Soviet Testing of F-5E after Fall of Saigon

[razo+r]

1 hour ago, LowRider88 said:

From my perspective, I feel you are mixing it up.  Prior to us clarifying that not all the flap options in your diagram are feasibly available for the F-5 during combat or landing, you were implying max AoA would be higher with the flap UP setting.  That is why I ask you what would happen if you are already at max AoA with flaps down, and then retract the flaps at that point.  The point is with UP setting the max AoA is lower, based on the diagram from the manual and your diagram.

No. Do you know how to read the diagram I posted? If not, let me explain:

The horizontal axis is AoA, Angle of Attack. The vertical axis is CL, lift coefficient. So, the highest (vertical) point is not the max. AoA, it's the lift provided at a certain AoA.

You even have a few marks at the bottom, let's use them. I'll use the plain wing and flaps only curve for this example. Note, let me emphasize again that this is a generic diagram not related to the F-5, but depicting general behaviour. Actual behaviour varies depending on designs.

Example: 

You can clearly see on the diagram, the critical AoA for the wings with flaps deployed is 13 degrees. This is the point where you will get the most lift out of the wing. Any degree more and it will stall.

Now if you retract the flaps but keep 13 degrees of AoA, you will lose lift, as clearly visible on the curve, jumping from the with flaps curve straight down to the plain wing curve.

Looking at the plain wing curve and the 13 degrees, you can see that the lift provided at 13 degrees and more does not drop until you reach 15 degrees. This is the critical AoA for this specific plain wing. More AoA and it stalls.

If you now draw a line upwards from 15 degrees, you will note that it does not intersect the flap curve. Meaning, the wing with flaps does not provide lift anymore at 15 degrees, as you already passed the critical AoA.

Result: You can clearly see that the critical AoA increases if you retract flaps, as well as maximum lift decreasing for the plain wing.

And again: The diagram does NOT depict what high lift device setting is feasable during combat. It shows the general effect of that particular addition to a general airfoil in relation with AoA on the horizontal axis and CL in the vertical axis.

1 hour ago, LowRider88 said:

 So, no, in game retracting the flaps should not allow you to pull more in the F-5.  The combination of extending both the slot and flap together to any degree (I.e autoflaps) still provides more AoA and lift than with both retracted.  So greater pull snapshots with UP flaps is not possible.[...]

Why don't you just try it out yourself.

 

1 hour ago, LowRider88 said:

"But even that additional drag might simply be not enough to create as much drag as a Mig can, especially when it stalls and then becomes a flying brick with the wings almost perpendicular to the airflow."

Yes, that is exactly my point about the LERX.  You both keep focusing on the rate of speed loss as a comparison between more or less AoA on the same LERX enabled plane, while my original comment is with reference to the LERXs preventing the F-5 from comparable speed loss of something like a MiG-21 with no LERX, due to said drag.

Why don't you simply forget your nonesense comparsion which does not work anyway. My original reply in this regard was to correct you from thinking LERX help keeping speed (or reduce induced drag as you said) to trying to explain to you that they add drag and do not help keep speed.

Now, why does your comparsion not work? Easy. Completely different designs. It starts with different weights, engines, and goes over to different wing shapes, high lift devices or the lack of, all the way up to trying to match the performance of a completely different aircraft/flying outside the optimum performance regime of an aircraft.

1 hour ago, LowRider88 said:

No my understanding of LERX is not wrong.  It is your interpretation of my words which is wrong.  [...]

" The violent vortices they produce help to keep the airflow on the wings, and so lower induced drag"

I don't know man. The last part in your sentence seems pretty wrong to me. Even NASA would disagree here.

1 hour ago, LowRider88 said:

"But even that additional drag might simply be not enough to create as much drag as a Mig can, especially when it stalls and then becomes a flying brick with the wings almost perpendicular to the airflow."

You say without LERX there is less speed loss.  Well not if you tried to pull as much G as you could with LERX.  If you did, you would be the flying brick that the 21 would be.

Without LERX there is less speed loss since 1) You do not get the vortices (read: drag) from them and 2) you will not be able to pull as much AoA (read: more AoA -> More lift -> more induced drag).

And no, you would not fly just like a 21. They have completely different designs. Just because you leave away the LERX, you will not fly like a 21. Again, this comparsion is just nonesense.

1 hour ago, LowRider88 said:

I don't see why I can't compare a 21 as a plane with no LERX to the 5 as plane with LERX.  How else will I illustrate the type of speed lost I was referring to?  I have no pert data on an F-5 with no LERX.  Using the 21 is even better since it performs worse in a turn but has better wing loading.  The lack of comparative turn perf is mainly due to the lack of LERX.

In the end I was originally referring the overall speed loss during combat, while you chose to dissect the comment and drill deep into the technical aspect of something I was not referring to.

Let me make it more clear. What if you compare the F-18 with the MiG-19? (Hint, because of the LERX the 18 can pull way more AoA and thus generate way more drag than the 19)

Again, it's not just about LERX. The whole design of the wing including high lift devices, wing shape (especially aspect ratio), engine power, weight and other things all contribute to the turning capability.

[LowRider88]

9 hours ago, razo+r said:

No. Do you know how to read the diagram I posted? If not, let me explain:

The horizontal axis is AoA, Angle of Attack. The vertical axis is CL, lift coefficient. So, the highest (vertical) point is not the max. AoA, it's the lift provided at a certain AoA.

You even have a few marks at the bottom, let's use them. I'll use the plain wing and flaps only curve for this example. Note, let me emphasize again that this is a generic diagram not related to the F-5, but depicting general behaviour. Actual behaviour varies depending on designs.

Example: 

You can clearly see on the diagram, the critical AoA for the wings with flaps deployed is 13 degrees. This is the point where you will get the most lift out of the wing. Any degree more and it will stall.

Now if you retract the flaps but keep 13 degrees of AoA, you will lose lift, as clearly visible on the curve, jumping from the with flaps curve straight down to the plain wing curve.

Looking at the plain wing curve and the 13 degrees, you can see that the lift provided at 13 degrees and more does not drop until you reach 15 degrees. This is the critical AoA for this specific plain wing. More AoA and it stalls.

If you now draw a line upwards from 15 degrees, you will note that it does not intersect the flap curve. Meaning, the wing with flaps does not provide lift anymore at 15 degrees, as you already passed the critical AoA.

Result: You can clearly see that the critical AoA increases if you retract flaps, as well as maximum lift decreasing for the plain wing.

And again: The diagram does NOT depict what high lift device setting is feasable during combat. It shows the general effect of that particular addition to a general airfoil in relation with AoA on the horizontal axis and CL in the vertical axis.

Why don't you just try it out yourself.

 

Why don't you simply forget your nonesense comparsion which does not work anyway. My original reply in this regard was to correct you from thinking LERX help keeping speed (or reduce induced drag as you said) to trying to explain to you that they add drag and do not help keep speed.

Now, why does your comparsion not work? Easy. Completely different designs. It starts with different weights, engines, and goes over to different wing shapes, high lift devices or the lack of, all the way up to trying to match the performance of a completely different aircraft/flying outside the optimum performance regime of an aircraft.

" The violent vortices they produce help to keep the airflow on the wings, and so lower induced drag"

I don't know man. The last part in your sentence seems pretty wrong to me. Even NASA would disagree here.

Without LERX there is less speed loss since 1) You do not get the vortices (read: drag) from them and 2) you will not be able to pull as much AoA (read: more AoA -> More lift -> more induced drag).

And no, you would not fly just like a 21. They have completely different designs. Just because you leave away the LERX, you will not fly like a 21. Again, this comparsion is just nonesense.

Let me make it more clear. What if you compare the F-18 with the MiG-19? (Hint, because of the LERX the 18 can pull way more AoA and thus generate way more drag than the 19)

Again, it's not just about LERX. The whole design of the wing including high lift devices, wing shape (especially aspect ratio), engine power, weight and other things all contribute to the turning capability.

Yes, I can read your diagram.  Are you able to apply the manual's diagram to this one?

If you did, you would see that your diagram now only has two lines.  One for plain, and one for slot plus flaps.  If you are at max AoA for slot plus flaps, e.g. 20 degrees, what happens when you pull up flaps?  How do you draw the line down in your chart to the plain line?  As I said there are only two lines in you diagram with respect to the F-5.  So with plain, you will lose both lift and AoA, if you use UP in combat.  Where then is you jerk pull snap shot?

 

There is no nonsense about comparing the F-5E to the MiG-21 bis.  The article compares the same.  Just as the article says, the 5 wins because of the aerodynamics.  Main reason for this is the aerodynamics.

You are talking about induced drag, during the process of inducing it on one plane.

I was talking about relative induced drag between the two planes when they are pulled already to the same high G.

 

Again, as you said:

"But even that additional drag might simply be not enough to create as much drag as a Mig can, especially when it stalls and then becomes a flying brick with the wings almost perpendicular to the airflow."

Which one here has relatively less end result induced drag when they are doing the same G, and the other turns into the brick?  These are your own words.  You just misinterpreted mine.

 

"Now, why does your comparsion not work? Easy. Completely different designs. It starts with different weights, engines, and goes over to different wing shapes, high lift devices or the lack of, all the way up to trying to match the performance of a completely different aircraft/flying outside the optimum performance regime of an aircraft."

Again, the experts in the article didn't bother with your pedantic generalization here, and did the same comparison anyway, and learned the advantages of the F-5 lift devices which the 21 did not have, enough to put them into the MiG-29.

You don't want the comparison?  Then please present concrete data of how an F-5E flys without LERXs.  I have already said the comparison is reasonable, because the 21 has both a wing loading and thrust to weight ratio advantage.  And the Soviets also assume on paper the 21 would win for similar reasons, but it didn't in the end.  Both of these two variables take into account many of the variables you needlessly introduced above to complicate the issue, with the exception of the LERXs in question.  If you don't have empirical data for your argument, then unclench about the comparison.

 

""The violent vortices they produce help to keep the airflow on the wings, and so lower induced drag"

I don't know man. The last part in your sentence seems pretty wrong to me. Even NASA would disagree here."

You can insert the word relative before induced drag.

If you want to be anal about it, then go ahead and send NASA my comment.  Although I don't think they would care as much as you do about correcting it, especially when no one asked for it.

 

"Without LERX there is less speed loss since 1) You do not get the vortices (read: drag) from them and 2) you will not be able to pull as much AoA (read: more AoA -> More lift -> more induced drag)."

Yes, until you try to pull the same G as you could with the LERX, in which case you will stall and then have end result relative speed loss I was referring to, and as you referred to in your brick example.  Again you are stuck on a technicality for an incorrect interpretation of my words, which was not what I was referring to but one you fail to let go of.

 

"And no, you would not fly just like a 21. They have completely different designs. Just because you leave away the LERX, you will not fly like a 21. Again, this comparsion is just nonesense."

Again, since you have no proof otherwise, where is your evidence that your assumption is more correct than mine?  The Soviet Test pilots in the article found they flew the roughly same until they pulled to G limits, the same scenario I was referring to about pulling to G limits and comparing the relative speed loss.

You should read more books like Clashes and Fighter Combat where they make similar comparisons and approximations and are not stifled by your pedantic and dogmatic restrictions.

 

"Let me make it more clear. What if you compare the F-18 with the MiG-19? (Hint, because of the LERX the 18 can pull way more AoA and thus generate way more drag than the 19)"

What's your point?  You didn't clarify what the significance of this new comparison is.  And again you are adding new variables into the beaten dead horse of an irrelevant offshoot of a topic this has become, just to prove you are right.

 

You are just wasting my time by being needlessly detailed about an off tangent subject that was not part of my original request.

I have already lost interest in my original experiment from your nitpicking.

[razo+r]

@LowRider88At this point it's much easier if you just try it out yourself.

Take the F-5 and do a slow level flight with a config, check AoA and then change config and see what happens.

Same if you do a turn, enter it with a config you want, check AoA. When changing config, check the behaviour of the AoA.

From my testing, you will gain at least 1-2 degrees of AoA with flaps up compared to down. Not much, but it's an increase.

[LowRider88]

On 12/23/2021 at 11:37 AM, LowRider88 said:

Not that anyone may care at this point , but I did extend my mini experiment mentioned above.

Beyond timing myself for how long it took for me to defeat the Trained AI 21 with a 5, I setup a purely AI battle where both planes were Trained.  In this case the battle lasted way longer than the 4 minutes of the article.  I had to leave the 21 at Trained and set the 5's AI to Ace to achieve the same under 4 min time I got, and the article had.

Based on this I believe the F-5 AI FM is not optimized.  I raised a bug report over a year ago believing the F-5 AI does not utilize its flaps, and I think this experiment illustrates this.

I just updated to the latest version.  The new F-5E AI FM seems to be way off.  Flying against it with a MiG-19, and the Rookie F-5E is a fighting like an energy fighter, with 2 circle fights, and out climbing the 19 in a straight up vertical and stalling later than the 19, despite having piddly wings and engines.  The 19 at max dry thrust has a better Thrust to Weight ratio than the F-5E at full afterburner.

Why with every update we are getting even more UFO behaviour, rather than less?

In my quoted post above, according to the article the 5 should beat the 21 in under 4 mins.  This should be via a low slow turn fight, but in the quoted post's test, it always flies an energy fight.  So why is it do this with both the 19 and the 21 which both have superior T/W?

For the record, flying the 19 against the 21 both before and after my update doesn't not seem to have any change.  So it seem s the 5's FM just went UFO arcade on its own.

No point in doing any more experiements on questionable, moving target AI FMs, with no explanantion as to why they are changing for the worse.

 

[LowRider88]

Below are 2 videos I posted showing a comparison of the Ace AI FMs of the F-5E and the F/A-18C, against a player flown MiG-19P.

In both cases, afterburner was not used, and at most Max dry thrust was used.

The F-5E video shows the AI is able to meet every 1 or 2 circle fight with a head on pass, while the second video shows it is actually easier to get on the tail of the Hornet.

This should not be the case, as the MiG-19P has both better wingloading, and thrust/weight ratio, over the F-5E.

The F-5E is retaining too much speed in turns, recovering from dives better, and climbing better than both the F/A-18C and the MiG-19P.

These comparisons are even more extreme when the AIs are set to the lower Trained level, as the F-5E seems to have less turning ability and decides to turn less, opting for even greater climbs, while still retaining too much speed, with such tiny engines.

 

Edited January 12, 2022 by LowRider88

[Tiger-II]

On 11/10/2021 at 2:32 PM, DmitriKozlowsky said:

A combat pilot intimately familiar and combat experienced in F-5E, will comfortable take on and defeat a greenhorn in Mig-29SMT or SU-27.   An experienced combat pilot in Mig-29, will kill a USAF 2Lt. out of flight school and conversion training on F-22 or F-35, more times then he would loose.  A Marine or Navy WWII combat F-4U Corsair pilot in Korean thing, shot down a NorK or Chinese Mig-15. A guns kill by a radial prop from WWII, on 1st gen turbojet fighter.   A really rare, really talented Vietnamese Mig-21PF(?) 'Colonel Trang" or similar had kills on F-4s of USAF and almost killed Randy 'Duke' Cunningham and his WSO. They were outflown and outfought by this guy in his puny Mig-21 export (probably a Chinese clone of a Russian Mig-21 export), and they were in F-4B or C of the Navy and had Sparrows and Sidewinders, and could not get him, so they separated.  Then man in cockpit , often counts more then plane the cockpit is attached to. 

Israelis studied captured Syrian Mig-23. They thought that at high altitude and high speed, Mig-23 could have an energy advantage over then F-16A Block 10 of IAF. They were also impressed with radar integrated into HUD concept. Something Western Air Forces never quite got. Maybe they had too much on HUDs already.

Point is, you as pilot fight the aircraft you have, not the aircraft you wish you had.

A point many pilots don't understand!

As I say in my sig... "An average aircraft with a skilled pilot, will out-perform the superior aircraft with an average pilot."

Edited March 23, 2022 by Tiger-II