WINGSUIT FLYING – AERODYNAMICAL BASICS

[robibird 2]

WINGSUIT FLYING – AERODYNAMICAL BASICS

Does wingsuit fly or it is just an aerodynamic drag that lowers its vertical speed? Well, wingsuit really flies, since available area is not enough to produce such a low vertical speeds and flat flight path. But, the only force available to propel the wingsuit through air is gravity. What wingsuit tries to do is to use the gravity induced vertical free fall and turn it into as horizontal flight as possible. The same principle applies as for gliders, hang gliders and even square parachutes everybody is familiar with. Wingsuit flies because it IS an AIRFOIL, just like aircraft wing, square canopy or Space Shuttle (actually, by its basic flying form and flying characteristics wingsuit is more comparable to space shuttle then to any other flying object).

Wingsuit, like any airfoil, creates LIFT and DRAG. The better the ratio between lift and drag, the better flying body is. For a particular aerodynamic shape, this ratio between lift and drag varies with speed. There is a speed at which this ratio is the best, and this speed is usually 30 – 40 % higher than the stall speed (ask any glider pilot about minimum and best gliding speed, 90% of times the answer will be 55-65 km/h minimum speed and 80-90 km/h best gliding speed). Flying at the best gliding speed, the flying body will cover most distance for available height. Flying below or above that speed, the flying object will cover less distance for particular height. Every flying body has its minimum airspeed at which it will still generate enough lift to fly. Below that speed it looses lift and will stall (remember, square parachutes will also stall and lose lift. Forward speed in that case is close to zero, while vertical speed will more then double). The same goes for wingsuit. It requires speed to fly. But there is a question what is the best speed for the best glide in wingsuit. This is very complex question since wingsuit is not rigid airfoil. Every flyer flies differently, using slightly different arms, legs or body position. This means that every flyer is different airfoil. Add different pilot weight and size and different length of arms and legs and the issue gets even more complicated.

This is why it also very difficult to measure minimum speed for the wingsuit. But there is general rule for any flying body. Ratio between effective wing area and weight of the flying body is known as wing loading. Most of skydivers are familiar with that term in relation with their canopies. The higher the wing loading is, the canopy will fly faster, but will also have higher stall speed. Today, square canopies are operated with wing loading between 0,5 and 3,0 lbs per square foot. Hang gliders have wing loading around 1,2 and 1,5 lbs/sqft, and their minimum airspeed is around 35 km/h (22 mph). Cessna aircrafts have in general wing loading of 20 lbs/sqft, and their minimum airspeed is 80 – 90 km/h (50 – 55 mph). Space Shuttle, with its short span wings and extremely high wing load, lands at more then 350 km/h (220 mph!!!).

For average person size, wingsuit has wing area of 15 – 16 lbs/sqft, and the weight is 170 – 190 lbs. This gives us wing loading of 10,5 – 12,5 lbs/sqft, ten times higher then square canopy. Some basic math will tell us that for ten times bigger wing loading, the minimum airspeed will be roughly 3 times higher. This is consistent with measurements of wingsuit flights, where the best glide ratio was achieved at airspeeds of 130 km/h (75 mph). At that airspeed the vertical speed was 40 – 50 km/h, resulting in glide ratio between 2 and 2,5. You can go for lower vertical speed, but that will also result in significantly lower horizontal speed and poor glide ratio.

Regarding attempts of landing the wingsuit, much bigger wing area will be needed to generate more lift and reduce minimum airspeed. But human body has definite shape, which is not suited for flight at all, and we'll need at least few million years of evolution effort to change it to more appropriate shape for wingsuit flying. That means that wingsuit potential for more lift is limited by human inadequate shape and available strength. The only option for more lift will be some kind of rigid wings, but we already have these. They are called airplanes.

Also, if you are still thinking of landing the wingsuit, do one normal parachute jump, but when you open the canopy, try to position your body horizontally (can be done by hooking your feet around rear risers) and try to land small elliptical canopy in that position. After that painful experience, multiply pain and injuries by 9 (three times the speed = nine times the forces of impact = 9 times the consequences), and decide if you are willing to give it a try.

Robert Pecnik
[email protected]
www.phoenix-fly.com

[grega 0]

Quote

try to position your body horizontally (can be done by hooking your feet around rear risers) and try to land small elliptical canopy in that position.

Hmm sounds like another Pro Swooping Tour Freestyle move

Good point Robi! We're not birds (not yet) we don't have hollow bones, neither we weight as little as birds do. And as soon as we get little "wings" we want to land. Like he said, we need some million years of evolution to be able to land our bodies.

But anyway, wings main job is for flying not landing. So you all wingsuit flyers use suits for flying and have fun at it. for landing them, i'd wait for another few million years

Unless some super duper great awesome mega technology is invented earlier...

"George just lucky i guess!"

[redfox 0]

Hello Robi,

everyone who has flown one of your suits knows that it works this way and that you understand this very well - obviously this basics are not clear for everyone...

I never understand why some people think landing a wingsuit is the ultimate goal.

For me, the ultimate goal would be to go up to the air from the ground without help.
If than I have to use my parachute to land save, it doesn't matter!

An old teacher told me once for driving a car:
"If you think you stand at 50km/h, try to step out of it" - speed is good in air, but not on ground...

For me skyflying is "enjoy the feeling being a bird"!
You know that you have done it right if after a weekend of skyflying you come home and are afraid that your cat will catch you...

Cordially,

Herwig

[nicknitro71 0]

Good post Robi.

I hope you were kidding when it came to evolution

You did not mention flaring at all. It has been shown that WS can be flared after a dive to nearly zero MPH vertical speed. In theory if that flare is done at the right altitude the 0 MPH vertical speed can occur at ground level leaving you with just horizontal speed that we know it is not much of an enemy. Now we have to wait for somebody with little brains or big balls to try it out

Memento Audere Semper

903

[ryoder 1,384]

Quote

I never understand why some people think landing a wingsuit is the ultimate goal.

Because, (like me), they REALLY hate packing!

"There are only three things of value: younger women, faster airplanes, and bigger crocodiles" - Arthur Jones.

[ManBird 0]

Quote

Quote

try to position your body horizontally (can be done by hooking your feet around rear risers) and try to land small elliptical canopy in that position.

Hmm sounds like another Pro Swooping Tour Freestyle move

It's called the Batman. Clint Clawson has alreaded evolved this trick into the no-handed BlindBatMan. He used a 39 cell canopy. He had to do a slider down Utah McRollover to open the canopy safely. It was rad.

"¯"`-._.-¯) ManBird (¯-._.-´"¯"

Click

[CancerChris 0]

Hello, I live on drop zone in Fl. and have made over 535 birdman suit jumps. I have some ideas on flying the suit in general. Maybe we could compare notes sometime?