startup, or what, but it doesn't seem quite right lol. I also confirmed that my throttle maxes out in the axis control settings, and in the pit I can see the throttle moving all the way to the end of it's rotation. Sorry if I should have started a new thread on this..

This is what stuck out to me. Granted, yes.... it's a light jet, and is much more influenced by stores, tanks, and extra weight so it's definitely going to be slower.

However... the engine rpm isnt crossing 90% for.me either fully loaded.

Bignewy and nineline have acknowledged engine, fuel, AB and others are heavily WIP and will be worked on.

Its early, it will be worked out.

This is what stuck out to me. Granted, yes.... it's a light jet, and is much more influenced by stores, tanks, and extra weight so it's definitely going to be slower.

However... the engine rpm isnt crossing 90% for.me either fully loaded.

Bignewy and nineline have acknowledged engine, fuel, AB and others are heavily WIP and will be worked on.

Its early, it will be worked out.

Loadout would have nothing to do with engine RPM. Again the RPM should be 108% regardless of anything else.

The GE engine is just like the Pratt an twin spool engine. The core engines RPM is shown in cockpit (N2) the Fan RPM however is not shown but is limited by the DEC.

That's why I posted. It seems that the engine rpm just isn't getting up to where it should be. And I know it's WIP. And am totally okay with that, just wanted to make sure and get the team aware :) Loving the flight model for the most part, and Can't wait for the first update!! :D

I just wanna clarify that the Engine limits are hard limits: So the stated 108% (+/- 1%) and 980 degrees (+/-10 degrees) are realtime limits. When a pilot is in AB or full military power he expects the engine to meet those limits. If the engine does not the pilot will go home and the engine is written up.

Loadout would have nothing to do with engine RPM. Again the RPM should be 108% regardless of anything else.

The GE engine is just like the Pratt an twin spool engine. The core engines RPM is shown in cockpit (N2) the Fan RPM however is not shown but is limited by the DEC.

Bouli306,

Trying to understand what your saying. In you experience, running the engine at max AB always get 108% RPM at FTIT 980°C? All the engine run I have done I looked obvious that those parameter where not exceeded, but I never got close. FTIT gets close on a pickle engine run (that first pickle Run does make you "pucker" a bit when you see how fast that FTIT rises) and you might have to motor once or twice, but never sen RPM reach close to the limit, unless you conciser 100% close. To me it would be 106% before I call it close.

any news about this in the last update?