Dec 26, 2012, 6:20 PM
Post #1 of 18
(3083 views)
Shortcut
Decrease student wing loading when HOT?
Can't Post
Are you aware of any DZs which modify the student wing loading if the weather gets really hot? If the weather gets hot, do the weight limits come down?
If so: ----what is the temperature threshold? ----what is the % decrease in loading?
Are you aware of any DZs which modify the student wing loading if the weather gets really hot? If the weather gets hot, do the weight limits come down?
If so: ----what is the temperature threshold? ----what is the % decrease in loading?
Not aware of any dropzones that do this, I understand what happens when the temperature rises but you can only baby people so much, enough is enough imo. If they cant land an already lightly loaded canopy in warmer weather then maybe they are one of the students we should weed out of the sport there and then.
... just have a look at http://en.wikipedia.org/wiki/Density_altitude ... and never forget to think about elevation, atmospheric pressure and temperature while choosing the canopy (of your student).
(This post was edited by holie on Dec 27, 2012, 1:37 AM)
If a DZ needs to have a policy in place to upsize strudents on a hot day, their student WL are too high to begin with. The idea of a low WL for a student is to build a margin for error into their canopy choice, and if a hot day can erase that, there's not enough margin.
By all means, instructors should be considering the day when picking student canopies. If the day is hot and humid, err on the conservative side, and if it's a chilly fall day with a steady breeze, maybe one size smaller could be employed, but both sizes need to be large enough to be 'too big'.
You have to remember that there's no harm in a canopy that's too large, if you're pickign between two sizes, you're not going to hurt anyone by 'going big'. It's easy to forget that flying a canopy is something that takes some getting used to, but talk to some newer jumpers about their recent downsizes, and you'll get some perspective. When a guy with 50 jumps describes a 190 as 'quick, with responsive turns', you get the picture that a student will be literally thrilled with a 280 at .6 to 1 WL.
On the really hot days in Texas we have sometimes had the opposite problem. Downsized a student a bit ( still below 1-1 though ) because twice in one weekend we had students take a half hour to land. One student pulled at 5500 and got up to 7500 before he started coming down.
It's common even on my 120s on those days for me to gain altitude on my downwind leg. Multiple times after letting off double fronts I had so much lift I didn't have to flare at all. The thermals get crazy in tx when it's hot.
The tandem masters have learned where to fly so they can actually come down and land.
I once got a ways out on a crw jump but covered 3 miles from 3000 feet by following the thermals back from the highway. Fun stuff!
At the same DZ I was in the playground area to the west. I went about 2000' back and forth in a line 3 times under the student 270 and only lost about 50' in altitude. I was still on the radio and the instructor had me pull a 360 to get down a bit.
It might be fun to nearly paraglide under a skydiving canopy if traffic and time permits this coming summer.
At the same DZ I was in the playground area to the west. I went about 2000' back and forth in a line 3 times under the student 270 and only lost about 50' in altitude. I was still on the radio and the instructor had me pull a 360 to get down a bit.
It might be fun to nearly paraglide under a skydiving canopy if traffic and time permits this coming summer.
Are the thermals similar at San Marcos?
Those farm fields with dark earth exposed and a hot sunny days, yes you can expect some thermals. Around the Dallas DZ are some really dark fields and I know they will give you a ride. San Marcos has some farm fields as well. I don't know if the soil is dark or what type of year crops will not cover the ground. Ask around the DZ when you get a chance. The locals should know.
Agreed. You need to be about 45 degrees (F) above "normal" temperature to get a 5% increase in landing speed.
Yeah, that sounds about right.
For an article I once wrote, I worked out the following approximations for the relationship between temperature, altitude, speed, and canopy size:
+10 deg. C (=18 deg F) = +1200’ altitude = +1.8% airspeed = 3.6% reduction in canopy area = a need for a 3.6% increase in canopy area to fully counteract the density effect
For simplicity I tend to round off the percentages even though it slightly overstates the effect of temp or altitude:
+10 deg. C (=18 deg F) = +1200’ altitude = +2% airspeed = 4% reduction in canopy area = a need for a 4% increase in canopy area to fully counteract the density effect
(These are linear approximations of non-linear relationships, but reasonable over typical ranges.)
Are you aware of any DZs which modify the student wing loading if the weather gets really hot? If the weather gets hot, do the weight limits come down?
If so: ----what is the temperature threshold? ----what is the % decrease in loading?
You have the right to also ask this same question of the aircraft at your local DZO! Perhaps the next time your in a Cessna product and you see 5 other faces, the prudent thing would be to question this.
C
(This post was edited by ChrisD on Jan 13, 2013, 3:00 PM)
On a similar topic, I jump at Ocana which is approx 2000 foot above sea level. I have been told my 260 Nav (I am a low number jumper) is the same as a 240 Nav at sea level. No reason to query it, just if you consider temp, maybe altitude above sea level needs to be considered?
Are you aware of any DZs which modify the student wing loading if the weather gets really hot? If the weather gets hot, do the weight limits come down?
If so: ----what is the temperature threshold? ----what is the % decrease in loading?
You have the right to also ask this same question of the aircraft at your local DZO! Perhaps the next time your in a Cessna product and you see 5 other faces, the prudent thing would be to question this.
C
Really? At my home DZ's me plus 5 would be a light load in our Cessna..... Caravan.
Yes, I get your point. However, not all Cessna's are alike.
On a similar topic, I jump at Ocana which is approx 2000 foot above sea level. I have been told my 260 Nav (I am a low number jumper) is the same as a 240 Nav at sea level. No reason to query it, just if you consider temp, maybe altitude above sea level needs to be considered?
Of course elevation plays a HUGE role. However, in the case that I implied at the outset, we are discussing changes with temperature at a given DZ. If any DZ is experiencing sufficient changes in elevation to warrant thinking about canopy size....there are much bigger problems to deal with! (Think: earthquake, landslide, volcano, etc)
Thread Options
