F-16 vs F-15 WVR

Agreed, it will never be a fair fight but how would the F-16 match up against the ... ?
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by eleanordriver » 02 Jul 2009, 07:16

For the F-15 A/C I have read that the wing loading is lower than the F-16 under most circumstances. I have also read that the F-15 has a higher thrust-to-weight ratio under most circumstances. The body and control surfaces of an F-15 are larger, allowing airflow to be diverted for a higher turn rate. The overall surface of the bottom of the F-15 should allow it to fly at slower speeds, and the higher thrust to-weight ratio should allow a lower loss of altitude during a turn-battle in a dog-fight.

How is it that I have read about and seen videos of F-16s winning dog fights (in turn battles) against F-15s?

Shouldn't the F-15 be able to out-turn the F-16 if similarly loaded?

Is this based on the pilot's skill and ability to handle G forces?


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by johnwill » 02 Jul 2009, 17:16

Here are the factors you mention:
1. F-15 has lower wing loading.
2. F-15 has higher thrust to weight.
3. F-15 has larger body and control surfaces.

Here's why the F-16 can overcome those factors:

1. Nominal wing loading is not a direct indicator of manueverability. In most WVR encounters, the F-16 horizontal tail is strongly loaded up, providing additional lift. The angle of attack will be lower as a result. The F-15 tail is down loaded, meaning the wing and fuselage must provide additional lift. The angle of attack will be higher as a result.

2. Thrust to weight is not a good indicator of energy loss during turning fights. (Thrust - drag) to weight is a better indicator. F-16 lower AoA results in less drag, while the F-15 higher AoA results in more drag. So the F-16 has better (thrust - drag) to weight than the F-15 and maintains higher energy.

3. F-15 larger body and control surfaces compared to weight are no better than the F-16. F-16 fuselage lift is very high, as much as 40% of total lift.

Two other items are important to F-15 vs. F-16 WVR capability, g limit and leading edge flaps. F-16 g limit is significantly higher than F-15 and is automatically limited. That means the F-16 pilot can pull right to the limit without fear of breakiing anything, while the F-15 pilot must monitor his g to prevent over g (and AoA). The F-16 LEF provides optimum lift for all A0A, while the F-15 has no such device.

The F-15 is a wonderful fighter, but in WVR fights, the F-16 can handle it (in most circumstances).


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by eleanordriver » 02 Jul 2009, 22:43

I see, I thought that the F-15 was G limited for the pilot's sake. No wonder the F-16 is internationally recognized as such a great dog-fighter.
Thanks for your response.
I hope these advantages have been considered in the design of the F-35, increasing its WVR capabilities as well. Obviously they can't add LEFs to a stealth fighter (easily), but I would like to see what it can do first hand someday (the F-16 too).


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by johnwill » 02 Jul 2009, 23:42

eleanordriver wrote:I hope these advantages have been considered in the design of the F-35, increasing its WVR capabilities as well. Obviously they can't add LEFs to a stealth fighter (easily), but I would like to see what it can do first hand someday (the F-16 too).


All fighters designed since the F-16 appeared have tried to emulate those characteristics in one way or another. You can bet the farm that LM designed the F-35 to be at least as good as the F-16 in WVR combat and a whole lot better in BVR.

The F-22 and F-35 both have LEF.

Concerning F-15 g limit, it, like most other fighters, does exactly as it was designed. Designers all over the world are able to design to meet the reqirements of the customer.


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by sprstdlyscottsmn » 02 Jul 2009, 23:56

what are the g- limits of an F-15? 9 G at half fuel only?
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by johnwill » 03 Jul 2009, 04:21

F-15 was designed as 7.33g at half fuel (I believe) in the early 70s. Could be different now.


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by bazdriver » 03 Jul 2009, 17:03

F-15A non OWS : 7.33g at full air-to-air weight (OWS= Overload warning sytem)

F-15A and F-15C OWS equiped: 9g at full air-to-air weight

F-15 operationnal AOA envelope: 45 deg full air-to-air load wirhout external tanks.

F-16 operationnal AOA envelope: 28 deg air-to-air config.

Check SETP documents about High AOA and OOCF behaviour of F-16 and F-15


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by eleanordriver » 06 Jul 2009, 14:00

"Check SETP documents about High AOA and OOCF behaviour of F-16 and F-15 "

Where?


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by outlaw162 » 06 Jul 2009, 14:22

http://208.77.90.112/whoglue/setpPaper/ ... ?view=1158

You may have to pay for it.

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(not to be confused with those child psychology sites)


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by eleanordriver » 06 Jul 2009, 21:25

ok, thanks outlaw.


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by Pilotasso » 06 Jul 2009, 22:00

Word is that Both planes are balanced at low altitudes with the 16 having a slight edge, however the F-15 beats the 16 hands down at higher altitudes.


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by Kryptid » 07 Jul 2009, 23:36

I know that originally the F-15 had positive static stability. Have any more recent models been given negative static stability by, for example, moving the center gravity and modifying the flight control systems?
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by Des » 24 Jul 2009, 03:49

If they are both carrying the helmet mounted cueing AIM-9X's then i suppose it will be whoever gets the first look.


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by F16guy » 24 Jul 2009, 07:23

Pilotasso,

I'll have to say I don't agree. Maybe you need to define High altitude, (40+). Even then I've got to say the Viper holds its own in a dogfight up high. Having started maneuvering that high WVR the jets have what appears to be similar rates and turn radii, the Vipers' thrust(air-air configured) and low energy loss rate usually mean that both jets end up descending in a neutral fashion (if the set up was from high aspect) until the lower attitudes. I've never had an Eagle stay high and use the altitude against me or go where I could not, the multiple pilots I've fought in that jet always seemed to have as much difficulty turning an advantage up high as I had. That's my words anyway. Oh and for the Viper lovers on this forum, the Eagle is an outstanding jet with some awesome avionics with respect to the Viper. I'm glad that jet is on our side.

Des is right, First look and shot will usually result in the first kill, however, in todays' combat everything could go right for the blue pilot and he might still end up under a chute just like the guy he shot, since having the first shot does not mean it is exclusive and the other guy won't get a shot off in return before impact.


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by bazdriver » 24 Dec 2009, 14:30

Johnwill, before getting into some comments, I will just say that I fully appreciate all your comments about the F-16. But I think you miss some knowledge about F-15 aerodynamics.


1. Nominal wing loading is not a direct indicator of manueverability. In most WVR encounters, the F-16 horizontal tail is strongly loaded up, providing additional lift. The angle of attack will be lower as a result. The F-15 tail is down loaded, meaning the wing and fuselage must provide additional lift. The angle of attack will be higher as a result.


As you know, the F-16 is only unstable below Mach 0.8/15 °AOA(whichever came first), above this values it is neutrally stable. The F-15 is statically stable at low speed. At high subsonic speed the position and shape of its intake ramps have a destabilizing effect and unload the tail by 10%. At supersonic speed their unloading effect is 30%. It's why without CAS the F-15 is very limited. The wing is optimized for maneuvering under high g, NOT for top speed(secret of which is on variable intakes ramps/engine optimization).Without getting into to much details an F-15 with CFT at an overall weight of 42000lbs needs only 12°AOA to load up to 9g at Mach 0.72.

2. Thrust to weight is not a good indicator of energy loss during turning fights. (Thrust - drag) to weight is a better indicator. F-16 lower AoA results in less drag, while the F-15 higher AoA results in more drag. So the F-16 has better (thrust - drag) to weight than the F-15 and maintains higher energy.

I mean you talk about Ps(specific excess thrust). Throughout the flight envelope the F-15 has higher values (particulary above Mach 1.5),largely compensating for the slight incrase in drag.

3. F-15 larger body and control surfaces compared to weight are no better than the F-16. F-16 fuselage lift is very high, as much as 40% of total lift.


Upper body lift of the F-15 is no less impressive. This, combined with the awesome power control of its tail surfaces( both vertical and horizontal) saved an Israeli F-15 years ago in a well known accident. Not sure an F-16 in similar circumstances would have survived.

Two other items are important to F-15 vs. F-16 WVR capability, g limit and leading edge flaps. F-16 g limit is significantly higher than F-15 and is automatically limited. That means the F-16 pilot can pull right to the limit without fear of breakiing anything, while the F-15 pilot must monitor his g to prevent over g (and AoA). The F-16 LEF provides optimum lift for all A0A, while the F-15 has no such device.


G limit advantage of the F-16 is only in a very very small part of the flight enveope.(though it can be decisive in some case). Full authority FCS has its advantages and drawbacks. It will take much more time and training to an F-15 driver to master the full flight envelope, no question about this, but it can give him the edge in some( but rare) conditions. You don'nt need to monitor the g or AOA, you just need to listen. OWS will provide you with cues(two tones beep rate) to not overstress your airplane. Now you can take F-15 flight manual from first page to last page, AOA limitations are provided only for specific cases:
- external tanks

- out of limits weight lateral asymmetry

- CAS-off operation or default(any axis)

- above 60°/s yaw rate

About LEF I would just say that F-15 wing is optimized for maneuvering( to the detriment of cruise drag). They are few available data about L/D concerning the two aircraft, but the only available show that F-16 has much higher L/D at low AOA/g combination, the F-15 wing closing the gap as you get to high AOA/g values. The F-15's wing is a masterpiece of engineering. Sukhoi and Tsagi tried to emulate it on the first T-10 prototype but never succeeded, reverting to LEF design(and successful)


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