Has supersonic performance been adjusted?

[Bremspropeller]

The F1 used to accelerate like a hot knife through butter in the supersonic region - with a bit of a struggle through the transonic region - but since 2.8 it seems like achieving max Mach is taking a good deal longer. Anybody else have the same impression?

Is this behaviour intended? The changelog only reads "reduced induced drag near transonic speeds".

[bones1014]

that sounds like it would be better performance

[sasquatch98]

17 hours ago, Bremspropeller said:

The F1 used to accelerate like a hot knife through butter in the supersonic region - with a bit of a struggle through the transonic region - but since 2.8 it seems like achieving max Mach is taking a good deal longer. Anybody else have the same impression?

Is this behaviour intended? The changelog only reads "reduced induced drag near transonic speeds".

I’ve noticed they exact same behavior but didn’t notice anything about it in the patch notes.

[Shmal]

Yes we also noticed that!

[Bremspropeller]

@Flappie do you possibly know anything about any tweaks?

I'd say it's okay under ISA conditions up to about M1.45, when it kind of runs into a brick wall. I've tried several profiles to minimize time spent in the transonic region, but at the end of the day, you'll always kind of hang yourself up around 1.5 to 1.6, where it seems to enter a region of quicksand. It used to blow through this region rather well before 2.8, with a pretty constant acceleration right up to the LIM light. Now you get a slight leap at M1.35 to M1.4 (when survitesse comes on) but that slows down again around 1.45. Getting from 1.4 to 1.6 almost takes as long as getting from 0.9 to 1.2.

There might be some additional testing to be done, but I'll call it a night for now.

 

F1-Mach_test1.trkF1-Mach_test2.trkF1-Mach_test3.trkF1-Mach_test4.trk

Fun fact, I also did a test climbing to 40000ft and the accelerationg in level flight just to see where it would take me. Not a good idea - you'll just bimble around in the transonic region with too much AoA to push past M 1.1 before the alternator-light comes on. It's interesting to see the shock travel around slowly on the pitot and play games with the altimeter and Autopilot, though. Both altimeters read an altitude difference of around 1500ft at one point.

Edited November 2, 2022 by Bremspropeller

[dolfo]

Try this and see how it goes:

Clean aircraft, full fuel. Climb to 36000ft. I used M0.94 for the climb. Accelerate to M1.35-1.4 (your perceived speed jump window) at 36000ft.  Pitch up to hold that Mach and climb to 44000-45000. Then shallow dive back to 36000. I used a pitch of -5° I think. Should get you down to 36000-35000 at M1.6+. Level accel to M2.0, climb at M2.0 to desired altitude. Seems credible enough to me.

[Bremspropeller]

Dolfo, thanks for the suggestion - I'll give it a try tonight!

The reason why I opened this thread is to ask whether this is intentional, or if it's just a byproduct of some other change in DCS that has slipped through. So my point is not necessarily looking for the most efficient profile (which would be nice to know anyway, though), but to figure out what's going on in the first place.

"Back in the old days" (before 2.8), there really was no need to optimise for Ps - the aircraft would be accelerating well enough to not seek out more performance by climbing and bunting over. You'd just accelerate and at M 1.8 (if you wanted or needed to), start a climb to the desired altitutude.

I'll test your suggested profile and report back.

[Bananabrai]

43 minutes ago, Bremspropeller said:

Dolfo, thanks for the suggestion - I'll give it a try tonight!

Excuse me Maverick, you meant "we" give it a try.

 

[Bremspropeller]

11 hours ago, dolfo said:

Try this and see how it goes:

Clean aircraft, full fuel. Climb to 36000ft. I used M0.94 for the climb. Accelerate to M1.35-1.4 (your perceived speed jump window) at 36000ft.  Pitch up to hold that Mach and climb to 44000-45000. Then shallow dive back to 36000. I used a pitch of -5° I think. Should get you down to 36000-35000 at M1.6+. Level accel to M2.0, climb at M2.0 to desired altitude. Seems credible enough to me.

I just tried it out - I didn't perfectly follow your profile (bunted over at 430 or 440) - it doesn't yield greater performance. You'll cover more ground and use about as much fuel to Mach (give or take 100-200l maybe) as with the other methods. She's sticky at around 1.2, 1.5 and 1.9, where acceleration slows down.

Note I fell out of survitesse twice during the climb from 360 to the mid 40s for a couple of seconds each, because I wasn't maintaining Mach perfectly. That doesn't change much about the result, though.

F1-Mach_test6.trk

[Bremspropeller]

Here are my results from the tests above - all tests are starting at M0.85 at FL250 with two Magics. Caucasus map, zero wind and 15°C.

1) climb to 350 @ M0.9 => push over at -10° down to 285 @ M1.2 => climb back to 305 @ M1.2 => level acceleration to LIM @ M1.98

Fuel remaining ~2620l after 6:33min (I substracted 20s of "idle time" in the track)

2) climb to 400 @ M0.9 => push over -15° down to 305 @M1.25 => level acceleration to LIM @ M2.0

Fuel remaining ~2750l after 6:17min ==> quickest profile tested

3) climb to 405 @M0.9 => push over -10° to 315 @M1.25 => level accel to M1.4 and climb to 360 @M1.45 => level acceleration to LIM at M2.1

Fuel remaining ~2680l after 7:22min

4) climb to 400 @ M0.9 => push over -10° to 320 @M1.25 => level accel to M1.4 and climb to 400 @M1.45 => push over -2.5° to 350 => level accel to LIM @ M2.1

Fuel remaining ~2630l after 7:47min

5) climb to 300 at M1.05 => A/P misuse clusterduck with shallow climbs and descents => level accel at 300 to LIM @ M1.98

Fuel remaining ~2580l after 6:29min

6) climb to 360 @M0.94 => level accel to M1.4 and climb to 440 @ M1.4 => push over -3.0° down to 355 @ M1.6 => level accel to LIM @ M2.1

Fuel remaining ~2300l after 10:54min

 

After reviewing all tracks, it's evident that there's somewhat of a struggle in the M1.45 to M1.55 region. Flying dolfo's suggested profile makes you sped a lot of time not accelerationg (in a climb at high'ish AoA) or stagnating in the M1.5 region through the descent. Maybe lowering the nose a couple of degrees more would have yielded a quicker punch through that region but still it would have taken longer, covered more ground and used up more fuel.

Note that reaching LIM higher yields a higher final Mach, which takes additional time to reach. Quickest to M2.1 is probably just short of 7mins from the starting point.

 

 

 

[IvanK]

Supersonic climb I disagree with constant Mach climbs. The so called "Rutowski" profile is the optimum way to get to any High energy state and best times to it and requires constant IAS increasing Mach climb in the supersonic schedule.

The Profile in the F1 KED Pocket checklist is:

Climb to 30,000' via the Sub sonic Climb schedule 500kts into 0.92M

Accelerate at 30,000' to 650Kias then climb at 650Kias (Increasing Mach) to Mach 1.8 then climb at Mach 1.8

Based on a Mirage III  method I think you can do better and get closer to a genuine Rutowski profile. You don't want to be going through the transonic region in level flight !

Subsonic 500/0.92M climb to 35000'

Push over (0.5G) to achieve min time through the transonic region to max 10 deg nose down not below 30,000' accelerate to 650Kias

At 650Kias Climb 650Kias to M1.8

At M1.8 0.5G push over to achieve M2.0/VNE

If we had access to the relevant Mirage F1 Ps info this could be optimized even further.

Edited November 3, 2022 by IvanK

[Bremspropeller]

I'll give it a try, thanks Ivan.

[Bremspropeller]

Okay, so I did two tests that were reproducing Ivan's suggestions. Safe for the 650KIAS to M1.8 part, which wasn't available due to 1.8 being below 650KIAS at both altitudes I tried.

1) climb to 360 @M0.92 => push over 0g* to -10° down to 300 and level accel to LIM at M1.98

Fuel remaining 2640L after 6:12min

2) climb to 350 @M0.94=> push over 0g to -10° down to 320 and level accel to LIM at M2.05

Fuel remaining 2620L after 6:50min

 

F1-Mach_test7.trk

F1-Mach_test8.trk

 

Seems like the profile "2" from the prior test-run with a higher initial climb and a more aggressive, steeper dive to M1.2+ is the better way, preserving 100l of fuel.

*0.5g pushover was too timid and had me bust the pushover altitude

[IvanK]

I can go 0.95 to M2.0 in 3:28 for 990 litres burnt Clean aeroplane

Profile: 0.95/F350 Start the clock , 0.5G pushover to 10deg nose down, level at F300 accel to 650Kias , climb at constant 650Kias (Increasing Mach) till achieving M2.0.

Tried the same using Mir III profile climbing at 580Kias took 10 seconds longer.

 

Machrun.zip

Edited November 5, 2022 by IvanK

[Bremspropeller]

I can just about match that. My airplane is a tiny bit heavier and my flying is a bit sloppier than yours

F1-Mach_test10.trk

 

The question that remains is whether the last patch did anything to the performance. All those people I've been flying with do feel that the aircraft has lost some performance and it's evident in the Mach-run, which used to be quicker. Note that leaving 25% of fuel at home (75% instead of 100%) cut almost 20s off the time to reach M2.0 in this profile.

What do you think about the M1.5 speed-bump? It almost seems like the intakes need a bit of time to adjust and once they're in the correct position, the aircraft picks up it's acceleration again. It's more evident when the aircraft is heavier.

[Iron Sights]

Is the rpm level climbing after 1.4? I haven’t tried it lately, but the engine would go to higher rpm’s before and then that would take you to higher speeds. Then you would need to air brake or maneuver to slow down. I’ll have to check it out since the patch.

[CrazyGman]

I find the subsonic acceleration has also taken a major hit. also it's turn rate used to be that you could be at 410knts and maintain that at 15 AoA, now trying to do the same thing you can only maintain it at 12 AoA, and also trying to get the speed up from 300 to 400 is now much more of a chore. Could be though that that is just how it's supposed to be.

[Bremspropeller]

8 hours ago, Iron Sights said:

Is the rpm level climbing after 1.4? I haven’t tried it lately, but the engine would go to higher rpm’s before and then that would take you to higher speeds. Then you would need to air brake or maneuver to slow down. I’ll have to check it out since the patch.

Yes, survitesse was working normally. My impression was, that the intakes might (might!) have a play here as you'll se a corellation between intake-position/ Mach and the acceleration-rate picking up again. My impression has the intake-position slightly ahead of the indicated Mach (comparing gauge vs gauge). But that could be normal and intended.

To slow down, you can always just come out of burner into max dry and stay at that RPM - just don't pull back the throttle and decrease RPM.

4 hours ago, CrazyGman said:

I find the subsonic acceleration has also taken a major hit. also it's turn rate used to be that you could be at 410knts and maintain that at 15 AoA, now trying to do the same thing you can only maintain it at 12 AoA, and also trying to get the speed up from 300 to 400 is now much more of a chore. Could be though that that is just how it's supposed to be.

Same here. You're now dead meat against a MiG-21 with a competent pilot, unless you manage to get into a scissors, where the F1 has superior controllability and about equal performance. The 21 will out-rate you and will turn inside you one-circle, where it can rely on the engine to power out of any lost energy.

The F1 will outpace the 21 quite well in max dry, which mirrors it's higher military thrust rating. In a side-by-side Mach run, the 21 will walk away from the F1. We didn't do any fancy profiles, just bunt over to get through to 1.2 and then level acceleration. Well, I did, the 21 started a shallow climb and walked away at a steady pace - he was about 0.2 faster than me at any given time beyond me getting through 1.2.

I didn't put this into the bug section, because I don't have 'facts over feels' either, so it can be handelled more as a discussion than a "teh plane iz br0ken" complaint. I was just really surprised to see a significant performance-drop without any indication of any linked factors in the change log.

Edited November 6, 2022 by Bremspropeller

[Bremspropeller]

Stagnated at 1.15 after performing a -12° dive from 420 in full stereo.

Two JULIs, one 530EM and two empty inboard wing-pylons.

WX was on the warm side.

On the bright side, she maintained 1.15 through the mil-power dive down to about 11k.

[Bremspropeller]

Okay, so in the quest for making sense of it all, I decided to "manual up" and got a hand on some handbooks.

I've seen there's a time-to-climb reference in the F1ED's kneecard which I tried to follow.

The figures are pretty close for a time-to-climb from a standstill to FL300 (time within a couple of seconds and fuel consumption within maybe 50l or so).

It all breaks down above FL300 where the aircraft in DCS overperforms significantly. It's reaching FL500 about 40s* sooner than according to schedule and uses up roughly 400l more gas. That adds up to DCS having a somewhat lacking rendition (non-existant?) of a tropopause with denser air and hence better performance at the cost of higher fuel consumption.

F1_0to500.trk

The FL300toM2.1 test has the aircraft almost two minutes ahead of schedule and using about 500l too little fuel (because it reaches Mach 2.1 so quickly). But that is most probably also down to a non-existant TROP.

F1_300toM21.trk

 

___

*it's actually more than 3 minutes sooner - I looked up the wrong number

 

 

Edited November 8, 2022 by Bremspropeller

[cmbaviator]

Why is at 8000-10 000ft around M1.2, the engine is coughing and aircraft is shaking ? Max IAS reached ?

[IvanK]

On 11/9/2022 at 4:52 AM, Bremspropeller said:

That adds up to DCS having a somewhat lacking rendition (non-existant?) of a tropopause with denser air and hence better performance at the cost of higher fuel consumption.

Thats an interesting speculation. Does DCS actually have a tropopause ? is there any way in game we can determine it ... like temp v alt etc ?

[Bremspropeller]

14 hours ago, cmbaviator said:

Why is at 8000-10 000ft around M1.2, the engine is coughing and aircraft is shaking ? Max IAS reached ?

Yes, the limit is 700KIAS up to 20,000ft and 750KIS above that.

3 hours ago, IvanK said:

is there any way in game we can determine it ... like temp v alt etc ?

We'd have to see if any airplane has a TAT or SAT gauge and do some upper atmosphere soundings, I guess.

[IvanK]

2 hours ago, Bremspropeller said:

We'd have to see if any airplane has a TAT or SAT gauge and do some upper atmosphere soundings, I guess.

Going to ask the devs directly

[Dirty Rotten Flieger]

I just flew the F1 after months away.  I was flying super sonic about 30 000 ft and descended with out backing off the throttle. When I went below 10 000 ft and over sped doing about 1.5 M. The controls locked up, the nose wondered and tucked. It felt like I was lucky to regain control.  

If this is realistic then great.  It makes me wonder why this doesn't happen to more planes in DCS?  Or what are the specifics of what is happening. I have read that high speed, low altitude flight is limited by the melting temp of aluminium. I knew about the sped limits but I was expecting the engine to just flame out. Not the controls to lock up. 

  PS

I just tested it again at high speed low alt and didn't lock up or Mach tuck. So maybe it was battle damage earlier. 

Edited November 17, 2022 by Dirty Rotten Flieger