Forum: F-16 Design & Construction

Hi everyone, here?s my question about the F-16 wing loading. I got to www.codeonemagazine.com and had the following information fom the editor (an aerodynamicist working on F-16 wind tunnel models) : wing loading, based on current aircraft gross weight / wing area is not sufficient to accurately account for actual lift being generated. Actually, the F-16 LERX generates as much as about 35 % of total lift when the aircraft flies in the 5 degrees to 28 degrees AoA range. Although the F-16 cannot take advantage of high AoA flight regimes (being restricted by its FBW system), it indeed has a lower wing loading when flying in that AoA range, except I think when leading-edge slats are actuated at low speed (since lift increases but drag also).

Therefore, as an example: take a clean F-16C-30 (GE engine) : unarmed, full internal fuel, average fuel density being 0,785.

Wing loading is about 384 kg/m2 (if anybody remembers how to go from kg/m2 to lbs/sq.ft, tell me). Such a figure is broadly comparable to the MiG-23 ML Flogger G, anyway more than the 365 kg/m2 of the lightest F-16A-15 version. To make the difference with this powerful aircraft, the combination of high T/W (1,16), Combat Edge suit, and canted seat alone wouldn?t be sufficient in a 8-9 G sustained turn when faced to the MiG 0,87 T/W ratio. Therefore there must be a wing loading advantage somewhere for the F-16 to be this great continuous 9G turning machine that we all admire. So we get a wing loading of 270 kg/m2 when adding the LERX area.

Would anybody know at what speeds do the strakes vortices actually improve overall lift ?
I doubt such a 28° AoA be reachable at supersonic speeds... Question

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Good questions, Snap

Cylon and STBY will have more current data, but here's the poop from the initial design (and it hasn't changed much in 25 years).

- The leading edge flaps (LEF) are not 'slats'. In fact, they were viewed as a 'variable camber' feature by the early design team. They simply move up and down according to a mach/angle of attacks schedule. Above M 1.0, they are fixed. Look at the T-bird crash cockpit video on that thread and you can see them go all the way to 2 degrees up when the pilot unloads and rolls. Then they go all the way down as he pulls toward the earth.

- The LEF system greatly reduces buffet and increases directional stability, especially above 15 deg AoA. They also 'smooth' out the CL versus AoA curve, so there's no conventional 'stall' point that you can get to.

- The 'strakes', or leading edge extensions prove a strong vortex. This results in increased directional stability as well as the 30% increase in lift you mentioned. They don't help much below 15 deg AoA, but by 25 deg AoA they have the max effect. You can't simply add area of the strakes to compute wing loading. Finally, the strakes don't do much when supersonic, if anything except add drag. and I can't remember seeing above 10 or 15 deg AoA when supersonic, as we hit the 9-gee limit, then started to slow down.

- We all laughed about the 30 deg seat, as it's best use is turning at 9 g's and 15 deg AoA. Above that, the gee command is reduced until you can't command more than 1 gee at 25 deg AoA. With FLCS set to Cat 3, it's even less gee command. Still in all, 45 deg from your flight path reduces the blood flow from your brain to your toes (and other places) enough to help.

- "Although the F-16 cannot take advantage of high AoA flight regimes (being restricted by its FBW system)" is a misunderstanding by many. Trust me, 20 degrees AoA is a high AoA regime. Remember that if you want to fly around at ridiculaous AoA's, you won't be doing it very long. The drag quickly overcomes the available thrust and soon you are a 'strafe target' for the bandit. Instantaneous AoA above 25-30 degrees has it's place, but you better not have another bandit closeby. So the F-16 was designed more as a sustained high-gee plane than the existing fighters of that era.

- The sustained turn rate of the F-16 was and maybe still is the highest around. It's one reason it beat out the Northrop YF-18 in the fly-off. Even with the limiters, we could lay on the old 'bat turn' in front of folks and next thing you know we were 90 degrees to one side and gaining nose position by the second.

More from Cylon and STBY, I'm sure

out,

Snapshot, you want to know how to go from kg/m2 to lbs/sq.ft. So, a little help:
One kilogramme is 2.20 pounds and a square meter is about 10.76 square feet. So you have to mulitply kg/m2 by 2.20 and divide by 10.76 to get lbs/sq.ft Wink

. Hence 384 kg/m2 equals to about 78.5 lbs/sq.ft .

It's all in the units: kg/(m^2) x (m^2)/(ft^2) x lb/kg = lb/(ft^2)

I'm sure this just got lost in the translation, but: the editor of Code One magazine is a good friend of mine and, while he's one helluva nice guy, he's no aerodynamicist... Wink

He is however a very good journalist and photographer. Smile

Wow, you have a great forum here, bunch of connected people, and here I am just a punk who's still in high school Embarassed

f100pw229 wrote:

wow, you have a great forum here, bunch of connected people, and here I am just a punk who's still in high school Embarassed

Ya gotta start somewhere! Look how Gums turned out! Very Happy

(just kiddin' Wink

)

f100pw229 wrote:

Quote:

wow, you have a great forum here, bunch of connected people, and here I am just a punk who's still in high school

Well, don' be ashamed, I'm still in high school too......teaching Laughing

.

1 kg/m^2 is [Link pending approval] lb/ft^2.
1 lb/ft^2 is [Link pending approval] kg/m^2

I suppose that's 0,204817 and 4,8824 for you [Link pending approval] I don't think I'll ever get use to that

For more unit conversions check this site. I've found it very useful for the last couple of years.

[url][Link pending approval][/url]

well for wing loading you have to add all the lifting surfaces on the 16, and that includes the stabs as well!!

Mike Spick puts the wing loading figure on the latest 50/52 F-16s at 921lb/sq ft, as compared to 721 lb /sqft of the f-16A. I assume this would be with a combat load rather then a full weapons load.

However does any one if you guys know the loading on the f-2 and what benefits it got from changing the sweep ?

Forum: F-16 Design & Construction

F-16 wing loading debate