F-16 wing surface - why 300sq ft ?

agilefalcon16 · by **agilefalcon16** » 04 Feb 2005, 21:35

I read in a book that the F-16's wing area was originaly going to be 280 square feet, but the legendary pilot John Boyd pushed to increase the wing area to 320 square feet. The Air Force finaly settled on 300 square feet to prevent the Viper from outmaneuvering the Eagle.

How much more maneuverable would the F-16 have been if its wing area was 320 square feet instead of 300 square feet?

Also, I'm pretty sure that even though the Viper's wing area is only at 300 square feet, it can still outmaneuver the Eagle.

LinkF16SimDude · by **LinkF16SimDude** » 04 Feb 2005, 22:27

agilefalcon16 wrote:Also, I'm pretty sure that even though the Viper's wing area is only at 300 square feet, it can still outmaneuver the Eagle.

In the right hands?...yes....absotively.

I kinda don't think it was an Eagle vs. Viper performance thing. Perhaps G-loading was one of many issues. How much extra G capability would 320 sq. ft. give ya compared to 300 or 280?

agilefalcon16 · by **agilefalcon16** » 04 Feb 2005, 23:22

I to first thought that the reason why the USAF choose the Viper to have a wing area of 300 sq. ft. instead of 320 sq. ft. would have been because of
the higher G-loading issue, however in the book Eye of the Viper, it said that USAF choose 300 sq. ft. because they did not to question their need for the Eagle, which is more expensive to buy and maintain than the Viper.

Stefaan · by **Stefaan** » 05 Feb 2005, 16:52

This topic was split off from the <a href="http://www.f-16.net/f-16_forum_viewtopic-t-2163.html">Super maneuverable F-16 - Theoretical question</a> topic.

agilefalcon, when going off-topic, please start a new topic :-)

Stefaan

agilefalcon16 · by **agilefalcon16** » 05 Feb 2005, 23:47

Thanks Stefaan, I sort of have a bad habit on going off topic, but now I will make sure that I will stay on topic.

Also, does anyone else have an reason why the the USAF made the F-16 have an area of 300 sq. ft. However, even if the F-16 did have a wing area of 320 sq. ft., would have very much impact on its maneuverability?

vinnie · by **vinnie** » 05 Feb 2005, 23:55

Could have been to keep the cost down, remember the USAF doesn't have a blank checkbook. Read up on the development of older jets like the F-105, lots of things were tried to keep the unit price down.

Roscoe · by **Roscoe** » 06 Feb 2005, 05:00

Man, you guys overthink everything. G-forces come from lift. Lift bends wings. More wing means more stresses means beefier (ie heavier) wings means means...

The aero on this airplane was all optimized to work together. You just don't change the wing area on a whim to suck up to somebody. 300 was picked becasue that was what made the most sense. Agile Falcon had more wing area and the resulting design was never built (by us that is) because of structural issues.

Pumpkin · by **Pumpkin** » 06 Feb 2005, 06:42

There are some nice articles here that might shed some light.

Origin of General Dynamics F-16 Fighting Falcon
Structure of F-16 Fighting Falcon

cheers,

VYPRFXR · by **VYPRFXR** » 26 Feb 2005, 03:05

Boyd originally had gd design the wing to be at 280 sq. feet. Thats what his E M theory called for. Then the air force went and added weight to the airframe in various ways. In order to get back to the performance before the weight gain, his theory showed him he need to add the extra 40 sq feet to the wing surface. The air force said no. They wanted to stay at 280. Boyd wanted 320 so eventually they settled on 300.

Read it for yourself in "<ahref="aviation_books_book3117.html">Boyd : The Fighter Pilot Who Changed the Art of War</a>" pages 307-308.

allenperos · by **allenperos** » 26 Feb 2005, 07:35

OK, agilefalcon16 - this is not a classified issue so I will address it as best as I can.

The larger the wing surface area, the more wing-loading per sq/ft. You can carry more ordinance, fuel, even accomodate more avionics and even another cockpit. As the Falcon burns fuel, drops ordinance, it becomes lighter for the cruise back home. This is where you are capable of engaging an enemy, you can out turn and maneuver in general, so it was a comprimise of the weight of a 320 sq/ft wing and a 280 sq/ft wing, so Gen Dynamics or Lockheed, I don't know which decided on a happy medium with the 300 sq/ft wing.

I would give you equations, but I can't do that. Suggested reading: Aerodynamics for Naval Aviators, you can order it at Sporty's pilot shop. I hope I have answered your question.

By the way, it really doesn't matter if you are in an Eagle or Falcon, a 9G turn is the same radius of action in either airplane, this means there is no trade-off between aircraft weight and wing surface area, the basic lift equation resultant will be equal for both jets.

Roscoe · by **Roscoe** » 26 Feb 2005, 13:57

Not quite. The larger the wing the LOWER the wing loading. Wing loading is defined as weight (or more accurately lift but...) per wing area (w/s). SO if you increase the wing size you lower the loading.

That can be good and bad. Big wings have to be either flexible (sailplanes, Buff) or really strong because even though they are less loaded they tend to me longer and have larger bending moments. Low wing loadings also tend to really ride rougher and have more violent gust response.

As for maneuverability...that's a tough word to pin down. Do you mean instantaneous turn rate, sustained turn rate, roll rates...it all varies. Instantaneous turn rate is a function of available G's and stall speed. Below corner velocity, your ability to turn “quickly” is limited by lefties. Above corner velocity, instantaneous turn rate is structurally limited. (Corner velocity is defined as where these two limiting curves meet). Sustained turn rate on the other hand is a function of thrust and drag. Yank on the stick and the plane turns but it generates a lot of drag doing so, so the speed will drop until drag equals thrust. This is why sustained turn rate is less than instantaneous turn rate.

A big wing may hurt this more than help. Yes, you can pull more g’s because you have more lift. But if the pilot g-tolerance is the limiting factor (and since the Viper can already go to 9g, I would say that is the case here), then the bigger wing gets “out voted”. A larger wing will also affect the drag. More skin drag will be produced but since you can pull the same g’s with less AOA (because more lifties are available) then less profile drag is created. Induced drag is a function of lift so that would stay the same.

Structurally, you may get more hardpoints and more fuel, but more structure in a 9g jet, meaning more weight, which requires more lift, which cancels out the reduced profile drag I discussed above.

Bottom line, bigger wing does not automatically equate to more maneuverability.

agilefalcon16 · by **agilefalcon16** » 26 Feb 2005, 15:01

Thanks guys, I'm understanding this better now.

So all in all, is 300sq. ft. pretty much the perfect wing area for the Viper?

hansundfranz · by **hansundfranz** » 26 Feb 2005, 19:27

There is no perfect wing area.

Designing is always balancingdifferent needs and reaching a good compromise.

In general big wings are bad for acceleration, top speed but good for instantaineous turn rate.

squirl · by **squirl** » 27 Feb 2005, 08:27

By the way, it really doesn't matter if you are in an Eagle or Falcon, a 9G turn is the same radius of action in either airplane, this means there is no trade-off between aircraft weight and wing surface area, the basic lift equation resultant will be equal for both jets.

Not quite. A 9G turn is a 9G turn, yes. However, the wing loading makes a huge difference in how a plane is able to maintain these conditions. For example, we have two 40,000 pound planes. One has a wing loading of 80 lbs./sq. ft., the other has a wing loading of 160 lbs./sq. ft. In a 9-G turn, both planes' centrifugal force will increase ninefold. In order to maintain a 9-G turn, the lift (centripetal force) must also increase ninefold. To do this, the 160 lbs./sq. ft. wing-loaded plane must increase its angle of attack a certain amount, but the 80 lbs./sq. ft. wing-loaded plane doesn't have to increase its angle of attack as much as the first plane has to. Because the second plane can make a 9-G turn at a lower angle of attack, it can increase it's G-forces (rate of turn), to turn inside the first plane. In other words, at the same angle of attack, the second plane is producing more lift proportional to G-forces than the first plane is.

Wing loading is one indicator of turning ability, but others (such as wing geometry, camber, aspect ratio, etc.) all have influence as well.

Also keep in mind that if lift acts perpendicular to the chord line then a higher angle of attack will creater a higher backwards vector and create a resultant which works against forward motion.

Roscoe thinks along this tack as well.

allenperos · by **allenperos** » 27 Feb 2005, 19:14

Got you squirl, I stand corrected, I knew this but wasn't sure how to explain it to agilefalcon, thank you for the clarification, allenperos.