GPS under canopy

[nigel99 474]

I have a wrist mounted GPS (Garmin Foretrex 301) and I want to play around with ground speed under canopy.

First of all I realise it is a distraction and needs to be recognised as such. When I jump it, I will do a solo H&P at altitude so traffic won't be a problem.

One thought that I have had is that I could wear it under my jumpsuit, reducing the snag potential and distraction and simply grab the data retrospectively. I'll probably do this first regardless.

I know people are using GPS with wingsuits but there isn't much on GPS and canopy flight.

Experienced jumper - someone who has made mistakes more often than I have and lived.

[theonlyski 8]

There are some days I wish my N3 was IFR equipped.

GPS would be cool to check your ground speed and whatnot, but I couldn't imagine using it more than once in a while. Wingsuiters like to get lost so they need a way back!

"I may be a dirty pirate hooker...but I'm not about to go stand on the corner." iluvtofly
DPH -7, TDS 578, Muff 5153, SCR 14890
I'm an asshole, and I approve this message

[nigel99 474]

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There are some days I wish my N3 was IFR equipped.

GPS would be cool to check your ground speed and whatnot, but I couldn't imagine using it more than once in a while. Wingsuiters like to get lost so they need a way back!

I am only intending using it every now and again not a regular thing.

Next toy on the agenda is an orange flashing beacon and fog horn for when I am jumping in cloud

Edited to add picture showing size and speed display.

Experienced jumper - someone who has made mistakes more often than I have and lived.

[davelepka 4]

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Edited to add picture showing size and speed display

Looks compact, and easy to read. Regardless, make sure you limit this to solo jumps with no other canopies in the sky.

Ground speed info, for canopies, is generally just for shits and giggles. You can't really control your speed that much, you're not trying to time an arrival at a waypioint, and you're not trying to manage fuel consumption, all the things an aircraft pilot would use the info for.

The catch is to remember that an aircraft pilot in flight is generally not in the direct vicinity of other aircraft (unlike a canopy) and when it is, it's in radio contact with the tower or the other aircraft themsleves. Times when they're using the GPS for IFR flight, they're definitaly in contact with ATC, as are all other aircraft in the sky.

Keeping your eye up and scanning for traffic is (literally) one million times more important than knowing your ground speed under canopy. The problem with your GPS being so compact and easy to read is that it's tempting to wear and read it more often. Keep in your jmpsuit or on the ground on anything but solo jumps with no other jumpers exiting on that pass.

[nigel99 474]

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Edited to add picture showing size and speed display

Looks compact, and easy to read. Regardless, make sure you limit this to solo jumps with no other canopies in the sky.

Ground speed info, for canopies, is generally just for shits and giggles. You can't really control your speed that much, you're not trying to time an arrival at a waypioint, and you're not trying to manage fuel consumption, all the things an aircraft pilot would use the info for.

The catch is to remember that an aircraft pilot in flight is generally not in the direct vicinity of other aircraft (unlike a canopy) and when it is, it's in radio contact with the tower or the other aircraft themsleves. Times when they're using the GPS for IFR flight, they're definitaly in contact with ATC, as are all other aircraft in the sky.

Keeping your eye up and scanning for traffic is (literally) one million times more important than knowing your ground speed under canopy. The problem with your GPS being so compact and easy to read is that it's tempting to wear and read it more often. Keep in your jmpsuit or on the ground on anything but solo jumps with no other jumpers exiting on that pass.

Thanks Dave. I agree on the solo jumping and scanning for traffic being a much higher priority.

[theonlyski 8]

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Next toy on the agenda is an orange flashing beacon and fog horn for when I am jumping in cloud

Little early in the morning, but I believe small aircraft pilots are encouraged to turn off their strobes while flying in clouds because they can cause vertigo.


http://flighttraining.aopa.org/students/crosscountry/skills/night.html:

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Sparkles illuminated by your strobes indicate precipitation such as rain or snow showers. Remember that landing lights and strobes can cause vertigo when flying in clouds and precipitation, so don't hesitate to turn them off.

BTW, don't expect an aircraft to hear a fog horn, gotta love those noise canceling headsets, wind noise and big ole spinny thing on the front of the plane!

"I may be a dirty pirate hooker...but I'm not about to go stand on the corner." iluvtofly
DPH -7, TDS 578, Muff 5153, SCR 14890
I'm an asshole, and I approve this message

[LouDiamond 1]

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I have a wrist mounted GPS (Garmin Foretrex 301) and I want to play around with ground speed under canopy.

First of all I realise it is a distraction and needs to be recognised as such. When I jump it, I will do a solo H&P at altitude so traffic won't be a problem.

One thought that I have had is that I could wear it under my jumpsuit, reducing the snag potential and distraction and simply grab the data retrospectively. I'll probably do this first regardless.

I know people are using GPS with wingsuits but there isn't much on GPS and canopy flight.

What information exactly are you trying to capture? You will find that if you're looking at GR and or GS on some units that info is only available if you look at the unit while under canopy depending on the software you use to look at the data in post. Paralog is the most skydiver friendly and specific software for post analysis of a jump and you can gather just the time under canopy till landing if thats what you want to look at. The only thing to be aware of going into this is that the GPS based altitude readings you may see on your flights can actually be off based on what you recall from the flight.

"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

[nigel99 474]

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What information exactly are you trying to capture? You will find that if you're looking at GR and or GS on some units that info is only available if you look at the unit while under canopy depending on the software you use to look at the data in post. Paralog is the most skydiver friendly and specific software for post analysis of a jump and you can gather just the time under canopy till landing if thats what you want to look at. The only thing to be aware of going into this is that the GPS based altitude readings you may see on your flights can actually be off based on what you recall from the flight.

Primarily I am interested in getting a feel for the actual forward speed of my canopy, including different configurations like deep brakes. I know that wind speed will need to be accounted for.

Besides that getting a better feel for the glide ratio would be interesting. I don't have the 401 which has a barometric altimeter though, and I have no idea how well GPS altimeters work. But it should be good enough for the level of interest I have.

Experienced jumper - someone who has made mistakes more often than I have and lived.

[rrmtopo 1]

I have the Garmin Forerunner 305 and it logs my data, if you plan your test case you can just go back and look at the logged data after you're on the ground for the results.

[popsjumper 2]

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Primarily I am interested in getting a feel for the actual forward speed of my canopy, including different configurations like deep brakes. I know that wind speed will need to be accounted for.

Besides that getting a better feel for the glide ratio would be interesting.

Nigel, I applaud your desire to learn. Good stuff. Not many would even think of things like this.

Sorry about the ones razzing you.

To everyone:
Learning by listening to information that is being passed down verbally is all well and good but nothing beats actual testing in many, many cases.

My reality and yours are quite different.
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239

[Hellis 0]

Remember to ask the pilot for winds aloft charts too.
If you don't know the winds up there you can't really read the data

[nigel99 474]

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Remember to ask the pilot for winds aloft charts too.
If you don't know the winds up there you can't really read the data

I disagree. The winds aloft are necessary for a correct spot. But to work out canopy speed all that is needed is a controlled slow turn. The slowest speed will be read going into the wind, and the highest when flying downwind. It is then simple maths to subtract the wind. By the way this is one of the reasons that I believe this type of learning/playing should be done on a solo exit.

Unless of course I have missed something?

Experienced jumper - someone who has made mistakes more often than I have and lived.

[dninness 4]

There wasn't much analysis of the data in terms of brakes, no brakes, etc, but here's a map overlay from an XC jump using my Garmin 12XL about 8 years ago:

I do recall that the uppers were quite strong that day, and at one point the Ground Speed indication was > 80mph.

NIN
D-19617, AFF-I '19

[SethInMI 174]

I have wanted to generate some polar curves for my canopy for some time, but have not got around to it.

Nigel has the right idea, you don't need to know the winds aloft to determine the airspeed of the canopy as long as you fly in a circle or in several directions at a constant trim (full flight, etc). A spreadsheet or a simple program could remove wind effects.

Once you knew the full flight airspeed and glide ratio, determining other flight modes glide ratio and airspeeds (half brakes, full brakes, rear risers, front risers) would be easier, just fly at full flight at a given altitude, and then your spreadsheet/program could extract the wind speed from the known airspeed, and then used to determine true glide and airspeed for any subsequent flight modes (assuming wind stays constant over the next 1000 feet or so, not always valid).

If you generate polar curves, you can determine which flight mode is best for a given wind direction and speed.

Of course the cool thing (I think) would be to have a GPS device that could tell you what flight mode to use for the situation you found yourself in and estimate what altitude you would arrive at the pattern entry point for the programmed LZ. If the estimated altitude was too low even with the best flight mode, it would flash a warning "find alternate landing area!!!" Flysight's have some customizing ability, but I just don't have the time to work on something like that. And I digress...

So good luck, Nigel, let us know what you determine.

It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

[bryanburke 10]

Hi Nigel,

I've made a lot of jumps with a Garmin Foretrex and with a Garmin 72 in a special pouch. Here's a few tips.

You can't lock onto the GPS satellites in a plane unless you are right by the door or under a windshield so the reciever can "see" satellites during the climb to altitude. Metal blocks the signal. If you lose the signal you will need to re-acquire it under canopy. Give your landing area a simple name so you can "go to" it quickly once the GPS comes on.

Personally I don't think wearing a Foretrex is going to present any more of a snag hazard than an altimeter, but I'd suggest not having it on your pilot chute hand just in case.

To calculate air speed I would fly a four sided box and average the ground speeds. Eloy is layed out in a nice checkerboard so it's easy to go almost exactly 90* to each new leg, but you can do that with the heading indicator as well. Wait for the canopy to stable out after the turn and you'll see the speed stable out as well. About ten seconds per leg is enough.

The difference in speed due to density altitude is significant. Just as you see higher freefall speeds at 10,000 than you do at 4,000, you'll find the same under canopy.

Most people will be surprised at how fast they go, even with brakes set at deployment configuration.

When I first started playing with canopy performance numbers I realized I needed a way to record stuff, so I had a pouch made to hold an audio recorder on my bicep. I could observe a number and then turn and talk into the recorder. With the wind noise your mouth needs to be close to the mic.

I finally got a Flytec 6015 to get better numbers on airspeed and glide ratio, and have the machine do the recording. Flytec's US rep, Steve, was extremely helpful and I'm confident I'll get some great data once I figure out all the bells and whistles. As soon as the busy winter season is over I plan to get that in the air on a lot of different canopies! If anyone visiting Eloy wants to learn more about this project, say hi when you are visiting!

I'll need some advice on how to convert all the data to standard pressure and altitude so it can be used for meaningful comparisons.

Bryan Burke
STA at SDAZ

[nigel99 474]

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Personally I don't think wearing a Foretrex is going to present any more of a snag hazard than an altimeter, but I'd suggest not having it on your pilot chute hand just in case.

To calculate air speed I would fly a four sided box and average the ground speeds. Eloy is layed out in a nice checkerboard so it's easy to go almost exactly 90* to each new leg, but you can do that with the heading indicator as well. Wait for the canopy to stable out after the turn and you'll see the speed stable out as well. About ten seconds per leg is enough.

The difference in speed due to density altitude is significant. Just as you see higher freefall speeds at 10,000 than you do at 4,000, you'll find the same under canopy.

Thanks very much Bryan. Lots of useful information. I hadn't realised the density altitude would make a significant effect.

I am aware of at least 2 people who have noted ground speeds of over 90MPH at full altitude! But I had contributed this entirely to strong uppers.

[nigel99 474]

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I have wanted to generate some polar curves for my canopy for some time, but have not got around to it.

This sounds interesting. Do you have more information what the raw data required is and how it is presented?

[LouDiamond 1]

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Of course the cool thing (I think) would be to have a GPS device that could tell you what flight mode to use for the situation you found yourself in and estimate what altitude you would arrive at the pattern entry point for the programmed LZ. If the estimated altitude was too low even with the best flight mode, it would flash a warning "find alternate landing area!!!"

Something along those lines has existed for some time in the military community for use on HAHO jumps.

"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

[Hellis 0]

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Remember to ask the pilot for winds aloft charts too.
If you don't know the winds up there you can't really read the data

I disagree. The winds aloft are necessary for a correct spot. But to work out canopy speed all that is needed is a controlled slow turn. The slowest speed will be read going into the wind, and the highest when flying downwind. It is then simple maths to subtract the wind. By the way this is one of the reasons that I believe this type of learning/playing should be done on a solo exit.

Unless of course I have missed something?

Ok, go ahed.
I'm just basing it on my own expirience.
It's much easier with the winds aloft data.

Do yourself a favor and get the data from the pilot so that you atleast will have it when you need it.

[spikes2020 0]

I used my cell phone droid app "My Tracks" it takes ground speed, average speed, average speed moving, your altitude, your change in altitude. It also plots it on a map. You can export the file to google earth and check out your skydive from google earth...

Just make sure you turn up your refresh rate on it... i did it to 1/second... =)

I didnt bring my cable for my phone today but i can upload it later.

http://tech.chandrahasa.com/wp-content/uploads/2011/04/screenshot_4.png

Cheers

Jon W

[SethInMI 174]

Nigel,

I should have said "a polar curve" instead of "polar curves". A Polar curve for a given canopy and wingloading is pretty simple: a plot of the horizontal distance travelled vs. the vertical distance lost for a variety of canopy inputs. The result can be used as a simple visual method of determining what input to use for the amount of tail wind or head wind the parachutist finds herself in.

To generate a curve you only need to know the descent rate and horizontal travel rate for a range of canopy inputs.

http://avia.tion.ca/documentation/polar/ has some background.

It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

[SethInMI 174]

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Of course the cool thing (I think) would be to have a GPS device that could tell you what flight mode to use for the situation you found yourself in and estimate what altitude you would arrive at the pattern entry point for the programmed LZ. If the estimated altitude was too low even with the best flight mode, it would flash a warning "find alternate landing area!!!"

Something along those lines has existed for some time in the military community for use on HAHO jumps.

I figured there must be. A quick google search turned up this device: http://nanohmics.com/content/experience/commercialization-successes/glideline-systems/

One of the features is "collision avoidance with other jumpers". Nice.

It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

[LouDiamond 1]

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Of course the cool thing (I think) would be to have a GPS device that could tell you what flight mode to use for the situation you found yourself in and estimate what altitude you would arrive at the pattern entry point for the programmed LZ. If the estimated altitude was too low even with the best flight mode, it would flash a warning "find alternate landing area!!!"

Something along those lines has existed for some time in the military community for use on HAHO jumps.

I figured there must be. A quick google search turned up this device: http://nanohmics.com/content/experience/commercialization-successes/glideline-systems/

One of the features is "collision avoidance with other jumpers". Nice.

Yes, that is one of them and one I was involved with developing for several years. It has come a long way since its inception, they all have, but they are all very much a military only item and using them for civilian skydiving would not only be cost prohibitive but very impractical given the differences in sport jumping and military jumping practices.

"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

[nigel99 474]

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Nigel,

I should have said "a polar curve" instead of "polar curves". A Polar curve for a given canopy and wingloading is pretty simple: a plot of the horizontal distance travelled vs. the vertical distance lost for a variety of canopy inputs. The result can be used as a simple visual method of determining what input to use for the amount of tail wind or head wind the parachutist finds herself in.

To generate a curve you only need to know the descent rate and horizontal travel rate for a range of canopy inputs.

http://avia.tion.ca/documentation/polar/ has some background.

Thanks you have inspired a project. I had never thought of going into that much detail. The web link is very informative.

Experienced jumper - someone who has made mistakes more often than I have and lived.

[spikes2020 0]

here is one of my jumps at couch freaks, i have made some modifications to the settings since this jump to make it more accurate....

Attached
Pic 1 My entire jump
Pic 2 Close up of just the canopy flight

Cheers

Jon W