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Wing Drop, Aerotow vs Winch, Grass vs Pavement.



 
 
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  #11  
Old March 21st 21, 06:51 PM posted to rec.aviation.soaring
Frank Whiteley
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Posts: 2,099
Default Wing Drop, Aerotow vs Winch, Grass vs Pavement.

On Saturday, March 20, 2021 at 8:56:44 PM UTC-6, 2G wrote:
On Saturday, March 20, 2021 at 8:40:53 AM UTC-7, Bob W. wrote:
On 3/20/21 7:52 AM, Hartley Falbaum wrote:
"What else did I miss?"---the other side of the equation in risk
analysis. What is the worst that can happen if I don't release? vs
What is the worst that can happen if I do? There may be a 1-2 second
"startle factor" in some cases. So, the decision must be
pre-loaded. There is very little cost (usually) to a release.

Kudos to BFC for attempting to take this particular
incident/accident/discussion beyond "mere panacea declamations" to which
the RAS medium seems (to me, dry chuckle) prone.

On the off chance there're some lurkers "somewhat earlier along" the
soaring learning curve - as opposed to long-time RAS regulars (which
includes me, and who seem to in recent years be hogging the forum ) -
this thread-to-date contains potentially-personally-useful,
seriously-good, food for thought.

Hartley's "reduction-ad-absurdem" post above is but one example. In my
view, "panacea fixes" (should they in fact be viewed within one's mind
as such) are too-often a blind alley when it comes to such things as
future learning and "properly preparing one's mind" to commit soaring in
as personally-healthy a manner as possible.

A common example of "panacea thinking" - at least in my part of the
Rocky Mountain Front Range west - is close-minded variations of: "I'll
be OK height-wise so long as I have X-thousand feet msl at location Y
back in the hills". Well, yeah, most of the time, maybe...but how to
reconcile that thinking with the thinking inherent within H. Falbaum's
hypothetical line of thought? One size "generally" can't *possibly* fit
every situation, and it's up to Joe Glider Pilot to decide how best to
approach this conundrum.

Given the inherent imperfections in humanity - imperfect
judgment/skills, lack of omniscience, etc. - while perfection isn't an
option, Joe Glider Pilot can still do a whole lot, and go a long way, to
avoid known (to those with greater experience & skills)
situations/physical-harm/death that *should* be avoidable, given their
existing skills/knowledge.
- - - - - -

Switching here from "Sermon from the Mount" mode to (so I hope)
illustrative examples from experience, O'beer thirty, tale-telling mode....

Early in my post-1-26, 15-meter glass, "somewhat-nose-hooked", aerotow
state, while attempting to take off from a grass strip in the mountains
north of Sun Valley, ID, several things made me pre-launch nervous:
slight crosswind, new-to-me tug/pilot of unknown provenances, knee-high
grass to either side of runway. I and my wing-runner/partner discussed
the situation and pre-planned things best we could (both "local
strangers" and prolly 200 hours total time each) and off I went. Pulled
the plug after an upwind wing drop followed by progressive swerving
into-wind along w. failure of the wing to lift. No harm, no foul was the
result outside the cockpit; inside the cockpit...not so much. Serious
dismay, as I felt that "somehow" I could've done better under existing
circumstances.

And so it proved on the 2nd launch attempt following further discussion
w. my partner *and* the tow-pilot, and some refining of my mental launch
go/no-go plan as well as techniques and "overall awarenesses".

Zooming ahead mightily through time, in that and two other ships (HP-14
w. "50% nose/CG hook, 15-meter span, no negative flaps, V-tail, tail
skid; and 15-meter Zuni *with* negative flaps, "somewhat nose-hooked",
heavily-weighted tailwheel) I aborted 1-each aerotow, both times
followed by successful launches behind the same tug/pilot. Both were
5,300'msl, summertime, concerning-but-far-less-so than the C-70

experience...because of successfully pre-planned/decided "mental
scenario-ing". In both ships, I also made more-than-one (several? many?)
no-wing-runner takeoffs entirely w/o incident.

Bragging? Not intended as such. Rather trying to illustrate how
"preparing one's mind 'properly'" can be, likely *will* be, a good thing
for Joe Glider Pilot, if avoiding adrenaline, negative-excitement, and -
potentially - accidents, is deemed personally desirable.

Other than what I've read on RAS, I know zip about the situation and the
pilot in this particular unfortunate - seemingly, avoidable - accident.
I wish him a speedy and full recovery and continued good soaring, if he
so chooses. And part of this *particular* Joe Glider Pilot would
genuinely appreciate hearing from the horse's mouth at some point in the
future, by way of refining my mental picture.

YMMV,
Bob W.

Another factor not mentioned is what do you have on the wing tip: a skid or a wheel. If it is a wheel and you are towing on a hard surfaced runway a wing drop will be a non-event. If fact, when I self launch (with a wing tip wheel) I want the wing down even if offered a wing runner. A wing that starts down can't drop.
If, however, you are launching off of turf there will be more resistance than a hard surface. I don't ever fly off of turf so I can't say if it would make a difference. Probably depends upon how long the grass is.
A nose hook does provide some self-correcting force, but how much? the nose hook is, at most, one meter ahead of the main; an 18m glider gives forces on the wing tip a 9:1 lever arm to the nose hook. While that is better than nothing, what are the restorative forces? Say the towplane is exerting 200lb on the glider and the nose is 10 degrees off centerline; the restorative force is 35lb. This would only offset about a 5lb force on the wing tip - not very much.

Tom

Lush turf is pretty grabby and if a pilot tries to roll the glider with ailerons, the down wing aileron only grabs more turf and makes the situation worse. Only opposite rudder should be used until the wing starts to rise.
  #12  
Old March 21st 21, 08:52 PM posted to rec.aviation.soaring
Eric Greenwell[_4_]
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Posts: 1,939
Default Wing Drop, Aerotow vs Winch, Grass vs Pavement.

Frank Whiteley wrote on 3/21/2021 10:51 AM:
On Saturday, March 20, 2021 at 8:56:44 PM UTC-6, 2G wrote:

....
Bragging? Not intended as such. Rather trying to illustrate how
"preparing one's mind 'properly'" can be, likely *will* be, a good thing
for Joe Glider Pilot, if avoiding adrenaline, negative-excitement, and -
potentially - accidents, is deemed personally desirable.

Other than what I've read on RAS, I know zip about the situation and the
pilot in this particular unfortunate - seemingly, avoidable - accident.
I wish him a speedy and full recovery and continued good soaring, if he
so chooses. And part of this *particular* Joe Glider Pilot would
genuinely appreciate hearing from the horse's mouth at some point in the
future, by way of refining my mental picture.

YMMV,
Bob W.

Another factor not mentioned is what do you have on the wing tip: a skid or a wheel. If it is a wheel and you are towing on a hard surfaced runway a wing drop will be a non-event. If fact, when I self launch (with a wing tip wheel) I want the wing down even if offered a wing runner. A wing that starts down can't drop.
If, however, you are launching off of turf there will be more resistance than a hard surface. I don't ever fly off of turf so I can't say if it would make a difference. Probably depends upon how long the grass is.
A nose hook does provide some self-correcting force, but how much? the nose hook is, at most, one meter ahead of the main; an 18m glider gives forces on the wing tip a 9:1 lever arm to the nose hook. While that is better than nothing, what are the restorative forces? Say the towplane is exerting 200lb on the glider and the nose is 10 degrees off centerline; the restorative force is 35lb. This would only offset about a 5lb force on the wing tip - not very much.

Tom

Lush turf is pretty grabby and if a pilot tries to roll the glider with ailerons, the down wing aileron only grabs more turf and makes the situation worse. Only opposite rudder should be used until the wing starts to rise.


Flapped ships can start in a negative setting, and avoid the turf grabbing by the ailerons.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
  #13  
Old March 21st 21, 09:03 PM posted to rec.aviation.soaring
[email protected]
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Posts: 5
Default Wing Drop, Aerotow vs Winch, Grass vs Pavement.

Before a wing tip even touches the ground, any tailwind component counteracts any aerodynamic control input. The more deflection, the more OPPOSITE effect you get, causing pilot-induced problems. (Why is this glider shooting off to the left when I have full right deflections **!!) It can be mistakenly blamed on the wing runner, prop blast, rogue gust, etc. Hang on a split second longer, and you suddenly have positive control, maybe (?), when forward speed overcomes the tailwind. But by then you just scared yourself and innocent people. Neutralizing the controls, or using "opposite" inputs for the brave, until the tailwind vanishes should help.

Better yet, I just avoid any tailwind tow (for multiple good reasons), especially on an unassisted wing-down takeoff.
  #14  
Old March 22nd 21, 05:50 PM posted to rec.aviation.soaring
Aldo Cernezzi
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Default Wing Drop, Aerotow vs Winch, Grass vs Pavement.

I suggest everyone have a look at this accident report from France.
It is significant and unusual, as a tow operation lead to a violent groundloop with the sailplane landing inverted, as in a classic and tragic winch accident.
The reason is most probably to be found in the strong headwind.
The accident started with a wing drop, and was irrecuperable within 3 seconds.
The French text shouldn't be a big issue, as the photographic sequence illustrates the event very well and is self-explanatory (especially if you look at the time stamp of each picture.

https://www.bea.aero/uploads/tx_elyd...f-dd140430.pdf

Safe flights,
Aldo Cernezzi
www.voloavela.it
  #15  
Old March 22nd 21, 09:03 PM posted to rec.aviation.soaring
Accounts Receivable
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Posts: 1
Default Wing Drop, Aerotow vs Winch, Grass vs Pavement.

On the winch, if the wing drops, release immediately, you don't have time to consider your options. There's a good chance you can't do it fast enough, and it's going to hurt.
The wing runner isn't going to do a lot of running, if they start you from a balanced position, (which might be slightly different than wings level), and your control inputs are neutral, you will have aileron control and flying speed very quickly after the "All Out" calls.




  #16  
Old March 23rd 21, 01:41 AM posted to rec.aviation.soaring
waremark
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Posts: 377
Default Wing Drop, Aerotow vs Winch, Grass vs Pavement.

On Monday, 22 March 2021 at 20:03:39 UTC, Accounts Receivable wrote:
On the winch, if the wing drops, release immediately, you don't have time to consider your options. There's a good chance you can't do it fast enough, and it's going to hurt.
The wing runner isn't going to do a lot of running, if they start you from a balanced position, (which might be slightly different than wings level), and your control inputs are neutral, you will have aileron control and flying speed very quickly after the "All Out" calls.


At my club we try to emphasise that the wing runner should not allow the launch to start if there is a significant up or down force on the wingtip.

Someone mentioned water ballast - I think that is very significant, as a low wing allows water to flow towards the tip and make that wing heavier, making recovery less likely.
  #17  
Old March 23rd 21, 01:57 AM posted to rec.aviation.soaring
Martin Gregorie[_6_]
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Posts: 699
Default Wing Drop, Aerotow vs Winch, Grass vs Pavement.

On Mon, 22 Mar 2021 17:41:30 -0700, waremark wrote:


At my club we try to emphasise that the wing runner should not allow the
launch to start if there is a significant up or down force on the
wingtip.

Same at my club. In addition, if there's a cross wind for a winch launch
and the pilot is using aileron to hold the downwind tip up rather than
leaving the stick central while the wing runner moves the tip up or down
to zero the force he's feeling, the wing runner is encouraged to stop the
launch until the stick is centralised.

This is safer because the pilot can't feel what the up- or down-force of
the wingtip is - only the wing runner knows that. And so, if the
balancing is left to the pilot, the chances of an immediate tip drop is
raised.

Someone mentioned water ballast - I think that is very significant, as a
low wing allows water to flow towards the tip and make that wing
heavier, making recovery less likely.

Agreed.


--
Martin | martin at
Gregorie | gregorie dot org

  #18  
Old March 23rd 21, 05:30 AM posted to rec.aviation.soaring
Brian[_1_]
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Posts: 399
Default Wing Drop, Aerotow vs Winch, Grass vs Pavement.

On Monday, March 22, 2021 at 10:50:24 AM UTC-6, Aldo Cernezzi wrote:
I suggest everyone have a look at this accident report from France.
It is significant and unusual, as a tow operation lead to a violent groundloop with the sailplane landing inverted, as in a classic and tragic winch accident.
The reason is most probably to be found in the strong headwind.
The accident started with a wing drop, and was irrecuperable within 3 seconds.
The French text shouldn't be a big issue, as the photographic sequence illustrates the event very well and is self-explanatory (especially if you look at the time stamp of each picture.

https://www.bea.aero/uploads/tx_elyd...f-dd140430.pdf

Safe flights,
Aldo Cernezzi
www.voloavela.it


Very interesting and worth translating.
This data point would seem to indicate higher energy tows are a higher risk of having an issue wshould a wing drop occur. In this event it appear the strong headwind made it an even higher energy tow.
With that much headwind I would not have expected a wing drop as I would have expected to have good aileron and rudder control immediately. But as the report hints to, the combination of a gust and the prop wash may have overpowered the controls.

Thanks for posting.

Brian
  #19  
Old March 23rd 21, 05:34 AM posted to rec.aviation.soaring
Brian[_1_]
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Posts: 399
Default Wing Drop, Aerotow vs Winch, Grass vs Pavement.

On Monday, March 22, 2021 at 6:57:59 PM UTC-6, Martin Gregorie wrote:
On Mon, 22 Mar 2021 17:41:30 -0700, waremark wrote:


At my club we try to emphasise that the wing runner should not allow the
launch to start if there is a significant up or down force on the
wingtip.

Same at my club. In addition, if there's a cross wind for a winch launch
and the pilot is using aileron to hold the downwind tip up rather than
leaving the stick central while the wing runner moves the tip up or down
to zero the force he's feeling, the wing runner is encouraged to stop the
launch until the stick is centralised.

This is safer because the pilot can't feel what the up- or down-force of
the wingtip is - only the wing runner knows that. And so, if the
balancing is left to the pilot, the chances of an immediate tip drop is
raised.
Someone mentioned water ballast - I think that is very significant, as a
low wing allows water to flow towards the tip and make that wing
heavier, making recovery less likely.

Agreed.


--
Martin | martin at
Gregorie | gregorie dot org


Good point about wing runners. What I teach wing runners is if the wing wants to go up, to let it go up as high as you can reach. If it goes low, let it go as low as is practical, as this will signal the pilot to put the correct input in to correct for wing low or wing high condition.

Brian
  #20  
Old March 23rd 21, 05:20 PM posted to rec.aviation.soaring
Dan Marotta
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Posts: 4,601
Default Wing Drop, Aerotow vs Winch, Grass vs Pavement.

Not so much if the wing tanks are full and not interconnected.

Dan
5J

On 3/22/21 6:41 PM, waremark wrote:
Someone mentioned water ballast - I think that is very significant, as a low wing allows water to flow towards the tip and make that wing heavier, making recovery less likely.

 




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