Engine Flameout and stall. This is extreme!

[pepin1234]

Well, I died more because the Flameout and stall than F-5 kills. I can not keep the Mig-21 running away longer. the stall come like a trigger. Even when I care negative G's. I even have flameout and stall with autopilots on.

 

Also the Mig-21 is pitching up itself when we keep horizontal straight fly, forcing us pulling the stick down (is not any reason for this, under airframe the Mig-21 is clean, physically this is not right). Sometime I think fly straight and inverted to avoid this unreal situation.

 

Stop this please.:huh:

Edited July 26, 2016 by pepin1234

[Frederf]

The engine is perhaps too eager to flameout.

 

However at about the limit alpha for wing stall there is also a pitch instability which causes pitch up at the same stick input of lesser AOA. There is still a lot of lift in the post-stall regime but controllability and pitch moment are a concern.

 

Oddly very high AOA (35-60) should have nearly flat pitch moment but currently has severe negative pitch moment.

 

It would be very interesting to see AOA sweep from 0-60° for CL and pitch moment at min-neutral-max tail surface angle for various Mach for current model. 53° sweep wing should have very soft lift falloff post stall due to vortex layer.

 

Note pages 7-10

[gavagai]

I just had two flameouts in one sortie. Both happened in level flight when I gently touched the stick.

 

:disgust:

[golani79]

Couldn't this be due to overspeeding?

 

It seems to me that the 21 is a bit more forgiving even when it comes to maneuvering than it was some time ago.

[iFoxRomeo]

Show some videos with the problem.

 

Fox

[Pocket Sized]

The MiG-21 is very picky. It has lots of power but doesn't like it when you force all that power into level flight.

 

Never exceed 1250 km/h indicated. I've found this applies to most if not all flight regimes. Never exceed Mach 2.1. At about 2.15 (which you will reach VERY quickly) the engine stalls.

[probad]

you better give us a track or something better to go on

[Redglyph]

DCS 1.5.5.60565.216

 

Here is a track file, take-off at 30", flame-out at 2'19", at 1440 km/h TAS (1400 IAS), so Mach 1.18.

 

This is at 715 m ASL, no wind, 15°C.

 

Not the smoothest take-off, I had to put a lot of right rudder for some reason.

 

It's comparable with what I observe in DCS 2.0.4, though the altitude there is of course higher.

 

Note that the table in pg 31 shows a limitation at 1300 km/h or Mach 2.05. I'm not too sure what to make of it, if that's the worst of the two, it means 1300 km/h IAS below 30 kft-ish (so about 1300 km/h TAS at sea level), then Mach 2.05 above. The confusion may come from that, I need to get more information about that.

 

Something weird though, is the debriefing shows an engine shutdown at the very beginning, before actually taking off. And an engine start at the end. I've often seen those weird events in the case of the Mig-21Bis, there are usually a bunch of engine shutdown/engine start, when nothing really happened during the flight.

 

EDIT: the replay is a little weird even when not changing the view, but it still works (at least for me, take-off was very bad when I replayed it but we still see the flame-out).

Mig21bis.flameout.trk

SARPP_DATA_2017_00_03_11_43.txt

Edited January 3, 2017 by Redglyph
SARPP file

[grunf]

 

Note that the table in pg 31 shows a limitation at 1300 km/h or Mach 2.05. I'm not too sure what to make of it, if that's the worst of the two, it means 1300 km/h IAS below 30 kft-ish (so about 1300 km/h TAS at sea level), then Mach 2.05 above. The confusion may come from that, I need to get more information about that..

It's 1300km/h IAS, or M2.05, whichever comes first. Depends on altitude ofc, you'll never reach 1300kmh IAS at high altitudes, nor M2.05 at sea level :D. As a rule of thumb, I keep my eyes on IAS below 10000m, and on the M number above that.

 

Something weird though, is the debriefing shows an engine shutdown at the very beginning, before actually taking off. And an engine start at the end. I've often seen those weird events in the case of the Mig-21Bis, there are usually a bunch of engine shutdown/engine start, when nothing really happened during the flight.

Yeah I've noticed it too, it happens all the time during normal flight, it's been like this for a while. It's in 2.0 too.

[Redglyph]

It's 1300km/h IAS, or M2.05, whichever comes first. Depends on altitude ofc, you'll never reach 1300kmh IAS at high altitudes, nor M2.05 at sea level :D. As a rule of thumb, I keep my eyes on IAS below 10000m, and on the M number above that.

 

Makes sense, that's how I saw it; I haven't found more details about these but it's worth keeping those rules in mind to avoid bad surprises :D

[Pocket Sized]

Zero G will flameout the engine much faster than negative G due to the design of the feed tank IIRC. Watch for the fuel pressure warning light when doing anything that isn't positive G.

[zaelu]

So I asked a former MF Mig21 pilot about this issue... sure MF is not Bis just like the version USA tested is not the Bis... but he said when I asked if it was any limitations on these zero G and negative G maneuvers that they had none beside the fuel quantity. I asked him again if he had any fear of shutting the engine if he had done a "lid" (this is how we say usually to a negative G maneuver executed from level flight... when you simply push the stick and you start diving) and he said simply: "No".

 

The only problem he said was that the fuel tank for negative g /upside down flying is very small but still you could fly a bit over 5 seconds upside down without worrying.

 

He joked that the designer of the fuel pump got some big decoration in former URSS. :)