Question about differences in sea level??

[simplechris 0]

I am currently a student on lvl 11 in Houston and I will be heading to Ogden next week to do some tunnel time. I was hoping to do some coach jumps at Ogden Skydiving while I was there but I was curious as to how much of an impact the difference in altitude will make. I know they said they are 4500ft above sea level and according to what I have found on here you are supposed to add 10 sq ft of canopy for every 2000ft. I am currently jumping a Nav 260 and a 240. What all needs to be considered if I try to jump there? Or should I just wait till I get back to Houston lol?

[NWFlyer 2]

Well, sea level's the same wherever you go, but the altitudes above sea level might vary.

All other things being equal, canopies move faster at higher altitudes. The instructional staff at the dropzone in Utah may recommend that you jump a larger canopy at the higher altitude, or they may feel that you'll be fine under the same size if your wingloading is light enough. Your best bet would be to discuss it with them either before you go or when you get there.

"There is only one basic human right, the right to do as you damn well please. And with it comes the only basic human duty, the duty to take the consequences." -P.J. O'Rourke

[ufk22 33]

You'll come down a little faster and have to flair a little higher

This is the paradox of skydiving. We do something very dangerous, expose ourselves to a totally unnecesary risk, and then spend our time trying to make it safer.

[shropshire 0]

When I first started jumping/flying, I was told be be aware of the 3 'H's .... Height, Heat and Humidity... They all affect canopy performance.

(.)Y(.)
Chivalry is not dead; it only sleeps for want of work to do. - Jerome K Jerome

[DrewEckhardt 0]

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You'll come down a little faster and have to flair a little higher

Your forward speed will be like jumping a canopy 1-2 sizes smaller (the later in summer, where it's both high and hot)

[simplechris 0]

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Well, sea level's the same wherever you go, but the altitudes above sea level might vary.


lol I had a feeling someone was gonna say something like that

[Beachbum 0]

I went through AFF in the Houston area also, and did my first level 8 (same as your first post AFF jump these days) up at Lost Prairie. I was on a 215 here, and they put me on a Nav 280 up there (about 3200' if I remember right). I agree about flaring just a tad higher - even with a low experience level you can notice a difference.

As long as you are happy with yourself ... who cares what the rest of the world thinks?

[rlucus 0]

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I am currently a student on lvl 11 in Houston and I will be heading to Ogden next week to do some tunnel time. I was hoping to do some coach jumps at Ogden Skydiving while I was there but I was curious as to how much of an impact the difference in altitude will make. I know they said they are 4500ft above sea level and according to what I have found on here you are supposed to add 10 sq ft of canopy for every 2000ft. I am currently jumping a Nav 260 and a 240. What all needs to be considered if I try to jump there? Or should I just wait till I get back to Houston lol?

You'll love Ogden the tunnel and the DZ are great, but your landings will suck I did my 100 jumps in Ogden and under a Nav 240 I only stood up once, (of course that was only 5 jumps) Under a Spectra 230 it required a full hard flare to get a good stop. My first landing at sea level was pretty funny (for everyone else)

Great facility, Grand Caravan, awesome people, 10 minutes from Hill AFB and the tunnel. (I used to jump during my lunch break on Wednesdays when they opened for tandems)

[erdnarob 1]

If you have an average weight (150-180 lbs for a guy) a student parachute (240 to 280 sq.ft) ie. with a loading at 0.75 to 0.88 (for a 240) should be OK for landing even at 4500 ft provided you use a good technique. Jumping at high altitude has its full effect when you start loading a parachute quite higher (1.3 to 2). As somebody mentioned, a hot and humid summer day will have similar effects since that kind of air is lighter than cold dry air.

The atmospheric pressure at 18000 ft is half (50%) of what it is at sea level. That means at 4500 ft the atmospheric pressure (or thickness of the air) is reduced to 0.875 % (with respect to sea level).
According to some fast physics calculation : ...(square root of (1/0.875))-1... your canopy speed should increase by about 0.069 or 7% (I wish an aeronautical engineer will validate this result).

But at higher speed the canopy flare will be more powerful. That's why you need a good technique.

Learn from others mistakes, you will never live long enough to make them all.

[simplechris 0]

Thanks for all the info. Not sure about the avg size thing lol. I'm 6'3 and like 194 and out the door with that 260 I've been jumping I'm like 230. I guess I'll just leave it up to them to decide what they think is right for me. Hopefully the tunnel doesn't take everything out of me so I can still put 100% into jumping there.

[timmyfitz 0]

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The atmospheric pressure at 18000 ft is half (50%) of what it is at sea level. That means at 4500 ft the atmospheric pressure (or thickness of the air) is reduced to 0.875 % (with respect to sea level).
According to some fast physics calculation : ...(square root of (1/0.875))-1... your canopy speed should increase by about 0.069 or 7% (I wish an aeronautical engineer will validate this result).

But at higher speed the canopy flare will be more powerful. That's why you need a good technique.

(This all refers to the OP, student canopy, straight in approaches, sea level compared to 4500')

The canopy will fly faster at higher altitudes because the air is less dense. For the same reason your flare will be less powerful because the air is less dense. A little speed may help the flare to be more powerful (at lower altitudes) but what you gain from added speed you lose because of the less dense air.

[erdnarob 1]

I see what you mean but it's not quite that way. You have an aerodynamics formula such as : F(aero) = kS V^2

F = the aerodynamics force applied on a body
k = a constant depending on the shape of the body (CX) and on the units
S = the the surface of the cross section of the body with respect to the direction
V = the body speed (which is squarred)

ie. If your speed increases by a factor of 3 for instance, the force applied will inscrease by a factor of 3^2 = 9

That is why you have to avoid opening a parachute at very high altitude because of the speed in thin air.
Therefore the thin air will only compensate very partially for the speed. Records in Canopy piloting in distance are due to the fact it was in Colorado high altitude ground thin air.

Learn from others mistakes, you will never live long enough to make them all.

[timmyfitz 0]

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Therefore the thin air will only compensate very partially for the speed.

That's what I said. Higher altitude, straight in approach, more speed, less powerful flare than at a lower altitude.

Thanks for agreeing with me.

[pinkfairy 0]

Landing at a higher altitude or landing with weights is not like flying a smaller canopy.

When you get a smaller canopy, you get more speed, but you also get some other characteristics, a smaller canopy will give you more of a pendulum effect while turning sharply, and might also be more sensitive to harness input. You also get an increase in the power of the flare that corresponds to the increase in speed.

When you put on weights, you get the increase in speed and flare, but not the other characteristics, and at a higher landing altitude, you just get the increase in speed.

I've seen many people been done bad landings at a DZ with an unfamiliar altitude MSL, but most do fine. I think you shouldn't think too much about it, and flare out your canopy like normal, the navigator 260 and 240 is big and forgiving, and it has a really good flare. It's not a bad idea in any case to know how to do a PLF in any case.

Relax, you can die if you mess up, but it will probably not be by bullet.

I'm a BIG, TOUGH BIGWAY FORMATION SKYDIVER! What are you?

[MakeItHappen 15]

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I am currently a student on lvl 11 in Houston and I will be heading to Ogden next week to do some tunnel time. I was hoping to do some coach jumps at Ogden Skydiving while I was there but I was curious as to how much of an impact the difference in altitude will make. I know they said they are 4500ft above sea level and according to what I have found on here you are supposed to add 10 sq ft of canopy for every 2000ft. I am currently jumping a Nav 260 and a 240. What all needs to be considered if I try to jump there? Or should I just wait till I get back to Houston lol?

See Density Altitude - Wing Loading Converter

BTW density altitude is the important variable, not elevation.
see Density Altitude for a chart to convert pressure altitude to density altitude.
Use any weather site to estimate the temp.

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