Finish Gate Accident no. 2

At 02:00 27 March 2005, Bill Daniels wrote:

The wing drop thing is easy to judge. Just watch the
ailerons. If they
don't start to move until the wing hits the ground
or nearly so, it's pilot
error. If they move to the stop as soon as the glider
tilts a tiny bit yet
the wing still goes down, he gets a pass. Any good
instructor, towpilot, or
any good pilot for that matter, can watch a takeoff
and get a good idea of
how well a pilot flies.


I'd be surprised if you'd see many examples of reactions
that slow on the
contest circuit. In my experience 90+% of wing drops
happen despite full
opposite controls. A really experienced pilot will
hold off on control input
until he has enough speed, otherwise the downward deflection
of the
aileron will increase the angle of attack and stall
the tip. So sometimes it's
best to wait until the wing is nearly on the runway.
In this test you'd flunk
the pilots who are really inattentive as well as the
ones who are really
experienced.

I wish it were simple.

9B

At 03:00 27 March 2005, Jack wrote:
Andy,

I was not implying that anyone is stupid. I would never
do that,
either. I was trying in my poor manner to suggest that
I was a
knucklehead for flying at all.

Gotcha - we were making basically the same point with
different wording.

Smart, competent pilots can get into trouble because
they don't recognize
that their normally inconsequential decisions can have
potentially adverse
consequences under slightly different circumstances.
Tolerances can
accumulate in the wrong direction on any given day.
Medication +
dehydration + lack of sleep + windy day can make you
a hazard, but any
one or two of these might not.

The important thing is to recognize it.

9B

M B wrote:
It occurs to me that if someone is on final glide at
the end of a competition, they may pick a speed (like
85 knots) which their computer says is optimal for
points, but which is both:

1) too fast for a rolling finish/landing
and
2) too slow for a pull up, turn around, and landing.

Is that an accurate assessment? Would a competition
pilot be put in a situation where he must decide between
points and safety of the landing?

This is exactly right. The mathematically optimal point score comes
when you cross the finish (50 feet, middle of the airport) at the
regular inter-thermal glide speed, 70-80 kts rather than 130. This is
of course about the worst place from which to start a sensible pattern,
especially when 50 other guys are doing the same thing at the same
time. You see fast finishes because most of us are a bit chicken and
hold some reserve, losing a few points in the process.

Everyone in these threads has been advocating "just do a rolling finish
if it seems touchy" but that's a hard decision too. The finish gate is
typically downwind, so the following pattern is only a 180 to land into
the wind. Thus, a rolling finish is a downwind landing, often in a
substantial wind, with a huge fleet landing in the opposite direction.


Furthermore the pilot in the typical marginal situation, with enough
energy to cross the gate at 50-100 feet with 70-80 kts, has to
dissipate a lot of energy to roll a finish at the far end of the
runway. If not, this pilot would cross the runway threshold at say
100-200 feet and 80 kts. At this point it's really too late to roll
(remember all those guys landing into the wind at the other end of the
runway!) and you don't have enough energy to do a proper flying finish.
Coffin corner.

So the decision to roll - accept a downwind landing into the face of
traffic - has to be made at least a mile or two out, while there is
still substantial energy left and a good chance of picking up 50-100
feet of energy, or misjudging your total energy by 50-100 feet. I think
I can start to sympathize with people who get in this mess.

John Cochrane
BB

"Andy Blackburn" wrote in message
...
At 02:00 27 March 2005, Bill Daniels wrote:

The wing drop thing is easy to judge. Just watch the
ailerons. If they
don't start to move until the wing hits the ground
or nearly so, it's pilot
error. If they move to the stop as soon as the glider
tilts a tiny bit yet
the wing still goes down, he gets a pass. Any good
instructor, towpilot, or
any good pilot for that matter, can watch a takeoff
and get a good idea of
how well a pilot flies.


I'd be surprised if you'd see many examples of reactions
that slow on the
contest circuit. In my experience 90+% of wing drops
happen despite full
opposite controls. A really experienced pilot will
hold off on control input
until he has enough speed, otherwise the downward deflection
of the
aileron will increase the angle of attack and stall
the tip. So sometimes it's
best to wait until the wing is nearly on the runway.
In this test you'd flunk
the pilots who are really inattentive as well as the
ones who are really
experienced.

I wish it were simple.

9B



Depends on where "enough speed" occurs. I think most gliders will have at
least some aileron control at 12 Kts IAS or so. I've watched gliders reach
15-20 knots groundspeed and the ailerons didn't move until the wing touched
the ground. I think experienced pilot/observers can tell when a pilot is
waiting for the ailerons to get a grip on the air.

In the event of an actual test, the pilot could brief the observer that his
particular glider needs a non-standard technique and the observer would make
allowances for it.

Whenever I've made a fully ballasted takeoff in my N2C, I've carefully
briefed both the wing runner and the tow pilot (as well as the peanut
gallery who wanted to see a glider take off with 600 pounds of ballast.) So
far, I haven't dropped a wing.

Bill Daniels

At 06:30 27 March 2005, Bruce Hoult wrote:

A pull up from 85 knots to 50 knots will give you about
a 200 ft height
gain, plus whatever height your finish was at. We
give students rope
breaks at 200 ft, right? So a competent and alert
pilot should have no
trouble deciding whether to land straight ahead after
the pull up or do
an abbreviated circuit.

Bruce's numbers are a pretty accurate rule of thumb.
In an earlier thread
there was some doubt expressed as to whether these
'theoretical'
numbers can be achieved in flight. I took a look at
some flight logs and
found most of the time you convert into height ~90%
of your kinetic
energy (+/- the accuracy of my logger). There was one
pull up where I
only got 75% and one case where I got 100% (!). Best
not to count on
getting every last inch.

I wouldn't recommend anyone try a pull up into a pattern
unless they had
confidence they were going to have at least 120 knots
on the deck. I also
fly my patterns a bit faster than 50 knots.

9B

At 16:00 27 March 2005, Bill Daniels wrote:

I think experienced pilot/observers can tell when a
pilot is
waiting for the ailerons to get a grip on the air.

In the event of an actual test, the pilot could brief
the observer that his
particular glider needs a non-standard technique and
the observer would
make
allowances for it.

Whenever I've made a fully ballasted takeoff in my
N2C, I've carefully
briefed both the wing runner and the tow pilot (as
well as the peanut
gallery who wanted to see a glider take off with 600
pounds of ballast.)
So
far, I haven't dropped a wing.

My 27B has ailerons with the chord of a popsicle stick.
I don't know what
speed I need to hold a wing up against a gust, but
when I'm full of water at
5,000' on a 95 degree day I want a heck of a fast wing
runner.

I'll take your point that an experienced observer can
pick out poor piloting
technique at any phase of flight.

I remain skeptical of this whole test idea. While you
might flunk some good
pilots, it's principal shortcoming is that you are
trying to catch something
that for even moderately skilled pilots happens relatively
infrequently, so
the odds of it being useful is low, plus you have to
set up the whole test
process on top of whatever else you're doing to run
a contest.

I still think it's best left to the subjective assessment
of the CD to determine
if someone
has a piloting deficiency.

9B

Fantastic. Two great posts, from 59er and from Mr.
Cochrane. I am starting to lean towards the idea of
a 500ft or 1000ft finish.

My remaining question is still whether safety is best
served by the idea of a narrow cylinder, remote 'control
point' at 500-1000ft, or the standard 500-1000ft cylinder
over the airport.

I do think that low passes AFTER the finish as a crowd-pleaser
are at contest organizer discretion, but I don't think
these should be encouraged by extra contest points.

Forgive me for this, but
there is one perhaps morbid and a little tasteless
observation about an advantage of low passes. The
finishers who were dehydrated ended up stall/spinning
somewhere near the airport that was likely unoccupied,
instead of a half-uncoscious landing and swerving off
into the poor spectators lining the runway.

I have been in a situation with a problem aircraft
where I purposely decided to fly over an ocean so that
if anything went wrong further, I wouldn't hurt people
on the ground. So I do take this seriously.

I wonder if we will now see less of these stall/spin
accidents and more of the final approach landing accidents
instead, just shifting the problem.

Well, since by far the most common victim is the pilot,
and survivability seems much better with a miffed landing
than a stall/spin, we're all maybe still better off
with 500-1000ft finish altitudes and miffed landings
instead.

I'll get to watch all this in the coming contest, and
I'm sure I'll see at least a few dehydrated pilots
do 'interesting' things. Hopefully not TOO interesting...

Hmmm...perhaps Alhambra or Evian would be a good contest
sponsor?

At 16:00 27 March 2005, Bb wrote:

M B wrote:
It occurs to me that if someone is on final glide
at
the end of a competition, they may pick a speed (like
85 knots) which their computer says is optimal for
points, but which is both:

1) too fast for a rolling finish/landing
and
2) too slow for a pull up, turn around, and landing.

Is that an accurate assessment? Would a competition
pilot be put in a situation where he must decide between
points and safety of the landing?

This is exactly right. The mathematically optimal point
score comes
when you cross the finish (50 feet, middle of the airport)
at the
regular inter-thermal glide speed, 70-80 kts rather
than 130. This is
of course about the worst place from which to start
a sensible pattern,
especially when 50 other guys are doing the same thing
at the same
time. You see fast finishes because most of us are
a bit chicken and
hold some reserve, losing a few points in the process.

Everyone in these threads has been advocating 'just
do a rolling finish
if it seems touchy' but that's a hard decision too.
The finish gate is
typically downwind, so the following pattern is only
a 180 to land into
the wind. Thus, a rolling finish is a downwind landing,
often in a
substantial wind, with a huge fleet landing in the
opposite direction.


Furthermore the pilot in the typical marginal situation,
with enough
energy to cross the gate at 50-100 feet with 70-80
kts, has to
dissipate a lot of energy to roll a finish at the far
end of the
runway. If not, this pilot would cross the runway threshold
at say
100-200 feet and 80 kts. At this point it's really
too late to roll
(remember all those guys landing into the wind at the
other end of the
runway!) and you don't have enough energy to do a proper
flying finish.
Coffin corner.

So the decision to roll - accept a downwind landing
into the face of
traffic - has to be made at least a mile or two out,
while there is
still substantial energy left and a good chance of
picking up 50-100
feet of energy, or misjudging your total energy by
50-100 feet. I think
I can start to sympathize with people who get in this
mess.

John Cochrane
BB


Mark J. Boyd

In article ,
Andy Blackburn wrote:

Bruce's numbers are a pretty accurate rule of thumb. In an earlier
thread there was some doubt expressed as to whether these
'theoretical' numbers can be achieved in flight. I took a look at
some flight logs and found most of the time you convert into height
~90% of your kinetic energy (+/- the accuracy of my logger). There
was one pull up where I only got 75% and one case where I got 100%
(!). Best not to count on getting every last inch.

Agreed, and thanks for the confirmation.

Could headwind account for the 100% example? And tailwind for the 75%?
In other words, your airspeed was not the same as your ground speed?

--
Bruce | 41.1670S | \ spoken | -+-
Hoult | 174.8263E | /\ here. | ----------O----------

At 23:30 27 March 2005, Bruce Hoult wrote:
Could headwind account for the 100% example? And tailwind
for the 75%?
In other words, your airspeed was not the same as your
ground speed?

I did a quick check at the time and in most cases there
was a light crosswind of 5-8 knots, so I ignored it.
Obviously a few knots at the high end makes a big difference
in energy (10 knots below redline costs 130 feet).
Maybe I'll do a more rigorous analysis.

9B

"Bruce Hoult" wrote in message
...
In article ,
Andy Blackburn wrote:

Bruce's numbers are a pretty accurate rule of thumb. In an earlier
thread there was some doubt expressed as to whether these
'theoretical' numbers can be achieved in flight. I took a look at
some flight logs and found most of the time you convert into height
~90% of your kinetic energy (+/- the accuracy of my logger). There
was one pull up where I only got 75% and one case where I got 100%
(!). Best not to count on getting every last inch.

Agreed, and thanks for the confirmation.

Could headwind account for the 100% example? And tailwind for the 75%?
In other words, your airspeed was not the same as your ground speed?

--
Bruce | 41.1670S | \ spoken | -+-
Hoult | 174.8263E | /\ here. | ----------O----------
I doubt it. More likely pulling up into rising/sinking air would account
for the differentials.

Frank Whiteley
40-26N 104-38W