Mach 2 climb profile explained + video

[Pocket Sized]

So you want to take the fishbed up to her top speed of Mach 2.1? I think it's something we've all attempted with varying degrees of success.

 

When I first got the plane I tried many times but always arrived at my destination or burned nearly all my fuel before reaching cruising altitude/Mach.

 

I figured out some key points recently and I'd like to share them with you guys.

 

1. Never exceed 1250km/h indicated or Mach 2.1 indicated, whichever is slower (will depend on altitude) The Mach limit is VERY important once at altitude. If either is exceeded the engine will flame out and can't be restarted until descending below 10km and Mach 1. Due to the amount of fuel it takes to get back up to speed, a flameout pretty much scrubs the rest of the flight.

 

2. The aircraft's acceleration is very poor in the low supersonic range (1.2-1.5) but very good in the high subsonic range. This was the realization that led to me developing the climb profile I describe

 

The climb profile:

 

The name of the game is to stay subsonic until about 10-12km (using pitch to control speed while throttle stays at full mil or afterburner), then level off and accelerate to nearly Mach 2. Then, slowly climb to cruising altitude or as required to stay below the IAS limit. 15km seems to be a good altitude, but I'm sure it can be taken higher. If the engine is left at full burner at cruising altitude, you WILL exceed the Mach limit and kill it. Easiest way to manage throttle is by watching EGT. A clean airframe will stay at Mach 2 with an EGT of 700 degrees.

 

Finally, a video in which I demonstrate a flight from Nalchik to Kobuleti. Clean airframe, full internal fuel, and emergency burner used for the initial climb until it disengaged itself at 3km. It still amazes me how quickly this plane gets going!

 

(Might still be uploading)

 

I sorta rushed this post, so let me know if there's anything that needs clarification.

Edited November 26, 2016 by Pocket Sized

[303_Kermit]

 

It shall work like the man says I think...

[DmitriKozlowsky]

I kind of given up on Mig-21Bis long time ago. I don't understand , my failure, to achieve the kind of speeds, altitude, and climbs that are claimed in DCS, and RL documentaries. With empty aircraft , fuel only, on standard day. In full AB and Emergency AB for 7 second increments, I cannot get above 40K. Around 38500-39200 MSL, aircraft departs into stall and strong yaw. I tried zoom to 35K, leveling off. Slight dive to 30K, then in full emergency AB climb to max. FAIL! Cant do it. Aint't happening. At 39K aircraft departs. Though it is stall due low KIAS, so flaps down. Helps maybe 1000, but slows down and departs. 

I have never been above 42K since I got this module in 2015. Maybe with initial version I had with older DCS around 2015, I may have gotten 42-43K MSL. With naked bird. How are these 60K altitudes happen?

If I get flameout twice on same mission with e-AB, there is no third re-light. Engine is , maybe, 'core-locked'. Even though temp never goes above 800.

[corn322]

4 hours ago, DmitriKozlowsky said:

Emergency AB for 7 second increments

Why? Also, do note that the second AB only works under 4000 meters altitude.

4 hours ago, DmitriKozlowsky said:

Though it is stall due low KIAS, so flaps down

You need more airspeed, not flaps.

[Freddo]

Climb with or without afterburner and with 600 to 900km/h IAS to 9000m or more, hold and speed up, to break faster the sound barrier descent a bit until you reach Mach 1.2 then level out and speed up to minimum M1.4 then climb and climb and climb. If you cant hold 400 IAS you are in trouble and to high (70.000ft) Check the speed 1300 IAS/Mach 2.1 if needed reduce the throttle and fly with half afterburner. Test it with a ZB800 and drop the empty pod on the way to 9000m. 

[corn322]

Here's a track and tacview. I flew a profile similar to the one Freddo described.

Take off, accelerate to about 850kmh TAS, climb at 850 TAS until 10km altitude, accelerate to mach 1.2, climb at mach 1.2 to 15km, accel to mach 2, climb to 18km.

Flaming out while turning around is optional.

Tacview-20211109-152246-DCS-Flight Test.zip.acmi Test flight.trk

[DmitriKozlowsky]

2 hours ago, corn322 said:

Why? Also, do note that the second AB only works under 4000 meters altitude.

You need more airspeed, not flaps.

There is no more airspeed. An naked plane, with fuel, and afterburner full. In 15 degree climb. After 35K climbrate drops to low. Thats what I dont understand. Above 35K, in full AB, there is no more additional power. As aircraft nears 40K, it stalls, and yaws violently.

 

Edited November 9, 2021 by DmitriKozlowsky

[rossmum]

Don't hold 15 degrees, hold 900TAS. Holding angles is probably why you have absolutely no speed. This isn't an F-15, your thrust to weight ratio is good but it isn't 'literally a rocket' levels of good, plus you're fighting a lot of induced drag off the delta wing as you lose speed and gain AoA.

From takeoff, accelerate level to 900TAS, pull and hold and then adjust pitch as necessary to maintain the thin needle on the Mach meter over 0.9 until you reach 10km altitude or so. From there, go into a slight dive to break through the sound barrier, level off and continue accelerating to M 1.4 or more, then pull the stick back just enough to try hold onto that speed. If you're feeling sporty, you can climb to 12-13km, accelerate to M 2.05, and then pitch for like 50 degrees and see what DCS looks like from 30 kilometres above the ground.

 

[Frederf]

The official manual procedure is a climb constant TAS of 950 km/h for afterburner-only interceptions and 850-870 TAS when afterburner is used after the initial climb to 10km. The less drag (2 missiles, center fuel tank jettisoned) corresponds to the faster number. Those are for combat interceptions which prioritize distance and altitude in a time minimum. There are other regimes which are used for training and demonstrating high speed or zoom climbing without a time pressure.

If the goal is simply to demonstrate high speed then after 600 km/h IAS, select maximum dry thrust and climb at 870 TAS (guessing this demo is done without external tank in training). The afterburner is avoided for two reasons: it is less fuel efficient (fuel you need for the high speed run) and you want to gain distance from the airfield. The high speed run travels a long distance so you fly out this far, turn around, and then do the high speed run which ends over the airbase. This way if there is a problem: low fuel or engine failure you can glide home.

The first video has a climb speed which is too high. Being very close to Mach 1.0 has exceptionally high drag. Much fuel is burned for little benefit. I find about 1000 km/h TAS (about M0.9) is good. Level acceleration at 10km is alright but the exact level depends on your weight and drag. I climb until IAS is about 550 km/h. For an immediate acceleration I do a shallow dive to help break quickly through the M1.0 +-0.05 "Mach wall" drag region. Too steep of a dive ends up in thick air which makes accelerating difficult but too shallow requires more AOA which has drag which slows the process as well. I try to start at 11km and not get much below 9.5km. Starting at M1.1 I convert back to the acceleration altitude of 10km. When at 1200 km/h IAS climb to 11.5km and then proceed to maximum Mach.

If the purpose is maximum TAS then climb above 11.5 km is unnecessary. Mach is related to temperature and temperature is constant for a large altitude band. Energy for climbing can instead be used to get to M2.05 sooner.

For higher altitude flight accelerate as before, 10km then 1200 IAS then 11.5km. Continue climbing at 1200 IAS until Mach 1.80-1.85 and then follow this Mach (IAS will be less than 1200). Continue this flight until vertical speed is less than 5m/s.

Zoom climbing is done at 15.5-16km at M1.9 then a pitch up of an addition 10-15° with 1.5-2.0g load. Cancel the zoom climb at an airspeed of 500-530 IAS. Press over 0.3-0.4g load at idle to recover which should not have speed less than 400 IAS. In DCS this will likely flameout the engine.

For fast interceptions without maximum Mach a cruise segment of M1.4-1.8 requiring nearly minimum afterburner is a good balance between speed and fuel consumption.

[DmitriKozlowsky]

What? I cant hold 900 TAS and get to altitude. I wind up following this stair stepping profile, climb, level off hold until speed gain, climb. DOES NOT WORK FOR ME? My time I am at 39K, my KIAS is barely 165, and aircraft begins to stall. I am in full non-emergency burner.

[Snappy]

4 hours ago, DmitriKozlowsky said:

What? I cant hold 900 TAS and get to altitude. I wind up following this stair stepping profile, climb, level off hold until speed gain, climb. DOES NOT WORK FOR ME? My time I am at 39K, my KIAS is barely 165, and aircraft begins to stall. I am in full non-emergency burner.

Post a track? Or video. That way maybe people can better tell you what exactly you re doing wrong.

Edited November 10, 2021 by Snappy

[randomTOTEN]

Got up to M2.0 and 70,000ft+ last night on internal fuel only. Pretty nice actually, I usually tank a drop tank and now realize that's quite a bit of drag.

Are your speed brakes deployed?

[Frederf]

10 hours ago, DmitriKozlowsky said:

What? I cant hold 900 TAS and get to altitude. I wind up following this stair stepping profile, climb, level off hold until speed gain, climb. DOES NOT WORK FOR ME? My time I am at 39K, my KIAS is barely 165, and aircraft begins to stall. I am in full non-emergency burner.

The constant TAS climb is just to get to 10km or so. The service ceiling (w/o AB) with two missiles only is 12km (11km four missiles). To climb above that you need to accelerate and climb according to the supersonic profile.

MiG-21bis Training Mach.trk

[Knock-Knock]

https://www.mig-21-online.de/home-2/stoeberecke/methodik-des-fliegens/
Look at the two 'Steigprofile für Flüge in die Stratosphäre' images.

[Ala13_ManOWar]

Interesting since it says what Frederf explained before. Very nice info in this thread mates, thanks.

 

S!