Budget Data Mining

[ManBird 0]

Unless you've got a GPS unit and a way to record data, you probably don't know much about your wingsuit flights other than your fall rate and the amount of time you spent in the air -- if you aren't exceeding 119 seconds. Getting gadgets and software will always give you the most accurate data about your flights, but it can be a real financial burden. However, you can still collect some pretty accurate data using nothing but a ProTrack and a little math. Here's how to track different aspects of your flight on a budget.



FREEFALL (f)

This is the other piece of fairly accurate information that your ProTrack provides. Just subtract your deployment altitude from your exit altitude to get your total freefall.

a - b = f

a = exit altitude
b = deployment altitude
f = freefall



FALL RATE (r)

This is one of the two pieces of data that you can accurately track with a ProTrack. Your overall average will be the most important type of the four rates you can get with a ProTrack. If you are getting fatigued in the second half of your flight, you may want to use your first half's average to monitor progress, but you'll want to refer to your overall average for other calculations. Even if you break 119 seconds of freefall, your overall average will still be accurate.

Fall rates should be measured using TAS (true airspeed) and the ProTrack should be worn in a place that gets constant, clean air, such as your front pants pocket or ankle. Wearing a ProTrack on your head will give you inaccurate results.

( f / s ) / c = r

c = converter: 1.4667 (mph to fps), 0.2778 (kph to mps)
r = fall rate



DELAY (s)

This is accurate if your delay is under 119 seconds. If it is over 119 seconds, you can calculate your delay based on your fall rate and freefall.


f / ( r * c ) = s

s = seconds in freefall



DISTANCE (d)

This one can be tricky, but if you get to know the terrain well and/or have a GPS-equipped aircraft, then you get a good idea of just how far you traveled. The most surefire way is to plan a distance and coordinate exiting from that distance with your pilot. Going for longer distances will often leave you in the aircraft long enough to be able to fly straight back to the drop zone without flight line issues.

Most GPS units in aircraft uses nautical miles. A nautical mile is 1.1508 miles and a mile is 0.8688 nautical miles. If you want to travel three miles, you must exit when the aircraft is 2.6 nautical miles from the drop zone.

You can only very accurately track the distance between your exit and the location on the drop zone where the GPS is set to 0nm. If you go over that point, you can still calculate your glide ratio and adjust the exit point accordingly.

Look at aerial photos and maps of your drop. Study them with a key that indicates how long a mile is on the map. Plan routes, learn their distances, and follow the plan. If you do not cover the length of the route, remember where you deployed, go back to your maps, and find out how far you went. If you go beyond your route, do the same. If you cannot exit where planned, adjust the route accordingly. If you are a quarter mile further back than desired, then put your target back a quarter mile further than planned. This method is crude and the accuracy is questionable, but it will give you information to monitor your progress, understand your flight, give you an idea of what your glide ratio is, and understand the effects of the relative wind on your flight.

e - p = d

e = distance from drop zone at exit
p = distance from drop zone at opening
d = distance traveled



GLIDE (g)

Glide ratio is simply your distance divided by your freefall. If you know that you traveled 24,000 feet, and your freefall was 10,000 feet, then your glide ratio is 2.4:1. This can be difficult to assess if you do not know the distance of your entire dive. If you hit your distance target early, check your altitude, and only use that piece of data. If you exit at 14,000 feet and travel 15,000 feet horizontally by the time you reach 8,000 feet, then your glide ratio is 2.5:1.

d / f = g

g = glide ratio



ANGLE OF DESCENT (m)

You may find out what your glide angle was by dividing 180 by Pi and multiplying that value by the tangent of your freefall divided by the square root of the combined squares of your freefall and distance. You'll probably need a calculator on this one.

( 180 / pi ) * tangent (f / (square root ( d ^ 2 + f ^ 2 ) ) = m

m = angle of descent


INDICATED AIRSPEED (i)

You may find your indicated airspeed by multiplying your glide by your fall rate. If you've found that you had a glide ratio of 2.4:1 and an average fall rate of 48 mph, then your forward speed was 115.2 mph.

g * f = i

i = indicated airspeed



RELATIVE WINDSPEED (w)

The effect of windspeed on your forward speed will vary depending on the angle of the wind direction relative to your heading. You can usually get windspeeds at different altitudes from various weather reporting sources, or simply take the difference between the aircraft's indicated airspeed and airspeed and apply it to your own flight. Wind direction averages are applicable. If you spent 1/2 of your flight with the wind right behind you, 1/4 of the flight with the wind at a 45 degrees angle, and the last quarter in a crosswind, your average wind direction, 123.75 degrees, is applicable to your entire flight. Use the appropriate formula to calculate the relative windspeed:

If q is greater than 0 degrees and less than or equal to 90 degrees:
0 - ( u / 90 ) * q = w

If q is greater than 90 degrees and less than or equal to 180 degrees:
u - ( u / 90 ) * ( q - 90 ) = w

If q is greater than 180 degrees and less than or equal to 270 degrees:
u - ( u / 90 ) * ( q - 180 ) = w

If q is greater than 270 degrees and less than or equal to 360 degrees:
0 - ( u / 90 ) * ( 360 - q ) = w

q = wind direction in degrees relative to heading
u = windspeed in knots
w = relative windspeed in knots



AIRSPEED (l)

Windspeeds are usually measured in knots. Convert the relative windspeed to the appropriate measurement system and subtract it from your indicated airspeed to get your actual airspeed.

i - w * k = l

k = converter: 1.1507 (knots to mph), 1.8516 (knots to kph)
l = airspeed



VELOCITY

Your total velocity is the square root of the combined squares of your indicated airspeed and fall rate. If you are traveling 90 mph forwards and your fall rate is 45 mph, then your velocity would be 100.623 mph.

square root ( i ^ 2 + r ^ 2 ) = v

v = velocity

"¯"`-._.-¯) ManBird (¯-._.-´"¯"

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[SkymonkeyONE 4]

The way we here track distance travelled is to exit at a predetermined distance from the center of the dropzone; this measured by the GPS in the Otter. Once we open, we look straight down and note our position over the terrain below us. We then go over to our overhead picture and figure out how short or long we were in comparison to the middle of the dropzone. It helps that most guys here are military and we have a shitload of military MGRS maps to make absolute calculations if we so desire.

Chuck

[ManBird 0]

Exactly. You got it, monkey. That's how we do it, as well. Even if we pass our distance target (the drop zone), we can still just remember where we opened and figure out how far we got from the exit point.

It's definitely a good think to pay attention to, as you get to know what your forward speed and glide ratio is as well as fall rate. The same way you can hear and feel your fall rate after consistently checking your data and matching it your memory, so that in the air you know that you're doing "about 42 down", you can also start assessing forward speed and glide ratio on the fly. This will allow to make quick calculations in flight for all sorts of purposes... flying to a canopy, a student or flock that sunk on you, a pylon (if we get this crap going), a far off distance target (or outs if you realize the target is too far), maintaining a certain angle (for fixed object or cloud swooping), etc.

This is also a good way to completely rid yourself of any friends or association with the rest of the world.

"¯"`-._.-¯) ManBird (¯-._.-´"¯"

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