Tracking Suit question

I think this question is best asked here in the wingsuit forum, though perhaps basejumper.com is where I'll find the tracking experts.

I was wondering about my body angle down, relative to the horizon, in order to achieve what I think is my best glide ratio (still air) of 1.2:1, or 1.3:1 when using my PTS tracking suit.

If I assume for simplicity that my best glide ratio is 1:1, that would mean I am flying/tracking along a 45 degree angle flight path with respect to the ground/horizon.

If my body was pointed exactly along this 45 degree flight path, I would have a zero degree angle of attack. The angle of attack is the angle between my body (line from head to toe) and the relative airflow (opposite direction to the 45 degree flight path). I think that I should probably have a positive angle of attack to achieve this 45 degree flight path. Therefore, if I assume and angle of attack of 5 degrees, my body angle would be tilted up 5 degrees from the 45 degree angle down, or more simply, 40 degrees body angle down.

Realistically I think I can achieve 1.2:1 glide ratio, which approximates a glide angle of 40 degrees down from the horizon. If I assume a 5 degree angle of attack, then my body angle should be 35 degrees down from the horizon.

So, my question, does the above seem realistic? Those of you who have experienc in tracking suits, do you think you are in the 30-35 degree angle down when tracking for max glide performance.

I'm sure many will have suggestions for improving tracking performance, but I'm not asking that right now. I just want to know if the consensus is that a body angle of 30-35 degrees below the horizon seems about right.

Thanks for your time.

John

Okanagan_Jumper

I was wondering about my body angle down, relative to the horizon, in order to achieve what I think is my best glide ratio (still air) of 1.2:1, or 1.3:1 when using my PTS tracking suit.

As you wrote later, it's the angle of attack, not the angle in relation to horizon that makes you fly.

Okanagan_Jumper

If my body was pointed exactly along this 45 degree flight path, I would have a zero degree angle of attack.

Nope. In this situation (without any magical power pushing/pulling you) you'll not be flying 0 AoA. Just because your body is turned 45 degrees in respect to the horizon, doesn't mean it's flying in that exact direction
Zero AoA would be if you'd be flying head-down.

Don't focus on the numbers. It's good to have some mathematical knowledge but if you get too much fixation you'll become paranoid :) . (However if you do, you could read a bit more about AoA
However you are definitely right that you need that angle to fly with good glide ratio. Most people tend to fly way to flat (focusing on time and not speed), thus not having enough speed and lift for good glide ratio. (and actually stalling the suit)

The best advice is to either fly with others and see what angle works the best, or get a flysight which will give you even better feedback.

Also, for the sake of comparison, try always flying cross-wind. Many people track downwind and on windy days they achieve super good GR, but doesn't necessary mean that their skills have improved.

Okanagan_Jumper

If I assume for simplicity that my best glide ratio is 1:1, that would mean I am flying/tracking along a 45 degree angle flight path with respect to the ground/horizon.

If my body was pointed exactly along this 45 degree flight path

... you would present a smaller profile to the relative wind, pick up airspeed, potentially generate more lift and your glide ratio could increase and become higher than 1:1. It's in this zone, the speed zone, where tracking gets really interesting.

Okanagan_Jumper

Realistically I think I can achieve 1.2:1 glide ratio

Certainly possible and higher certainly feasible. One of my friends was doing 1.8:1 in his PTS recently but whether it was sustainable is another question. Also one body type can achieve things another can't.

Okanagan_Jumper

do you think you are in the 30-35 degree angle down when tracking for max glide performance.

Looking back on some footage of myself I'm surprised at how flat I look when I feel like I'm going steep and fast when I track. Pic attached.

More on angle of attack:
http://topgunbase.ws/angle-of-attack-for-dummies/

Angles relative to horizon:
https://www.youtube.com/watch?v=c_0K4jBp97E
https://www.youtube.com/watch?v=PkUxB_oIpvg

Hi guys. Thanks for the feedback. I think I could have done a better job of explaining myself, as I'll be pushing pack from the gate in just under 2 hours at the command of a 737NG. Ergo, I've got the theory of flight fundamentals in the bag . I was trying to dumb down the essentials of aerodynamics for those who haven't studied the subject.

I have two FlySights and I will be loaning one to a newbie tracking suit friend tomorrow. Last week when we flew together, he was flying much too slowly, and consequently his performance suffered. Yesterday I was thinking of how best to explain the need for a steeper angle in order to achieve a better glide ratio.

For a conventional general aviation airfoil, the angle of attack required to achieve the best L/D is along the order of 5 degrees. I *think* I'm okay in assuming that it will be similar for tracking in a tracking suit. Therefore, if I am capable (and I am) of a sustained, no wind, glide ratio (GR) of 1.2:1, then my body angle (zero wind) will be 40 degrees (flight path for 1.2 GR) - 5 degrees (angle of attack) = 35 degrees.

I have an app on my iPhone that measures inclination. Disregarding accelerometer errors (for my needs I think that's reasonable), I will measure my body angle down by strapping the phone to my chest tomorrow and listen to the audio readout of my angle to see if it's close to the 35 degrees predicted.

I realize I won't be tracking on a regular basis, and maybe never again, with an iPhone strapped to my chest, but I just want to see if the 35 degrees is accurate. It seems to me that in the videos of trackers they look flatter than 35 degrees down.

Standby for data!

Cheers,

John

Best trackers can sustain 1.6-1.8 glide ratio in PTS from what I gather. Hard to max out your suit without reference points, I think the only way to see how good your tracking is actually base jumping same exit point over and over again. But then again, base tracking is more about how you can get most horizontal distance by playing with your AOA through the alltitude window you get, gaining speed, creating lift, bleeding off speed to fly as far as possible. Skydiving will not get you very far

I think optimal AoA for glide in trackingsuit will be much higher than 5 degree. Trackingsuit is nowhere near to the optimal airfoil.
I have a outside wideo of me tracking from Brento in classic PhoenixFly trackingsuit with GR around 1.4:
https://youtu.be/P_slFCiOHkc
It's not the best part to judge the optimal pitch angle, because it is during a small flare. So to keep the speed and GR constant the position will be more head low for sure, but definitely not 35 degrees down from horizontal.

Okanagan_Jumper

I was trying to dumb down the essentials of aerodynamics for those who haven't studied the subject.

I don't have a background in aerodynamics and for me it's about how I feel when I'm in the air. It's fascinating and useful thinking about the equations and data after the fact but in the moment for me it's just about just trying to be like a missile, not a glider.

I kind of figured 35 degrees was too steep. Hopefully I’ll satusfy my curiousity tomorrow. And that’s what it is, curiousity. Luckily the sport is big enough for jumpers who jump for whatever reason and with whatever goals and there’s no need to justify why you jump, or how you jump.

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Okanagan_Jumper

there’s no need to justify why you jump, or how you jump.

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Unless you are tracking slow.

Okanagan_Jumper

For a conventional general aviation airfoil, the angle of attack required to achieve the best L/D is along the order of 5 degrees. I *think* I'm okay in assuming that it will be similar for tracking in a tracking suit. Therefore, if I am capable (and I am) of a sustained, no wind, glide ratio (GR) of 1.2:1, then my body angle (zero wind) will be 40 degrees (flight path for 1.2 GR) - 5 degrees (angle of attack) = 35 degrees.

As stated above, tracking suit is definitely not a good airfoil, not even close to it (for starters it's not rigid)
Also most air-crafts in general aviation have some kind of engine which provides thrust. This can in no way be applied to tracking.

Also I'm quite puzzled by your logic. You got some number (5 degrees) which in no way relates to tracking suit flying, and subtracted it from another one (40 degrees), which in no way relates to the first one, to obtain some result. What is the reasoning behind this?

With this thinking after flying at 35 degrees, could you subtract another 5 degrees to get even better?? (rhetorical question
Also, if you talk about such small values as 5 degrees, how are you planning to exactly measure it?

Hello, skow. The 5 degrees angle of attack was definitely in correct as you surmised. The 40 degrees was based on my glide/flight path angle of 45 degrees down (based on a 1:1 glide ratio), minus the incorrect hypothesis of an angle of attack of 5 degrees.

I managed to used my iphone strapped to my stomach yesterday to record inclined angles in the range of 20-21 degrees down yesterday. Admittedly there was a bit of movement of the phone, and I wasn't able to record the readouts (once per second). Achieved glide ratio at peak sustainable (before translating airspeed into lift) was in the 1.0:1 to 1.2:1 range. If the data was valid, and that's a big if, then the angle of attack would be in the range of 43 degrees (angle down) - 21 degrees (body angle) = 22 degrees angle of attack.

I'll set up an Arduino with an accelerometer, along with an SD card to record results, in the nect few months. I assume tracking suit manufacturers can use wind tunnel data or some other means of gathering experimental data. I'm just doing it because I find this type of stuff interesting. It doesn't need an end goal...

I was flying a PTS and my friend was in the original Sumo. He flew much faster this weekend so I ended up concentrating on trying to keep up with him. The flysight shows me edging him a race to the lake water's edge at the DZ, but he did achieve higher groundspeeds and glide ratios at times.

Cheers

John

Have a read of Yuri's essays in the other recent threads, they may interest you.

Okanagan_Jumper

If the data was valid, and that's a big if, then the angle of attack would be in the range of 43 degrees (angle down) - 21 degrees (body angle) = 22 degrees angle of attack.

I'm guessing you're measuring this based on resulting GR and your body angle? i.e. 43 degrees is ~ 1:1 GR and 21 degrees is your body angle (with respect to horizon)?

If so, there's a huge variable here, which will mess everything up - i.e. wind.
If you have the exact same body position, your resulting GR will differ based on direction you're flying (i.e. down or upwind). If the wind is strong, it'll differ quite a lot

I realize this thread is old, but thought I would chime in anyhow. It seems like taking FlySight data without accounting for wind is *almost* worthless. With strong uppers you could easily see a swing of around +/- .4 G/R. Quite possible OP was already adjusting for wind, but it seems like a must know for anyone trying to hone in their tracking suit performance and I haven't really seen much on this topic in the forums.

 

Link on how to adjust for wind with the FlySight viewer: 

 

 

You can still train, for example if you're going for glide ratio you just adjust to get the highest number you can, like usual. Of course then the data isn't easy to compare to other jumps in other conditions, but I think it's always worth training with a Flysight, wind or not (and I've never tried adjusting for wind - but I should give it a go).

Oh, certainly. The live feedback will still give you information as to whether a change in body position you make is better or worse. Looking at the data post-jump will also give you a sense of what worked well and what didn't. It's just that the specific numbers themselves won't be reliable, especially if your pattern involves one or two turns. And comparing those numbers across different days / wind conditions would hold even less value.

Yes absolutely.

However if you're looking at tracking in the BASE environment and training for that, that's a whole different ballgame, the data gets really interesting there. I found reviewing the data from my BASE jumps really helpful. That being said, one of the best and most hardcore trackers I've known never trained with a Flysight at all.