Mig-21Bis Why the engine RPM drops to 20%? (randomly?)

[in memoriam of Sharky]

Hello,

I've just bought this module four days ago and I try to learn this awesome plane. I have played the F15 only before so I am kinda beginner in DCS. I have played Falcon 3.0, MS Flight simulator and other Flight sims in the past but the complexity of those were not on this level back than. I almost memorized the starting procedure I can safely taxi , take off, land, I have just started to learn to use the radar and combat/navigation. I have also "read"(scan) the manual.

My problem is when I fly this plane after a short while the engine rpm drops to around 20% randomly and the throttle becomes dead , I mean I can move it forward backward but the trust level won't change any more. I have been monitoring the instruments oil pressure, etc but can't see what could be the issue. I turned everything in the options menu to simulation mode but I ticked the "Special Engine Management" option "ON" only.

Maybe I missed something?

edit: "Simplified Engine Management" is turned On

[ButterCookie]

Sounds like the engine had a flame out.

Have you been in negative G maneouver whe this occured? The Mig 21 is very sensitive to that, only a few seconds are enough for a flame out.

Same goes for high speed at low altitude. When about Mach 1.2 in low altitude you can get a compressor stall and the engine shuts down, windmilling at 20% RPM.

[in memoriam of Sharky]

Originally posted by ButterCookie:

Sounds like the engine had a flame out.

Have you been in negative G maneouver whe this occured? The Mig 21 is very sensitive to that, only a few seconds are enough for a flame out.

Same goes for high speed at low altitude. When about Mach 1.2 in low altitude you can get a compressor stall and the engine shuts down, windmilling at 20% RPM.

Thanks for your fast reply!

Maybe its that it. I usually go around 1 Mach when it happens but its always above 5.000m Usually when I try to ascend above 10.000m. Hmm. What instrument I have to monitor and how can I avoid this situation?

Now I know that I have to learn about these flame outs. I have no idea what is it yet but I remember I have seen this at the ED forum at the Mig section. :)

[Cyber_Chupacabra]

Check out 162 page of miG-21 maual - its about the issue you have and will tell you what to do to restart the engine.

2.3. Engine Flameout
Symptoms:
- a peculiar pop or change of engine noise;
- abrupt decrease of the engine speed and jet-pipe temperature;
- the cone position indicator pointer might deflect to the extreme right position.
Actions to be taken:
- set the throttle lever to SHUT-OFF;
- disengage the AFCS (PS4);
- establish an altitude and airspeed providing for reliable engine relight, relight the engine;
- after relighting the engine, smoothly shift the throttle lever to FULL THROTTLE to check the
engine for proper operation.


If engine surge (or flameout) occurs at an altitude of less than 3000 m, or during launch of missiles or
rockets, proceed as follows:
- immediately shift the throttle lever to SHUT-OFF keep it in this position and for at least 1.5
to 2 s,
- bring the aircraft into climb at a vertical speed of 7 to 10 m/s while turning to a direction
permitting safe ejection or dead-engine landing;
- make sure that the AIR RELIGHT circuit breaker is turned on (turn on the circuit breaker if it
has not been turned on before the launching);
- shift the throttle lever to any non-reheat power setting required for flight continuation,
without any delay;
- check the engine run, then turn off the AIR RELIGHT circuit breaker.

[ButterCookie]

Originally posted by Sharky:

Thanks for your fast reply!

Maybe its that it. I usually go around 1 Mach when it happens but its always above 5.000m Usually when I try to ascend above 10.000m. Hmm. What instrument I have to monitor and how can I avoid this situation?

Now I know that I have to learn about these flame outs. I have no idea what is it yet but I remember I have seen this at the ED forum at the Mig section. :)

I had a look at the Manual for the Engine limitations in flight. Have a look at Page 35, Point 20 onwards.

To see if you are in negative or near zero G load have a look at the Accelerometer, which is below your RWR (See Manual Page 45, Instrument #37).
Also the red markers on the Accelerometer are showing the highest and lowest G load you reached during your flight.

EDIT: Also what mordin86 said :)

[in memoriam of Sharky]

Thank both of you very much I will check out the manual.

[JDarksword]

Having the advanced engine management ticked on dictates that flameout simulation will be active. Basically follow what mordin said.

[in memoriam of Sharky]

Originally posted by Джо Темно - меч:

Having the advanced engine management ticked on dictates that flameout simulation will be active. Basically follow what mordin said.

Ahh... I wrote "Special Engine Management" although its called "Simplified Engine Management" so It is turned on in my game special options so there shouldn't be engine shut downs according to the manual. But these "flame out shut downs" still happens. Is this normal?

"SIMPLIFIED ENGINE MANAGEMENT - If this option is selected, in-flight engine failures and shutdown
due to any kind of stress will be prevented. Engine shutdown can be a frequent event for
inexperienced players. Every time the engine stops in the air, you will have to attempt to relight it.
Note that you have a limited number of restart attempts. Restarting the engine in the air can be
complicated or even impossible in some circumstances."

So is this option working as intend?

[JDarksword]

Ahh ok I misunderstood, the manual should be right. If you suspect a bug report it on the ED forums.

[ButterCookie]

I just tried it out, both with simple engine management checked and unchecked.

After about 3 seconds at ~0 G the engine flamed out.
Could be a bug. Then again the Tooltip for the simplified engine management option (when you hove over it with your mouse) says it prevents the engine from shutdown "in most cases".

[in memoriam of Sharky]

Originally posted by ButterCookie:

I just tried it out, both with simple engine management checked and unchecked.

After about 3 seconds at ~0 G the engine flamed out.
Could be a bug. Then again the Tooltip for the simplified engine management option (when you hove over it with your mouse) says it prevents the engine from shutdown "in most cases".

Yes. Thanks!

I have just read the forum at ED and it seems the flame out happens for everyone with on/off so its normal.

[GorillaRoyale]

Hey Sharky,

welcome to the wonderful world of soviet cold war era engineering. The migs apparently (and im just going by my own reading here) operate a sort-of gravity feed for the engine that rapidly drys up and disconnects temporarily even at slightly negative G-forces.

To avoid G-induced flame-outs, the 21 thus has a internal aux. fuel tank that supplies the engine with fuel for brief periods of neutral or negative forces. This tank, however is only about a dozen gallons in size and thus expires rapidly according to fuel consumption. As flight normalizes, the aux. tank should refill.

It is actually possible to fly extended periods in near negative g, if interrupted by periods of positive G-loads to give the aux. tank opportunity to refill, but even in doing so one can only go about 3 seconds at negative with the afterburner on.

So no, dear Viper Pilots, no unloaded extensions here ;)

I've started flying the DCS-MiG-21 a couple of months ago and noticed so far that fuel managment is deceivingly difficult and requires near constant pilot attention for anything but the shortest of missions. Especially when using external tanks.

In general I find it practical to think in terms of litre per second, as it gives you a pretty good picture for most of the flight.

Sorry for this novel-sized post. I hope some of it is helpful.

[in memoriam of Sharky]

Originally posted by GorillaRoyale:

Hey Sharky,

welcome to the wonderful world of soviet cold war era engineering. The migs apparently (and im just going by my own reading here) operate a sort-of gravity feed for the engine that rapidly drys up and disconnects temporarily even at slightly negative G-forces.

To avoid G-induced flame-outs, the 21 thus has a internal aux. fuel tank that supplies the engine with fuel for brief periods of neutral or negative forces. This tank, however is only about a dozen gallons in size and thus expires rapidly according to fuel consumption. As flight normalizes, the aux. tank should refill.

It is actually possible to fly extended periods in near negative g, if interrupted by periods of positive G-loads to give the aux. tank opportunity to refill, but even in doing so one can only go about 3 seconds at negative with the afterburner on.

So no, dear Viper Pilots, no unloaded extensions here ;)

I've started flying the DCS-MiG-21 a couple of months ago and noticed so far that fuel managment is deceivingly difficult and requires near constant pilot attention for anything but the shortest of missions. Especially when using external tanks.

In general I find it practical to think in terms of litre per second, as it gives you a pretty good picture for most of the flight.

Sorry for this novel-sized post. I hope some of it is helpful.

Thanks for your input. I have read about this in the Mig21 bis manual I think. I meant the limitations of "0-0,2G"(near zero) and negative G manouvers. Interesting stuffs. :)

[in memoriam of Sharky]

It happened a lot when I did "push forward" moves on the stick so I realized I kept near zero G for too long to level my course thats why there were so many flame outs for me. But at least now I have learned about this and I could learn the engine relight procedure also.

Its so much fun to learn these systems I am happy with my purchase. :)

Thanks again!

[Chameleon_Silk]

ya you dont want to push the nose down with the stick, that floaty feeling you get when you crest a hill is something you want avoid unless you like flame outs :)

[Ratata]

The mig-21 hates hates and really hates negativ g, especially if applied through pushing the stick down, the more sudden you move the easier the flameout happens. always rotate and pull. They really should write that in big sovjet red letters on the manual =).