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Undershoot Vs. Overshoot airport landing accidents



 
 
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  #11  
Old April 18th 19, 03:00 PM posted to rec.aviation.soaring
Tango Whisky
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Default Undershoot Vs. Overshoot airport landing accidents

Le jeudi 18 avril 2019 15:36:08 UTC+2, Steve Leonard a écritÂ*:
On Thursday, April 18, 2019 at 8:12:20 AM UTC-5, Tango Whisky wrote:

Go and try that with a DuoDiscus.

Bert TW


But, only on a runway that is clear off the departure end. Because you will depart, right, Bert?

Steve Leonard


Well, you will float over the runway forever.
I always prefer a slip (which works extremely well in both ASK21 and DuoDiscus) - no change of attitude, and dosage is much easier.

But in the end, I prefer to train people to do a proper approach pattern, where you end up un final with 50% airbrakes.
  #12  
Old April 18th 19, 03:47 PM posted to rec.aviation.soaring
Tim Taylor
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Default Undershoot Vs. Overshoot airport landing accidents

Please don't teach the dive to lose altitude technique. The problem is total energy, simply the kinetic plus potential energy. Most pilots are trained with judgment on altitude (potential energy) but have poor judgment how speed (kinetic energy) will impact touch down point and speed. Our brains are much better at doing estimates with constant speed. Yes, it is a neat trick to dive at the ground but has a higher probably for error than simpler techniques. See the article in soaring about the pilot that flew off the end of the runway. If you are really high, 500 to 1000 feet agl, the glider polar works both ways around the best l/d, rather than speeding up it is better to slow down and use full spoilers and a slip. I have modeled both techniques and the achieved l/d over the ground is just as low with the slower technique and there is no speed to scrub once you are back in correct height band for the approach. If you are really high, slow down to near stall speed, use full spoilers and slip. As you get lower (about 400 feet agl) accelerate to normal approach speed for the conditions.

Even better is to teach students to be flexible and not get fixated on completing a traditional pattern, S-turns or a 360 if a pilot is really too high are better options.
  #13  
Old April 18th 19, 04:03 PM posted to rec.aviation.soaring
Andreas Maurer[_2_]
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Default Undershoot Vs. Overshoot airport landing accidents

On Thu, 18 Apr 2019 07:00:39 -0700 (PDT), Tango Whisky
wrote:

Steve Leonard

Well, you will float over the runway forever.
I always prefer a slip (which works extremely well in both ASK21 and DuoDiscus) - no change of attitude, and dosage is much easier.


100% agree.


But in the end, I prefer to train people to do a proper approach pattern, where you end up un final with 50% airbrakes.


.... not to mention that precise speed control is the thing that
counts.

It is absolutely necessary in an outlanduing, and in my humble opinion
ought to be trained in any landing, even if there''s a 6.000 ft
runway.

Cheers
Andreas
  #14  
Old April 18th 19, 04:13 PM posted to rec.aviation.soaring
Tango Eight
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Default Undershoot Vs. Overshoot airport landing accidents

On Thursday, April 18, 2019 at 10:47:26 AM UTC-4, Tim Taylor wrote:
Please don't teach the dive to lose altitude technique. The problem is total energy, simply the kinetic plus potential energy. Most pilots are trained with judgment on altitude (potential energy) but have poor judgment how speed (kinetic energy) will impact touch down point and speed. Our brains are much better at doing estimates with constant speed. Yes, it is a neat trick to dive at the ground but has a higher probably for error than simpler techniques. See the article in soaring about the pilot that flew off the end of the runway. If you are really high, 500 to 1000 feet agl, the glider polar works both ways around the best l/d, rather than speeding up it is better to slow down and use full spoilers and a slip. I have modeled both techniques and the achieved l/d over the ground is just as low with the slower technique and there is no speed to scrub once you are back in correct height band for the approach. If you are really high, slow down to near stall speed, use full spoilers and slip. As you get lower (about 400 feet agl) accelerate to normal approach speed for the conditions.

Even better is to teach students to be flexible and not get fixated on completing a traditional pattern, S-turns or a 360 if a pilot is really too high are better options.


No 360s please. That has disaster written all over it.

Kai Gersten introduced me to the "reversed base leg" approach years ago. This works great, it's easy to fly, easy to teach and the technique is the same in any glider. You extend the (too high) base leg past the runway centerline some appropriate distance, make a 180 (turn towards the runway), make a second base leg from the other side of the runway.

I've experimented with S-turns (after reading George Moffatt). They work well. I was able to turn a much too high approach into a spot landing twice in two tries. Glider folk on the ground won't enjoy this, they'll think something is wrong.

best,
Evan Ludeman / T8
  #15  
Old April 18th 19, 05:22 PM posted to rec.aviation.soaring
[email protected]
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Default Undershoot Vs. Overshoot airport landing accidents

I've experimented with S-turns (after reading George Moffatt). They work well. I was able to turn a much too high approach into a spot landing twice in two tries. Glider folk on the ground won't enjoy this, they'll think something is wrong.

best,
Evan Ludeman / T8


Yeah, S-turns work well. They were part of our curriculum 50+ years ago but I"m not sure how many U.S. pilots have experience with them now. I've used them at the airport and going into fields. At the airport, they can confuse folks on the ground and, especially, others in the pattern. But MUCH preferable to a 360 once you're down to pattern altitude.

I like coming in fairly high with plenty of airspeed. I can always get rid of it. Diving it off works but, as Tim observes, can be deceptive. I love slips.

Chip Bearden
JB
  #16  
Old April 18th 19, 05:37 PM posted to rec.aviation.soaring
[email protected]
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Default Undershoot Vs. Overshoot airport landing accidents

Bert, Would you accept an Arcus vs a Duo?
  #17  
Old April 18th 19, 05:44 PM posted to rec.aviation.soaring
Mike the Strike
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Default Undershoot Vs. Overshoot airport landing accidents

On Thursday, April 18, 2019 at 7:47:26 AM UTC-7, Tim Taylor wrote:
Please don't teach the dive to lose altitude technique. The problem is total energy, simply the kinetic plus potential energy. Most pilots are trained with judgment on altitude (potential energy) but have poor judgment how speed (kinetic energy) will impact touch down point and speed. Our brains are much better at doing estimates with constant speed. Yes, it is a neat trick to dive at the ground but has a higher probably for error than simpler techniques. See the article in soaring about the pilot that flew off the end of the runway. If you are really high, 500 to 1000 feet agl, the glider polar works both ways around the best l/d, rather than speeding up it is better to slow down and use full spoilers and a slip. I have modeled both techniques and the achieved l/d over the ground is just as low with the slower technique and there is no speed to scrub once you are back in correct height band for the approach. If you are really high, slow down to near stall speed, use full spoilers and slip. As you get lower (about 400 feet agl) accelerate to normal approach speed for the conditions.

Even better is to teach students to be flexible and not get fixated on completing a traditional pattern, S-turns or a 360 if a pilot is really too high are better options.


I've been playing with the high base approach lately as it was suggested by a visiting instructor and was also taught to me at a British glider site that suffers from bad rotor (a traditional approach at that site on a breezy day would have you whack into a stone wall well short of the runway!).

Many gliders handle the high speed descent very well - 70+ knots and full spoilers. I find the PW-6 is a delight in this approach and slowing down at landing quite natural. Some other gliders not so much! A colleague suggests that the Grob 103 prefers slower speeds where its sink rate is also quite high. Soaring pilots should be familiar with all landing approaches at their disposal and use the appropriate one for their glider and site conditions.

Far more pilots end up short through insufficient height or low energy than the reverse - the only two observations in this thread about overshooting a home field were pilots who mistook the flap handle for spoiler! I know of one outlanding overshoot in which the pilot deliberately flew across a huge field in an attempt to finish close to the gate and overran into a hedge..

Mike
  #18  
Old April 18th 19, 05:56 PM posted to rec.aviation.soaring
George Haeh
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Default Undershoot Vs. Overshoot airport landing accidents

Drag increases with the square of the airspeed (not exponentially).

So increasing airspeed from 55 to 70 increases drag by 62%.

Judgement is needed in round out.

Our Grob 103 can get frisky close to the ground with extra speed, single panel spoilers and one pilot. Older two seat trainers tend to have lots of wing area and small spoilers; so, you can go a long way in ground effect.

But no problem when your aim point is the threshold - much more interesting on hangar landings.

Kinetic energy remains constant with constant airspeed. On final we are using drag to dissipate potential energy instead of allowing it to convert to kinetic energy.
  #19  
Old April 18th 19, 06:01 PM posted to rec.aviation.soaring
Bob Whelan[_3_]
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Default Undershoot Vs. Overshoot airport landing accidents

On 4/18/2019 9:13 AM, Tango Eight wrote:
On Thursday, April 18, 2019 at 10:47:26 AM UTC-4, Tim Taylor wrote:
Please don't teach the dive to lose altitude technique. The problem is
total energy, simply the kinetic plus potential energy. Most pilots are
trained with judgment on altitude (potential energy) but have poor
judgment how speed (kinetic energy) will impact touch down point and
speed. Our brains are much better at doing estimates with constant
speed. Yes, it is a neat trick to dive at the ground but has a higher
probably for error than simpler techniques. See the article in soaring
about the pilot that flew off the end of the runway. If you are really
high, 500 to 1000 feet agl, the glider polar works both ways around the
best l/d, rather than speeding up it is better to slow down and use full
spoilers and a slip. I have modeled both techniques and the achieved l/d
over the ground is just as low with the slower technique and there is no
speed to scrub once you are back in correct height band for the approach.
If you are really high, slow down to near stall speed, use full spoilers
and slip. As you get lower (about 400 feet agl) accelerate to normal
approach speed for the conditions.

Even better is to teach students to be flexible and not get fixated on
completing a traditional pattern, S-turns or a 360 if a pilot is really
too high are better options.


No 360s please. That has disaster written all over it.

Kai Gertsen introduced me to the "reversed base leg" approach years ago.
This works great, it's easy to fly, easy to teach and the technique is the
same in any glider. You extend the (too high) base leg past the runway
centerline some appropriate distance, make a 180 (turn towards the runway),
make a second base leg from the other side of the runway.

I've experimented with S-turns (after reading George Moffatt). They work
well. I was able to turn a much too high approach into a spot landing
twice in two tries. Glider folk on the ground won't enjoy this, they'll
think something is wrong.


Apologies for 'going further off into the weeds' here - at least relative to
the OP's explicit original question - but this is the sort of discussion I: 1)
find personally interesting, because 2) it touches upon 'stuff' that every
'serious' gliderpilot likely also finds interesting. I'm defining 'serious' in
this context as every Joe Glider Pilot interested in preservation of
self/glider for another fun flight tomorrow, regardless of whether it's to
sit-on-the-flagpole or go XC or whatever...

If JGP has somehow botched a pattern to the point he's 'uncomfortably high' on
final - and haven't we all done so for various reasons, ranging from
intentional practice, to unexpected serious/sustained lift on base or final,
to 'something(s) else' - he'll be faced with 'What to do about it to safely
salvage the situation?'

FWIW, I'm not a believer in 'specific rules of thumb that are always 100%
correct/applicable,' but am more a 'fundamentalist thinker.' In high-final
terms, I fall into the category that believes salvation is most likely safely
accomplishable for Joe Average Glider Pilot (me!) by avoiding - as far as
'reasonably possible' - edging into Joe Test Pilot territory. I put 360's on
final into the JTP category, for example...*somewhat* akin to 'practicing
departure-from-controlled-flight in the pattern,' in the sense that the
potential 'good return' isn't worth the unavoidably-accepted 'in-flight risk.'
("Hey! Lemme practice turning my back on the field at the last minute; it
seems like a good idea just because it flashed into my mind as 'salvation.'
Woohoo!")

At my specific home field (Boulder, CO), doing so would also guarantee either
crossing (twice!) through a parallel power-plane-runway's final approach, or
(again, twice) 'somewhat below' the glider pattern's final/base legs. Not so
wise in my book, regardless of the 'wisdom' (Not!) of turning one's back on
one's intended touchdown area.

Those times I (intentionally, mostly, but rarely, unintentionally) found
myself 'WAY too high on shortish final approach' at Boulder I opted either for
landing long (once convinced it was safely possible) or,(seriously considered,
but never actually required) S-turning along final to lengthen the final's
flightpath length. The latter was always Option 2, in a preferred sense, for
the reasons Tango Eight alludes to. (It's bad enough to alarm myself; no need
to go out of my way to alarm other pilots who may be sharing nearby airspace!
Ground-pounders? Worry about 'em later...)

I rejected the 'dive-n-drag' approach (commonly used 'for fun' at one time by
the gliding FBO's ride pilots in their 2-32s 'just because hey could') cuz I
never ended up 'ridiculously high' in a spoilered ship, only in (my own)
large-deflection-landing-flapped ships, and if there's a *second* situation
such ships don't handle particularly gracefully (the first being low, slow,
and short), it's being in ground-effect with excess speed and full flaps.
(Kids, can you spell: F - L - O - A - T ???)

WRT off-field approaches, both the S-turning option and the 'extended/reversed
base leg seem 'eminently-safely-usable' to me, without 'messing about with'
(for the first time, likely, for many) the suddenly-increasing-kinetic-energy
playground associated with a diving-final-approach. (Best to avoid JTP-land,
again...)

YMMV, of course.

Bob W.

P.S. I believe it's GOOD (for JGP) to seriously consider, and 'safely practice
this sort of stuff' by way of self-education and preparation for their own,
personal 'Reality Show!'

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  #20  
Old April 18th 19, 07:08 PM posted to rec.aviation.soaring
ProfJ
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Default Undershoot Vs. Overshoot airport landing accidents

On Wednesday, 17 April 2019 09:28:44 UTC-6, wrote:
I always assumed that there are more overshoot airport accidents than undershoot ones. That is mainly due to our general knowledge that it's better to be too high than not high enough.
Am I correct here ?
Dan


Some good take-homes here that are generally true:

1. You are more likely to err and land short on airport landings.
2. You are more likely to err and land long or with too much energy on outlandings.
3. You can dump more energy with drag at high speed BUT...
4. This is very glider-dependent (i.t.o. your state at the threshold of runway)
5. Lengthening your glide path safely is easy BUT...
6. Not that easy to practice, depends on your home site.
 




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