Help estimating altitude without altimeter?

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

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.
Snip

It's not easy at first, you will get the hang of it. It is a vital
skill though - flying circuits by landmarks is awful easy to get into
doing, but if you come to land out you must be able to fly a circuit
somewhere you've never, ever seen before.

--
Surfer!
Email to: ramwater at uk2 dot net

On Oct 26, 2:11*pm, Surfer! wrote:
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.

Snip

It's not easy at first, you will get the hang of it. *It is a vital
skill though - flying circuits by landmarks is awful easy to get into
doing, but if you come to land out you must be able to fly a circuit
somewhere you've never, ever seen before.

--
Surfer!
Email to: ramwater at uk2 dot net

Just yesterday I heard another instructor say he coaches his students
to look for the aimpoint a certain distance out the wing when they're
flying level. For his plane (K-21) it works if the aimpoint is about
a
third of the wing out.

Another method I suggest is to find telephone poles. In the US,
barring other circumstances (like having to go around curves) the
poles are spaced about 200 feet apart. When you cross a road
count how many telephone poles to a point 45 degrees below
level you see from your flight path. 5 poles is 1000 feet.

I'll also point out that you've gotten a good demonstration of how
hard it really is to measure distances with your eyes. You can
get a rough idea but ultimately you won't be that accurate.
However, by using the angles around the pattern you can
make a safe approach.

-- Matt

Tom:

How many patterns have you flown since you began your training? Until
you develop a clear picture in your mind of how your airfield looks at
different points in the pattern, you are experimenting and this will
work eventually. I have found a way to accelerate this process a bit. I
have my students fly their patterns at precise altitudes at specific
points in the pattern. And I insist on precise airpeed control as well..
This accomplishes two things..precise pattern flying...the same picture
every time and this "groove becomes epoxied into their brain more
quickly. Then, when I take their altimeter away and change runways, they
have no problems repeating the maneuver properly. Now I am all too
familiar with the argument against this technique i.e. what are they
going to do if they are landing at a field without the familiar
landmarks? It's that profile to the runway that they are really learning
by repeating the same profile time after time.





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

ZZ wrote:
Tom:

How many patterns have you flown since you began your training? Until
you develop a clear picture in your mind of how your airfield looks at
different points in the pattern, you are experimenting and this will
work eventually. I have found a way to accelerate this process a bit. I
have my students fly their patterns at precise altitudes at specific
points in the pattern. And I insist on precise airpeed control as well..
This accomplishes two things..precise pattern flying...the same picture
every time and this "groove becomes epoxied into their brain more
quickly. Then, when I take their altimeter away and change runways, they
have no problems repeating the maneuver properly. Now I am all too
familiar with the argument against this technique i.e. what are they
going to do if they are landing at a field without the familiar
landmarks? It's that profile to the runway that they are really learning
by repeating the same profile time after time.

Tom
I mashed on the Send Button prematurely.

So to wrap this up, fly your patterns as precisely as possible, as you
progress, learn to detect smaller and smaller errors and correct them
early. Fly the same groove to the runway every time and you will soon be
comfortable landing almost anywhere without no stinking altimeter.

Paul
ZZ





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

In message , ZZ
writes
Tom:

How many patterns have you flown since you began your training? Until
you develop a clear picture in your mind of how your airfield looks at
different points in the pattern,
Snip

I would say it's 'how the reference point looks'. We can have a
reference point anywhere, but if landing out we won't be seeing our own
familiar airfield. Is the reference point technique taught in the US?

--
Surfer!
Email to: ramwater at uk2 dot net

On Oct 28, 2:25*am, Surfer! wrote:
In message , ZZ
writesTom:

How many patterns have you flown since you began your training? Until
you develop a clear picture in your mind of how your airfield looks at
different points in the pattern,

Snip

I would say it's 'how the reference point looks'. *We can have a
reference point anywhere, but if landing out we won't be seeing our own
familiar airfield. *Is the reference point technique taught in the US?

--
Surfer!
Email to: ramwater at uk2 dot net

The best 'reference point' is the intended landing surface. Anything
else is likely to be misleading. Even telephone poles are not all the
same height or spacing.

There are lots of clues to height which taken together can give a
pretty accurate estimate. Pilots may not even be aware of all the
clues they're using, just that with increasing experience, their
estimates begin to work.

One old skydiver clue is that when people stop looking like ants and
start looking like people, it's time to pull. That's about 2000' AGL
and not a bad height to be over the landing area looking for wind and
obstacles.

On Oct 28, 1:08*pm, bildan wrote:
On Oct 28, 2:25*am, Surfer! wrote:





In message , ZZ
writesTom:

How many patterns have you flown since you began your training? Until
you develop a clear picture in your mind of how your airfield looks at
different points in the pattern,

Snip

I would say it's 'how the reference point looks'. *We can have a
reference point anywhere, but if landing out we won't be seeing our own
familiar airfield. *Is the reference point technique taught in the US?

--
Surfer!
Email to: ramwater at uk2 dot net

The best 'reference point' is the intended landing surface. *Anything
else is likely to be misleading. *Even telephone poles are not all the
same height or spacing.

There are lots of clues to height which taken together can give a
pretty accurate estimate. *Pilots may not even be aware of all the
clues they're using, just that with increasing experience, their
estimates begin to work.

One old skydiver clue is that when people stop looking like ants and
start looking like people, it's time to pull. *That's about 2000' AGL
and not a bad height to be over the landing area looking for wind and
obstacles.

Anyone try using the wing vs. runway relationship? In the Skyhawk I
was taught to keep the runway 1/2 to 2/3 up the strut, correcting for
wind. I know that this would lead to flying an ever closer pattern as
you descend, but could it not be used to get you in the groove up to
abeam the touchdown point? Then it would be a matter of TLAR from
there to touchdown.

I offer this as a question, not a suggestion. I've done very little
flying away from the home field, and I live in a very flat state.

Anyone try using the wing vs. runway relationship? In the Skyhawk I
was taught to keep the runway 1/2 to 2/3 up the strut, correcting for
wind. I know that this would lead to flying an ever closer pattern as
you descend, but could it not be used to get you in the groove up to
abeam the touchdown point? Then it would be a matter of TLAR from
there to touchdown.

I offer this as a question, not a suggestion. I've done very little
flying away from the home field, and I live in a very flat state.

This is sort of how I ultimately did it... when my aimpoint was at 9
o'clock, it appeared about 1/3 of the way down from the wing tip, just
under the air brake. This was about 800'.

-tom