http://ozreport.com/forum/viewtopic.php?t=60556
My launch on Tuesday
Mick Howard - 2019/08/21 16:24:23 UTC
I used to fly a lot with Cowboy Up Hang Gliding (CUHG). I understand that Bart and Tiki (CUHG) acquired their teaching styles and methods from the years they spent at Wallaby. They prefer to set a higher angle of attack than I typically use. I think what they do works well for students on novice and intermediate gliders, which have a lot of washout compared to higher performance gliders. They set the angle of attack such that the wing tips are parallel to the ground. On a Falcon this places the root and keel of the wing at a very high angle of attack - probably around 30 degrees or more.
From discussions with Bart I believe the reasoning for this is to allow the glider to leave the cart as soon as possible to avoid excessive ground speed. Bart said that if the cart was to hit a hole or for some other reason come to an abrupt stop the glider would nose over and cause serious injury but injury would be much worse at higher ground speeds. Setting a high angle of attack and having the pilot hold that position during the take-off roll was the simplest way to teach students to launch, as this technique requires minimal student input until the glider leaves the cart. I also believe the thought is that the high angle of attack in the cart mimics the angle of attack of the tandem glider used for training, so the transition from tandem to solo glider was minimized. There could be other reasons that I don't know about but this technique has worked extremely well and proven successful for Wallaby and Cowboy Up, so there's no reason to change as long as this technique is applied in a controlled environment. In other words I believe that this technique mainly works in the appropriate conditions such as zero or negligible cross wind, very low gust factor, minimal turbulence and grass surfaces, which is the environment typically used for training and for less experienced pilots.
There's a difference between towing from grass surface versus a concrete surface in midday summer conditions. Concrete is typically a source for thermals whereas green grass isn't, so thermals are more likely to kick off when launching from concrete, plus the turbulent wind blast (prop blast) from the tug propagates and is far more pronounced on concrete whereas on grass it seems to have less effect on the glider possibly due to being absorbed and dissipated by the grass, I don't the physics but I do feel the difference - this was also clearly evident in Big Spring.
The weather conditions for cross country and competitions are far more variable and active compared to conditions during training and local recreational flying. During launch pilots may have to deal with stronger winds, wind gusts, crosswinds, thermals and prop blast. Holding a high angle of attack on the cart at the start of and during the takeoff roll in a cross wind will likely cause the upwind wing to lift while the downwind wing is stalled. The consequences are obvious unless brought under control - many of us have seen it happen. Setting a high angle of attack in gusty conditions can cause both wings to lift prematurely. Add thermals to the mix and getting lifted prematurely by the wind gust and or thermal or both and then getting slammed back down due to prop blast or because the gust dropped etc. is a recipe for disaster.
Setting an appropriate angle of attack will reduce the effect of the above mentioned conditions. For example the appropriate angle of attack will reduce the effect of the crosswind component by ensuring both wings reach flying speed before leaving the cart so typically the wing will yaw to the upwind side rather than lift the wing. Maintaining the appropriate angle of attack during the take-off roll prevents both wings lifting prematurely, so the glider and cart remain on the ground while passing through the prop blast and leave the cart at safe flying speed.
Maintaining the appropriate angle of attack during the take-off roll prevents the wings lifting prematurely which I believe is a common cause of accidents where the base bar touches the ground when it sinks in front of the cart i.e. the wing is lifted prematurely and then settles back down in front of the cart. Carrying the appropriate speed prior to leaving the cart mitigates this risk.
Setting the appropriate angle of attack reduces the likelihood of popping up above the tow plane on take-off This is the other extreme often seen when pilots hold their weight back (pushed out) as they leave the cart. This is a concern to tow pilots who have to maintain control close to the ground while the tail is being picked up and is a concern when pilots pop up high and break the weak link, then stall and crash because of the high angle of attack and immediate loss of airspeed.
Carrying the appropriate speed leaving the cart makes dealing with a premature release at the tug or glider a routine landing.
So what is the appropriate angle of attack on the cart? In the absence of information from USHPA I refer BHPA (British Hang Gliding & Paragliding Association).BHPA Technical Manual (Section-2 Chapter 7) says "The glider should sit at a low +ve angle of attack (keel at approx 18° - high angles of attack produce problems with wind gusts)".
What does this mean in practice. Depending on the glider, but generally, when laying down in the harness with the glider on the cart, the base bar will be at around neck/chest level (best glide) when the angle of attack of attack is around 20 degrees (BHPA says approximately 18° - Approximately to me is 18° to 22°). This has always worked well for me and I have a fair number of tows under my belt in various conditions. In the event the cart isn't adjustable then the appropriate angle of attack should be established during the take-off roll by pulling in until about best glide position.
Whenever someone starts this discussion about angle of attack I ask if they would attempt a hill or mountain launch with their glider nose high e.g. running down the slope with 30 degree angle of attack? Of course the answer is no. I ask the same about foot launching on flat surfaces behind payout winches, stationary winches or tow planes (aerotrow), and of course the answer is no. So I wonder why we feel it's ok to have a high angle of attack when launching from a cart? My thought is that a high angle of attack creates too many risks for the type of glider and the areas and conditions in which I fly, but it seems to work in a controlled environment such as flight parks/schools.
I used to fly a lot with Cowboy Up Hang Gliding (CUHG).
Cool. So I guess you're totally onboard with:
http://ozreport.com/forum/viewtopic.php?t=24846
Is this a joke ?
Bart Weghorst - 2011/08/28 20:29:27 UTC
Now I don't give a shit about breaking strength anymore. I really don't care what the numbers are. I just want my weaklink to break every once in a while.
I understand that Bart and Tiki (CUHG) acquired their teaching styles and methods from the years they spent at Wallaby.
- So then also:
http://www.wallaby.com/aerotow_primer.php
Aerotow Primer for Experienced Pilots
The Wallaby Ranch Aerotowing Primer for Experienced Pilots - 2019/08/23
A weak link connects the V-pull to the release, providing a safe limit on the tow force. If you fail to maintain the correct tow position (centered, with the wheels of the tug on the horizon), the weak link will break before you can get into too much trouble.
- Yeah, figures.
They prefer to set a higher angle of attack than I typically use.
Six of one, half a dozen of the other.
I think what they do works well for students on novice and intermediate gliders...
Just not so much with 582 Dragonfly propwash.
...which have a lot of washout compared to higher performance gliders. They set the angle of attack such that the wing tips are parallel to the ground. On a Falcon this places the root and keel of the wing at a very high angle of attack - probably around 30 degrees or more.
The set angle is only supposed to be relevant before the wing (not the wing and pilot) gets up to flying speed. The idea is that a high angle exposes a lot of undersurface and renders the glider more vulnerable to getting rolled and/or pitched up by gusts and turbulence. Then the wing's supposed to start flying and trim very quickly into the takeoff roll and the set angle then becomes totally irrelevant.
From discussions with Bart I believe the reasoning for this is to allow the glider to leave the cart as soon as possible to avoid excessive ground speed.
Bull fucking shit. This is absolutely totally clueless. And where the hell are Bart and Tiki commenting on this? Bart's got ONE post here - 2019/08/16 13:07:59 UTC. 29 words spread out over the course of three sentences. And this isn't worth five or ten minutes worth of his extremely precious time?
Bart said that if the cart was to hit a hole...
...the victim on the back end would likely be demolished the way Sheryl Zayas was with the total fucking douchebags at Florida Ridge on 2008/01/12.
http://www.hanggliding.org/viewtopic.php?t=5089
The Good-The Bad-The Ugly....
So we need to have fucking douchebags who allow this kind of criminal negligence at their operations sued outta existence to send the proper message out to other criminally negligent total fucking douchebags.
...or for some other reason come to an abrupt stop...
Like maybe the known defective launch carts Davis and his asshole buddies were trying to use...
http://ozreport.com/pub/images/fingerlakesaccident2.jpg
http://ozreport.com/pub/images/fingerlakesaccident3.jpg
...at Finger Lakes on the afternoon of 2004/08/02.
...the glider would nose over and cause serious injury but injury would be much worse at higher ground speeds.
Yeah, brilliant idea. Let's set the glider's nose high 'cause we can afford to run into holes and use defective launch carts at lower speeds 'cause obviously the injuries would be less severe. And if we only take off straight into twelve mile per hour straight-in headwinds we can cut the minimum required groundspeed in half and only have a quarter of the impact energy. How many more times are ya gonna force me to say totally fucking moronic?
Setting a high angle of attack and having the pilot...
You don't have an actual pilot participating in lunatic bullshit like this. We know how to design safe, stable launch carts and check for holes on runways.
...hold that position during the take-off roll was the simplest way to teach students to launch...
And we all know that the simpler something is the better and safer it is. Just look at the easily reachable Bobby Fucking-Genius Bailey pro toad bent pin barrel release ferchrisake. Bart...
http://www.hanggliding.org/viewtopic.php?t=21033
barrels release without any tension except weight of rope..
Bart Weghorst - 2011/02/25 19:06:26 UTC
But I've had it once where the pin had bent inside the barrel from excessive tow force. My weaklink was still intact. The tug pilot's weaklink broke so I had the rope. I had to use two hands to get the pin out of the barrel.
No stress because I was high.
...can tell ya all about those.
...as this technique requires minimal student input until the glider leaves the cart.
And we certainly don't want our students having to engage in anything as demanding as pitch control. (Got any videos of them landing?)
I also believe the thought is that the high angle of attack in the cart mimics the angle of attack of the tandem glider used for training, so the transition from tandem to solo glider was minimized.
Sounds iffy to me. If the high angle of attack in the cart mimics the angle of attack of the tandem glider used for training they might not realize they're flying solo and fail to steer around trees, buildings, parked gliders.
There could be other reasons that I don't know about but...
...I'm sure many will soon become apparent after we get this new approach ramped up and standardized in the SOPs.
...this technique has worked extremely well and proven successful for Wallaby and Cowboy Up, so there's no reason to change as long as this technique is applied in a controlled environment.
- If it ain't broke...
- And the sky has always been such a marvelously controlled...
http://ozreport.com/forum/viewtopic.php?t=30971
Zach Marzec
Paul Tjaden - 2013/02/07 23:47:58 UTC
When the lift/turbulence was encountered, the weak link on the tow line broke as the nose of the glider pitched up quickly to a very high angle of attack. Apparently, the glider stalled or possibly did a short tail slide and then stalled and then nosed down and tumbled. Eye witnesses said the glider tumbled twice and then struck the ground with the base tube low. Due to the extremely low altitude, there was no time for the pilot to deploy his reserve parachute.
Zach was conscious immediately after the accident but died in route to the hospital.
Beyond these facts anything else would be pure speculation. I have personally had numerous weak link breaks on tow, both low and high, after hitting turbulence and have never felt in danger of a tumble. I have witnessed countless others have weak link breaks with no serious problems. We train aero tow pilots how to handle this situation and I am certain that Zach had also encountered this situation many times before and knew how to react properly. Apparently, Zach simply hit strong low level turbulence, probably a dust devil that could not be seen due to the lack of dust in Florida, the nose went too high and he tumbled at a very low altitude.
Strong dust devils in Florida definitely do exist even though they are rare. My wife had a near miss when she encountered a severe dusty a couple years ago and I almost lost a brand new $18,000 ATOS VX when it was torn from its tie down and thrown upside down.
I wish I could shed more light on this accident but I am afraid this is all we know and probably will know. Zach was a great guy with an incredible outlook and zest for life. He will be sorely missed.
...environment.
In other words I believe that this technique mainly works in the appropriate conditions...
With, of course, an appropriate weak link with a finished length of 1.5 inches or less.
...such as zero or negligible cross wind, very low gust factor, minimal turbulence and grass surfaces, which is the environment typically used for training and for less experienced pilots.
Everything totally oozing with safety. Makes my mouth water just thinking about it.
There's a difference between towing from grass surface versus a concrete surface in midday summer conditions. Concrete is typically a source for thermals whereas green grass isn't, so thermals are more likely to kick off when launching from concrete, plus the turbulent wind blast (prop blast) from the tug propagates and is far more pronounced on concrete whereas on grass it seems to have less effect on the glider possibly due to being absorbed and dissipated by the grass, I don't the physics but I do feel the difference - this was also clearly evident in Big Spring.
Clearly. Just watch what was going on with Prequel Davis and Davis.
What a load o' crap. You wanna avoid thermal turbulence then fly in the mornings and evenings. You fly in thermal conditions you expect strong turbulence and adjust your flying accordingly. You avoid concrete 'cause it's hard and abrasive.
The weather conditions for cross country and competitions are far more variable and active compared to conditions during training...
Thank gawd.
...and local recreational flying.
I do my recreational flying in the strongest, most violent thermal conditions I can get my hands on. AT is primarily a flatlands launch option and I have zero interest in sled runs and hanging out on ridges. And I equip myself to be able to handle anything that can be thrown at me - save for some douchebag fixing whatever's going on back there or the focal point of his safe towing system doing the same thing.
During launch pilots may have to deal with stronger winds, wind gusts, crosswinds, thermals and prop blast.
Manned Kiting
The Basic Handbook of Tow Launched Hang Gliding
Daniel F. Poynter
1974
"A bad flyer won't hurt a pin man but a bad pin man can kill a flyer." - Bill Bennett
"The greatest dangers are a rope break or a premature release." - Richard Johnson
Holding a high angle of attack on the cart at the start of and during the takeoff roll in a cross wind will likely cause the upwind wing to lift while the downwind wing is stalled.
Really? So maybe it's a BAD idea to hold a high angle of attack on the cart at the start of and during the takeoff roll in a crosswind?
The consequences are obvious unless brought under control - many of us have seen it happen. Setting a high angle of attack in gusty conditions can cause both wings to lift prematurely. Add thermals to the mix and getting lifted prematurely by the wind gust and or thermal or both and then getting slammed back down due to prop blast or because the gust dropped etc. is a recipe for disaster.
Yet a TOTALLY AWESOME recipe for training student pilots.
Setting an appropriate angle of attack will reduce the effect of the above mentioned conditions. For example the appropriate angle of attack will reduce the effect of the crosswind component by ensuring both wings reach flying speed before leaving the cart...
Unless you get hit by 582 Dragonfly propwash. We're still working on that issue.
...so typically the wing will yaw to the upwind side rather than lift the wing. Maintaining the appropriate angle of attack during the take-off roll prevents both wings lifting prematurely, so the glider and cart remain on the ground while passing through the prop blast and leave the cart at safe flying speed.
But that's off the table for students due to safety issues.
Maintaining the appropriate angle of attack during the take-off roll prevents the wings lifting prematurely which I believe is a common cause of accidents where the base bar touches the ground when it sinks in front of the cart i.e. the wing is lifted prematurely and then settles back down in front of the cart. Carrying the appropriate speed prior to leaving the cart mitigates this risk.
See above.
Setting the appropriate angle of attack reduces the likelihood of popping up above the tow plane on take-off This is the other extreme often seen when pilots hold their weight back (pushed out) as they leave the cart. This is a concern to tow pilots who have to maintain control close to the ground while the tail is being picked up and is a concern...
It's at total bullshit concern. Tugs don't get the least bit fazed by gliders way the hell above them - which never happens on launch anyway - and if they did they've got a lever on the joystick to instantly and seamlessly dispense with the annoyance.
...when pilots...
You mean passengers?
...pop up high and break the weak link...
This is the first and last acknowledgement of the focal point of our safe towing system in this entire now 83 post thread. (And no "line breaks".)
...then stall and crash because of the high angle of attack and immediate loss of airspeed.
- Oh bullshit. A weak link success always increases the safety of the towing operation and the high angle of attack / immediate loss of airspeed is an easily dealt with inconvenience. You hafta be a total douchebag to crash as a consequence of this safety device kicking in. (Davis? You gonna let this total crap slide without comment?)
- So what strength is this weak link nowadays, Mick? And how was that figure determined?
Carrying the appropriate speed leaving the cart makes dealing with a premature release at the tug or glider a routine landing.
At the cost of a high risk of coming off the cart and flying into the ground. Doesn't sound like a very good plan to me.
So what is the appropriate angle of attack on the cart?
Who the fuck cares? We fly these things by FEEL just fine.
In the absence of information from USHPA I refer BHPA (British Hang Gliding & Paragliding Association).BHPA Technical Manual (Section-2 Chapter 7) says "The glider should sit at a low +ve angle of attack (keel at approx 18° - high angles of attack produce problems with wind gusts)".
Fuck BHPA.
What does this mean in practice. Depending on the glider, but generally, when laying down in the harness with the glider on the cart, the base bar will be at around neck/chest level (best glide) when the angle of attack of attack is around 20 degrees (BHPA says approximately 18° - Approximately to me is 18° to 22°). This has always worked well for me and I have a fair number of tows under my belt in various conditions.
Do you adjust your pitch in accordance with conditions?
In the event the cart isn't adjustable then the appropriate angle of attack should be established during the take-off roll by pulling in until about best glide position.
Not pushing out? Aren't we risking a lethal nose-in?
Whenever someone starts this discussion about angle of attack I ask if they would attempt a hill or mountain launch with their glider nose high e.g. running down the slope with 30 degree angle of attack? Of course the answer is no. I ask the same about foot launching on flat surfaces behind payout winches, stationary winches or tow planes (aerotrow), and of course the answer is no. So I wonder why we feel it's ok to have a high angle of attack when launching from a cart?
Because we are Cowboy Up and AT operators can say and/or do no wrong.
My thought is that a high angle of attack creates too many risks for the type of glider and the areas and conditions in which I fly...
Actual real world stuff? Who'da thunk?
...but it seems to work in a controlled environment such as flight parks/schools.
It SEEMS to work in a controlled environment such as flight parks/schools. High praise. In other words this moronic bullshit is gonna kill somebody sooner or later - the way we saw things go down with Davis's stupid ass at the beginning of this thread - if we're moronic enough to keep it up.