Afterburner and nozzle animation

[bkthunder]

I noticed that the nozzle fully opens BEFORE the A/B actually lights up. Not sure if this is normal behavior for the MiG-21, but usually the nozzle starts to open up when the first stage of the A/B is already on, and it looks like the "pressure" of the flame opens the nozzle (of course I know it's operated by hyd. actuators, just saying that it looks that way).

 

for example:

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[mvsgas]

I noticed that the nozzle fully opens BEFORE the A/B actually lights up. Not sure if this is normal behavior for the MiG-21, but usually the nozzle starts to open up when the first stage of the A/B is already on, and it looks like the "pressure" of the flame opens the nozzle (of course I know it's operated by hyd. actuators, just saying that it looks that way).

 

for example:

 

Not sure how it works on the Mig-21, but using your example (F-16)

- The pressure of the flame does not open the nozzle, the nozzle is move (in and out) to try to maintain a certain exhaust pressure. This helps control turbine RPM as well.

- Also, the engine on the video uses mechanical actuator, which are actuated by Convergent Exhaust Nozzle Control ( CENC) The CENC is operated by 13th stage compressor engine and controlled by the Digital Electrinic Engine Control (DEEC).

- Also, this engine on the F-16 has different schedules of the nozzle in the air and in the ground, where in the air the nozzle tries to stay close except during AB.

 

I think we need to look at the different Mig-21 engine to see their behavior for comparison.

[spyro23]

It is not a bug, it is a feature.

You must remember that MiGs engine is controlled by the hydro-mechanical controller not the DEEC or even EEC. For various reasons nozzle had to be opened before augmentor was lit. Try to search forums - some ppl explained this already, I believe.

 

I think we need to look at the different Mig-21 engine to see their behavior for comparison.

:doh:Apples and oranges Sir.

[Buzzles]

I noticed that the nozzle fully opens BEFORE the A/B actually lights up. Not sure if this is normal behavior for the MiG-21

 

Yes, it is correct behaviour for the Mig-21.

[mvsgas]

It is not a bug, it is a feature.

You must remember that MiGs engine is controlled by the hydro-mechanical controller not the DEEC or even EEC. For various reasons nozzle had to be opened before augmentor was lit. Try to search forums - some ppl explained this already, I believe.

 

 

:doh:Apples and oranges Sir.

 

I agree, I was referring to the OP, my point was we need to compare DCS Mig-21 to information from MIG-21 not to an F-16 video.

[mvsgas]

According to the DCS manual, the engine nozzle is powered by aircraft hydraulics. So different.

 

bkthunder

Could you post a video or track, according to the manual, page 161, the nozzle should not open prior to Reheat.

Edited October 16, 2014 by mvsgas

[mvsgas]

http://forums.eagle.ru/showthread.php?t=125066&highlight=r25+reheat

[p1t1o]

The nozzle is adjusted to manage the area of the aperture, this manages the mass flow of exhaust gases, maintaining the efficiency of the nozzle, and also managing internal engine pressures.

 

If nozzle pressures are too high, instead of flowing out of the nozzle, they can flow forward back into the combustion chamber, and in extreme cases out through the front of the engine - this is called an "un-start" and is...quite bad.

 

It is likely that the nozzle opens before the AB is lit as the nozzle is not directly controlled by the exhaust gases. If the nozzle were closed when the AB was lit, the sudden jump in exhaust pressure (caused by the increased mass flow without increasing the diameter of the nozzle) may well trigger an un-start.

 

tl:dr - open the door before you run through it.

[bkthunder]

Lo, guys, I'll auto-quote myself

 

(of course I know it's operated by hyd. actuators, just saying that it looks that way).

 

Anyways, if that's correct then great. I was wondering because nozzle scheduling has been known to be wrong in so many simulation titles / aircraft (including Lock-on, FC3, falcon 4 etc), it's one of the things that are prone to be overlooked.

 

:thumbup: