Sep 24, 2012, 7:49 PM
Post #1 of 9
Wind Corrected Wingsuit Flight Tracks
How about a thread on wind corrected wingsuit flight data.
Perhaps we can share info instead of what the usual threads degrade into. Anyone dare to actually post data on each post instead of the all too common BS talk and attacks?
Here's one from today, working on speed. I noticed the plane was not falling away as usual so I gave chase from 10 sec to about 30 sec then was working on body position. Looks like it would have been better to keep chasing the plane!
At about 25 seconds in on the flight I started to have a very small porpoise like action. Reminded me of over correcting, as a student, while learning to fly a hang glider. Very controlled and dampened but a minor pilot induced oscillation I suspect (can't really see it in the data well). I'll push for more time at that speed range on the next flights.
Aprox 150 mph +/- ground speed, corrected for winds - any more in it?
When I fly the same suit at roughly a 45 degree angle, 1:1 glide ratio, the fall rate increases, the 3D speed increases and the ground speed decreases compared to the attached run. This suit seems to fly best in the 1.3 to 1.5 glide ratio range for speed - lift vector(?). Anyone found similar results where forward speed decreases as you approach a 1:1 glide?
How are you correcting for wind? I thought a Flysight couldn't get that sort of data. Honest question - I haven't played around with GPSs enough to understand what you're doing here (though I do have some ideas on how to correct for wind).
How are you correcting for wind? I thought a Flysight couldn't get that sort of data.
The most common way to correct for wind is just to measure wind speed/direction on the climb to altitude (the pilot can estimate this), and then subtract that from the recorded data. It's not perfect--the wind can obviously vary with altitude--but it's better than nothing.
I've been giving some thought to a method for estimating the wind given GPS data from the climb to altitude... I think it should be possible to calculate wind speed and direction accurately given a GPS track with the following characteristics:
Good satellite visibility through the "competition" window (2000 m AGL to 3000 m AGL for PPC). This probably means the GPS is placed at the front of the plane. I doubt the limited view out a side window will do the trick.
Pilot flies as near as possible to constant airspeed through the competition window. The airspeed doesn't need to be known (it can also be calculated), but it needs to be constant.
Pilot flies through a wide range of azimuths within the competition window--ideally, at least one full 360 degree turn.
The idea is do a calculation similar to what is done visually with a rate-one turn, but with a lot more flexibility in terms of flight path etc. The main question, in my mind, is if it's really worth the extra trouble. A good pilot can tell you quite accurately the speed and direction of the wind. Do we need a more accurate measurement?
One place a system like this might help is with verifying records... At the moment, we can trade GPS tracks, but wind corrections are dependent on what the pilot estimates. With a solid method of estimating winds from a second GPS track, there would be a bit more objective data to work with.
Any thoughts? Snow's on the ground here, and I don't think I'll be able to get to the DZ to gather test data for a while. If someone out there is interested in gathering data following the above guidelines, I'd love to see what information we can extract from it. FlySight data would be ideal, since the 3D velocity is also stored in the log file.
Step 2) If using Paralog, check the box on the right side of the screen for "Wind Correction" and make entries in the popup window for winds. You can see it on the attachements in my posts. If not using Paralog, you need to build a spreadhseet with formulas to calculate the wind component based on the winds and your heading/track.
-------------------------------------------------------- Here's an example (winds are given as the first two numbers are the wind 'From' direction and the second two numbers are knots, +/- number is temperature):
(Extracted from FBUS31 KWNO 070202) FD1US1 DATA BASED ON 070000Z VALID 070600Z FOR USE 0200-0900Z. TEMPS NEG ABV 24000
So for ACY above ACY 2011 2416+02 2620+00(Atlantic City NJ, USA) the winds at 3000' are from 200 degrees (From the South South West) at 11 Knots (times 1.15 for MPH), at 6000' winds from 240 degrees (south west) at 16 kts and the temp is +02 degrees, 9000' is wind from 260 at 20 kts temp is zero degrees out and 12000' 270 (west) at 24 kts, temp is a brisk minus 6 degrees (so I won't be jumping there anytime soon!). CRW is interesting in this group of data, you can have a 30 knot (34+ mph tailwind through the comp window). If you fly at 150 mph avg, you would have a 185 mph groundspeed downwind.
What's the wind speed for 9k to 12k' for CLE above? Think taking winds out of gps data makes sense yet for performance comparisons?
*****Details / Extra long answer and more details******** Alternately, use weather balloon data and computer models for winds (convert knots to mph if using Paralog, direction is 'From' i.e. 16 knots/18.4 mph from 303 degrees ar 9268 ft in the example below). Do a search on Skew-T charts if you want more info on this data it is more detailed and time consuming - here's an example from a prior flight. It's done in millibars (mb), a pressure reading, so altitude/ft numbers are different than above:
Alt (ft) Pressure(mb) DD Dir Spd(kts) ---Temp F C --- DewPt C
91 1009.0 A 290 4 79.3 26.3 14.8 164 1007.0 A 292 4 77.7 25.4 14.7 308 1002.0 A 293 4 77.0 25.0 14.5 374 1000.0 A 293 4 76.6 24.8 14.4 531 994.0 A 294 5 75.7 24.3 14.3 826 984.0 A 296 5 74.1 23.4 14.0 1272 969.0 A 297 5 71.8 22.1 13.7 1725 953.0 A 300 6 69.3 20.7 13.3 2181 938.0 A 304 6 66.9 19.4 12.9 2591 925.0 A 308 6 64.8 18.2 12.5 2644 923.0 A 308 6 64.4 18.0 12.4 3113 908.0 A 311 6 62.1 16.7 11.9 3589 892.0 A 313 6 59.5 15.3 11.5 4068 877.0 A 314 6 57.0 13.9 10.9 4553 862.0 A 317 7 54.9 12.7 9.1 4944 850.0 A 316 7 53.4 11.9 4.9 5045 846.0 A 316 7 53.1 11.7 3.8 5544 831.0 A 307 9 51.4 10.8 1.4 6053 816.0 A 292 9 49.8 9.9 0.7 6564 801.0 A 290 9 48.4 9.1 0.1 7089 785.0 A 289 10 46.8 8.2 0.0 7621 770.0 A 292 11 45.1 7.3 -0.1 8159 755.0 A 295 11 43.5 6.4 -0.8 8710 739.0 A 299 13 42.3 5.7 -1.2 9268 724.0 A 303 16 40.6 4.8 -1.4 9849 709.0 A 302 18 39.4 4.1 -1.3 10190 700.0 A 295 17 37.9 3.3 -1.5 11578 664.0 A 268 12 32.2 0.1 -2.4 12237 647.0 A 234 14 32.0 0.0 -3.9 13011 629.0 A 227 17 31.3 -0.4 -4.6 14888 585.0 A 241 19 24.3 -4.3 -5.8
You can cross check your wind forecast information against prog charts and local weather patterns to see if the general conditions match up and if they match up across time. You will start to recognize good setups i.e. in isobar lines for certain conditions, consistency of wind patterns etc as you gain experience - or also when heavy winds are coming with compressed iso lines.
***Important*** Next item: For wingsuiting, since we tend to sit near the front of the plane close to the pilot, look at the onboard GPS (or your own) and cross reference the GPS ground speed readout, airspeed and mag heading (or directional gyro). When cross referencing these three in the plane, you can tell if the winds being experienced at points on the climb match the forecast winds. Most onboard gps's can do this automatically, talk to the pilot for more info. If forecasts to in air data match fairly closely, go ahead and use them, if not ignore it all for that flight/day.
After some flights, over time, you will see that your metrics repeat fairly closely. Sometimes I get repeatability (loosely stated) within about 3 mph of certain events in a flight such as peak speed or best glide with glide ratio and ground speed numbers matching closely on several flights. Going into all the detail with fine granular winds, cross checking the aircraft gps/airspeed/direction etc is good for testing prototypes and getting very detailed data while working on goals or changes in a suit. Most of the time the basics are good enough for general use.
A much more fun way to do all this is to just jump from a balloon, turn your gps on before takeoff and on short climbs to altitude, the winds can be fairly accurate that you just took on the ride up (to be subtracted out from your flight down).
"What if the WS flight was done cross-wind, and the measurements were able to factor in wind direction? That way wind speed wouldn't matter." For ground based reference: No matter what you do, the ever present wind affects you. No matter what you do...
Go here: http://www.csgnetwork.com/e6bcalc.html Scroll down and click on the "Course, Ground Speed, And Wind Correction Angle" calculator Punch the following in: Wind Speed: 30 Wind Direction: 360 True Airspeed: 100 Heading: 270
If you hold a 270 heading your course (ground track actually flown) is 253 degrees.
Result: Ground speed 104 (not 100)
What's it worth? In your drawn example, 4% (or the perception that you are achieving 4% better performance when in reality, not). If you could actually improve a suit by 4% and race at competition level this past year, you would have won $20,000 in China - the difference between 1st and 3rd or 4th in most races is a fraction of one percent.
If you fly one day in the above conditions and the next with only a 12 kt wind. The result is a ground speed of 101. "so what?" you might ask - but now, you came in last place in the race... How about a 40 kts tail wind on a pilot that runs 150 airspeed? 190 ground speed, fly the next day in no wind and you are a slug.
Blasting across the ground at 190 would be fun though!
So why do this - to see an accurate picture of performance and to be able to compare and most importantly, improve! It makes it possible to actually understand if a suit is faster or glides better with real information instead of hearsay or much guessing. You can also change a suit and see if it made a difference or if you are flying better instead of it being a wind change.
(This post was edited by decwa on Dec 7, 2012, 9:00 AM)