Glider Crash - Minden?

Mike Schumann wrote:
My point is not to try to avoid the collision, but show how big of a problem
it is when you get too close to some fast iron. It really gets to be
problematic to figure out what the best evasive maneuver is when you have a
very high closure rate.

The best solution is to try to avoid getting into this situation in the 1st
place. Having an operational transponder would be a good way to start.


Start with PCAS it's cheaper, uses less power, and helps you control
your own destiny -- if you only have room for one unit. However, the
transponder/PCAS combination gives you everything you need to avoid
the scary big fast airplanes, AND the friendly little gliders in your
own club which are the ships you are most likely to hit. If all
gliders were so equipped we would all be safer.

Stall/spin in the pattern, midair anywhere -- these are the things
that kill glider pilots.

I suspect that after a pilot has flown with PCAS for awhile and has
come to realize how much traffic there is that he was not aware of
before, that pilot will be even more likely to want the transponder, too.


Jack

"Martin Gregorie" wrote in message
...
Stop turning and stick the nose down steeply at the same time.

That's about the quickest way to exit a given volume of air that I can
think of if you're starting from a low airspeed.

That's precisely the problem: exactly what volume of air do I need to exit?
At those distances and rates of closure it is very difficult to estimate the
point of impact in 3D, especially given the extremely limited time for
decision. No ball game that I know comes close to the order of magnitude of
parameters that we deal with here. This is closer to dodging bullets than it
is to any ball game.

Oh, and by the way, from the other side this situation does not look nearly
as dramatic. If initiated 20 seconds before impact, a mere 2g pull (in
either direction) for 5 seconds (followed by straight flight) puts the jet's
trajectory nearly a mile from the point of impact -- the distance that
glider can not possibly cover in the same time even in the worst case. This
assumes the jet speed of 300 kts.

(Could this possibly have been at least the part of the logic behind giving
gliders right-of-way over powered aircrafts?)
--
Yuliy

Zooms maintain total energy, assuming no losses.

Total energy = potential energy + kinetic energy = mgh + 1/2 mv2.

If v(elocity) reduced from 80 knots to 50 knots then
Gain in h (eight) = 170 feet.
From 100 knots to 50 knots then gain = 330 feet.

Hence those pull-ups into thermals and after racing finishes.

If you were at 80 knots and dived 350 feet, then you would
Accelerate to 120 knots.

However if you are low and slow at 50kts then a pull up
Will only give you 40 feet before you stall at 40 knots.

Rory


Author: Edward Winchester
Date/Time: 16:10 07 September 2006
------------------------------------------------------------

If you're cruising fast between thermals, it may work better to put the
stick in your lap, which would zoom you at least a couple hundred feet.
(don't ask me how I know this.)

In article , Martin Gregorie
writes
Yuliy Gerchikov wrote:
"kirk.stant" wrote in message
oups.com...

Plus, 20 seconds is an eternity when it comes to getting out of the
way.

I asked this question several times, and never saw a convincing answer:
exactly how do you use even the 20 seconds if you have them to avoid
something coming at you at 300 (or, it was suggested, possibly much more)
knots?

Stop turning and stick the nose down steeply at the same time.

That's about the quickest way to exit a given volume of air that I can
think of if you're starting from a low airspeed. I'll be interested to
hear of anything that would be faster and/or of something what would
work if you're too low to dive away from the threat.


Yebbut, what if the threat is coming from below? This happened to me
when I spotted what I took to be a glider and tug combination, below and
at my 10 o'clock, which rather too rapidly resolved itself into 2 A-10s
climbing to my level. They went by about 100 feet higher, one each side.
I filed an airmiss report, but by the time it was investigated, the A-10
drivers concerned had returned home across the Pond.
--
Mike Lindsay

In article , Martin Gregorie
writes
Mike Schumann wrote:
If you are on a collision course, how are you going to know whether going
down is the right solution? He might be 50 ft below you, and you are going
to dive right into him. Or he might also decide to descend.

If you need to get out from in front while thermalling, you'll need some
more airspeed to do so and that means lowering the nose to accelerate
while, hopefully, turning to aim off to one side of him.

The opposition has first to see you in order to decide to descend. If we
assign equal probabilities to him climbing, turning or diving then
anything you do to move away from his current course has a 75% chance of
being right.

Now lets be generous and give him a 50% chance of seeing you.
Probabilities multiply when they are combined, so that gives you an 87%
chance of being right.

This brings to mind an interesting suggestion that I was taught when I got
my power license about avoiding collisions with birds: Always climb, as the
birds will tend to dive.

That's only useful if you have an engine or airspeed. If you're
thermalling and try that you'll end up descending about 2 seconds later
and, if the opposition saw you pull up, he'll be down there waiting for
you. Besides, if he read the same book you're quoting he'll be more
likely to pull up than to dive.

In any case, you didn't say what you'd do, so I'll ask again. What would
you do that's better than diving out of the way?


Most of the threats round these parts find it a lot easier to
avoid you at the last second by pulling up, so I reckon Martin's advice
is the best going.

One day about 15 years ago I was downwind to land on 03 in the
tug. I saw an A-10 passing west to east about at 500ft over the approach
to this runway. Of course, he would be long gone by the time I got
there, so no problem.

When I landed, people rushed up and said "Did you see him?"
"Who?"
"The A-10"
"Oh, yes, but he was half a mile away over the end of the
airfield"
"No, not him. The other one, which we saw screaming towards you
when you were downwind. He must have seen you at the last moment, he
pulled up and missed you by about 5 feet. We thought we'd be looking to
get a new tug."

I never saw the second A-10. But I'm glad they all went home
when the cold war ended.


--
Mike Lindsay

Martin Gregorie wrote:
Edward Winchester wrote:

I agree with Martin, but for the thermalling case,
I'd amend that to put the top rudder on the floor and
the stick in the opposite corner, at least at first.
You'll lose hundreds of feet in 10 seconds, and not
gain a ridiculous amount of airspeed.
I like that! Must add it to my mental store and/or try it with plenty
of height and an empty sky. I've had a very similar maneuver demoed in a
Puchacz but don't know what my Libelle would do.

Following up on that:

Yesterday I tried that in both the Puchacz and then in my Std. Libelle
and the answer as to whether its a good idea is "it depends".

In either gliders the descent rate didn't feel particularly rapid. I had
a logger running in the Libelle, which showed the descent rate to be
somewhere around 1000 ft/min., or 166 ft in 10 seconds - respectable
though hardly "hundreds of feet in 10 seconds".

Its easily controlled in the Puchacz, thanks to its large side area and
huge rudder: exit speed was essentially the same as entry speed and the
flight path during the descent was a gentle curve toward the side with
the canopy on it.

The Libelle is a different case. It hasn't enough side area or rudder
power to control your speed unless you also have some back stick and
that makes your descent path into a spiral rather than a gentle curve.
Although its a fairly controllable descent mode I don't think I'd use it
again in a Libelle.



--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Assigning equal probabilities won't always work. In the case of the Hawker
collision, the jet was descending, so diving would not have increased
separation as fast as climbing. In that particular region, jets are more
likely to be descending than climbing, so maybe the choice should be
influenced by what one knows about likely traffic in the area. South of
Reno, climb. North of Reno, dive. 'Course, that depends on which way ATC is
directing traffic... which is why Minden's glider educational materials tell
us to listen to ATC once in a while.

But that aside, on average it seems to me that (in a glider) diving would be
better because one will accelerate over time, increasing the distance from
where one started out. Zooming would not be as effective because speed will
decay, so the separation will initially grow but then will not grow so much.
Then one will either have to stay up there or descend back down through the
original altitude.

Since both pilots are nearly equally likely to choose climbing or diving,
leaving a 50% chance of ending up near each others' altitude, it seems to me
that diverting horizontally 90 degrees (perpendicular to the approaching
aircraft's heading) will help just as much as as changing altitude. Again,
both pilots could choose to turn the same way, so a 50% chance of still
being on a collision course. So turn AND climb/dive, and you end up with
more like a 25% chance of being in each others' way.

Roger (who's only had close encounters of the feathered kind)

"Martin Gregorie" wrote in message
...
Mike Schumann wrote:
If you are on a collision course, how are you going to know whether
going
down is the right solution? He might be 50 ft below you, and you are
going
to dive right into him. Or he might also decide to descend.

If you need to get out from in front while thermalling, you'll need some
more airspeed to do so and that means lowering the nose to accelerate
while, hopefully, turning to aim off to one side of him.

The opposition has first to see you in order to decide to descend. If we
assign equal probabilities to him climbing, turning or diving then
anything you do to move away from his current course has a 75% chance of
being right.

Now lets be generous and give him a 50% chance of seeing you.
Probabilities multiply when they are combined, so that gives you an 87%
chance of being right.

This brings to mind an interesting suggestion that I was taught when I
got
my power license about avoiding collisions with birds: Always climb, as
the
birds will tend to dive.

That's only useful if you have an engine or airspeed. If you're
thermalling and try that you'll end up descending about 2 seconds later
and, if the opposition saw you pull up, he'll be down there waiting for
you. Besides, if he read the same book you're quoting he'll be more
likely to pull up than to dive.

In any case, you didn't say what you'd do, so I'll ask again. What would
you do that's better than diving out of the way?


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Considering that the glider in question was in a left thermalling turn, that
the pilot caught just a brief glimpse of the inbound jet, just enough to
identify it as having two engines, before it tore into his glider, and that
the Hawker hit his upper wing about mid-span (or so I'm told), pulling up
may not have been such a good idea (g).

As someone else posted, most power pilots are trained to pull up for birds,
as the bird will invariably fold its wings and dive. I'd venture to say that
absent definitive altitude information about the threat, most power pilots
will pull up to avoid an impact.

My choice goes to diving to avoid a collision while flying a glider. If one
is thermalling at a relatively low speed, there's not going to be a lot of
energy to climb much, or fast.

bumper


"Roger Worden" wrote in message
. net...
Assigning equal probabilities won't always work. In the case of the Hawker
collision, the jet was descending, so diving would not have increased
separation as fast as climbing. In that particular region, jets are more
likely to be descending than climbing, so maybe the choice should be
influenced by what one knows about likely traffic in the area. South of
Reno, climb. North of Reno, dive. 'Course, that depends on which way ATC
is
directing traffic... which is why Minden's glider educational materials
tell
us to listen to ATC once in a while.

But that aside, on average it seems to me that (in a glider) diving would
be
better because one will accelerate over time, increasing the distance from
where one started out. Zooming would not be as effective because speed
will
decay, so the separation will initially grow but then will not grow so
much.
Then one will either have to stay up there or descend back down through
the
original altitude.

Since both pilots are nearly equally likely to choose climbing or diving,
leaving a 50% chance of ending up near each others' altitude, it seems to
me
that diverting horizontally 90 degrees (perpendicular to the approaching
aircraft's heading) will help just as much as as changing altitude. Again,
both pilots could choose to turn the same way, so a 50% chance of still
being on a collision course. So turn AND climb/dive, and you end up with
more like a 25% chance of being in each others' way.

Roger (who's only had close encounters of the feathered kind)

"Martin Gregorie" wrote in message
...
Mike Schumann wrote:
If you are on a collision course, how are you going to know whether
going
down is the right solution? He might be 50 ft below you, and you are
going
to dive right into him. Or he might also decide to descend.

If you need to get out from in front while thermalling, you'll need some
more airspeed to do so and that means lowering the nose to accelerate
while, hopefully, turning to aim off to one side of him.

The opposition has first to see you in order to decide to descend. If we
assign equal probabilities to him climbing, turning or diving then
anything you do to move away from his current course has a 75% chance of
being right.

Now lets be generous and give him a 50% chance of seeing you.
Probabilities multiply when they are combined, so that gives you an 87%
chance of being right.

This brings to mind an interesting suggestion that I was taught when I
got
my power license about avoiding collisions with birds: Always climb,
as
the
birds will tend to dive.

That's only useful if you have an engine or airspeed. If you're
thermalling and try that you'll end up descending about 2 seconds later
and, if the opposition saw you pull up, he'll be down there waiting for
you. Besides, if he read the same book you're quoting he'll be more
likely to pull up than to dive.

In any case, you didn't say what you'd do, so I'll ask again. What would
you do that's better than diving out of the way?


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Yuliy Gerchikov wrote:

That's precisely the problem: exactly what volume of air do I need to exit?

Only that volume of air (the size of your glider) through which the
traffic is about to pass. Quite small, really.


At those distances and rates of closure it is very difficult to estimate the
point of impact in 3D, especially given the extremely limited time for
decision.

Difficult? Limited? Relative to what?


No ball game that I know comes close to the order of magnitude of
parameters that we deal with here.

Then you don't know Baseball.

If you'd ever stood in the batter's box and had a good pitcher throw a
fast ball high and inside, and then compared that experience with a
high speed closure with another aircraft, you'd find that the numbers
don't really tell the story. No number can describe the actual
experience -- you just have to be there, in the game or in the cockpit.

But if you do prefer numbers, here they a at 420 kts closure with
another aircraft (708.8667 fps) from only 1/2 nm out (3038 feet) you
have a leisurely period of 4.2857 seconds which you can use to avoid
impact; compare this with the release of the baseball from the pitcher's
hand at considerably less than the nominal 60' 6" to the plate (but call
it 60 feet) at 90 mph (132 fps, and 13 mph SLOWER than the fastest
recorded pitch) which gives you 0.4545 seconds until impact (hopefully
with your bat and not your head). If this gives you renewed respect for
Ted Williams (life time batting average .344) as a baseball player as
well as a fighter pilot, that's good too. Of course, we need to bat
1.000 when it comes to traffic avoidance, but even with only 0.5 nm
separation at 420 kts we have almost ten times as long as we would when
standing in the batter's box to decide what to do, and make our move.

I assume you have already found out that you can hear a powered
aircraft from the cockpit of your glider. You can hear that baseball
coming too, which adds to the fun. And, you will remember that sound
also, but only if the ball misses your head.


This is closer to dodging bullets than it
is to any ball game.

At a muzzle velocity of 860 fps, the .45 pistol bullet is traveling at
509.5458 kts, or about 21% faster than the aircraft in this example.
However, it has a diameter of 0.45 inch whereas the cross section of the
Hawker 800XP is a 2-3 meter oval, sans wings and tail. Not at all
comparable. I'll take the Hawker 800XP challenge at a half mile every
time over the .45 ACP challenge at 20 paces. YMMV. As for the baseball,
at ~three inches in diameter, it's a better deal than the 230 gr FMJ,
but the Hawker 800XP is still the easiest of all to deal with, by far.

None of these three "sports" is for the indecisive, or the feint of
heart. The advantage is very definitely to the observant, the trained,
and the confidant. One must deal successfully with the numbers, and the
experience -- and it can be done.


Jack

I don't share your confidence in your ability to avoid a Hawker. Not only
do you have to luck out and see him in time, but you need to be able to tell
exactly where he is going compared to your airspace, not only if he
continues on a straight path, but also if he sees you and tries to maneuver.

The best strategy is to get and use a transponder so you never get close to
this situation.

Mike Schumann

"588" wrote in message
m...
Yuliy Gerchikov wrote:

That's precisely the problem: exactly what volume of air do I need to
exit?

Only that volume of air (the size of your glider) through which the
traffic is about to pass. Quite small, really.


At those distances and rates of closure it is very difficult to estimate
the point of impact in 3D, especially given the extremely limited time
for decision.

Difficult? Limited? Relative to what?


No ball game that I know comes close to the order of magnitude of
parameters that we deal with here.

Then you don't know Baseball.

If you'd ever stood in the batter's box and had a good pitcher throw a
fast ball high and inside, and then compared that experience with a
high speed closure with another aircraft, you'd find that the numbers
don't really tell the story. No number can describe the actual
experience -- you just have to be there, in the game or in the cockpit.

But if you do prefer numbers, here they a at 420 kts closure with
another aircraft (708.8667 fps) from only 1/2 nm out (3038 feet) you have
a leisurely period of 4.2857 seconds which you can use to avoid impact;
compare this with the release of the baseball from the pitcher's hand at
considerably less than the nominal 60' 6" to the plate (but call it 60
feet) at 90 mph (132 fps, and 13 mph SLOWER than the fastest
recorded pitch) which gives you 0.4545 seconds until impact (hopefully
with your bat and not your head). If this gives you renewed respect for
Ted Williams (life time batting average .344) as a baseball player as well
as a fighter pilot, that's good too. Of course, we need to bat 1.000 when
it comes to traffic avoidance, but even with only 0.5 nm separation at 420
kts we have almost ten times as long as we would when standing in the
batter's box to decide what to do, and make our move.

I assume you have already found out that you can hear a powered
aircraft from the cockpit of your glider. You can hear that baseball
coming too, which adds to the fun. And, you will remember that sound also,
but only if the ball misses your head.


This is closer to dodging bullets than it
is to any ball game.

At a muzzle velocity of 860 fps, the .45 pistol bullet is traveling at
509.5458 kts, or about 21% faster than the aircraft in this example.
However, it has a diameter of 0.45 inch whereas the cross section of the
Hawker 800XP is a 2-3 meter oval, sans wings and tail. Not at all
comparable. I'll take the Hawker 800XP challenge at a half mile every time
over the .45 ACP challenge at 20 paces. YMMV. As for the baseball, at
~three inches in diameter, it's a better deal than the 230 gr FMJ, but the
Hawker 800XP is still the easiest of all to deal with, by far.

None of these three "sports" is for the indecisive, or the feint of heart.
The advantage is very definitely to the observant, the trained, and the
confidant. One must deal successfully with the numbers, and the
experience -- and it can be done.


Jack