alot of engine flameout and 80% unable to relight

[MarkP]

Hey,

 

whats your guys chacne to relight the engine? I have only like a 10% success rate. Below angles 10 you need to be above 500kts, thats like Mach 1 already? Seems crazy crazy fast for me

[GrmlZ]

Mine pretty much always relights, as long as it isnt damaged. Are you sure your engine is only flamed out and not destroyed? You can destroy the engine when going to fast for example.

[ShadowFrost]

The inflight restart procedure generally looks something like this "idle, in-flight relight control forward, trim for airspeed, wait for restart, push throttle forward". 

 

If you use the starter button with the engine turning... it may restart.... but you will and should break your starter. 

 

Edited August 12, 2022 by ShadowFrost

[MarkP]

guys just to confirm, its idle, not cutoff, am i right?

 

Problem is the required airspeed. According to the document its 500kts below 10k which is effectively close to Mach 1. I cant believe that this it correct, way too fast, is it?!

[Panthir]

Gents, Mirage F-1 engine was very reliable. For your info, 2 HAF F-1CG squadrons, in a period of more than 25 years, had no more than a succesfully relighted  flame out and no more that two succesfully recovered partial compressor stalls. In DCS, it needs a lot of work to reach this reallity. 

Edited August 12, 2022 by Panthir

[GrmlZ]

Its reliable in DCS as well as long as you fly the plane right.

[Riesling]

5 hours ago, MarkP said:

guys just to confirm, its idle, not cutoff, am i right?

 

Problem is the required airspeed. According to the document its 500kts below 10k which is effectively close to Mach 1. I cant believe that this it correct, way too fast, is it?!

Most of time, if the altitude is above 2000 feet => throttle to idle  + relight switch + keeping 300kts speed and 10° dive are enough to run the engine again. 

If the airplane is "shaking" or if you have engine misfires, it's maybe a  compressor surge => Cut off the engine and then follow relight procedure.

 

[ShadowFrost]

9 hours ago, Panthir said:

Gents, Mirage F-1 engine was very reliable. For your info, 2 HAF F-1CG squadrons, in a period of more than 25 years, had no more than a succesfully relighted  flame out and no more that two succesfully recovered partial compressor stalls. In DCS, it needs a lot of work to reach this reallity. 

 

I'd argue its hard to make that comparison as its not apples to apples. As DCS pilots will generally fly their planes much more aggressively or in wrong envelopes/techniques. 
That being said, there have been more than a few times I've flamed out unnecessarily due to wake turbulence in MP. 

[Panthir]

18 hours ago, ShadowFrost said:

I'd argue its hard to make that comparison as its not apples to apples. As DCS pilots will generally fly their planes much more aggressively or in wrong envelopes/techniques. 
That being said, there have been more than a few times I've flamed out unnecessarily due to wake turbulence in MP. 

Mate I can assure you that in real life you could behave to F-1 so bad and aggressive without any impact in engine operation. In DCS you cross the  exhaust turbulence of an aircraft that is half a mile away and you get a flame out present. They have to fix this. In real life could happen several times without any issue.

[turkeydriver]

6 hours ago, Panthir said:

Mate I can assure you that in real life you could behave to F-1 so bad and aggressive without any impact in engine operation. In DCS you cross the  exhaust turbulence of an aircraft that is half a mile away and you get a flame out present. They have to fix this. In real life could happen several times without any issue.

Not true.  The engine is susceptible to flameout as a single spool turbojet.  The current model does seem too liberal in how frequent it happens, but the real jet will flameout and have engine problems, IRL I can assure you. 

[Foogle]

52 minutes ago, turkeydriver said:

Not true.  The engine is susceptible to flameout as a single spool turbojet.  The current model does seem too liberal in how frequent it happens, but the real jet will flameout and have engine problems, IRL I can assure you. 

Panthir was an actual F1 pilot, if his 1500 hours of experience say that it shouldn't flame out, then it shouldn't. 

 

Unless you have experience flying the F1? 

[ShadowFrost]

11 hours ago, Panthir said:

Mate I can assure you that in real life you could behave to F-1 so bad and aggressive without any impact in engine operation. In DCS you cross the  exhaust turbulence of an aircraft that is half a mile away and you get a flame out present. They have to fix this. In real life could happen several times without any issue.

I'm not disagreeing, I quote "That being said, there have been more than a few times I've flamed out unnecessarily due to wake turbulence in MP. " and created a bug report about it. 

Edited August 13, 2022 by ShadowFrost

[turkeydriver]

23 hours ago, Foogle said:

Panthir was an actual F1 pilot, if his 1500 hours of experience say that it shouldn't flame out, then it shouldn't. 

 

Unless you have experience flying the F1? 

 I'll defer to a pilot with the hours.  But the relight process is extremely reliable and should be improved if its not relighting in the envelope.

Edited August 14, 2022 by turkeydriver

[Panthir]

On 8/13/2022 at 9:30 PM, turkeydriver said:

Not true.  The engine is susceptible to flameout as a single spool turbojet.  The current model does seem too liberal in how frequent it happens, but the real jet will flameout and have engine problems, IRL I can assure you. 

My dear friend Mirage F-1 was not like F-5, that it was suffering by often flameouts. ATAR engine was very reliable, as F-16 engine is. 
 

 

[Stratos]

One question I have, I'm not a real pilot, but I encounter many times that after a extreme recovery maneuver, mostly after dive bombing, the engine starts losing and recovery RPM, it does not goes to 0 RPM, it keeps increasing/decreasing RPM, I lost all speed and must Eject, cause I cannot relight the engine, after all is not stopped, it simply keeps doing that strange thing. Is that a compressor stall? How can I recover from it?

[Panthir]

3 hours ago, Stratos said:

One question I have, I'm not a real pilot, but I encounter many times that after a extreme recovery maneuver, mostly after dive bombing, the engine starts losing and recovery RPM, it does not goes to 0 RPM, it keeps increasing/decreasing RPM, I lost all speed and must Eject, cause I cannot relight the engine, after all is not stopped, it simply keeps doing that strange thing. Is that a compressor stall? How can I recover from it?

It should be a bug. It is not a compressor stall. Engine is not correctly modelled. It needs some work. I am sure that they will find a fix soon. 

[ARM505]

5 hours ago, Stratos said:

One question I have, I'm not a real pilot, but I encounter many times that after a extreme recovery maneuver, mostly after dive bombing, the engine starts losing and recovery RPM, it does not goes to 0 RPM, it keeps increasing/decreasing RPM, I lost all speed and must Eject, cause I cannot relight the engine, after all is not stopped, it simply keeps doing that strange thing. Is that a compressor stall? How can I recover from it?

I'm not commenting on the realism, or what it's supposed to be, only that when this happens you must shut it down completely and follow the relight procedure. This is the only way I've got it to behave properly again.

My 2c, my opinion, never flown a Mirage IRL - if this were to happen to engines I know, reducing thrust until the abnormal behaviour stops would be sufficient. Once normal airflow through the engine has been restored, it should behave normally again, assuming there was no previous damage. I'm not sure what is supposed to be happening here. I'd assumed a compressor stall as well, but it should be correctable by reducing thrust IMHO (again, I'm not an expert with the Atar)

[Rex854Warrior]

So it's not entirely impossible that a compressor stall would result in such behavior, the recirculating air nested within the stalled compressor stage (the air is in such a state because of the stall) can contaminate perfectly good incoming air causing the phenomenon to self sustain. Now it's in theory and frankly I'm curious as to why it's not flushed out almost immediatly or at least why it's so hard to get moving after going into the right parameters which would be to unload the compressors by going to idle and playing with the aircraft's speed (accelerating if my memory is correct). Bleeding this polluted airflow is done on some air intake designs I believe.

This does work in the Mirage F1 currently, you'll get a compressor stall when pulling extreme maneuvers and it seems impossible to get out of it but diving and getting sufficient airspeed does get rid of the problem after some time in those parameters with the throttle at idle.

Edited August 15, 2022 by Rex854Warrior

[Panthir]

12 hours ago, Rex854Warrior said:

So it's not entirely impossible that a compressor stall would result in such behavior, the recirculating air nested within the stalled compressor stage (the air is in such a state because of the stall) can contaminate perfectly good incoming air causing the phenomenon to self sustain. Now it's in theory and frankly I'm curious as to why it's not flushed out almost immediatly or at least why it's so hard to get moving after going into the right parameters which would be to unload the compressors by going to idle and playing with the aircraft's speed (accelerating if my memory is correct). Bleeding this polluted airflow is done on some air intake designs I believe.

This does work in the Mirage F1 currently, you'll get a compressor stall when pulling extreme maneuvers and it seems impossible to get out of it but diving and getting sufficient airspeed does get rid of the problem after some time in those parameters with the throttle at idle.

 

In accordance with the flight manual, there were no restriction for throttle usage in all flight envelope. If I remember well, a compressor stall could be recognized by the followings: Max EGT 600, RPM max ~70% (maybe some flactuation as well), loss off thrust and a special noise like BRRRRRR. But it was almost impossible to happen, what ever you do. It happend to me to recover one of the two compressor stalls incidences of HAF F-1s that occoured in a Total of more than 90.000 hours in around 27 years. In my case the compressor stalled didn't cleared by setting idle throttle and dive to get 300knots. It cleared after applying relight procedure (under 10000 feet). They technicians haven't found any problem but If I am sure that it was most probably due to malfunction of SRL, cause it happened when I set MAX AB in at very low speed, nose high attitude with high AoA at 15000ft. If I am not mistaken the other compressor stall incidence happened during a very violent high speed adverse yaw and cleared by setting idle and dive up to 300knots. I don't remember if the found the cause for it. 

Edited August 16, 2022 by Panthir

[Bremspropeller]

On 8/13/2022 at 8:30 PM, turkeydriver said:

The engine is susceptible to flameout as a single spool turbojet.

I'd actually argue the opposite is true, since the single-spool turbojet's compressor blades are mostly working far off their max efficiency point and hence aren't brought to a stall as easily as in a two- or three-spool design, where a greater pressure-ratio can be achieved across a single blade, creating a more adverse pressure-gradient under non optimal intake-flow (e.g. high alpha, beta or combinations of the two) or transient conditions.

Not sure whether the Atar uses bleed-air for compressor-stability, but in general terms, a low pressure-ratio across the compressor should indicate a higher resistance to stalls. It helps having only nine compressor-stages (the J79 had 17 and needed VSVs and bleed-air to make it's magic happen).

The J65 in the Skyhawk had no gun-gas ingestion issues. The two-spool J52 had. The Orpheus also seems to have been quite fool-proof. The single-spool turbofan (somebody actually came up with that!) M53 also seems quite carefree.

[sedenion]

4 hours ago, Bremspropeller said:

I'd actually argue the opposite is true, since the single-spool turbojet's compressor blades are mostly working far off their max efficiency point and hence aren't brought to a stall as easily as in a two- or three-spool design, where a greater pressure-ratio can be achieved across a single blade, creating a more adverse pressure-gradient under non optimal intake-flow (e.g. high alpha, beta or combinations of the two) or transient conditions.

Not sure whether the Atar uses bleed-air for compressor-stability, but in general terms, a low pressure-ratio across the compressor should indicate a higher resistance to stalls. It helps having only nine compressor-stages (the J79 had 17 and needed VSVs and bleed-air to make it's magic happen).

The J65 in the Skyhawk had no gun-gas ingestion issues. The two-spool J52 had. The Orpheus also seems to have been quite fool-proof. The single-spool turbofan (somebody actually came up with that!) M53 also seems quite carefree.

My two cents: I tend to second that. It seem american engine manufacturers often faced reliability and stall problems with their new - and very powerfull - engines when released (this is also true for the P&W F135 engine) because they make more complex engines they push to their bounds. French manufacturer have another history, and tend to make more simple design, less powerfull, but with reliability and maintenability as one of main goals (and this is also true for the M88-2).

Edited August 16, 2022 by sedenion

[turkeydriver]

12 hours ago, Bremspropeller said:

I'd actually argue the opposite is true, since the single-spool turbojet's compressor blades are mostly working far off their max efficiency point and hence aren't brought to a stall as easily as in a two- or three-spool design, where a greater pressure-ratio can be achieved across a single blade, creating a more adverse pressure-gradient under non optimal intake-flow (e.g. high alpha, beta or combinations of the two) or transient conditions.

Not sure whether the Atar uses bleed-air for compressor-stability, but in general terms, a low pressure-ratio across the compressor should indicate a higher resistance to stalls. It helps having only nine compressor-stages (the J79 had 17 and needed VSVs and bleed-air to make it's magic happen).

The J65 in the Skyhawk had no gun-gas ingestion issues. The two-spool J52 had. The Orpheus also seems to have been quite fool-proof. The single-spool turbofan (somebody actually came up with that!) M53 also seems quite carefree.

It's listed as susceptible to compressor stall in its own manuals - not as bad as the module currently has it, but it happens.  I like your logic though, well thought out and explained and makes sense.  The ATAR 9K50 was supposed to change to the M53 and we would all be flying Super Mirage F1s- though a single spool like you said.  I thought dual spool turbofans is what finally practically negated compressor stalls altogether- perhaps the dual spool has little to do with it.    

[Rex854Warrior]

On 8/16/2022 at 9:11 AM, Panthir said:

In accordance with the flight manual, there were no restriction for throttle usage in all flight envelope. If I remember well, a compressor stall could be recognized by the followings: Max EGT 600, RPM max ~70% (maybe some flactuation as well), loss off thrust and a special noise like BRRRRRR. But it was almost impossible to happen, what ever you do. It happend to me to recover one of the two compressor stalls incidences of HAF F-1s that occoured in a Total of more than 90.000 hours in around 27 years. In my case the compressor stalled didn't cleared by setting idle throttle and dive to get 300knots. It cleared after applying relight procedure (under 10000 feet). They technicians haven't found any problem but If I am sure that it was most probably due to malfunction of SRL, cause it happened when I set MAX AB in at very low speed, nose high attitude with high AoA at 15000ft. If I am not mistaken the other compressor stall incidence happened during a very violent high speed adverse yaw and cleared by setting idle and dive up to 300knots. I don't remember if the found the cause for it. 

 

Thank you for your input, just to be clear I have no idea how this air intake/engine combo should behave exactly but this is ciritical terriroty for fighter aircraft, I should imagine that my collegues from way back then made sure it isn't a 50/50 chance of your engine dying when you go there.
As for the behavior in DCS, well I managed to recover two-three compressor stalls in DCS doing what I said (didn't test that much further as I pretty much learned my lesson from dying to compressor stalls), otherwise I went for the relight however always using the starter but the "start" process is not the same for an in flight relight so that procedure is just wrong, I'll have to test without.

 

On 8/16/2022 at 11:49 AM, Bremspropeller said:

I'd actually argue the opposite is true, since the single-spool turbojet's compressor blades are mostly working far off their max efficiency point and hence aren't brought to a stall as easily as in a two- or three-spool design, where a greater pressure-ratio can be achieved across a single blade, creating a more adverse pressure-gradient under non optimal intake-flow (e.g. high alpha, beta or combinations of the two) or transient conditions.

Not sure whether the Atar uses bleed-air for compressor-stability, but in general terms, a low pressure-ratio across the compressor should indicate a higher resistance to stalls. It helps having only nine compressor-stages (the J79 had 17 and needed VSVs and bleed-air to make it's magic happen).

The J65 in the Skyhawk had no gun-gas ingestion issues. The two-spool J52 had. The Orpheus also seems to have been quite fool-proof. The single-spool turbofan (somebody actually came up with that!) M53 also seems quite carefree.

On 8/16/2022 at 12:11 PM, sedenion said:

My two cents: I tend to second that. It seem american engine manufacturers often faced reliability and stall problems with their new - and very powerfull - engines when released (this is also true for the P&W F135 engine) because they make more complex engines they push to their bounds. French manufacturer have another history, and tend to make more simple design, less powerfull, but with reliability and maintenability as one of main goals (and this is also true for the M88-2).

 

It's due to the fact that adding spools allows for the associated compressor stages to run at their most efficient load which does indeed bring stalling territory closer. On single spool turbojets the turbine stages are the limiting factor but a stall is not impossible nor is it necessarily more difficult to achieve (do not forget the air intake here which plays a role in managing the incoming air, wether that is well or poorly) but in general, there should be more room for design problems/constraints and/or pilot errors.

As for the F-35 I'm afraid it's mostly an air intake problem, the boundary layer deflection bump is seriously cool in terms of aerodynamics but also has it's drawbacks. And cutting the intake section to a minimum was probably a necessity to ensure stealth so it's really a match made in heaven to get engine problems.

 

22 hours ago, turkeydriver said:

It's listed as susceptible to compressor stall in its own manuals - not as bad as the module currently has it, but it happens.  I like your logic though, well thought out and explained and makes sense.  The ATAR 9K50 was supposed to change to the M53 and we would all be flying Super Mirage F1s- though a single spool like you said.  I thought dual spool turbofans is what finally practically negated compressor stalls altogether- perhaps the dual spool has little to do with it.   

 

A lot of research, modelling and testing happened in the same time which brought a better understanding of the phenomenon and ways to predict/negate the effects of such an event. Take a look at the engines on the F-14A, the TF-30s, earlier two spool turbofan, not particularily stable .

Edited August 17, 2022 by Rex854Warrior

[Stratos]

Thanks, I feel the engine stalls a bit too much, but maybe is my aggresive (AKA poor) way of flying!

[Super727]

Hi,

I found that when flying supersonic, do NOT reduce the throttle when above Mach 1.4.  To reduce speed, deploy the airbrakes and leave the throttles at full afterburner until slowing to less than Mach 1.4.   Once you are below Mach 1.4 you can SLOWLY reduce the throttles to further decelerate.  

Also try not to fly above 50.000 feet.  The engine may stall when above this altitude.