Options

My point is that people should be shown how to do it as safely as possible.

Nick.

"Stewart Kissel" wrote in
message ...


I think it should be treated as any other aerobatic
manouver.


Ahhh, hmmm....let's see if I understand this concept...

Unsynchronized group aerobatics done at low level and
high speed...in the landing pattern of an open airport....by
fatigued pilots.

Thanks but no thanks.

"If by ignorance, you mean "poor judgement", I agree with you, and I
think this is the theory behind the finish cylinders, isn't it?"

No... the cylinder is a placebo. Ignorance (and its primary effect -
poor judgement) are dangerous anywhere. The finish cylinder presents
the very same problems as the old high speed start gate. Next time you
see Rick Indrebo, ask him about separation of traffic.

I'll give you an example of a lack of situational awareness. You
responded to the following:

Will the pilot above and
behind me pushing to redline notice I'm in front flying at best L/D
in
an attempt to avoid missing the bottom of the cyliner?

"He's safe - he'll separate from you when he pulls up, and you aren't
going to pull up. That's a good situation. It seems unlikely he won't
see you ahead of him as he approaches. I've seen the same situation
finish gates, anyway"

Eric, he'll never pull up because he just flew through me several
hundred yards short of the gate. Been there. Seen it happen. Seen many
more come damn close. All your responses to my questions make
assumptions that aren't necessarily shared by all pilots. IE, the
cyclinder suffers the same problems that the finish gate does: it is
foiled by ignorance and resulting poor judgement.

The strongest arguement is that of density. A one mile radius circle
makes for alot more space than a 1 km line. Unless everyone is coming
home from the same turnpoint, in which case they are flying to the same
point, same altitude, and at a variety of speeds, with too much
attention on computers and altimeters. Implosion. And no regulation.
Performance information is on the panel, not outside.

The closest I've come to a midair in the past decade was at Hobbs two
years ago, in a 10-mile radius turn cylinder. I was distracted by
several gliders converging from about 45 degrees of arc to the very
extreme end of the turn area. I nearly hit someone below me as I
started my turn at the edge of the cylinder. I'm guessing at least half
the 15M nationals turned at that same point within about two minutes of
each other. So much for density management. At least we were all doing
about the same speed: 90 knots. So things happened pretty slowly. Let's
throw in some 60 and 140 knot traffic at the other end of the task,
just to keep things interesting.

As I said before, ignorance is much more obvious at low and fast. But
it's not any less dangerous high and slow. I think the number of pilots
who don't read the rules before competing is an indication of where the
problems lie. If a pilot is unwilling to take two hours to read the
rules, then he probably hasn't given much thought to the environment
he'll be flying in. This equals IGNORANCE.

Yeah, well, Tom is getting old too. For many of us, it's not about
showing off. It's the satisfaction of doing something well. Otherwise,
what's the point of flying at all?

At 05:00 12 March 2005, Marc Ramsey wrote:
Kilo Charlie wrote:
Don't argue with 9B re the logic of the math issue....trust
me....he's a
very bright guy and never leaves his calculator!
He is offering the
mathematical explanation of why cylinder finishes
may not be any safer. Of
course it supports my point so I'm thinkin' he's a
rad dude!

Hmm, I pegged him for a lawyer or politician, the numbers
may have some
basis in reality (assuming you fly in a vacuum), but
the logic is, uh,
'interesting'.

The point was pretty simple - I added the analysis
because without it I'm just a guy with an opinion (no
shortage of those here). So here's the point in simple
language: A low energy finish at 500' and 1 sm is
not significantly 'safer' than a low energy finish
at 50' over the airport. Either way you will be low
and slow in the pattern.

The numbers assume viscous, incompressible flow - gliders
can't fly in a vacuum. Bet you knew that. ;-)

9B

Andy Blackburn wrote:
The point was pretty simple - I added the analysis
because without it I'm just a guy with an opinion (no
shortage of those here). So here's the point in simple
language: A low energy finish at 500' and 1 sm is
not significantly 'safer' than a low energy finish
at 50' over the airport. Either way you will be low
and slow in the pattern.

Your analysis is flawed, because you miss one little point. Let's assume
we're comparing a finish gate adjacent to the center of the runway, and
a 1 mile radius cylinder centered on the runway. If you hold all other
factors constant, in particular the altitude at which you leave the last
thermal and the speed at which fly the final glide, if you pull up to
best glide at 1 mile you will always end up over the runway as high (if
your are already flying at best glide) or higher than if you pull up at
the gate. In other words, if you are low energy at 1 mile, you will
have as low or lower energy if you don't pull up until you reach the
gate, because you can't recover the drag you lose by flying faster than
best glide for the last mile.

Now, if you assume that you leave the last thermal when the computer
says final glide is made (or you leave with a constant offset from the
computer indication), then the 500 foot 1 mile case will require that
you climb higher, as it obviously takes less energy to get to the gate
at 50 feet (unless you are flying final glide at a speed where your L/D
is less than 10:1, which is ridiculous in modern gliders). You will
start a marginal final glide with more energy in the cylinder case, than
you will in the gate case. If your final climb is capped by the height
of the thermal, then you may have to opt for a rolling finish using a
cylinder, and still be able to make a gate finish, but you will be
making that final glide at essentially best glide, and have no energy
left to pull up after you go through the gate.

My point is also pretty simple. In no realistic case will you ever end
up with more energy for landing by delaying your pull-up until you reach
the airport. You will always end up with more energy over the airport
by making a final glide to 1 mile and 500 feet. This also means that
you have more margin for screw ups in the cylinder case.

The numbers assume viscous, incompressible flow - gliders
can't fly in a vacuum. Bet you knew that. ;-)

I do, but I'm not so sure you do. The exchange of energy implied by
your pullup from 50 feet at 150 knots that results in "something more
than 900'", either includes no losses for drag or you're doing a tail
slide at the top. If you have a trace where you actually manage to pull
up to 900 feet above your finish altitude, I'd love to see it...

Marc

With a center of airport 50' finish you still need to do a pattern including
up to three 90 degree turns after finishing (ignoring rolling finishes).
With a 500'/1 mile cylinder you can do a straight in or several possible
patterns, and you don't need to go to the center of the airport first, so
the distance is really 3/4 mile or much less to a downwind or base leg.
-Bob Korves

"Marc Ramsey" wrote in message
...
Andy Blackburn wrote:
The point was pretty simple - I added the analysis
because without it I'm just a guy with an opinion (no
shortage of those here). So here's the point in simple
language: A low energy finish at 500' and 1 sm is
not significantly 'safer' than a low energy finish
at 50' over the airport. Either way you will be low
and slow in the pattern.

Your analysis is flawed, because you miss one little point. Let's assume
we're comparing a finish gate adjacent to the center of the runway, and
a 1 mile radius cylinder centered on the runway. If you hold all other
factors constant, in particular the altitude at which you leave the last
thermal and the speed at which fly the final glide, if you pull up to
best glide at 1 mile you will always end up over the runway as high (if
your are already flying at best glide) or higher than if you pull up at
the gate. In other words, if you are low energy at 1 mile, you will
have as low or lower energy if you don't pull up until you reach the
gate, because you can't recover the drag you lose by flying faster than
best glide for the last mile.

Now, if you assume that you leave the last thermal when the computer
says final glide is made (or you leave with a constant offset from the
computer indication), then the 500 foot 1 mile case will require that
you climb higher, as it obviously takes less energy to get to the gate
at 50 feet (unless you are flying final glide at a speed where your L/D
is less than 10:1, which is ridiculous in modern gliders). You will
start a marginal final glide with more energy in the cylinder case, than
you will in the gate case. If your final climb is capped by the height
of the thermal, then you may have to opt for a rolling finish using a
cylinder, and still be able to make a gate finish, but you will be
making that final glide at essentially best glide, and have no energy
left to pull up after you go through the gate.

My point is also pretty simple. In no realistic case will you ever end
up with more energy for landing by delaying your pull-up until you reach
the airport. You will always end up with more energy over the airport
by making a final glide to 1 mile and 500 feet. This also means that
you have more margin for screw ups in the cylinder case.

The numbers assume viscous, incompressible flow - gliders
can't fly in a vacuum. Bet you knew that. ;-)

I do, but I'm not so sure you do. The exchange of energy implied by
your pullup from 50 feet at 150 knots that results in "something more
than 900'", either includes no losses for drag or you're doing a tail
slide at the top. If you have a trace where you actually manage to pull
up to 900 feet above your finish altitude, I'd love to see it...

Marc

At 00:30 13 March 2005, Bob Korves wrote:

patterns, and you don't need to go to the center of
the airport first, so
the distance is really 3/4 mile or much less to a downwind
or base leg.

Actually it's 50/50 as to whether it's 3/4 or 1-1/4
mi depending which side of the pattern you're finishing
on. Of course you can always do a rolling finish, but
that's true of the gate too.

Like I said, I don't see one type of finish as obviously
safer than another from an energy perspective - I've
flown both a fair number of times. The thing I do find
a little troubling about the cylinder is that it can
be a more 'head's down' process, since it's impossible
to 'eyeball' the cylinder either in terms of height
or location. This means that some pilots will be looking
at their computers rather than outside at exactly the
wrong time. I don't think its a huge deal, since most
pilots don't try to cut it that close anyway.

Also, I don't think there's anything in the rules that
says you can't do a pass over the field after a cylinder
finish is there?

9B

"Andy Blackburn" wrote in message
...
At 00:30 13 March 2005, Bob Korves wrote:
(snip)
Actually it's 50/50 as to whether it's 3/4 or 1-1/4
mi depending which side of the pattern you're finishing
on. (snip)
9B

Well, if you are worried about being low on energy and then go an extra 1/2
mile to the other side of the field...
-Bob Korves

Well, if you are worried about being low on energy
and then go an extra 1/2
mile to the other side of the field...

...then JJ won't report you to the FAA for performing
an illegal pattern. I think most of this discussion
has been about whether you can create rules that will
protect pilots from doing exactly this sort of thing
- stretching too far to go to the 'legal' pattern entry
point - or trying to do a pullup instead of a rolling
finish. Both are errors in judgement resulting from
a marginal, but legal, finish.

9B

Marc,

How many CDs choose cyclinders? Of theses cyclinders, how many
are centered at the airport, and how many are remote (centered away
from) the airport?

If remote, are they 2-5km out at 1000ft minimum? What is the
cylinder radius? Is it 1/2km like the previous poster's
"control point"?

For us non-contest guys, this is quite interesting...

In article ,
Marc Ramsey wrote:
BTIZ wrote:
I thought finish "gates" moved to a line or cylinder at altitude away from
the airport.. like the start gates did with the advent of GPS recordings

The current SSA regional/national rules leave the contest director with
the option of using either a finish cylinder with a specified minimum
finish height (usually 500 to 1000 ft), or a finish gate with a 50 ft
minimum height. When using a finish gate, it needs to be adjacent to the
runway, or the worm burners won't be able to make it home...

Marc


--

------------+
Mark J. Boyd