Help estimating altitude without altimeter?

Hi, as a beginner I am still a little rough at this. I've done 3
successful patterns with no altimeter, but today I failed one
miserably with my instructor. There were two issues which threw me
off. 1) we towed higher than the past attempts, and 2) instead of
entering the pattern at a familiar entry point, he had me circle
directly over the airport which made judging the angle a bit
difficult.

While we did eventually land safely, I failed miserably at setting up
the first pattern (way too high) and was forced to land on the
opposite runway (which left me way too low). A little scary but a
good learning experience... one I do not care to repeat anytime soon.

I know I should be looking for the landing strip to be about 30
degrees below the horizon. But how can I do this when circling
directly over the field looking down at it?

I made a second attempt and moved my circle so that the outermost edge
of the circle was where I would enter the downwind.. I succeeded this
time. Unfortunately we also only towed to 1500' AGL which left me
with a much smaller chance of messing things up... so I can't say I am
completely confident despite the success.

Are there any easy methods for estimating the angle from the horizon?
For example a fist at arms length is 10 degrees, but obviously I can't
hold my first at arms length through the canopy. The method I've
used is to wait until my aim point aligns with the outer most edge of
the air brakes. To measure 45 degrees I look directly over the top of
my shoulder... is there a better method?

Thanks
-tom

On Oct 25, 8:51*pm, tstock wrote:
Hi, as a beginner I am still a little rough at this. *I've done 3
successful patterns with no altimeter, but today I failed one
miserably with my instructor. * There were two issues which threw me
off. 1) *we towed higher than the past attempts, and 2) instead of
entering the pattern at a familiar entry point, he had me circle
directly over the airport which made judging the angle a bit
difficult.

While we did eventually land safely, I failed miserably at setting up
the first pattern (way too high) and was forced to land on the
opposite runway (which left me way too low). *A little scary but a
good learning experience... one I do not care to repeat anytime soon.

I know I should be looking for the landing strip to be about 30
degrees below the horizon. *But how can I do this when circling
directly over the field looking down at it?

I made a second attempt and moved my circle so that the outermost edge
of the circle was where I would enter the downwind.. I succeeded this
time. *Unfortunately we also only towed to 1500' AGL which left me
with a much smaller chance of messing things up... so I can't say I am
completely confident despite the success.

Are there any easy methods for estimating the angle from the horizon?
For example a fist at arms length is 10 degrees, but obviously I can't
hold my first at arms length through the canopy. * The method I've
used is to wait until my aim point aligns with the outer most edge of
the air brakes. *To measure 45 degrees I look directly over the top of
my shoulder... *is there a better method?

Thanks
-tom

But but but...

You were flying with an instructor. Was this not addressed to your
satisfaction in the post-flight debrief? Its fresh in your mind then
and that's the time to get answers. Sorry but I cringe at these "where
was the instructor" questions on r.a.s.

If you are circling overhead you can use sized of common things (cars,
gliders, runway width (if known), runway markings, etc.) to judge
height. I think I saw some good slides on that once that Cindy
Brickner had.

But...You don't transition from just circling overhead to rolling out
on the runway. At some time you transition from that circle overhead
to picking up an the downwind or base or whatever leg and a relatively
steady state angle to the runway. Even if the whole approach is curved
your sight picture needs to transition from looking down to across at
that 30-45 degree picture. At that point if you look too high you
should be doing something about it, extend the leg, get on the
spoilers, slip, or all the above.

So you have at least two things to go over with the instructor.
Judging height from overhead and being on-top of altitude correction
in the pattern.

Darryl

On Oct 25, 9:30*pm, Darryl Ramm wrote:
On Oct 25, 8:51*pm, tstock wrote:



Hi, as a beginner I am still a little rough at this. *I've done 3
successful patterns with no altimeter, but today I failed one
miserably with my instructor. * There were two issues which threw me
off. 1) *we towed higher than the past attempts, and 2) instead of
entering the pattern at a familiar entry point, he had me circle
directly over the airport which made judging the angle a bit
difficult.

While we did eventually land safely, I failed miserably at setting up
the first pattern (way too high) and was forced to land on the
opposite runway (which left me way too low). *A little scary but a
good learning experience... one I do not care to repeat anytime soon.

I know I should be looking for the landing strip to be about 30
degrees below the horizon. *But how can I do this when circling
directly over the field looking down at it?

I made a second attempt and moved my circle so that the outermost edge
of the circle was where I would enter the downwind.. I succeeded this
time. *Unfortunately we also only towed to 1500' AGL which left me
with a much smaller chance of messing things up... so I can't say I am
completely confident despite the success.

Are there any easy methods for estimating the angle from the horizon?
For example a fist at arms length is 10 degrees, but obviously I can't
hold my first at arms length through the canopy. * The method I've
used is to wait until my aim point aligns with the outer most edge of
the air brakes. *To measure 45 degrees I look directly over the top of
my shoulder... *is there a better method?

Thanks
-tom

But but but...

You were flying with an instructor. Was this not addressed to your
satisfaction in the post-flight debrief? Its fresh in your mind then
and that's the time to get answers. Sorry but I cringe at these "where
was the instructor" questions on r.a.s.

If you are circling overhead you can use sized of common things (cars,
gliders, runway width (if known), runway markings, etc.) to judge
height. I think I saw some good slides on that once that Cindy
Brickner had.

But...You don't transition from just circling overhead to rolling out
on the runway. At some time you transition from that circle overhead
to picking up an the downwind or base or whatever leg and a relatively
steady state angle to the runway. Even if the whole approach is curved
your sight picture needs to transition from looking down to across at
that 30-45 degree picture. At that point if you look too high you
should be doing something about it, extend the leg, get on the
spoilers, slip, or all the above.

So you have at least two things to go over with the instructor.
Judging height from overhead and being on-top of altitude correction
in the pattern.

Darryl

BTW you can't use the horizon. It is hard to know where the true
horizon often is. What if you are in mountainous areas. In smoke or
haze etc. (which will cause enough problems with depth/distance
perception as is). Same reason you don't want to set up behind the tow
plane based on where the horizon looks. Even if you knew the location
of the true horizon you would not be able to estimate your altitude
from that to anything like a useful accuracy.

Darryl

On Oct 25, 10:00*pm, Darryl Ramm wrote:
On Oct 25, 9:30*pm, Darryl Ramm wrote:





On Oct 25, 8:51*pm, tstock wrote:

Hi, as a beginner I am still a little rough at this. *I've done 3
successful patterns with no altimeter, but today I failed one
miserably with my instructor. * There were two issues which threw me
off. 1) *we towed higher than the past attempts, and 2) instead of
entering the pattern at a familiar entry point, he had me circle
directly over the airport which made judging the angle a bit
difficult.

While we did eventually land safely, I failed miserably at setting up
the first pattern (way too high) and was forced to land on the
opposite runway (which left me way too low). *A little scary but a
good learning experience... one I do not care to repeat anytime soon.

I know I should be looking for the landing strip to be about 30
degrees below the horizon. *But how can I do this when circling
directly over the field looking down at it?

I made a second attempt and moved my circle so that the outermost edge
of the circle was where I would enter the downwind.. I succeeded this
time. *Unfortunately we also only towed to 1500' AGL which left me
with a much smaller chance of messing things up... so I can't say I am
completely confident despite the success.

Are there any easy methods for estimating the angle from the horizon?
For example a fist at arms length is 10 degrees, but obviously I can't
hold my first at arms length through the canopy. * The method I've
used is to wait until my aim point aligns with the outer most edge of
the air brakes. *To measure 45 degrees I look directly over the top of
my shoulder... *is there a better method?

Thanks
-tom

But but but...

You were flying with an instructor. Was this not addressed to your
satisfaction in the post-flight debrief? Its fresh in your mind then
and that's the time to get answers. Sorry but I cringe at these "where
was the instructor" questions on r.a.s.

If you are circling overhead you can use sized of common things (cars,
gliders, runway width (if known), runway markings, etc.) to judge
height. I think I saw some good slides on that once that Cindy
Brickner had.

But...You don't transition from just circling overhead to rolling out
on the runway. At some time you transition from that circle overhead
to picking up an the downwind or base or whatever leg and a relatively
steady state angle to the runway. Even if the whole approach is curved
your sight picture needs to transition from looking down to across at
that 30-45 degree picture. At that point if you look too high you
should be doing something about it, extend the leg, get on the
spoilers, slip, or all the above.

So you have at least two things to go over with the instructor.
Judging height from overhead and being on-top of altitude correction
in the pattern.

Darryl

BTW you can't use the horizon. It is hard to know where the true
horizon often is. What if you are in mountainous areas. In smoke or
haze etc. (which will cause enough problems with depth/distance
perception as is). Same reason you don't want to set up behind the tow
plane based on where the horizon looks. Even if you knew the location
of the true horizon you would not be able to estimate your altitude
from that to anything like a useful accuracy.

Darryl

I agree with Darryl - angle below the horizon only tells you the angle
to the runway, not your height. You can be at the right height 2,000
feet laterally from the runway or 3x the right height a nautical mile
from the runway and the angles will be the same. You really need to
judge height by looking at the angle between two points a known
distance apart on the ground. This can be the wingspan of an airplane,
the distance between phone poles the width or length of a runway,
circular crop fields - whatever works. Try guessing your height 20
times over the course of a flight - especially when you are between
1,000 and 2,500 feet AGL. You will build a pretty good sense faster
than you think.

9B

Andy wrote:
angle below the horizon only tells you the angle
to the runway, not your height. You can be at the right height 2,000
feet laterally from the runway or 3x the right height a nautical mile
from the runway and the angles will be the same.

The vertical angle is all you need to know. Gliders tend to glide at an
angle.

You will find this information in the book, "Glider Basics From First
Flight To Solo," available at most gliderports or
www.eglider.org

Tom

Since using the horizon is not reliable, I suppose placing the airport
a certain position above my shoulder could be a good technique to
estimate the angle. My shoulder will always be in the same place
unless my head has been removed.

On Oct 26, 6:40*am, tstock wrote:
Since using the horizon is not reliable, I suppose placing the airport
a certain position above my shoulder could be a good technique to
estimate the angle. *My shoulder will always be in the same place
unless my head has been removed.

I play a game with my students called "Guess our height" With the
student's altimeter covered, I ask them to guess our altitude and them
I tell them what the back seat altimeter says. (Of course, you must
HAVE a back seat altimeter.)

The first few guesses may be wildly wrong but they get better fast. A
few dozen repeats and they're pretty accurate. I'd never ask a
student to fly a no-altimeter pattern and landing until they were at
least passable in estimating altitude.

Bill D

On Oct 26, 3:51*am, tstock wrote:
Hi, as a beginner I am still a little rough at this. *I've done 3
successful patterns with no altimeter, but today I failed one
miserably with my instructor. * There were two issues which threw me
off. 1) *we towed higher than the past attempts, and 2) instead of
entering the pattern at a familiar entry point, he had me circle
directly over the airport which made judging the angle a bit
difficult.

While we did eventually land safely, I failed miserably at setting up
the first pattern (way too high) and was forced to land on the
opposite runway (which left me way too low). *A little scary but a
good learning experience... one I do not care to repeat anytime soon.

I know I should be looking for the landing strip to be about 30
degrees below the horizon. *But how can I do this when circling
directly over the field looking down at it?

I made a second attempt and moved my circle so that the outermost edge
of the circle was where I would enter the downwind.. I succeeded this
time. *Unfortunately we also only towed to 1500' AGL which left me
with a much smaller chance of messing things up... so I can't say I am
completely confident despite the success.

Are there any easy methods for estimating the angle from the horizon?
For example a fist at arms length is 10 degrees, but obviously I can't
hold my first at arms length through the canopy. * The method I've
used is to wait until my aim point aligns with the outer most edge of
the air brakes. *To measure 45 degrees I look directly over the top of
my shoulder... *is there a better method?

Thanks
-tom

Don't get hung up on the ' 30 degree' rule. Its a rough guide for
beginners to get them into the right ball park. The actual perspective
will vary depending on the performance of your glider. From any given
height the angle by which you assess the pattern in a Ka8 will be
steeper than in an ASH25. You have to make the judgements no matter
what your orientation to the airstrip so peering at your shoulder or
airbrake won't work. You must be able to make the assessments, as it
were, out of the side of your eye whilst flying the plane and looking
out for traffic so focusing short and agonising about angles is
potentially dangerous.

In the UK we put far more emphasis on 'whether it looks right' which
entails practise from all sorts of positions and heights. In that
respect your comment "one I do not care to repeat anytime soon" is
against your interests for it's only by having another go soon will
you learn. You need to get some right to achieve the 'Ahaa!' and some
wrong to give your brain the database needed to make good judgements.
The job of the guy in the back is to engineer all that safely. His is
to 'take you to peer over the edge of the abyss without falling in' to
quote one of our most respected national coaches.

Of course you can't judge your pattern from over the airfield. Your
general height judgement, unaided by altimeters, needs to be
sufficient to tell you it's time to move away to the position from
where you will start the circuit and use different judgements of
perspective to effect it. Darryl says that in his post. If you always
fly from the same place and do the same circuits you are at risk of
getting habituated on secondary fixed references and not exercising
the necessary judgement skills to land out in a pasture. If possible
set yourself targets of landing within pre-set boundaries on
different parts of the airfield so you keep sharp.

Given the luxury of sufficient height (which is usually denied by the
pilot himself attempting to soar too long and not being disciplined
enough to enter circuit mode in good time) you should ensure you are
outside (and usually up-wind) of the intended pattern so that you can
see it all. As circuits are roughly rectangular the high key point
wants to be as far from the centre line of your final line as you
would like you base leg to be long. Choose a ground feature under the
high key and lurk by it, still outside the pattern until the
perspective looks right - then set off on downwind.
Learn to ignore the altimeter. Monitor the ASI assiduously and pay
attention to the vario. And lookout, lookout, lookout.

Peter

COWS. I recall it was Tom Knauff who wrote that you could begin to
see the legs of a cow at 1,000' (300 meters) AGL.
I also use seeing the tires on a car, tractor or glider trailer. It
takes practice.
Lacking cows or vehicles you can correlate the TLAR ("That Looks About
Right") method with your altimeter on every pattern you presently fly
in preparation for XC / off-airport landings.

Also practice estimating altitude at different airports / landing
fields, and in different lighting / visibility conditions. You might
use a motorglider or airplane to fly to nearby airports and learn to
estimate 1,000' AGL. Take along a current aero chart so you know
those airport elevations and for obstacle / terrain clearance.

Landing on a field or gliderport next to a ridge is interesting, such
as on Harris Hill at Elmira, NY. You need to get down relatively low
on the adjacent parallel hill on your left downwind pattern then make
a close-in base to final over another hill with trees. Good fun. All
eyeball / TLAR in relation to your touchdown spot. Altimeter is not
the primary tool here. Indeed, it is a fairly unreliable instrument.
Use it to verify what you see, but be suspicious of it. Pressure
changes and lag can make it indicate inaccurate altitude.

Then there is the ongoing debate as to setting of the altimeter before
takeoff. Zero or field elevation (or correctly, the reported
pressure.) Read CFR 91.121.
Setting an altimeter to Zero may make it easier to teach a student
pilot a rote pattern that is OK only for that airport, but not ideal,
and depending on your interpretation of "cruising flight" in CFR
91.121, probably not in compliance with the regulation.

So I teach pressure / field elevation for altimeter setting, and make
'em do the math to determine height Above Ground Level. Essential for
XC flyin' and anywhere topography is not flat.

We start our landing checklist at 6,000' MSL over the airport at
Marfa, west Texas (MRF field elevation is 4,850' MSL) near the Davis
Mountains (8,400' MSL).
Visiting pilots taught elsewhere to set altimeters to zero have a heck
of a time with this reality, so I do covered altimeter training and
checkouts. And we have a nice large herd of cows on the grassy
plateau around the airport. No oil beneath this part of Texas -- just
water.

Burt Compton CFI / DPE
Marfa, west Texas USA
www.flygliders.com