Help estimating altitude without altimeter?

Someone wrote: "make my turn to base at 600' AGL, and my turn to
final at 400' AGL. "

(Oh my gosh. Now I must comment. Note to my students -- ignore this
"fly to an altitude before turning base" concept.)

I gotta ask: If you plan to turn base at 600' AGL and you've gone
thru lift on the downwind -- do you keep flying far downwind until you
descend to 600' AGL, far away from the airport?

HECK NO. Fly the angles! Follow Tom Knauff's advice. Ignore the
Altimeter, but use the Variometer to check your vertical speed on
downwind. I teach 500 fpm (or 5 knots) down is the maximum you need
until final. If the variometer is showing lift then add airbrakes but
be ready to respond with less airbrake in the sink beyond that lift
you just encountered. Watch the TREND of your variometer as well --
to see the near-future. I often fly thru 1,000 fpm DOWN (with no
airbrakes) and UP (full airbtrake) in my patterns year-round in west
Texas. Recognize and react to what's happening to your glider.

My perception is that we glider pilots fly lightly wing-loaded, slow
moving aircraft thru a constantly changing air mass (typical on a
thermic or windy day) so your glider is greatly affected by vertical
and horizontal changes in the air mass. Trying for the airplane type
"stabilized approach" for every pattern doesn't always work for me in
gliders. Most airplanes have heavier wing-loadings than gliders and
fly much faster thru the air mass in the pattern. And they have that
stinkin' motor.

So I fly the "goal-oriented approach" which means recognize and react
as needed (early turn to base if required by the "angle" / use
airbrakes in or out) to air mass and wind changes to fly to your
touchdown point and roll to your pre-determined stop point. Glider
patterns are rarely the exact same slope or route over the ground on
any landing. Another common mistake is to fly too close to the runway
on downwind, then fly too far downwind before turning base. A long
final back into a headwind combined with a bit of sink and you are
sunk. So the idea of flying downwind to 600' AGL may be hazardous.

Keep in mind on windy days that flying 55 knots on downwind translates
to perhaps 70 knots over the ground (with your tailwind aloft), so
your glider is traveling about 100 feet PER SECOND over the ground,
downwind from the runway. Any delay (5 seconds for instance) in
deciding when to turn base may mean you are 500 hundred feet further
downwind that you wanted to be, and now you must "buy back" those
extra 500 hundred over the ground, into a headwind and a lot slower
ground speed, and likely will lose more altitude than planned with
some sink / wind gradient effect on final.

Now consider how "time" is a huge factor in planning your pattern.
You have about 60 seconds from the moment you enter a pattern to
touchdown. How you use that time is based on your decisions on how to
respond to the air mass changes, and the path thru the sky that you
chose to fly to your pre-determined touchdown point. You are the
Pilot In Command. Don't wait for things to happen -- MAKE things
happen to a successful outcome. Indecision, wallowing around the sky
allowing wind drift and sink to put you deeper in jeopardy, then
making uncoordinated turns under stress is simply poor airmanship.
These airmanship skills must be taught and learned BEFORE solo.

So glance at the variometer, respond as needed to vertical changes
with airbrake in/out. Look outside 99% of the time and don't fly too
far downwind, Hold airspeed for the wind conditions aloft and your
drift over the ground. Watch the angles to your touchdown point (the
British call it the Reference Point, as I recall) and roll to your
desired stop point.

If another method works for you then so be it, but "landing short" of
a perfectly good runway you just passed on downwind seems silly, and
is a common incident worldwide. Long landings also occur quite
often, so learn to control your energy, nail your touchdown point and
stop point every time. I also teach flying thru the imaginary narrow
"mail slot" over your last obstacle (wires, trees, fence) on every
final approach.

So I had to comment. Honestly, I teach the glider landing pattern
alot different now at Marfa, in west Texas than I did back in Miami,
Florida a decade ago. The Miami air mass was relatively passive, so
we flew big rectangular patterns with the old school "hold 1/2
airbrake and wait until something changes" method, somewhat "behind"
the glider. But travel elsewhere to fly gliders and "interesting" and
sudden changes in the air mass near the ground will require more pilot
awareness, skills, flexibility in the pattern shape and faster
responses.

To the old-school CFIG's (like me), learn to embrace alternate methods
and consider teaching students to be flexible and creative in their
thinking. I did, and it works.

Burt
Marfa
www.flygliders.com

On Oct 30, 12:47*pm, Burt Compton - Marfa wrote:
Someone wrote: *"make my turn to base at 600' AGL, and my turn to

final at 400' AGL. "

(Oh my gosh. *Now I must comment. *Note to my students -- *ignore this
"fly to an altitude before turning base" concept.)

I gotta ask: *If you plan to turn base at 600' AGL and you've gone
thru lift on the downwind -- do you keep flying far downwind until you
descend to 600' AGL, far away from the airport?

HECK NO. *Fly the angles! *Follow Tom Knauff's advice. *Ignore the
Altimeter, but use the Variometer to check your vertical speed on
So I had to comment. *Honestly, I teach the glider landing pattern
alot different now at Marfa, in west Texas than I did back in Miami,
Florida a decade ago. *The Miami air mass was relatively passive, so
we flew big rectangular patterns with the old school "hold 1/2
airbrake and wait until something changes" method, somewhat "behind"
the glider. *But travel elsewhere to fly gliders and "interesting" and
sudden changes in the air mass near the ground will require more pilot
awareness, skills, flexibility in the pattern shape and faster
responses.
(CUT)
To the old-school CFIG's (like me), learn to embrace alternate methods
and consider teaching students to be flexible and creative in their
thinking. *I did, and it works.

Burt
Marfawww.flygliders.com

Burt, thanks for taking the time to write that lengthy and detailed
reply. I should clarify that I do not just fly down wind UNTIL I
reach 600 (!), but rather I watch the position of the aim point and
use air brakes as required to keep the angle "looking right" until it
is at my 45. At this point I have a quick glance to confirm I am
somewhere around 600 while I turn to base and from that point on I do
not typically look at the altimeter. I am primarily keeping an eye on
my glide angle and airspeed. Usually I'll try to get a quick glance
just to see if I am where I think I am. There was wind through most
of my training so I am used to altering my pattern to compensate for
tail wind or head wind.

Since I am flying in Florida, what you mentioned regarding altering
pattern in regards to sudden air mass changes is also good info.

So basically my issue is the first angle... knowing when I am between
800' and 1000' agl. Sounds like I just need to keep practicing.

Thanks
-tom