DZ Altitude Effects on landing

[melch 0]

I was surfing the incidents forum and came across a thread that scratched the surface of DZ altitude ASL and its effects on landings.

I was hoping someone could explain in detail what the effects the altitude have and why it is different than say jumping at sea level?

[DSE 3]

Here are some resources to help you understand better:
http://www.divemaker.com/trajectory/da.php

http://parachutehistory.com/eng/denalt.html

http://www.uspa.org/SIM/Read/Section5/tabid/168/Default.aspx#55c


It's a great question, one that many skydivers ignore, a few to their peril.

The short version is that the same canopy will fly faster forward and downward in thinner air/higher altitude than at sea level. Think of it another way; (very loose comparison, flame away)
A 190 sqft canopy at 4200' at will fly similar to a 220 at sea level.

[denoyerj 0]

It pertains to density altitude. Anything High, Hot, and Humid decreases performance. The air isn't as dense in those situations and therefor decreases lift. You'll need someone with a better understanding how it relates to canopies to explain how to compensate for it.

[Remster 24]

The higher the altitude, the less dense the air is.

As a ballpark estimate, 2000 feet elevation is comparable to a 1 size downsize in canopy size.

Also, the hotter the air, again, the less dense the air is. So, for example, at Eloy next weekend, when it will be 117, between the 1500 feet elevation and the temperature, it would be *like* a 2 size downsize from, say, sea level at 80f.

Remster

[melch 0]

Thanks guys.

That helps explain the noticible difference in the flares during my landing attempts coming from the east coast. I was making standing landings after my second jump back home and I have only been able to slide in at Eloy.

[denoyerj 0]

Remster

The higher the altitude, the less dense the air is.

As a ballpark estimate, 2000 feet elevation is comparable to a 1 size downsize in canopy size.

Also, the hotter the air, again, the less dense the air is. So, for example, at Eloy next weekend, when it will be 117, between the 1500 feet elevation and the temperature, it would be *like* a 2 size downsize from, say, sea level at 80f.

With respect to landing, do you need to increase your flare height slightly and use "stronger" inputs to compensate for the decrease in lift, or does your increase in speed make up for that?

[DougH 270]

DSE

Think of it another way; (very loose comparison, flame away)
A 190 sqft canopy at 4200' at will fly similar to a 220 at sea level.

You transposed the sizes. A 220 at 4200 will fly similar to a 190 at sea level.

"The restraining order says you're only allowed to touch me in freefall"
=P

[ryoder 1,396]

Remster

The higher the altitude, the less dense the air is.

As a ballpark estimate, 2000 feet elevation is comparable to a 1 size downsize in canopy size.

Also, the hotter the air, again, the less dense the air is. So, for example, at Eloy next weekend, when it will be 117, between the 1500 feet elevation and the temperature, it would be *like* a 2 size downsize from, say, sea level at 80f.

I was living in Northern IN when I took my 1.1-loaded canopy on a road trip and jumped at Marana in triple-digit temps in July.

I got a face-full of AZ desert on landing.

Tony Frost got his belly-laugh for the day:
"BWA-HA-HA-HA-HA!!! Welcome to high-density-altitude Arizona! BWA-HA-HA-HA-HA!!!"

"There are only three things of value: younger women, faster airplanes, and bigger crocodiles" - Arthur Jones.

[Remster 24]

denoyerj

***The higher the altitude, the less dense the air is.

As a ballpark estimate, 2000 feet elevation is comparable to a 1 size downsize in canopy size.

Also, the hotter the air, again, the less dense the air is. So, for example, at Eloy next weekend, when it will be 117, between the 1500 feet elevation and the temperature, it would be *like* a 2 size downsize from, say, sea level at 80f.

With respect to landing, do you need to increase your flare height slightly and use "stronger" inputs to compensate for the decrease in lift, or does your increase in speed make up for that?

Yes.

You will go faster, so inputs will have a stronger effect, but because of the extra speed, you may feel that the controls require more strength (or not, depending on the specific canopy, wingload, etc...)

And, Ryoder: ah ha!

Remster

[SecondRound 0]

[

As a ballpark estimate, 2000 feet elevation is comparable to a 1 size downsize in canopy size.

Also, the hotter the air, again, the less dense the air is. So, for example, at Eloy next weekend, when it will be 117, between the 1500 feet elevation and the temperature, it would be *like* a 2 size downsize from, say, sea level at 80f.

I was living in Northern IN when I took my 1.1-loaded canopy on a road trip and jumped at Marana in triple-digit temps in July.

I got a face-full of AZ desert on landing.

Tony Frost got his belly-laugh for the day:


"BWA-HA-HA-HA-HA!!! Welcome to high-density-altitude Arizona! BWA-HA-HA-HA-HA!!!"


Tony always was the sensitive sympathetic type. You can imagine the laughs he got watching us land 28' rounds at 4000' at Spearfish SD.

[denoyerj 0]

Remster

******The higher the altitude, the less dense the air is.

As a ballpark estimate, 2000 feet elevation is comparable to a 1 size downsize in canopy size.

Also, the hotter the air, again, the less dense the air is. So, for example, at Eloy next weekend, when it will be 117, between the 1500 feet elevation and the temperature, it would be *like* a 2 size downsize from, say, sea level at 80f.

With respect to landing, do you need to increase your flare height slightly and use "stronger" inputs to compensate for the decrease in lift, or does your increase in speed make up for that?

Yes.

You will go faster, so inputs will have a stronger effect, but because of the extra speed, you may feel that the controls require more strength (or not, depending on the specific canopy, wingload, etc...)

And, Ryoder: ah ha!

So... everything should be about the same. The increased speed from the decrease in DA will increase lift to normal. Controls should require the same input because of the same lift being generated... it's just happening faster. By stronger I meant that you would need more input than normal, but the extra speed should compensate. That is of course assuming everything equals out.

[Remster 24]

denoyerj

*********The higher the altitude, the less dense the air is.

As a ballpark estimate, 2000 feet elevation is comparable to a 1 size downsize in canopy size.

Also, the hotter the air, again, the less dense the air is. So, for example, at Eloy next weekend, when it will be 117, between the 1500 feet elevation and the temperature, it would be *like* a 2 size downsize from, say, sea level at 80f.

With respect to landing, do you need to increase your flare height slightly and use "stronger" inputs to compensate for the decrease in lift, or does your increase in speed make up for that?

Yes.

You will go faster, so inputs will have a stronger effect, but because of the extra speed, you may feel that the controls require more strength (or not, depending on the specific canopy, wingload, etc...)

And, Ryoder: ah ha!

So... everything should be about the same. The increased speed from the decrease in DA will increase lift to normal. Controls should require the same input because of the same lift being generated... it's just happening faster. By stronger I meant that you would need more input than normal, but the extra speed should compensate. That is of course assuming everything equals out.

Where and who said things should be about the same?????? I know it wasnt me!
They will be different. Expect different.

Remster

[Zlew 0]

+1 things will be different for sure.

Your wing will be flying faster, and also stall or stop flying at a higher true airspeed. The increased arispeed does not make up for , or wash out the difference in how the speed/timing of the flare happen.

Hot/high will mean faster fwd and down speeds on landing, and higher speeds at when your canopy throws in the towel and calls it quits.

[Amazon 7]

Remster

******The higher the altitude, the less dense the air is.

As a ballpark estimate, 2000 feet elevation is comparable to a 1 size downsize in canopy size.

Also, the hotter the air, again, the less dense the air is. So, for example, at Eloy next weekend, when it will be 117, between the 1500 feet elevation and the temperature, it would be *like* a 2 size downsize from, say, sea level at 80f.

With respect to landing, do you need to increase your flare height slightly and use "stronger" inputs to compensate for the decrease in lift, or does your increase in speed make up for that?

Yes.

You will go faster, so inputs will have a stronger effect, but because of the extra speed, you may feel that the controls require more strength (or not, depending on the specific canopy, wingload, etc...)

And, Ryoder: ah ha!

The first couple days at Lost Prairie are always a fun time.. there are some EPIC landings to observe in the high altitude heat induced thermals in the windy afternoons.

[DBCOOPER 1]

Where it really bites sea level jumpers is when there is no wind or light and variable winds, My first jump at Moab with density altitudes approaching 7000 feet at the Cave Man Ranch was a thing of beauty. Was jumping a Pilot 140 at about 1.4. Managed to get it to plane out but couldn't get it to slow down till I hit the edge of the helipad. Got up bleeding from both elbows and one knee. Ripped my reserve flap and jump suit.Crashed and burned at the airport landing area the next day in light and variable winds. And I wasn't alone. Then the winds picked up and I began to understand how people jump at that density altitude.UPT was there with demos so I managed to get a Pulse 170 for the rest of the boogie. It was quite an eye opener.

Replying to: Re: Stall On Jump Run Emergency Procedure? by billvon

If the plane is unrecoverable then exiting is a very very good idea.

[DrewEckhardt 0]

DSE

It's a great question, one that many skydivers ignore, a few to their peril.

The short version is that the same canopy will fly faster forward and downward in thinner air/higher altitude than at sea level. Think of it another way; (very loose comparison, flame away)
A 190 sqft canopy at 4200' at will fly similar to a 220 at sea level.

More precisely each 1000 feet of density altitude yields about a 2% speed increase which is like a 4% decrease in canopy size. Density altitude is the altitude at which standard temperature and humidity would produce a matching air density; where standard temperature decreasing with elevation implies density altitudes significantly higher on summer days at mountainous DZs than their field elevation suggests.

The change in effective size also means more altitude lost in speed inducing landing maneuvers.

At Mile Hi Skydiving (5052 feet field elevation with summer density altitudes breaking 8000 feet) in Longmont, CO a few visiting jumpers got ambulance rides when they decided to ignore that.

[FlyingRhenquest 1]

I'm told landing's faster here in Colorado than elsewhere. Having never jumped elsewhere I can't say. I'm guessing if I can manage a visit to Deland this winter, it'll screw up my flare for the first jump or two.

I was pondering what it'd take to do a demo jump from the King Air to the visitor's center on top of Trail Ridge Road at 12,090 feet MSL. I guess that's not such a good idea, even though it'd still be a 5K hop and pop at the altitudes we fly to (Bwahaha :-) Much more interesting would be to jump a picnic to the mountain across the valley, which has no discernible means of human access, have lunch, pack your parachutes and jump to the valley. That sounds like a fun day out! Less so if you break your leg trying to land at 12000 feet...

I'm trying to teach myself how to set things on fire with my mind. Hey... is it hot in here?

[DSE 3]

DougH

*** Think of it another way; (very loose comparison, flame away)
A 190 sqft canopy at 4200' at will fly similar to a 220 at sea level.

You transposed the sizes. A 220 at 4200 will fly similar to a 190 at sea level.

Oops, I did. I had originally put my sizes in there (correctly) but then changed it up to relate to the Utah fatality and transposed.
Thanks for the catch.

[GLIDEANGLE 1]

Ah, the joys of high density altitude:

1. I was at Eloy for a CReW camp. (My home DZ is ~750 ft elevation)
2. Someone loaned me a Lightning. (CReW canopy with a reputation for "challenging" landings.)
3. To match my WL to the other dawgs.... I was now @ 1.3 instead of my usual 1.1.
4. To improve the Lightning landings, I was told to use double fronts to build speed on final.
5. It was warm at Eloy.

Result: To call the landings "sporting" would be a massive understatement! I was delighted to walk away uninjured!

The choices we make have consequences, for us & for others!

[DSE 3]

FlyingRhenquest

I'm told landing's faster here in Colorado than elsewhere. Having never jumped elsewhere I can't say. I'm guessing if I can manage a visit to Deland this winter, it'll screw up my flare for the first jump or two.

I was pondering what it'd take to do a demo jump from the King Air to the visitor's center on top of Trail Ridge Road at 12,090 feet MSL. I guess that's not such a good idea, even though it'd still be a 5K hop and pop at the altitudes we fly to (Bwahaha :-) Much more interesting would be to jump a picnic to the mountain across the valley, which has no discernible means of human access, have lunch, pack your parachutes and jump to the valley. That sounds like a fun day out! Less so if you break your leg trying to land at 12000 feet...

You might ask Tom Noonan what it's like to land at 14K...They do use oversize canopies up there.

[Travman 6]

I've landed at Ama Dablam base camp in Nepal, at an altitude of 15,000ft. We were using PD Navigators, if I recall correctly I think I was on a 290. Typically I jump a Katana 120, so for me the landings were quite slow. Coming from such a ground hungry canopy, I found myself struggling to burn off altitude on finals with the Navigator so I didn't overshoot.

Since it's such a different canopy to what I normally jump, its hard to provide a comparison. Its about having the right equipment for the job.

[potatoman 0]

4500ft ASL at our club. Makes for some interesting landings when the guys from the coast come with their mini chutes.

They go home with dirty gear/clothes.

When I go down to the coast, my 150 feels like a Caddilac. (even at 1.5wl)

You have the right to your opinion, and I have the right to tell you how Fu***** stupid it is.
Davelepka - "This isn't an x-box, or a Chevy truck forum"
Whatever you do, don't listen to ChrisD.

[TomNoonan 1]

Quote

I'm told landing's faster here in Colorado than elsewhere. Having never jumped elsewhere I can't say. I'm guessing if I can manage a visit to Deland this winter, it'll screw up my flare for the first jump or two.

I was pondering what it'd take to do a demo jump from the King Air to the visitor's center on top of Trail Ridge Road at 12,090 feet MSL. I guess that's not such a good idea, even though it'd still be a 5K hop and pop at the altitudes we fly to (Bwahaha :-) Much more interesting would be to jump a picnic to the mountain across the valley, which has no discernible means of human access, have lunch, pack your parachutes and jump to the valley. That sounds like a fun day out! Less so if you break your leg trying to land at 12000 feet...

You might ask Tom Noonan what it's like to land at 14K...They do use oversize canopies up there.

I can speak from personal experience that the canopies I have landed at higher altitudes at our Everest Skydive dropzone land great, even in low and no wind conditions. In the 6+ years we've been jumping up there, I'd have to think back to 2008 to truly remember someone sliding in a landing on a sport canopy on a no wind day. We even stand up tandem landings up there often on TP-400s and Sigma II 370s in low wind conditions with lighter passengers (under 200lbs).

For sizing comparisons, my sport jump exit weight is 230lbs.
At sea level, I jump a Velocity 96.
At 12,350ft, I prefer to jump a Navigator 200
At 14,900ft, I prefer to jump a Silhouette 260
and
At 17,192ft, I jumped a Navigator 280.
All stand up landings in low wind conditions.

If you decide to make this jump and would like some more info, feel free to email me at [email protected] and I will offer any info/assistance I can on high altitude landings.

Namaste,
Tom Noonan

www.everest-skydive.com