Should the M2KC be able to hold up against the Viper in a 2 circle fights?

[HWasp]

Considering the 4,8G at 340 kts in the vid at around +1000 feet/minute (Ps= +16,6 feet/sec), I think the realistic STR G based on the video is around 4,9 to 5 Gs. +16,6 feet/second is really not that much looking at other EM diagrams, so I would consider this much less of a problem compared to the chevron being late at a high g-onset rate.

The chart would look like this:   

[HWasp]

For me this data point shows around +10%+ overperformance in STR at that speed. 

Edited November 5, 2022 by HWasp

[Galinette]

4 minutes ago, HWasp said:

For me this data point shows around +10%+ overperformance in STR at that speed. 

 

To be compared with the very likely 10% engine performance with the M53-5 and M53P2

[myHelljumper]

@HWaspI wasn't aware that the aircraft was a twin-seat with a M53-5 engine, this makes this comparison not very pertinent except for rough estimate of where the STR should be as 10% trust can change it a lot.

Thank you again for the detailed analysis of the other parts of the video that showed a difference with our model.

I just want to clarify that this particular video was not used as a data-point to tune the Mirage FM, as said before the turns are not perfect sustained turns and are there are too few of them to build a coherent model. I just watched it again recently and spotted some near sustain turns that we could use to have an idea of the accuracy of the Mirage FM.

[HWasp]

36 minutes ago, myHelljumper said:

@HWaspI wasn't aware that the aircraft was a twin-seat with a M53-5 engine, this makes this comparison not very pertinent except for rough estimate of where the STR should be as 10% trust can change it a lot.

Thank you again for the detailed analysis of the other parts of the video that showed a difference with our model.

I just want to clarify that this particular video was not used as a data-point to tune the Mirage FM, as said before the turns are not perfect sustained turns and are there are too few of them to build a coherent model. I just watched it again recently and spotted some near sustain turns that we could use to have an idea of the accuracy of the Mirage FM.

To be honest, I did not fully understand the points Kercheiz brought, on how exactly are we sure about what version this aircraft is. Information is very scarce, it's quite sad, if one of the only sources is not valid.

While I do really like the module and the FM overall now, it would be really important to back this up with some solid sources, because otherwise it will be constant debate without an end.

 

[Despayre]

27 minutes ago, HWasp said:

To be honest, I did not fully understand the points Kercheiz brought, on how exactly are we sure about what version this aircraft is. Information is very scarce, it's quite sad, if one of the only sources is not valid.

While I do really like the module and the FM overall now, it would be really important to back this up with some solid sources, because otherwise it will be constant debate without an end.

 

Even with solid sources, like every other FM, it will be constantly argued by some who think they know better (usually because they saw a single Youtube video, or just feel they're better at math for some reason), as is evidenced by at least one thread for pretty much every plane forum...

[Galinette]

26 minutes ago, HWasp said:

To be honest, I did not fully understand the points Kercheiz brought, on how exactly are we sure about what version this aircraft is. Information is very scarce, it's quite sad, if one of the only sources is not valid.

While I do really like the module and the FM overall now, it would be really important to back this up with some solid sources, because otherwise it will be constant debate without an end.

 

I don't know how to explain it better. There are several engine versions in the M2000, all variants of the Snecma M53.

M53-5 was the original engine of the first produced airframes, then M53-P2 was developped, installed on the later airframes. In the AdA, all M53-5 were gradually replaced by M53-P2 (retrofit) and the newer engine is now the only one for the whole french M2000 fleet. There are still M53-5 engines in service in other countries. The newer engine has significantly more thrust in both MIL and AB, for instance wikipedia states +8% in AB and +18% in MIL. All this info is publicly available if you search a bit.

Now the video : this is a pre-2007 video taken in Orange, France. This is likely a twin seater as B&W hudcam is typical (unless a color video was converted to B&W but unlikely). Twin seaters were still M53-5 in 2007 at Orange, so there is a significant chance this is video was recorded on an aircraft with a M53-5. This of course is, from my own source. It's not openly verifiable unless you have yours.

(I'm the FM author)

 

[myHelljumper]

48 minutes ago, HWasp said:

To be honest, I did not fully understand the points Kercheiz brought, on how exactly are we sure about what version this aircraft is. Information is very scarce, it's quite sad, if one of the only sources is not valid.

While I do really like the module and the FM overall now, it would be really important to back this up with some solid sources, because otherwise it will be constant debate without an end.

 

We can talk about the dead engine landing procedure if you want, this one was used to tune the aircraft drag and lift.

[HWasp]

6 minutes ago, Kercheiz said:

I don't know how to explain it better. There are several engine versions in the M2000, all variants of the Snecma M53.

M53-5 was the original engine of the first produced airframes, then M53-P2 was developped, installed on the later airframes. In the AdA, all M53-5 were gradually replaced by M53-P2 (retrofit) and the newer engine is now the only one for the whole french M2000 fleet. There are still M53-5 engines in service in other countries. The newer engine has significantly more thrust in both MIL and AB, for instance wikipedia states +8% in AB and +18% in MIL. All this info is publicly available if you search a bit.

Now the video : this is a pre-2007 video taken in Orange, France. This is likely a twin seater as B&W hudcam is typical (unless a color video was converted to B&W but unlikely). Twin seaters were still M53-5 in 2007 at Orange, so there is a significant chance this is video was recorded on an aircraft with a M53-5. This of course is, from my own source. It's not openly verifiable unless you have yours.

(I'm the FM author)

 

Thanks, now I understand better.

7 minutes ago, myHelljumper said:

We can talk about the dead engine landing procedure if you want, this one was used to tune the aircraft drag and lift.

That would be great, sounds interesting!

[myHelljumper]

25 minutes ago, HWasp said:

That would be great, sounds interesting!

So the procedure goes as follows:

• 280 kt indicated should give you 14 nm for 10 000 ft. 280 is chosen because it's close to the best glide speed (~260 kt) and inside the engine relight domain. The slats should be forced in.
• Stabilize at 5000 ft to slow down to 230 kt minimum.
• Maintain 230 kt in final.

This procedure does not give fuel or configuration information but we can guess that in such emergency external stores would be jettisoned so the procedure must be possible with basically full fuel and no stores.

I'll record a track later.

Edited November 5, 2022 by myHelljumper

[HWasp]

12 minutes ago, myHelljumper said:

So the procedure goes as follows:

• 280 kt indicated should give you 14 nm for 10 000 ft. 280 is chosen because it's close to the best glide speed (~260 kt) and inside the engine relight domain. The slats should be forced in.
• Stabilize at 5000 ft to slow down to 230 kt minimum.
• Maintain 230 kt in final.

This procedure does not give fuel or configuration information but we can guess that in such emergency external stores would be jettisoned so the procedure must be possible with basically full fuel and no stores.

I'll record a track later.

 

Thanks!

Is this a straight in procedure, or does it start over the airfield similiar to the MiG-21 for example? This would be quite important, as turns increase descent rate quite a lot.

[myHelljumper]

14 minutes ago, HWasp said:

Thanks!

Is this a straight in procedure, or does it start over the airfield similiar to the MiG-21 for example? This would be quite important, as turns increase descent rate quite a lot.

It's a straight in approach, you should be at less than 30° from runway heading when stabilizing at 5000 ft and should not have more than 45° roll angle.

[HWasp]

3 minutes ago, myHelljumper said:

It's a straight in approach, you should be at less than 30° from runway heading when stabilizing at 5000 ft and should not have more than 45° roll angle.

Ok, thanks.

It works, tried it, but I think this test is a bit "low resulotion" regarding the +/- 0,5 or 0,7 Gs sustained at 340, we are looking for. This is a very good reality check for gross errors, but I don't think there is any.

I would call this whole discussion "performance tuning discussion", and for this matter a HUD video, like the one you posted, or things with similiar detail are suitable I think.

 

It's very unfortunate, that hud footage is a 2 seater with different engine. 

[myHelljumper]

Unfortunately, as no public data exists, we cannot fully demonstrate that our model is realistic.

This is the limitation when working on these kind of aircraft, but people have to put a little bit of faith on the dev teams otherwise a lot of aircraft would not be doable.

[Galinette]

17 minutes ago, HWasp said:

Ok, thanks.

It works, tried it, but I think this test is a bit "low resulotion" regarding the +/- 0,5 or 0,7 Gs sustained at 340, we are looking for. This is a very good reality check for gross errors, but I don't think there is any.

I would call this whole discussion "performance tuning discussion", and for this matter a HUD video, like the one you posted, or things with similiar detail are suitable I think.

 

It's very unfortunate, that hud footage is a 2 seater with different engine. 

It gives a very accurate value of the minimum required optimal lift/drag ratio. Then if you keep the exact same angle of attack, adjust the engine thrust carefully, and find the speed at which you can sustainably turn in these conditions, it gives a minimum point on the STR chart. We are basically at this point.

[HWasp]

13 hours ago, Kercheiz said:

It gives a very accurate value of the minimum required optimal lift/drag ratio. Then if you keep the exact same angle of attack, adjust the engine thrust carefully, and find the speed at which you can sustainably turn in these conditions, it gives a minimum point on the STR chart. We are basically at this point.

 

14 hours ago, myHelljumper said:

So the procedure goes as follows:

• 280 kt indicated should give you 14 nm for 10 000 ft. 280 is chosen because it's close to the best glide speed (~260 kt) and inside the engine relight domain. The slats should be forced in.
• Stabilize at 5000 ft to slow down to 230 kt minimum.
• Maintain 230 kt in final.

This procedure does not give fuel or configuration information but we can guess that in such emergency external stores would be jettisoned so the procedure must be possible with basically full fuel and no stores.

I'll record a track later.

 

 

I think I have found a problem here, testing the procedure:

At 5000 feet I made an intentional error, and slowed down below 170 kts in level flight instead of the 230 minimum.

Problem is, I still made it easily, actually had to drop the gear at 2000 feet.

Also the flare is not a problem at all starting from this lower speed.

 

230 kts on final is a very high approach speed, there must be a good reason to keep it there. If I can do the same procedure with such an error, something must be off a bit. 

I tested the glide ratios at speeds 240 - 160:

240 : 8,1  AoA 5,5

220: 7,4  AoA 7

200: 6,75  AoA 8

180: 6      AoA 10

160: 5,4  AoA 12

 

I'm sure the approx 8 L/D base given by this procedure must be ok, but I find it very strange, that plane could still have 5+ L/D at 160 kts where AoA is 12

 

I would be very interested to see, what would happen, if the drag curve would be steepened a bit to hit the 4,8G / 340 sustained according to the video (I think AoA around 12)

Please see track attached:

M2000_engine_out_proc_err_170_1122.trk

Edited November 6, 2022 by HWasp

[myHelljumper]

43 minutes ago, HWasp said:

 

 

I think I have found a problem here, testing the procedure:

At 5000 feet I made an intentional error, and slowed down below 170 kts in level flight instead of the 230 minimum.

Problem is, I still made it easily, actually had to drop the gear at 2000 feet.

Also the flare is not a problem at all starting from this lower speed.

 

230 kts on final is a very high approach speed, there must be a good reason to keep it there. If I can do the same procedure with such an error, something must be off a bit. 

I tested the glide ratios at speeds 240 - 160:

240 : 8,1  AoA 5,5

220: 7,4  AoA 7

200: 6,75  AoA 8

180: 6      AoA 10

160: 5,4  AoA 12

 

I'm sure the approx 8 L/D base given by this procedure must be ok, but I find it very strange, that plane could still have 5+ L/D at 160 kts where AoA is 12

 

I would be very interested to see, what would happen, if the drag curve would be steepened a bit to hit the 4,8G / 340 sustained according to the video (I think AoA around 12)

Please see track attached:

M2000_engine_out_proc_err_170_1122.trk 1.06 MB · 0 downloads

 

230 kt is chosen because it keeps the engine rotating at at least 10%, which gives enough hydraulic power for the control surfaces. I should add to the dead engine landing procedure that you should at 230 kt from 5000 ft you should be able to fly 4 nm to the runway.

Why would we change the FM to make it match with a data point that we know is incorrect (wrong airframe and engine) ?

The Mirage can really take some AoA without much drag increase thanks to the unstable design that reduces the elevon drag at AoA, the slats (not relevant in the dead engine landing case) and the strakes.

This this video where a 2000D with a malfunctioning engine keeps flying way past 14° AoA: 

 

[HWasp]

12 minutes ago, myHelljumper said:

230 kt is chosen because it keeps the engine rotating at at least 10%, which gives enough hydraulic power for the control surfaces. I should add to the dead engine landing procedure that you should at 230 kt from 5000 ft you should be able to fly 4 nm to the runway.

Why would we change the FM to make it match with a data point that we know is incorrect (wrong airframe and engine) ?

The Mirage can really take some AoA without much drag increase thanks to the unstable design that reduces the elevon drag at AoA, the slats (not relevant in the dead engine landing case) and the strakes.

This this video where a 2000D with a malfunctioning engine keeps flying way past 14° AoA: 

 

 

Yes, and also to stay reasonably close to the best glide speed and not end up with a whole lot of induced drag at low speed range of the drag curve.

 

Look, I can fly the whole thing between 170 and 180 kts easily. (And still have hydraulics in DCS, but this is a different subject then)

 

The video looks like a partial engine failure, someone in the description says it was a control unit malfunction, so it's not a complete loss off thrust. How is that relevant for glide ratio?

Here is the same slowing below 180 already at 10000

M2000_engine_out_proc_err_180_alltheway_1122.trk

[myHelljumper]

17 minutes ago, HWasp said:

 

Yes, and also to stay reasonably close to the best glide speed and not end up with a whole lot of induced drag at low speed range of the drag curve.

 

Look, I can fly the whole thing between 170 and 180 kts easily. (And still have hydraulics in DCS, but this is a different subject then)

 

The video looks like a partial engine failure, someone in the description says it was a control unit malfunction, so it's not a complete loss off thrust. How is that relevant for glide ratio?

Here is the same slowing below 180 already at 10000

M2000_engine_out_proc_err_180_alltheway_1122.trk 1.03 MB · 0 downloads

It's relevant that the Mirage does not suffer from a critical increase in drag from high AoA as the engine thrust was reduced enough to decelerate but the higher AoA did not increase the speed loss rate further. 

I know it's not hard data but in the previous FM where the STR was lower than it was now, holding  above 14° AoA back then with a healthy engine was already not really a confortable situation so the reduced drag at high AoA and thus increased STR makes sense here.

Hydraulics is on our todo list for improvements.

The procedure being doable at lower speed is not a sign of an issue, you should just get less glide range as it not the best glide speed.

[BIGNEWY]

Please ensure you all stay on topic here, off topic posts will be removed 

thank you

[HWasp]

15 minutes ago, myHelljumper said:

It's relevant that the Mirage does not suffer from a critical increase in drag from high AoA as the engine thrust was reduced enough to decelerate but the higher AoA did not increase the speed loss rate further. 

That is a very big claim, given there is no info there about actual thrust.

Given, there are that many unknowns, it would be still better to try and interpolate data from the B-version video, because at least weight and thrust differences are known, so with those accounted for it might be less wrong, than vids like this.

 

The previous FM might have had too much drag increase above 14-15 degrees AoA, certainly possible, but please keep in mind, I am talking about the 5-12 AoA range mainly.

I think the high AoA range is ok, since it was fixed, and increasing the rate of drag increase slightly between 5-14 does not have to affect that area seriously.

[myHelljumper]

11 minutes ago, HWasp said:

That is a very big claim, given there is no info there about actual thrust.

Given, there are that many unknowns, it would be still better to try and interpolate data from the B-version video, because at least weight and thrust differences are known, so with those accounted for it might be less wrong, than vids like this.

 

The previous FM might have had too much drag increase above 14-15 degrees AoA, certainly possible, but please keep in mind, I am talking about the 5-12 AoA range mainly.

I think the high AoA range is ok, since it was fixed, and increasing the rate of drag increase slightly between 5-14 does not have to affect that area seriously.

Using the B version video is not pertinent as we have even less information on the engine performance. But we can agree to disagree here.

I only used the crash video to demonstrate that there is drastic increase in drag with AoA but I agree that it's not that useful.

If you want to talk about the 5-12° AoA range, we can use the break procedure as a reference as the initial turn is mostly done in that range:

• The initial turn should be started at 1500 ft AGL, 350 kt.
• Angle of bank should be 60°, engine at idle and airbrakes out.
• The turn should be maintained until 200 kt then the AoB should be reduced to 40-45°.

Since this turn uses the airbrakes, its accuracy is dependent on the airbrakes effect being accurate, but IIRC we used a good reference for their efficiency.

You will see that when close to the maximum landing weight, the above procedure can be followed with around a 40° turn left to the down wind at 200 kt. That's inline with the info that we have.

[HWasp]

46 minutes ago, myHelljumper said:

I know it's not hard data but in the previous FM where the STR was lower than it was now, holding  above 14° AoA back then with a healthy engine was already not really a confortable situation so the reduced drag at high AoA and thus increased STR makes sense here.

 

 

I have on more point for the HUD tape video: The Jx=0,68 on take-off. If that matches exactly the value we need on take-off on this version, that means in the vid external conditions (lower temperature) compensate for the different engine. 

If we could agree, that because Jx=0,68, ---> temperature is considerably lower than 15C ---> thrust in those conditions does actually match our version, because of the matching acceleration, that would mean, we only have to account for the possible weight difference of the B version (I know there are aerodynamic differences, but given the total lack of usable data...)

 

[myHelljumper]

1 minute ago, HWasp said:

 

I have on more point for the HUD tape video: The Jx=0,68 on take-off. If that matches exactly the value we need on take-off on this version, that means in the vid external conditions (lower temperature) compensate for the different engine. 

If we could agree, that because Jx=0,68, ---> temperature is considerably lower than 15C ---> thrust in those conditions does actually match our version, because of the matching acceleration, that would mean, we only have to account for the possible weight difference of the B version (I know there are aerodynamic differences, but given the total lack of usable data...)

 

No, thrust is not static and changes with speed and altitude.

We know the M53-P2 thrust profile from publicly available information, we don't know about the M53-5 thrust profile.

[HWasp]

5 minutes ago, myHelljumper said:

No, thrust is not static and changes with speed and altitude.

We know the M53-P2 thrust profile from publicly available information, we don't know about the M53-5 thrust profile.

Ok, that is understandable, but given the comlete lack of data otherwise, it might still be better to assume, that it has similiar thrust profile, and use that, (I really wouldn't think, that a slightly improved version of the same, with the same intake, etc, would be that completely different...)

Again, I really can't see how the break procedure can help us with this +/-0,5-0,7G difference. Especially with the airbrakes involved. It works, of course, but my problem is with drag between 5 - 12-ish AoA clean. I can't test that with airbrakes out at all....