F-16 vs F-35 aerodynamics by number

Agreed, it will never be a fair fight but how would the F-16 match up against the ... ?
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oab

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Unread post22 Apr 2013, 14:59

As a result of a bet between some guys...

By proven or theoretically approved / supported numbers only:

Of the F-16 vs F-35, which has:
1. The lowest drag coefficient overall (CDo) "naked body" at designed cruise speed?
2. The lowest CDo with designed combat setup at designed cruise speed?
3. The highest L/Dmax with normal setup?
4. The highest L/Dmax with designed combat setup?

Probably not very relevant questions for a fighter pilot, as these numbers don't mean much, as there is far more other variables to take into account such as power plant, maneuverability, etc., but we are only asking for the above data.

I sent the question directly to Lockheed Martin first, but was advised to ask the question here :wink: Should I also post the above questions in the F-35 forum as well?

Thanks in advance!
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fiskerwad

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Unread post22 Apr 2013, 15:33

Those who stand to gain from winning the bet should provide their own facts. Is there anything in the pot for those doing the work (research)?
fisk
Mipple?
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johnwill

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Unread post23 Apr 2013, 23:12

Comparison of drag coefficients of two different airplanes is pointless, since airplane Cd are calculated with wing area (extended to the fuselage centerline), not frontal cross section area. To be meaningful, you'd have to multiply each Cd by its reference wing area, then divide by its frontal area. Here is the equation for Cd:

Cd = Drag/ q S

q is dynamic pressure, S is reference wing area.

You'll have to find reference wing area and frontal cross section areas yourself.
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oab

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Unread post24 Apr 2013, 10:46

@Fiskerwad: A bottle of wine is at stake, so the winner would have to invite you over for a glass of wine from that bottle :lol:

@Johnwill: I perfectly agree with you when it comes to that just looking at pure drag data, without considering lift is somewhat pointless, as a purely drag optimized object will never fly unless you add some lift (causing drag). However, the posted questions are the numbers that we are making the bet over, as "someone" in this bet tried to have their way with that the most "streamlined" in terms of lowest air resistance would win, but didn't want to discuss lift as a function of that question.
I agree that for any flying object, the real term for aerodynamic performance in level flight is lift over drag, and thus that is a separate question.

Finding the numbers our self has been tried before, but there is some stubborn souls amongst the three of us not accepting data found by one any of the others. It should come preferably from Lockheed Martin or from someone with the knowledge within this forum, as Lockheed Martin pointed us to you for this question.

Thanks in advance :)
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johnwill

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Unread post24 Apr 2013, 19:33

If what you want is the "lowest air resistance", I guarantee you the F-16 is lower without knowing any numbers because it is so much smaller. However, if what you want is "most streamlined", you need to compare drag coefficients because of the size difference. If you made a half scale F-16 it would have the same drag coefficient as a full scale (except for small Reynolds effect). But like I said, you cannot compare drag coefficients from different airplanes. Lift has nothing to with it, as the basic Cd(0) is for zero lift angle of attack.

Let's look at what a drag coefficient is. It is the factor of actual drag divided by (dynamic pressure x frontal area). But airplane makers do not use frontal area to calculate Cd, they use reference wing area. Maybe a numeric example will make more sense.

Here are some made up numbers for two airplanes-

A. Drag = 3000 lb....... Frontal area = 30 ft^2...... Wing area (S) = 300 ft^2

B. Drag = 5000 lb...... Frontal area = 40 ft^2...... Wing area (S)= 500 ft^2

q = 600 lb/ft^2

True Cd = Drag / q x Frontal area

A Cd = .167
B Cd = .208


Published (aero industry) Cd = Drag / q x wing area.

A Cd = .0167
B Cd = .0167

So what does this prove? The published Cd is the same for both A and B. But the real Cd is quite different. So the published Cd cannot be used to compare with another airplane.
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oab

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Unread post25 Apr 2013, 15:05

Thanks. To ask the question differently; is there published data on the F-16 and F-35 on CD, CL, and L/Dmax naked and with combat setup? If not, what is the folks here on the forum qualified estimate on the two fighters?
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wrightwing

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Unread post26 Apr 2013, 17:09

The more important question, is what are the F-16's drag coefficients, when configured with 2 2,000lb JDAMs, targeting pods, jamming pods, external fuel tanks, and 2 AIM-120s. There's no point in comparing a clean F-16 to an F-35.
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tigerblack

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Unread post26 Apr 2013, 19:19

wrightwing wrote: There's no point in comparing a clean F-16 to an F-35.


Nope, the Viper would eat the F-35 alive ;) (i hope)


A clean F110 powerd viper is fearly both light on its feet and agile.

donno bout the F-35 but Im almost wiling to bet the Viper would give it a run for its' money.

Actually I know next to nothing about the F-35.. yet
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wrightwing

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Unread post27 Apr 2013, 16:09

tigerblack wrote:
wrightwing wrote: There's no point in comparing a clean F-16 to an F-35.


Nope, the Viper would eat the F-35 alive ;) (i hope)


A clean F110 powerd viper is fearly both light on its feet and agile.

donno bout the F-35 but Im almost wiling to bet the Viper would give it a run for its' money.

Actually I know next to nothing about the F-35.. yet


I think you missed my point. It's irrelevent how the F-16 flies clean. In combat, it's not clean, and the F-35 would eat it alive, as long as we're using those terms of reference.
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wrightwing

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Unread post27 Apr 2013, 16:10

tigerblack wrote:
wrightwing wrote: There's no point in comparing a clean F-16 to an F-35.


Nope, the Viper would eat the F-35 alive ;) (i hope)


A clean F110 powerd viper is fearly both light on its feet and agile.

donno bout the F-35 but Im almost wiling to bet the Viper would give it a run for its' money.

Actually I know next to nothing about the F-35.. yet


I think you missed my point. It's irrelevent how the F-16 flies clean. In combat, it's not clean, and the F-35 would eat it alive, as long as we're using those terms of reference.

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