How Low to Spin??

Tony Verhulst wrote:
Slightly off topic but the following is pretty good reading, IMHO.

http://home.comcast.net/~verhulst/GB...r_landings.htm

It really points out one of the largest differences between
power and glider flight: the increased need for no altimeter
approaches.

The Airplane Flying Handbook (AFH) suggests rectangular field engine failure
landouts just for this reason (to
eliminate the problem, just fly further on base).

I must say, however, that I vaguely recall that other countries don't
fly rectangles, but a V and then a 45 deg turn onto final.
Is this true? It seems like a better way to avoid looking
back over the shoulder for the touchdown spot...


--

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Mark Boyd
Avenal, California, USA

Kirk Stant wrote:
I like the BGA's idea of the angled base
leg, which approaches my preferred military-style one turn to final
pattern.

Yep, I think this is a better pattern too. I wonder
where the rectangle came from in the USA?
--

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Mark Boyd
Avenal, California, USA

Andy Durbin wrote:
(Kirk Stant) wrote in message

Not the same as max performance low altitude turning (thermalling),
which are definitely NOT ground reference maneuvers.

Thermalling close to the ground is not intended to be a ground
reference maneuver, but the visual feedback from the ground can have a
strong influence on control inputs. It is very important to keep
airspeed in the scan and not to be influenced by ground speed. The
input from ground reference can be very compelling, and misleading,
when thermalling low in a strong wind.

We had this discussion before. If the thermal is coming from a
stationary ground source, and the best performance is
zero sink in the thermal, doing it exactly as a ground
reference manuever (shallow upwind, steep tailwind) is correct.

Otherwise one is blown downwind of the thermal.

This was well discussed in threads about a year ago.

If one starts at 60 degree banks on the upwind, with
10+ knots of wind and zero sink, trying to core the thermal
on the downwind will be exciting...
--

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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."
--

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Mark Boyd
Avenal, California, USA

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...
--

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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

Kirk Stant wrote:

(which probably takes a bit more than one second, I would think) will
corkscrew the nose down and around, but you are not flying backward!

I agree. I don't think I am flying backward. I think I am,
to some degree, flying backward. What I mean is that some of the momentum
carrying me into the spin will cause a reduction of airspeed
which is most pronounced at 180 degrees from the entry heading.

including Maverick's F-14 spinning out to sea after
departing over the desert - I would have loved to have seen that for
real!)

Art Scholl lost his life in a fatal inverted spin into the Pacific
Ocean with no parachute (while filming for Top Gun).
Some say the weight of the cameras on the wingtips made the
spin unrecoverable...

Still a bad analogy, in my opinion. Think of the snap roll example -
at what point do you stop "rolling" and start "frisbeeing"? You
don't, your flightpath just curves more downward as you initiate the
spin slower.

At the 180 snap-roll point from entry, the nose isn't pointing in the other
cardinal direction. It simply isn't comparable.

It sure would be fun to take up a nice spinning glider (a 2-32 for
example), instument it, then take turns trying to make each other
sick!

Hmmm...on a calm wind day with a cheap GPS with a time track
set to every 1 second, if the GPS is synchronised with a
stopwatch and observer, it may get interesting. A
logger might do the same...

But don't you ever wonder why the most nose down part of a positive
spin is at the 1/2 spin point? Lowest airspeed perhaps? And
why IS that...

Broken glass ships have the same problem with weight in the tail...
G-103s are notorious for it. Othewise, instruments, batteries,
cheeseburgers, and beer tend to move the CG forward.

You have a BBQ and beer cooler in the nose? How inventive...
I suppose your landouts are quite a party...

Again, the aft CG doesn't cause the spin, it just make it easier to
initiate, and maybe harder to recover.

NASA thought it sometimes made it easier, and sometimes
harder to recover, depending on the aircraft. Go figure.

You still have to exceed the
stalling AOA, regardless of CG location. Winch launching is probably
a lot safer overall than aerotowing (from my limited experience in
Germany), with fewer potential gotcha's - plus it's really hard to
kill the winch operator (unless you crash on the winch, of course).

I must say it's a LOT of fun teaching aerotow. Formation flight
where you don't have to worry about airspeed is a real thrill for
a lot of folks. But yep, aerotow might be more complicated...
But I wouldn't know, I've never done a wench launch...

are not really "max performance" turns, and are usually no more than
90 - 100 degrees (unless you prefer the 180 degree one turn to final
approach, which I do).

I do rectangular bases, so others know I'm landing instead of
thermalling at the end of the runway :PPP

Well, most glider landing accidents only break the glider, or maybe a
bush or two - and the reasons are usually pretty consistent.

Shoulder harnesses probably have brought the stats down a
huge amount, and the lower stall speed, and fuselage shape,
of gliders compared to, say a Cherokee. Trike landing gear and
rough fields do not mix...

Not necessarily - the key is the lack of outside references, coupled
with moving the head too much so as to confuse the inner ear.

In an aileron roll, the head is moved. In max dutch rolls
45 to 45, the head is moved. So again, I guess you are agreeing with
me that high roll rates and steep banks can induce vertigo.
If you don't agree. Take a pax at night cover all instruments.
Head perfectly straight ahead. Close eyes. Then max roll rate
left 45 bank, then 90 degrees of turn, slow roll right,
and tell them to open eyes while level and recover. Fun, huh?

And yes, lack of coherent outside reference is important too.
Pretty easy to get when looking at clouds and fog and mountainsides...
And sometimes tough to correct without...
wait for it...moving your head

I have had the leans in
formation in cloud - interesting when you pop out and your internal
gyros cage up!

I've had them almost uncontrollably on several occasions, night IMC,
and straight and level on a rollout to a heading.
Absolutely bloodcurdling...

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!
It helps that my glider can get rid of a lot of energy fast when I
need to.

The only disadvantages I can find of very effective spoilers a

1) If they ain't locked for takeoff, a gnarly pio
2) If they don't have very fine controls, hard to be precise
about glide slope.
3) If at max out, landing flare is VERY fast, and stall speed
increased
--

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Mark Boyd
Avenal, California, 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.
--

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Mark Boyd
Avenal, California, USA

Kirk ... I couldn't agree with you more.

I guess it was all that training in the PI.


On 26 Aug 2004 10:15:33 -0700, (Kirk Stant)
wrote:

Eric Greenwell wrote in message ...

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.

Eric, what I want is to have the best look at the potential landout
field before actually landing on it. That means picking the field
early, looking at it carefully while making a last attempt to climb
out (if possible, then setting up a pattern close enough to be able to
see terrain details and pick the exact point to touch down at. That
usually means being downwind at about 500' or so, and that means being
pretty close in.

By fast, I mean about 60 to 70 knots (depending on wind, etc) in my
LS6 dry. That is plenty enough for aggresive turning if necessary to
adjust my pattern, and to float over a last minute fence, but slow
enough that with full divebrakes I can quickly slow down on short
final for a low energy tail first landing.

And I practice this often at my home field, using different runways
when possible to get used to different patterns. And it has worked on
my actual landouts, when necessary (obviously not a good idea when
landing at a big controlled field - that requires a totally different
pattern technique!).

I shudder when I watch 2-33s flying wide bomber patterns, downwind at
1000', and flying long finals. It may be FAA approved textbook, but I
think it is bad technique. I like the BGA's idea of the angled base
leg, which approaches my preferred military-style one turn to final
pattern.

Hope this clarifies things a bit.

Kirk

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.
--

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Mark Boyd
Avenal, California, USA