Supersonic Acceleration

Greetings,

First of all, I think RAZBAM has done a great job on the M2K thus far and I have great respect for them as a developer. I do understand the FM is still a WIP. I decided to share this data only to raise visibility on what, IMO, seems to be unrealistic performance. I also love the validation process. I would like to provide more V&V data using proper techniques but my current method is very time consuming (replay/tacview/export .csv/plot .xls) and my knowledge of export lua scripting is somewhat limited. If someone could provide help in that area it would be much appreciated.

After some virtual stick time in the Mirage I was very surprised by its supersonic acceleration at high altitude. The F-15C was chosen as a baseline as its level flight acceleration & climb performance correlates very closely with that documented in the -220 appendix B.

The flight profile was performed at max AB for both aircraft and a constant mach (0.95) climb schedule followed by transition to level flight.

Now on to the results. First, clean configuration performance both aircraft ~50% internal fuel. (Note mach is displayed on the secondary axis)

The F-15C achieves a higher rate of climb, reaching ~40,000 ft. approximately 10 seconds before the mirage. (Purely a SWAG on my part but seems reasonable)

What is remarkable is the M2K's level flight acceleration. Setting t=0 at the start of the level flight acceleration:

The M2K accelerates from Mach 1.0 to Mach 1.6 in 37 seconds. The F-15C reaches Mach 1.6 after ~77. In the above test, the M2K reaches M1.6 40 seconds faster than the F-15C..

Considering the M2K internal fuel capacity makes for a very light jet, we performed the test again, this time with stores for both jets. (configuration details on chart). The same constant mach climb schedule however the target altitude for level acceleration was reduced to ~37,000 ft.

The Eagle reaches the target altitude approximately 12s before the mirage. But again, the level flight acceleration of the Mirage, despite carrying stores, far outpaces the F-15.

Setting T=0 again for acceleration:

In this test, the M2K accelerated from Mach 1.0 to Mach 1.6 in ~74 seconds. The F-15C reaches mach 1.6 after 141 seconds. Again, the M2K drastically outperforms the eagle, reaching M1.6 67 seconds earlier.

Cheers!

Greetings,

 

First of all, I think RAZBAM has done a great job on the M2K thus far and I have great respect for them as a developer. I do understand the FM is still a WIP. I decided to share this data only to raise visibility on what, IMO, seems to be unrealistic performance. I also love the validation process. I would like to provide more V&V data using proper techniques but my current method is very time consuming (replay/tacview/export .csv/plot .xls) and my knowledge of export lua scripting is somewhat limited. If someone could provide help in that area it would be much appreciated.

 

After some virtual stick time in the Mirage I was very surprised by its supersonic acceleration at high altitude. The F-15C was chosen as a baseline as its level flight acceleration & climb performance correlates very closely with that documented in the -220 appendix B.

 

 

[...]

 

 

Cheers!

IIRC Cptsmiley is already working on acceleration performances for the upcoming FM patch.

Here : https://forums.eagle.ru/showpost.php?p=3249922&postcount=104

But it's a nice bug report even if I have little clue if the F-15 should accelerate faster than the 2000 :D.

Have a rep for your time :thumbup:.

Hi SinusoidDelta, this is a factor we have specifically worked and improved upon with the FM updates that are in work. I greatly appreciate your detailed and quantitative analysis!

 

We've gotten some real life data climb performance data points that we have worked with in multiple configurations and have improved the FM greatly from what it looks like currently in the released version. If we can I will try to publish those numbers, worst case I'll publish what the numbers were before to what they are now.

 

Again, I enjoyed your thought out and detailed analysis of this issue and for the most part you are spot on and you are in fact correct that the current state of climb performance you are seeing is not accurate. I would enjoy seeing your perform this analysis once I can get these FM updates out to you guys.

Thanks for such a quick response! I'm glad to hear you're already working on the climb data. Maybe it's just a mix up in wording but my concern lies with the rate of acceleration in level flight at high altitudes. Is this also a known issue?

Yes, apologies meant to include that as well. In the version you are flying, supersonic acceleration ESPECIALLY at high altitude is way too fast from the data we have. It has been corrected in the developmental build so hope to have that to you soon.

Wonderful! Thanks again for such quick responses :thumbup: I’ll look forward to making new plots once the updated FM is available :joystick: