How Low to Spin??

Chris OCallaghan wrote:

I've found over the years that my critical decision point to stop
searching for lift is between 400 and 200 feet agl, depending on
conditions. This is not when I enter the pattern, but when I put the
gear down and focus ENTIRELY on landing safely. Typically, I'll be at
least half way through a modified downwind (still looking for lift).
This means that I am viewing the field from less than 400 feet above
and 400 feet displaced from my intended centerline.

Yep, this is what happened to me. On downwind got a sniff of a thermal.
Was VERY leery.

Always assess the field after you've landed. What didn't you see? What
did you see that wasn't really a problem? This review will serve your
assessment of the next field you find yourself falling into.

Or while climbing away. I've found roads really suck, because they
always seem to have fences and signs and wires. Dirt roads
in fields are a little better, because if I don't like it (POLE!),
I can go left or right and still land in the field.

On this one particular downwind, and then climb away, I was most surprised
by my misjudgement of the wind. A flag below showed I had
set up for a tailwind landing. The winds aloft over the
ridge I'd gotten into the lee of were SW, and a nearby
flag (which I noticed only climbing away) said Northerly.

Maybe the field had convergence too, eh? But I was very
concerned that I'd not found any wind cues on the approach,
although I'd looked hard...

I think figuring out wind direction visually is sometimes VERY
hard. With no lakes, no flags, no tilling, no smoke, no
leaves on the trees, and no cow butts, I've sometimes
been visually stumped...
--

------------+
Mark Boyd
Avenal, California, USA

Andy Blackburn wrote:
I have often used somewhat higher speeds on approach
as well. The logic is simple: trade a little altitude
for airspeed and you will get a better perspective
on field slope, power lines and other features that
my not be visible at higher view angles.

I know this flys in the face of the traditional stabilized
approach philosophy - so I'm interested in counterpoints.

Effective airbrakes do a great job of dissapating speed too.
In a Lancair IVP recently, without them it was really
a headache to land. The glide angle even with power off
was at such a high speed that to clear terrain we were
way too fast every time. Speed brakes 4 miles out
got us to the airport at the right approach speed every time.

Having extra energy is great, if you can get rid of it
when you need to. But I've seen some manuals where the
best full spoiler descent rate is at a pretty slow speed.

And it seems different gliders respond very differently to slips.
So I'd definitely test out the slips too...

Some of my more exciting landings have been when I got a
lot of unforseen lift right before touchdown, rather than
problems with sink. At shorter runways, or with weak
spoilers, this could have been a big issue.

You guys in your flap only PIKs and such get my respect.
Adjustments on short final must be "interesting."
--

------------+
Mark Boyd
Avenal, California, USA

Andy Blackburn wrote:

I have often used somewhat higher speeds on approach
as well. The logic is simple: trade a little altitude
for airspeed and you will get a better perspective
on field slope, power lines and other features that
my not be visible at higher view angles.

I might not be visulizing this right: as you go down final approach, you
reduce the spoilers and speed up, so you end up on a lower glide path
but with an a more shallow approach?

At what altitude do you begin this speed/altitude trade?

There is practically nothing worse than having those
hidden power lines pop up above the horizon when you
are at 30' and 50 kts on final (this is the voice of
experience from the person who had to pick up the wreck).

So, the lines are hidden in the ground clutter, but by coming in at a
more shallow angle, you can see them above the horizon sooner (i.e.,
from farther away than with steeper approach)?



--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

Eric Greenwell wrote:
Andy Blackburn wrote:

I have often used somewhat higher speeds on approach
as well. The logic is simple: trade a little altitude
for airspeed and you will get a better perspective
on field slope, power lines and other features that
my not be visible at higher view angles.

I might not be visulizing this right: as you go down final approach, you
reduce the spoilers and speed up, so you end up on a lower glide path
but with an a more shallow approach?

At what altitude do you begin this speed/altitude trade?

There is practically nothing worse than having those
hidden power lines pop up above the horizon when you
are at 30' and 50 kts on final (this is the voice of
experience from the person who had to pick up the wreck).

So, the lines are hidden in the ground clutter, but by coming in at a
more shallow angle, you can see them above the horizon sooner (i.e.,
from farther away than with steeper approach)?

I think he's saying to use a flatter, faster glide slope on
far out final, until 50-100 ft AGL, and then use a steeper glide slope.
Remember he mentioned it wasn't a stabilized approach.
--

------------+
Mark Boyd
Avenal, California, USA

If you had of said you used your extra speed to take
you to the dust devil and climb away I would have been
far more impressed!

At 07:00 26 August 2004, Andy Blackburn wrote:
I have often used somewhat higher speeds on approach
as well.
It also helped me this summer
at Parowan when a huge dust devil kicked off right
in the middle of the runway when I was at 100' on final.
I was able to stretch my approach so that I didn't
have to flare in the middle of the sucker.

I know this flys in the face of the traditional stabilized
approach philosophy - so I'm interested in counterpoints.

9B




At 06:00 26 August 2004, Eric Greenwell wrote:
Kirk Stant wrote:


I fly my pattern based on where I want to touch down,
and adjust the
pattern accoding to my altitude and the wind. I prefer
low, tight,
fast patterns, so I can see what I'm getting into
during a landout!

And if you don't like what you are getting into, how
do you avoid if you
are low and tight? Even a high, large pattern will
eventually have you
as close to the 'what you are getting into', but in
the mean time, you
have a lot more time to look things over and change
your mind.

I don't think I like the idea of a fast landout, either.

--
Change 'netto' to 'net' to email me directly

Eric Greenwell
Washington State
USA

Nice reference to the original topic!

:-)

At 15:36 26 August 2004, Kirk Davis wrote:
If you had of said you used your extra speed to take
you to the dust devil and climb away I would have been
far more impressed!

At 07:00 26 August 2004, Andy Blackburn wrote:
I have often used somewhat higher speeds on approach
as well.
It also helped me this summer
at Parowan when a huge dust devil kicked off right
in the middle of the runway when I was at 100' on final.
I was able to stretch my approach so that I didn't
have to flare in the middle of the sucker.

I know this flys in the face of the traditional stabilized
approach philosophy - so I'm interested in counterpoints.

9B




At 06:00 26 August 2004, Eric Greenwell wrote:
Kirk Stant wrote:


I fly my pattern based on where I want to touch down,
and adjust the
pattern accoding to my altitude and the wind. I prefer
low, tight,
fast patterns, so I can see what I'm getting into
during a landout!

And if you don't like what you are getting into, how
do you avoid if you
are low and tight? Even a high, large pattern will
eventually have you
as close to the 'what you are getting into', but in
the mean time, you
have a lot more time to look things over and change
your mind.

I don't think I like the idea of a fast landout, either.

--
Change 'netto' to 'net' to email me directly

Eric Greenwell
Washington State
USA

Mark got it right.

Rather than fly from IP to the threshold at 55 knots
with, say, 1/2 spoiler, I will fly at 70-75 knots at
1/4 spoiler. This way I make all my turns at well above
stall speed and can handle gusts, etc better. I end
up on short final at a lower angle (better view), but
with more energy. If everything looks good, I go to
3/4 spoiler and bleed the energy down at constant altitude
(say 50-75'), then land as usual. If there is some
obstacle or other issue, I can close the spoilers and
have enough energy to pick a different touchdown point.
This requires that you have good spoilers and that
you don't over-do the extra speed - that could run
up the risk of over-shooting.

This is how I normally land, so it's not making everything
different just for outlandings.

Thoughts?

9B

At 04:30 27 August 2004, Mark James Boyd wrote:
Eric Greenwell wrote:
Andy Blackburn wrote:

I have often used somewhat higher speeds on approach
as well. The logic is simple: trade a little altitude
for airspeed and you will get a better perspective
on field slope, power lines and other features that
my not be visible at higher view angles.

I might not be visulizing this right: as you go down
final approach, you
reduce the spoilers and speed up, so you end up on
a lower glide path
but with an a more shallow approach?

At what altitude do you begin this speed/altitude trade?

There is practically nothing worse than having those
hidden power lines pop up above the horizon when you
are at 30' and 50 kts on final (this is the voice
of
experience from the person who had to pick up the
wreck).

So, the lines are hidden in the ground clutter, but
by coming in at a
more shallow angle, you can see them above the horizon
sooner (i.e.,
from farther away than with steeper approach)?

I think he's saying to use a flatter, faster glide
slope on
far out final, until 50-100 ft AGL, and then use a
steeper glide slope.
Remember he mentioned it wasn't a stabilized approach.
--

------------+
Mark Boyd
Avenal, California, USA

Andy,

I guess my only comment is a question: Does it really make any
difference in what you see? Framing wires against the sky (if that's
your intent) requires being lower than the wires. Which in turn means
you are at risk of hitting other wires.

What is the genesis of this approach? It clearly requires advanced
energy management skills, so it isn't appropriate for low time pilots
(the majority) or lower peformance sailplanes. Was it suggested by
someone, or is it someplace you arrived through time and experience?

I'll give it a try at the home drome during my next few flights. But I
guess I'm still having trouble determining what advantage I have by
flying a base and final leg low and fast. Would you apply the same
method for an approach over tall trees? Even if it meant losing sight
of your intended touch down point during much of the final leg?

As an aside, I'll suggest that best way to avoid wires is to land in
the very center of the biggest appropriately textured field you can
find. If the field is more than 500 feet wide and you see no poles,
you'll find no wires (unless of course, they're marked on your
sectional!). Alas, we can't get farmers to grow turf in such
proportions in appropriately spaced fields.

Chris OCallaghan wrote:
Andy,

I guess my only comment is a question: Does it really make any
difference in what you see? Framing wires against the sky (if that's
your intent) requires being lower than the wires. Which in turn means
you are at risk of hitting other wires.

What is the genesis of this approach? It clearly requires advanced
energy management skills, so it isn't appropriate for low time pilots
(the majority) or lower peformance sailplanes. Was it suggested by
someone, or is it someplace you arrived through time and experience?

I'll give it a try at the home drome during my next few flights. But I
guess I'm still having trouble determining what advantage I have by
flying a base and final leg low and fast. Would you apply the same
method for an approach over tall trees? Even if it meant losing sight
of your intended touch down point during much of the final leg?

I'm not agreeing or disagreeing with Andy yet, but
let's consider for a moment the psychological effect of
this idea: perhaps it helps focus the pilot on the
objects between the glider and the intended touchdown.
Or helps orient the pilot to the type of terrain found
on the way in, or gets him lower so it's easier to determine wind
direction from small cues on the ground.

Again, I'm not advocating the idea, but there are some more
subtle points...
--

------------+
Mark Boyd
Avenal, California, USA

I guess the question comes down to energy management.
At one extreme, if you come in low and slow on a long
final you run the risk of not being able to extend
your touchdown point should an obstacle become apparent.
At the opposite extreme, a short, high and fast approach
runs the risk of running too long on touchdown, even
with full spoilers.

I've opted for being a bit faster in the pattern to
keep some extra margin for wind gusts and to allow
more margin for moments of distraction turning base
or final. To keep total energy under control, this
means flying a bit lower pattern. Flying 70 knots instead
of 60 knots means about 50' lower in the pattern for
the same total energy. Obviously you'd start to slow
down before getting to treetops or other obstacles.


In a 'standard' approach you have to lose about 20
knots from final approach to touchdown. I need lose
30 knots, which means starting that process a few seconds
sooner. The flatter glidepath on short final means
that you are, for a brief period, at a lower angle
to your final touchdown point, so you do get a peek
at potential obstacles. I can't say that this has ever
directly benefitted me, but I do know of cases where
pilots have been too slow on final, with bad results.

9B

At 23:24 28 August 2004, Mark James Boyd wrote:
Chris OCallaghan wrote:
Andy,

I guess my only comment is a question: Does it really
make any
difference in what you see? Framing wires against the
sky (if that's
your intent) requires being lower than the wires. Which
in turn means
you are at risk of hitting other wires.

What is the genesis of this approach? It clearly requires
advanced
energy management skills, so it isn't appropriate for
low time pilots
(the majority) or lower peformance sailplanes. Was
it suggested by
someone, or is it someplace you arrived through time
and experience?

I'll give it a try at the home drome during my next
few flights. But I
guess I'm still having trouble determining what advantage
I have by
flying a base and final leg low and fast. Would you
apply the same
method for an approach over tall trees? Even if it
meant losing sight
of your intended touch down point during much of the
final leg?

I'm not agreeing or disagreeing with Andy yet, but
let's consider for a moment the psychological effect
of
this idea: perhaps it helps focus the pilot on the
objects between the glider and the intended touchdown.
Or helps orient the pilot to the type of terrain found
on the way in, or gets him lower so it's easier to
determine wind
direction from small cues on the ground.

Again, I'm not advocating the idea, but there are some
more
subtle points...
--

------------+
Mark Boyd
Avenal, California, USA