High altitude performance

[lokodehortaleza]

Yesterday I was doing some zoom climbs, sightseeing in the new engine, and was astonished by the Mig-21Bis performance. I was able to get past 29 Km altitude, please see screenshots. What i did was, get to 15 Km, accelerate to Mach 2.0, pull the stick smoothly until 60 degrees climb, emergency AB on.

 

Should it be able to do that? I don't have any real world data on Mig-21Bis zoom climb performance, but this seems excessive to me, as i'm unable to match this performance with a clean, low fuel Su-27. I forgot to save a track, I'll do more tests and upload the track whenever possible.

[JorgeIII]

Yeah, test it yesterday and find the same. I loved the power but doesnt look too realistic.

Theres is a problem with power / drag over 10,000 meters. Drag seems OK, I would say an excess of power seems to be the cause.

 

Climbing to 10,000 m by the manual at about 900 km/h TAS is ok. You can initially mantain a 35 degree climb angle and slowly lower it to about 15 degrees to keep you TAS till 10,000.

 

You can accelerate to mach 2.0 at this altitute like before but when you pull back to continue climbing while maintaining your mach speed you can keep almost a 35 degree nose up attitude and climb like a rocket (over 100 m/s vertical speed), with no limit, until you engine shuts down at about 21,000 meters (scripted, lack of oxigen?). If you pull up less than 35 degrees, lets say 20 degrees, with the current flight model, the mig will overspeed while climbing.

 

The Mig should be at the edge of flight envelope at arround 17,000.

 

 

 

This post should be moved to Flights Dynamics in the Bugs reporting section.

Edited October 4, 2015 by JorgeIII

[lokodehortaleza]

Ok this is weird, did another test, same result, got to 29000 meters but didn't get my nose down and entered a nasty spin. Recovered in time, got the engine started, all nice and dandy. I recorded this with Shadowplay:

 

 

However when I replay the track (attached), I crash into a mountain just after restarting the engine. Looks like there are still some issues with track playback.

Mig-21Bis Zoom Climb and flat spin.trk

Edited October 4, 2015 by lokodehortaleza
Video Added

[SNAFU]

Can confirm similar experience playing in MP environment as host in full real settings.

 

Climbed with 2.2M up to 24km where my engine went dead and could repeat this two times out of 2.

 

Maybe ED some changes along the high alt performance in DCS World since F-15C and Su-27 also have much more power at high alt?

 

But generally a step back for LNS I guess. Don´t give up... :joystick:

[Big Nuts]

The English Electric Lightning got to 80'000 feet in an intercept.

 

 

 

 

Amazing drop in pressure/drag;

 

 

 

 

 

 

 

Are we sure it's a bug?

 

 

 

 

 

 

 

?

Edited October 8, 2015 by Big Nuts

[Golo]

And what did you actualy tested and why it should be bug?

 

Have you tested service ceiling, absolute ceiling, max mach number, or just plain and stupid rocket climb to death?

 

Well, from what has been shown if you get to 15km at 2M and point the nose to the stars it will climb as a rocket it is, even after engine stall because of its momentum and it will get to 29+km.

 

Why this should be bug exactly?

 

Actual aircraft performance in service ceiling and absolute ceilnig has nothing to do with what you shown here.

[SNAFU]

According to my information the MiG21MF had a static service ceiling of 17.300m and a dynamic max. ceiling of 23.000m.

 

The Bis was designed for better low altitude performance so I do not believe it could easily climb to 25km with full tank and weapons loadout.

 

On the 28.4. 1961 G. Mossolow reached 34.714m with the E-66A, but this unique MiG had a rocket booster.

 

As I understand the books and manuals, the MiG should just be able to hold 18km, maybe zoomcimb to 23km, but should not reach 29km.

[Golo]

Have you actualy tried to fly in those altitudes in sustained flight, not just zoom past them?

 

I just tested it and in behaves prety close to what manuals say.

What manual states (higher isnt shown) is for 15 000m at 2M at 3g max.

 

I made a climb and achived level flight at about 17 300m at 1.8-2M 5-6AOA and was able to make a tunrn at 2,2g max.

So its pretty much what I would expect given the higher altitude.

 

Even so I climbed to about 20 500m at 1.9-2M 10-13AOA no turning this time because I didnt realy feel like it, but it could centainly go higher. And I dont see why real MiG-21bis would not depending on the engine performance.

 

As for max Mach number, 2.05 isnt its maximum speed its just its maximum allowed speed, it can certainly go faster. And it did, there are sorries about 21s that went somewhat faster so that their paint got sort of brownish color to them when they exceded this limit.

So there is still a power reserve in that engine for sure.

 

Maybe the FM its not perfect but its pretty damn close.

[Cobra847]

The MiG-21 has been known to climb to above 22 000m in a normal climbing profile. It has also been known to suffer engine failure at 19 000m. Take that for what you will.

 

Noted and resolved.

[SNAFU]

That's what I wrote, a dynamic climb to 23km and a certified service ceiling of 18km as stated in the books.

 

Generally the high altitude performance of most DCS planes changed drastically in 1.5 in my subjective opinion and 29km is not 23km. But if no feedback is wanted, it`s ok, go ahead.

[Golo]

Why are you keep talking about 29km?

That is not altitude that can be sustained in level flight. It is just some crazy climb profile at M2 from 16 000m.

[JorgeIII]

Thanks Cobra for answering.

 

 

As it is right now the Mig will SUSTAIN a climb of at least constant 25-30 degrees from 10000m to 21000m, until engine shuts down. It will climb much faster and with a greater angle from 10k to 21k meters than from ground level to 10k m.

 

Zoom climb from manual: At mach 1.9 and from 15.5 km- 16.0 km altitute (service celing 17.500m for full AFT and two missiles) pull up (up to 2G force max) 10-15 degrees (from initial) and mantain untils IAS is lower than 530 km/h, stop AFT, nose down (0.3-0.4 G), recover.

 

Here I dont know the value for "initial" angle. It should be the steady, sustainble, climb angle, but is not specified, 35 degrres seems too high IMO.

 

A zoom climbing as specified in the manual is not even needed as you can do a sustained climb at a greater angle (35 degrees) and with a heavier loadout. The limit is not engine thrust at high altitut but the scripted engine failure.

If you follow real manual instructions for the zoom the mig will just overspeed instead of loosing speed.

Edited October 9, 2015 by JorgeIII

[SNAFU]

Why are you keep talking about 29km?

That is not altitude that can be sustained in level flight. It is just some crazy climb profile at M2 from 16 000m.

 

Why do I have to repeat myself? Just test yourself, we are not talking about static/sustained level flight, we talking about the dynamic/zoom height.

[Golo]

Thanks Cobra for answering.

 

 

As it is right now the Mig will SUSTAIN a climb of at least constant 25-30 degrees from 10000m to 21000m, until engine shuts down. It will climb much faster and with a greater angle from 10k to 21k meters than from ground level to 10k m.

 

That is simply not true at all. I can get fom the deck to 10 000m in les than 90s.

And climb from 10 000m to 20 000m can take ages. It is all about climb profiles.

 

A zoom climbing as specified in the manual is not even needed as you can do a sustained climb at a greater angle (35 degrees) and with a heavier loadout. The limit is not engine thrust at high altitut but the scripted engine failure.

If you follow real manual instructions for the zoom the mig will just overspeed instead of loosing speed.

 

Nowhere in manual it states that that climb profile is a maximum limit the MiG can do, it just states recomended procedure for reaching service ceiling and altitudes above it.

 

Why do I have to repeat myself? Just test yourself, we are not talking about static/sustained level flight, we talking about the dynamic/zoom height.

 

Tested climb at 2.1+M from 16 000m. Max altitude in screenshot.

Let me ask you again. So what ?

[lokodehortaleza]

Tested climb at 2.1+M from 16 000m. Max altitude in screenshot.

Let me ask you again. So what ?

 

What do you mean, so what? So this is a simulator, can the real aircraft do it? If it can't, then neither should we ingame. And by the way, i posted this question in the general Mig-21Bis forum, one of the mods chose to move it in here afterwards.

 

IMHO there are some issues with high altitude flight, not in the Mig, but in the game engine itself. Su-25s are flying nice and level above their service ceiling, and Su-27s are "stupid rocket climbing to death", as you put it, over 34 Kms high, while retaining some control authority and with the engines still running in full afterburner. If you think that's normal behavior you're entitled to your opinion, but i beg to disagree.

[Golo]

I dont see a reason why it shouldnt be able to do that.

If you going fast enough at given altitude and point the nose to the stars you will go to the stars.

Engine will stop working at about 22 000m and you will ride the rest of the way on momentum exchanging your stored kinetic energy for potential energy.

What is so hard to comprehend here?

 

Service ceiling is not maximum level flight altitude for an aircraft, and as I dont fly Su-25, Su-27 Im not comenting their performance.

[howie87]

Originally the DCS MiG was underpowered at altitude, probably due to issues with the atmospheric modelling in DCS (the A-10 has always underperformed in DCS and could never reach its service ceiling).

 

In an earlier update the MiG's performance was increased to better match real world values.

 

If the atmospheric model has been given an overhaul in 1.5 to boost high altitude performance for all aircraft, the MiG maybe a little overpowered now.

 

For comparison, on September 4, 1959 a modified Su-9 (designated T-431 by the bureau) piloted by Vladimir Sergeievitch Ilyushin set a new world record for absolute height, at 28,852 m (94,658 ft).

 

I imagine an unmodified MiG-21 would struggle to beat this.

Edited October 9, 2015 by howie87

[JorgeIII]

Golo: take it easy. I can't tell if you are just trolling or you can't read /understand previous posts nor the mig manual and just have a bad attitute. I will answer you only once.

 

Why are you keep talking about 29km?

That is not altitude that can be sustained in level flight. It is just some crazy climb profile at M2 from 16 000m.

 

Snafu clearly said he was talking about 23 km, not 29.

 

That is simply not true at all. I can get fom the deck to 10 000m in les than 90s.

And climb from 10 000m to 20 000m can take ages. It is all about climb profiles.

 

If you are able, try to climb DCS Mig-21bis by the real manual, check you time, angle and vertical speed from ground to 10km and from 10km to 21km. Then come back and tell me im lying.

 

 

Nowhere in manual it states that that climb profile is a maximum limit the MiG can do, it just states recomended procedure for reaching service ceiling and altitudes above it.

 

With current FM with excessive performance you just don't have to follow the manual procedure for reaching higher altitudes.

 

 

Tested climb at 2.1+M from 16 000m. Max altitude in screenshot.

Let me ask you again. So what ?

 

I dont see a reason why it shouldnt be able to do that.

If you going fast enough at given altitude and point the nose to the stars you will go to the stars.

...

 

We are talking about high altitude performance, about a FM ability no mantintain a 35 degrees nose up sustained climb from 10km to 21km. (sustained = not loosing speed if not clear enough, not zooming, there is not need to zoom right now).

 

The DCS mig can pass through its service ceiling (17.5km), with at least a 25 degree climb while still accelerating, it will reach 21 km while still accelerating in the climb (horizontal and vertical acceleration).

 

Current service ceiling is = engine failure altitude (about 21km).

 

If it wasn't for engine failure at 21 km the mig climbs (sustained climb, again, no need of zoom climbing) as if it service ceiling was near 30 km.

 

I tested climbing to 21km only twice in DCS 1.5, I will do a hard testing this weekend and bring more specific data about hight altitude performance.

Edited October 9, 2015 by JorgeIII

[Golo]

If you are able, try to climb DCS Mig-21bis by the real manual, check you time, angle and vertical speed from ground to 10km and from 10km to 21km. Then come back and tell me im lying.

 

The climb from 1000m to 10 000m is done with constant TAS of 870kph, then you fly level at 10 000m until you reach IAS 1200kph that is about 1,9M (close to MiGs max. allowed speed). After that you climb at constant 1.85M to altitude you want.

Sorry, but those are two different climb profiles, so yes you are lying.

If I run up the 21 at 1000m close to its max. speed of IAS 1300kph I can be at 10 000m in 90s.

 

With current FM with excessive performance you just don't have to follow the manual procedure for reaching higher altitudes.

 

No you dont have to. But but you should, thats why they are as procedures in manual.

 

We are talking about high altitude performance, about a FM ability no mantintain a 35 degrees nose up sustained climb from 10km to 21km. (sustained = not loosing speed if not clear enough, not zooming, there is not need to zoom right now).

 

Ok, you show some data that sugests that you cant.

 

The DCS mig can pass through its service ceiling (17.5km), with at least a 25 degree climb while still accelerating, it will reach 21 km while still accelerating in the climb (horizontal and vertical acceleration).

 

Current service ceiling is = engine failure altitude (about 21km).

 

Clearly you dont know what service ceiling means, you should look it up.

If I test handling of a 21 in about 17 500m it behaves close to what service ceiling means.

 

If it wasn't for engine failure at 21 km the mig climbs (sustained climb, again, no need of zoom climbing) as if it service ceiling was near 30 km.

 

Well my AOA indicator was showing about 15 in level flight at 21 000m, so I dont know how higer it would go without staling.

 

I will agree to disagree on this subject.

[JorgeIII]

Fact: DCS-21 BIS performance at high altitude is excessive.

 

Not a big bug, but an evident one.

 

There is a tendency to over discuss some evident bugs, and sometimes are initially neglected by the devs, but eventually fixed. A few examples are the excessive horizontal acceleration and scripted speed limit bug. Speed limit was fixed but drag near max speed was not. This lead, with the lack of control of AFT thrust at different regimes, to a tendency to overspeed. For a time we had to manually use the nose cone to keep a steady mach speed. Fixed in DCS 1.5.

 

Tacview is not working for me in DCS 1.5, but here you have some basic numbers:

 

Sustained climb at 850-900 km/h TAS from under 1000m at 900km/h to 1000m (its fine): (clean plane)

 

Time: 105 seconds (01:45)

Average vertical speed: 85 m/s

Climb angle: from 35 (initial) to 15 (10,000m).

 

Starting at max IAS (aprox. 1250 km/h) sustaining 1250 km/h TAS brings a similar number. You can make a SUSTAINED (not zoom) climb to 10,000 m much faster.

 

Sustained Climb from 10,000 m to 20,000 m at mach 1.8-1.9 (its excesive):

 

Time: 58 seconds (00:58 )

Average vertical speed: 172 m/s (almost constant, should be around 125-150 m/s initial and SHOULD be lower at higher altitud)

Climb angle: constant 35 degrees

 

There is a nice page with historical mig-21 data, pilot study documents, etc.:

http://www.mig-21-online.de

 

 

Im sharing a hand made chart from this page. "High alttitude program example". Its a climbing profile chart with altitude and climb speed. It has some errors, lack some numbers, dosent state Mig-21 version nor loadout. But as far I can tell numbers go by the manual and basic aerodynamics concepts.

 

Basically you can see that initial climbing vertical speed from 10000 at mach 1.8, 1.9 is 125 m/s (other data indicates 150 m/s) but more important it shows how climbing speed lowers with altitude. Current DCS Mig-21 has a completely different chart, climbing speed dosent lower at all. In the chart would look like a line going straight up until 21,000 m (when engines fails)

 

 

 

Other data from this page suggest the MIG can sustain a clim rate of 0.5 m/s at 19,000m, current DCS mig-21 can sustain over 150 m/s at this alttitude.

Edited October 11, 2015 by JorgeIII

[JorgeIII]

Real Mig-21 F time for reaching 20,000 m: 8-10 minutes

 

DCS MIG-21bis (heavier than the F): 5:18 minutes from full stop at the runway to 20 km, at sustained climb (not zoom).

 

As the climb from 0 to 10 km is fine (about one and a half minute), the aprox. 3 to 5 minutes error is in hight altitude performance (between level flight at 11,000 km accelerating to mach 1,9 and the sustained climb to 20 km)

 

I really don't know if I want this bug fixed, I like the idea of outclimbing a FC F-15 in multiplayer ;).

[lokodehortaleza]

You ain't outclimbing a F-15C, nor Su-27, all aircraft are having excessive high altitude performance, and the engines don't even flame out in the FC3 jets. Check this out, 36875 meters, engines still running full AB, and you still have some control authority up there.

[Golo]

Im going to say that this chart is posibly another standard climb profile for hight alt. climb and not the MiG-21 max. performance.

Even max. 0.5m/s at 19 000m sounds way low, thats 1000m in about 30min.

I think he would be out of fuel by the time he got to 20 000m and MiG-21s could go higher than that for sure.

 

I agree with you on the fact that most of them didnt fly that high or that fast, due to munerous facts like pilot/plane safety, engine performance limitations, engine life preservation, whatever mainenance issues....

[FlyGuyF119]

Most after burning jet engines lose after burner or wont go into burner at certain speeds and altitudes. Also know as a "No Light" This would be nice to see modeled.

[JorgeIII]

Notice that this FM error is still present in current MIG-21 BIS for DCS 1.5 and 2.0.

 

The mig has unrealistic high performance at high altitude. At mach 1.6 - 2.0 it still accelerates while climbing at sustained 150 m/s from 10,000 m to 20,000 m.

 

I dont know if a real plane that can sustain a climb rate of over 150 m/s from 30,000 to 60,000 feets it even exist (excluding rocket powered ones like de X-15). Certainly none will sustain a 150m/s climb near its ceiling (maybe if it had a higher than 1 trust/weight ratio?).

Edited December 23, 2015 by JorgeIII