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OP's XC bad landings (stuck zipper, wind gradient)

Posted: Thu Apr 26, 2012 1:24 pm
by OP
Reading MikeL's story, I thought I'd add mine.

The stuck zipper and panic:

With about 300 AGL I went to unzip before staging a pattern above the airport. Pulling and pulling I found the zipper wouldn't budge. Cranking on the emergency velcro wasn't working either. In panic mode I tried to just kick through the zipper, no luck. Through all this, I wasn't flying the glider. Pulling on random parts of the harness I rocked back and forth losing more altitude. Pure panic, I wasn't thinking clearly. I couldn't foresee me panicking like this, but there I was. No organized thought, just fight or flight syndrome. Once I considered a belly landing, the panic left as suddenly as it came. With a clear head I thought out a good approach and had a smooth easy belly landing. Clothing stuck in the zipper was the culprit.

Moral of the story. Prepare for lading early. Practice using the velco escape hatch.

Wind gradient the next day:
With tired arms, that maybe didn't give the proper feed back, I turned to final approach. I thought I had a proper amount of speed, plenty of bar pressure indicating the gliders remaining energy. However about 30 feet above the ground all the bar pressure was suddenly lost. I pulled in as much as possible to regain pressure but I was too low. Dropping onto the tarmac I tried a flare. It was ineffective at slowing my vector down and into the earth. I got two steps on the ground before I couldn't keep up. Another, but less controlled, belly landing resulted. Harness, belt buckle, and shoes all took a mighty scrapping. No skin or down tubes were lost, luckily. Had this happened the previous day, with the stuck zipper, who knows what injury would have resulted. My chest would have taken the energy and not my legs. Had this happened over a boulder field... I don't want to continuing talking about this subject.

Moral: A previous assumption of their being less gradient above smoother terrain could have been a deadly misunderstanding. When in the desert, stuff the bar on final.

Re: OP's XC bad landings (stuck zipper, wind gradient)

Posted: Thu Apr 26, 2012 4:57 pm
by JD
OP wrote:....A previous assumption of their being less gradient above smoother terrain could have been a deadly misunderstanding. When in the desert, stuff the bar on final.
Great reporting Orian! Glad you didn't get injured on either day. There is another factor aside from gradient that can bite you in the ass real hard when landing in the desert. The wind can and will switch direction and velocity in any way, shape or form you can imagine while you are on final glide. Even the Big-T Wash will do this to you. Both will places can bite you well into the late afternoon and not just in mid-day, but mid-day tends to be a lot worse.

A sound piece of desert flying advice given to me by one of the most experienced CA desert X/C pilots is, "Don't land!". He meant it too. Diablo's advice was to remain in the air until late in the day and until you knew the retrieve truck was headed your way. This helps you prevent heat stroke as well as having a bad landing w/ no one around or aware of your status.

At the very least, if you are going to land mid-day in the desert, wait for a good flush cycle with steady sink. You are far less likely to expereince a sudden wind switch during sink than thermal. Thermals also my be an indication that there are active dust devils. Not all dust devils are visible either and many are clear or don't have enough dirt to be seen.

Getting back to the gradient issue--you have learned the hard way that gradient does not require mechanical wind blockage to occur. You are correct about diving in but beware as there is yet another troll under the proverbial bridge and that is the reverse gradient.

Yes, there are reverse gradients where the wind increases as you approach the ground. Now your 40mph dive turns into a 50mph dive and PIO at 10' AGL becomes a real issue. What's a pilot to do?

Again, it's best to stay aloft above the intended LZ and wisely pick your landing window just as you carefully choose when to launch. Once you have your windows picked out, get your glider down to the deck quickly before things change just as you want to leave the hill before your launch cycle erodes.

Posted: Thu Apr 26, 2012 6:45 pm
by OP
Now that I think about it. This is what must have happened when I witnessed T*** D******* pile into horseshoe meadows road near the postage stamp. I knew T*** was flying too slowly, but I couldn't explain why he simply fell from the sky, hitting the ground like a pancake. He broke a bottom bracket and a down tube. He tore a hole through his harness, through his jeans, through his pocket; which scattered his pocket change on the road. I have a photo of him posing next to the 1" deep divit his bracket made in the asphalt.

My hypothesis: though there is little ground cover to deflect the wind, the surface is very hot. The bubbling air next to the surface stops the prevailing wind. This bubbling boundary layer is all sorts of chaos.

I think the reverse gradient is a better place to be. It's easier to bleed speed than generate it. E = MHG, that is Energy is equal to the mass times height times gravity. With a limited height, the energy is constrained.

I like NME's point on waiting for a landing cycle. Just as in launch, where we wait for a pleasant cycle, we should also feel landing conditions for a good window. With the abundant lift I could have picked a better cycle to land in. I didn't at all.

I could have waited for later in the day to land. It would have been easily possible to float around until later in the day. However there where 2 trucks full of people not wanting to sweat their asses off in Trona for 3 more hours until I wanted to land. Even so, if it is too rowdy and injury is too high of a risk, maybe they will have to wait.

Posted: Thu Apr 26, 2012 9:40 pm
by nzlinus
Someone on the trip also mentioned the possibility that a layer of hot air could be present near the ground which would be substantially less dense, and would manifest as a loss of lift.

Posted: Thu Apr 26, 2012 11:01 pm
by JD
nzlinus wrote:Someone on the trip also mentioned the possibility that a layer of hot air could be present near the ground which would be substantially less dense, and would manifest as a loss of lift.

The air cannot be substantially less dense near the ground. The moment it becomes so, the conditions are called super-adiabatic and dust devils will form at the slightest disturbance and the surface air will rapidly circulate and return to the dry adiabatic rate or below. Where people come up with this and other superstitious and mythological nonsense is beyond me.

What you can have is surface level sink or lift. Yes, you can get drilled all the way into the ground with absolutely no ground effect whatsoever. It can and does happen and you better be prepared to experience things your mother never told you about. You can also enter ground skim at trim speed and glide for 1 or 200 yards all at trim speed across level or even rising ground.

Did you know that air can move through itself? Air can do some pretty amazing and disturbing things. It is not always some homogenous mass that behaves like a consistent and uniformly viscous fluid. It can also save you from your own fatal error and safely set you down as if on a feather pillow.

When the temperature in the L.A. basin exceeds 100 F be prepared for desert conditions at Kagel. That is when things get very strange and the rules begin to change.

Watch this video in HD and full screen:

There were microbursts going off every mile or so and the desert floor looked like bombs exploding each place they hit. It's hard to see clearly in the video but they're there. I recently bought some used HG gear from a helicopter pilot who was flying in the same vicinity that afternoon and was glad to compare notes about the conditions. Tug pilot Johnny Thompson and me thought we were both going to tumble together at several points.

Anyhow, if you flew into one of those microbursts you were pretty much guaranteed to get slammed into the ground in the worst way imaginable. Luckily the dusty desert floor of Maricopa made them easy to see from the air. That and other problematic phenomenon can happen where the sand is coarse and clean and you won't see a thing. You will never know what hit you.

I could go on and on about seemingly odd phenomenon I have experienced personally or witnessed. Just don't let your guard down and don't put yourself into spots where you expect your reserve chute to save you if things go all pear shaped.

Have fun and fly safe!

Posted: Mon Apr 30, 2012 2:54 pm
by Christian
Once with a stuck zipper I pulled the red Velcro pull-tab right off my Z5 harness, and landed on the wheels. Clothing was stuck. Even with plenty of time I was unable to open the Velcro.

Afterwards, Greblo recommended letting go of the control bar and using both hands to open Velcro: One hand to pull and the other to penetrate and work open the seal.

Posted: Mon Apr 30, 2012 5:52 pm
by skygeek AKA Seabass
A couple of pointers
1. If your shoe laces are long tuck them into themselves
2. Tuck your shirt into your pants
3. Don't wear really loose pants.
4. Unzip during staging.

Posted: Mon Apr 30, 2012 6:11 pm
by JD
skygeek AKA Seabass wrote:A couple of pointers
1. If your shoe laces are long tuck them into themselves
2. Tuck your shirt into your pants
3. Don't wear really loose pants.
4. Unzip during staging.
Good points except my weenie shrinks in the cold so I keep the barn door closed.

I always tie off the cuffs of my pants w/ Velcro cinch straps or they get caught in the harness zipper ropes.

hot air near the ground

Posted: Thu May 03, 2012 10:27 am
by gregangsten
Sorry, but I'm not buying the "no such thing as hotter, less dense air near the ground" statements. Tow up and land a few times from El Mirage and you will change your mind. The bottom falls out more often than not landing there, due to this effect when there is little or no wind. If packets of air could not become hotter and less dense at the ground, growing before they break through the blanket of cooler air blanketing them, there would be no thermals at all. This sharp temperature gradient is more likely in the desert than elsewhere so it is unexpected.

Posted: Thu May 03, 2012 9:22 pm
by Greg Kendall
A 50 degF temperature change will make about a 1 mph change in true stall speed. Pilots can decide how significant that is.

Re: hot air near the ground

Posted: Fri May 04, 2012 7:15 am
by JD
gregangsten wrote:Sorry, but I'm not buying the "no such thing as hotter, less dense air near the ground" statements.....
It causes micro circulation near the ground which can result in either surface-level downdrafts that will make the bottom fall out from under you or surface-level lift that will carry you hundreds of yards past your intended landing target. All of this in no wind. I've experienced plenty of this when I flew R/C sailplanes and it happens just as much in the farms of Illinois as in the California dry lakes beds. I have experienced this here as well.

On this flight I landed at 120' below sea level and it was 116 deg F in the shade and the air was completely stagnant. See what happens:

Posted: Wed May 09, 2012 4:20 pm
by OP
I did some googleing and apparently wind power people are really concerned with wind gradients. Their data confirms what we thought. Instability near the surface causes gradients over smooth terrain. I imagine the more unstable the sharper the cure.

The red line is what I suppose the gradient on that Sunday looked like.


Posted: Thu May 10, 2012 8:23 pm
by Fast Eddy
The SImple fact is. We are arguing small things here!!!!!!

I have read the last 3 or 4 posts and more than a couple show us common things.

As Experienced "PILOTS" we should be showing these people simple things to Improve their situations "when: this will happen again someday down the road.
What is the commonality here in their issues. They do not have a LIST of LANDING OPTIONS!!!! As experiemced Pilots we have a LOT of options Naturally going through our heads all the time. Landing Option A, B, C, D, E. F. the list goes on. Just as in my Post from 2 months back. I had practiced them all before I crossed the bridge.

Pilots should have more Options in there Index when it comes to landing. Just as I did. Just as WE ALL do. These are the things we should be Teaching and Talking to these Pilots about!!!!!!!!!! Not debating a MPH of wind or two etc. Lets not Nieche our flying friends into groups; instead, lets show them better and more Ideas that lead to being Better, and Safer pilots!~!~!


Posted: Mon May 28, 2012 6:02 pm
by vannoppen
Numbers and graphs confuse me, fly your glider


Posted: Fri Jun 01, 2012 10:55 pm
by vannoppen
Why doesn't anyone post after me. I'm in this for the humor. Make me laugh. You are all so good at this, am I toxic, ok don't answer that,I'll have another drink. Blah blah b

Re: Gradient

Posted: Fri Jun 01, 2012 11:01 pm
by JD
Van Apple Bobbin wrote:Why doesn't anyone post after me....
Because David....

Posted: Sat Jun 02, 2012 4:56 am
by TomS
Just because you're paranoid doesn't mean they're not out to get you.