distance traveled under canopy?

[jumpslo 0]

i know that there would be a lot of factors going into this such as wind, canopy size, etc. . but if you hop-n-popped at say 14k and maybe had some wind your way, how many miles could you travel? theres no real reasoning behind this i was just wondering haha.

"Good rule of thumb; is what you are doing the EASIEST for You? Because if it is, it ain't going to work for the people around you."

[JohnRich 4]

Here is my "simple" way of calculating that, which I do in my head, for cross-country jumps.

First, most canopies have a three-to-one glide ratio. That means that in zero wind, they will fly three feet horizontally, for every foot they descend vertically. So, at 14k feet, you'll fly about (14k x 3) 42,000 feet, or about 8 miles, just on glide ratio alone.

Second, you have to add the wind factor. Generally, you spend about one minute under canopy for every 1,000 feet of altitude descent, if you aren't spiraling. So from 14k, you'll be in the air about 14 minutes, or roughly a quarter-hour. That's the amount of time for which you will be subject to wind drift.

Third, get the "winds aloft" report from the FAA to get the wind speeds at various alititudes. You can just sort of average them for a ballpark figure. So let's say the upper winds from 3,000 feet to 12,000 feet average 20 mph. That means the wind will push you 20 miles in one hour. But since you are in the air only a quarter-hour, you'll get (20 x ¼) about 5 miles of push from the wind.

Finally, combine those two numbers: 8 miles from glide, and 5 miles from wind, and your maximum distance is about 13 miles.

Then you take that number and look at a map, and figure out what ground feature is 13 miles upwind from the airport. That's your spot. Then you adjust the spot based upon how conservative or how bold you are, or how many people behind you in the plane are beating on your back and yelling "GO! GO! GO!"

See how easy that was?

Good luck!

[jumpslo 0]

ha! yeah easy. . thanks! that was pretty awesome and great info. answered my question to a T

"Good rule of thumb; is what you are doing the EASIEST for You? Because if it is, it ain't going to work for the people around you."

[superstu 0]

couple of us were able to travel between 8-10 miles under our canopies ranging from 120sqf to 89sqf with about a 50knt tail wind from 12,000ft. my friend under his vx 89 got over the dz at about 500' and me under my alpha 120 got back over at about 3000'. very fun to do, especially if you have tail wind.

Slip Stream Air Sports
Do not go softly, do not go quietly, never back down

[FlyinseivLP2 0]

I have done a cross country jump that we covered 22 miles. We exited at 14K and the upper winds 79 knots. I was jumping a 220 loaded at about 0.8. I wasn't familiar with the area and flew well beyond our intended landing area.

[waltappel 1]

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Here is my "simple" way of calculating that, which I do in my head, for cross-country jumps.

First, most canopies have a three-to-one glide ratio.

I know that's the figure that's been used for years, but I don't really believe it.

Let's say the average canopy at full flight has roughly a rate of descent of about 20 ft./s.

That would mean a forward speed of 60 ft. per sec.

Since 1 mph. is rougly 1.5 feet per second, then that would mean a forward speed of about 40 mph.

Either canopies descend significantly slower than 20 ft./sec at full flight or they don't have a 3 to 1 glide ratio.

Walt

[indyz 1]

I've done 13 miles from 10,500 with a Triathlon 160 @ 1.3:1 on a "reverse cross country" with a stiff tailwind. Ground winds were near my limit and the uppers were just ripping.

[kelpdiver 2]

the Neptune gives ft/s rates when you're under canopy. When I briefly had one last year, I was seeing typical full flight in the range of 13-20 fps (about 1.1:1). I found it hard to look at while taking care of business, so it's not perfect data. But there are a lot of neptune owners out there that should be able to chime in.

[waltappel 1]

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the Neptune gives ft/s rates when you're under canopy. When I briefly had one last year, I was seeing typical full flight in the range of 13-20 fps (about 1.1:1). I found it hard to look at while taking care of business, so it's not perfect data. But there are a lot of neptune owners out there that should be able to chime in.

Ok, let's assume an average rate of descent of 15 ft/sec.

a 3:1 glide would give a forward speed of 45 ft/sec, which is about 30 mph. Still seems a little high, but more in the ballpark.

Walt

[TalkingCorpse 0]

Also a few more things to consider, higher your wingloading means that you travel down your glide path quicker, the faster you go down your glide path the less time the prevailing wind has to push you even further. Have to go downwind with the prevailing to go as far as possible.
Am more experienced with paragliding than skydiving, but can you gain any height on a XC flight but use of thermals, convergence, wave conditions as they use in paragliding with the skydiving canopies? Am assuming so even if your unable to use them as efficently as other types of wings.
Ramble over :)

[mjosparky 3]

No..

My idea of a fair fight is clubbing baby seals

[TrickyDicky 0]

This kinda thing was banned in the UK about 10-15 years ago. Some guy opened about 10miles from the DZ, and on the way back, managed to land on powerline (about 1mile short of the DZ) cos he was focussed on geting back.

All DZs in the UK now have a 1.5mile radius that you're allowed to exit in.

UK Skydiver for all your UK skydiving needs.

[damion75 0]

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This kinda thing was banned in the UK about 10-15 years ago. Some guy opened about 10miles from the DZ, and on the way back, managed to land on powerline (about 1mile short of the DZ) cos he was focussed on geting back.

All DZs in the UK now have a 1.5mile radius that you're allowed to exit in.

Almost true... that is the figure quoted in the BPA ops manual for standard parachuting operations. The main reason for this is the sheer number of other airspace users in the limited UK airspace rather than safety.

If the DZ applies for (and gets) a NOTAM (Notice to Airmen) to warn off other airspace users, then that area can be extended by a specified distance and for a specified time (say up to 10 miles for a 2hr window) Gosh I hope some DZ does that on some fine evening this summer...

***************

Not one shred of evidence supports the theory that life is serious - look at the platypus.

[JohnRich 4]

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First, most canopies have a three-to-one glide ratio.

I know that's the figure that's been used for years, but I don't really believe it...

Well, I'm an old fart and have been using that number for a while. Admittedly, it is based upon the days when everyone jumped larger canopies. Now, many people fly high-load rockets that come out of the sky much faster. So that number should be taken with a grain of salt, based upon canopy loadings.

I've done cross-country jumps, where everyone that landed short of the airport, was someone with a high wing-loading. So they need to exit first, and let the big-canopy boys go out a little further.

[jumpslo 0]

so, are you allowed to do this? have the pilot go some miles away from the DZ for the drop? is that the cross country jump you guys are talking about? or do they have to stay a certain miles from the DZ legally?

"Good rule of thumb; is what you are doing the EASIEST for You? Because if it is, it ain't going to work for the people around you."

[waltappel 1]

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so, are you allowed to do this? have the pilot go some miles away from the DZ for the drop? is that the cross country jump you guys are talking about? or do they have to stay a certain miles from the DZ legally?

As far as I know there is no legal limit on distance except the (IIRC) 25 nautical mile radius from the DZ.

Walt

[JohnRich 4]

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so, are you allowed to do this? have the pilot go some miles away from the DZ for the drop? is that the cross country jump you guys are talking about? or do they have to stay a certain miles from the DZ legally?

It's perfectly legal.

However, we have different types of airspace, such as "controlled" and "uncontrolled". In controlled airspace, like around busy commercial airports, you would have to get permission from the FAA for the jump, since you might create a hazard. But most drop zones aren't located in such places. For uncontrolled airspace, where there isn't much traffic, and where most drop zones reside, it is simply "see and be seen", and you can jump pretty much as you wish without special advance permission.

[superstu 0]

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Ok, let's assume an average rate of descent of 15 ft/sec.

my average decent rate on my JVX in full flight is about 45ft/s, so what does that mean for my forward speed?

Slip Stream Air Sports
Do not go softly, do not go quietly, never back down

[waltappel 1]

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Ok, let's assume an average rate of descent of 15 ft/sec.

my average decent rate on my JVX in full flight is about 45ft/s, so what does that mean for my forward speed?

1 mph is roughly 1.5 ft/sec, so your descent rate is roughly 30mph. I find that scary if you are talking straight ahead flight with no control input.

No way am I going to believe that you would have a 3:1 glide ratio in that case because that would imply that your canopy has a 90mph forward speed!

Looking at it another way, if you are under canopy at 3,000 ft, and didn't do anything to drastically change your rate of descent, you would be on the ground, in 67 secs. That's a really short canopy ride from that altitude!

Are you sure about your average rate of descent?

Walt

[superstu 0]

pretty sure of it, but i know for a fact that my forward speed is NOT 90mph would have to guess around 30mph or so. i don't have any d-bag, slider, and have HMA lines. i'm also loading a little higher than most

i've been able to get my decent rate to 150ft/s before doing multiple rotations, but cannot sustain that.

edited to add: i very rarely get out below 3.5k and if i go higher i'm usually pitching PC at 5k or right out the door. i also fly in a little bit of breaks when i'm finding my spot in the pattern.

Slip Stream Air Sports
Do not go softly, do not go quietly, never back down

[waltappel 1]

I have never jumped a heavily loaded canopy, but one of the most amazing canopy things I have ever seen was the incredible range of speed demonstrated by Derek at Spaceland a few years back.

I don't remember what canopy he was jumping, but I want to say it was a VX 79 or something like that. He used to do some really spectacular surfs. One day, he came up behind me while I was under my Triathlon 175 and stayed right there with me. He could have easily docked if he had wanted to.

You can likely vary your rate of descent and glide angle significantly depending on control input.

Walt

[pchapman 262]

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First, most canopies have a three-to-one glide ratio.

I know that's the figure that's been used for years, but I don't really believe it.

Hey Walt,
I agree that the 3:1 that people are sometimes taught is too high. I'd GUESS 2.5:1 for the average canopy and closer to 2:1 for small, ground hungry ones, at zero brakes.

The glide ratio in the air does go up with a little brakes, and of course for a strong tailwind like on a cross country, one will pretty much want whatever brake setting gives the lowest rate of descent. (Based on glide polar theory.)

The real data I have is old, from the mid '90s. I got the data with a calibrated anemometer, a variometer, density altitude calculations, etc. A few of the numbers:

At 170 lbs, corrected to sea level conditions for descent rates:

big baffed F-111 7-cell (Titan 265)

-At zero brakes:
2.45 glide ratio
28.5 mph airspeed
16 fps rate of descent

Sabre 1 120

-At zero brakes:
2.5 glide ratio
41.5 mph airspeed
22.5 fps rate of descent
-At an arbitrary "quarter brakes":
2.75 glide ratio
33 mph airspeed
16.5 fps rate of descent


Jonathan 92

-At zero brakes:
2.3 glide ratio
43 mph airspeed
25 fps rate of descent
-At an arbitrary "quarter brakes":
2.6 glide ratio
34 mph airspeed
18 fps rate of descent

Later on I got 47 mph at zero brakes on an FX 88.

The data may help a little in understanding glide ratios even if modern canopies aren't represented.

[waltappel 1]

That is some pretty spectacular data, particularly on the Sabre 1 120. What kind of loading were you putting on that canopy? a 40+ mph airspeed suggests you were loading the hell out of it!

You must have been loading the Titan pretty good too to get a 28.5 mph airspeed!

Walt

[pchapman 262]

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What kind of loading were you putting on that canopy? a 40+ mph airspeed suggests you were loading the hell out of it!

Everything was loaded with only about 170 lbs -- about 1.4 wing load on the Sabre 120, and 1.9 on the FX 88. (Without getting into different standards of canopy size measurement!)

Unless there was something fundamentally wrong with my data collection, the numbers seem OK to me, and their relationship is reasonable. I got 25 mph under a Manta 288. Basic canopy scaling laws suggest that a 120 canopy would fly 55% faster, or 39 mph. And the 88 at 45 mph. That's if "all else is equal" which it obviously isn't, yet the measured numbers are similar to the predictions. That gives me some confidence in the results.

[waltappel 1]

My thoughts on canopy forward speed in full flight come not from direct measurement under canopy but from comparing measured ground wind speeds to observed forward penetration of my canopy in those winds.

Some of your data suggests that jumping in 30mph winds would be fine as long as long as you could deflate your canopy *immediately* upon landing. In my experience, though, jumping in 30mph winds is dicey, at best, because of the lack of forward ground speed.

No way would I expect a Titan loaded with 170 lbs to get penetration in 25 mph winds. I'm not saying your data is incorrect but it doesn't match my largely subjective observations.

Very interesting data for sure!

Walt