Angle of Attack

[base754 0]

When flying a wing suit what part of your body actually controls your angle of attack. If your flying flat and want to go into a steep angle of attack what would you do to accomplish this. For max glide ratio, I was told I need to fly steep, but not sure if my head controls this, the wings, or something else……….I have 200 jumps on a prodigy, and just received my phantom, but 90% of my flights are solo.

[donkeyboy 0]

I flew a Prodigy and am now on a Phantom.
For me, I control the AOA with the leg wing using my stomach muscles to raise or lower it. My head position on the horizon let's me know where I'm at.

If I'm flying flat my legwing is almost all the way stretched and I'm really pushing down on it. Head is level with the horizon.

For distance (steep) legs in a bit, letting the air push the legwing up a little, still controlling it, head below the horizon.

[yuri_base 1]

You probably meant pitch angle, not angle of attack. You do not directly control AoA, but it is rather the "indirect" variable which depends on both your pitch angle and your glide angle. AoA is the angle the relative wind makes with [some reference line of] your body, and is simply glide angle G minus pitch angle P. For example, if you're 10 degrees headlow (P=10) and you're gliding at an angle G=45 degrees (L/D=1), your AoA=35 degrees. If you're the same 10 degrees headlow, but you're gliding much more efficiently (G=22 degrees, L/D=2.5), your AoA is 12 degrees.

For given pitch angle and body position, there could be different stable sustained flight modes (see wingsuit hysteresis). That's why you sometimes max out and yet barely move forward - because you did not arrive at efficient value of AoA by controlling the pitch in sync with the changing glide, and "got stuck".

If the balance is off (for example, you're able to achieve very good lift from your armwings, and it tips you up), then you cannot achieve high L/D because the equilibrium AoA is off. This is an example how achieving better aerodynamics without paying attention to this interdependence of pitch, glide, and AoA, can hurt the performance. In this case, rebalancing is needed - for example, either by adding trailing edge extensions, or by using weights. (using weight is an easy way to see the effects of balance and finding out what you need to change) Trying to achieve right balance by relaxing legs, arms, bringing knees down, dearching more, etc. does not necessarily improve L/D because of this interdependence.

Phantom has a very good armwing (solid inflation, smooth leading edge, easy-to-tension and not prone to flapping trailing edge, small and efficient inlets) which is easy to make produce a lot of lift, but the legwing lacks a bit of power, so Phantom is prone to put you in a bit head-high pitch angle. Managing weight distribution (e.g. 4lbs camera on helmet and sneakers vs. no helmet, heavy 4-5lbs boots) is important, as well is history, - or else you can get stuck at 1:1 glide ratio.

To summarize, the most important thing, in my opinion, is the constant visualization of AoA (by feeling the relative wind hitting your face, and by observing your glide and pitch angles and subtracting them) during your flight, awareness of balance, and managing the history of your flight to avoid hysteresis.

Yuri

Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

[KrisFlyZ 0]

Angle control(pitch) comes from the core(torso).

Kris

[ROK 0]

Quote

Managing weight distribution (e.g. 4lbs camera on helmet and sneakers vs. no helmet, heavy 4-5lbs boots) is important, as well is history, - or else you can get stuck at 1:1 glide ratio.

This is interesting...

I'm 5'9", 215lbs out the door.

I'm built pretty solidly. My center of gravity is close to the center of my body.

I have a difficult time with forward speed in my Phantom. I tend to be "floaty". When I put my camera on, my speed seems to increase a bit, as well as my flight time (about 9 seconds).

So if I were to move my center of gravity closer to my head, in theory my glide ratio should improve?

Or if I increased the size of my leg wing, the same should occur?

Am I correct?

[yuri_base 1]

Possibly. From your description it sounds like a misbalance you cannot compensate by changing your body position, in this case rebalancing by extending the leg wing might help.

Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio