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.
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

bildan wrote:

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.

My strategy was to let the students decide when to end the lesson and
head back to the airport. I'd just keep telling them to do stuff, or
showing them stuff, until they said "we're going back", then I'd shut up
and let them do it.

Since we flew off two different runways in varying conditions, they had
a lot practice returning from different directions and altitudes. After
each landing, we'd discuss how it went, and alternate choices. I never
asked them to estimate altitude, and I'm not any good at it anyway. The
standard was to arrive on downwind with enough altitude to do a typical
pattern. Too high or too low might mean a longer discussion, if I
thought there was a problem and not just the normal variation.

They all were good enough at it by the time they went solo, it was never
an issue. By doing it every flight, as soon as they could guide the
glider in more or less in the intended direction, it wasn't anything
that had to be taught later, or something they feared; after all, they
did it every flight except the first 3 or 4. I think it's something you
really have to *do* to learn, and watching someone else make the
decisions isn't useful.

I should point out that, in addition to "as soon as they could guide the
glider in more or less in the intended direction", they'd also received
instruction on the ground and during the first few flights on basic
pattern planning: pick the stop point, pick the aim point, pick the base
direction, pick the downwind entry.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* Sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

On Oct 26, 2:04*am, John Smith wrote:

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

It helps when you are in the pattern, but the issue here is what to do
when you are away from the pattern. Also, I wouldn't necessarily
recommend that a student focus solely on the angle. I would not
consider it equally good piloting to enter the pattern at 3,000' AGL a
mile abeam of the runway as at 1,000' 1/3 mile abeam of the runway.

For the circling over the airport problem you can get some indication
of altitude by looking at the path the wingtip traces on the ground
from a known bank angle. Above a certain height the path will be
counter to the turning direction, below that height it will be in the
same direction. Do the math to convince yourself. (Note: This is one
cue that creates problems as it tends to make skidding turns down low
seem "normal". A pilot will over-rudder to make the wingtip move
backward -- don't do this). You also get altitude cues from the rate
that objects on the ground change angle in straight ahead flight at a
known airspeed. The least precise cue except at very low altitudes (or
for very big objects) is the included angle from one end of a ground
object to another. Use the length of the ramp, not the length of a
car.

Another big issue is gaining the experience to know when you need to
"head for home" from 10-20 miles away to hit a point that's 1,000' AGL
for pattern entry. The angle for most gliders is very flat but looks
flatter and flatter the farther away you get because the glide
terminates well above the ground. For instance, if your glider can go
7 miles for every 1,000' (L/D= 37) the angle will "look" roughly half
as steep from 20 miles as from 5 miles away. Fortunately this builds
in some conservatism in the pilot's judgement rather than the other
way around.

Try some of these techniques from different altitudes the next few
times you fly. Eventually it becomes (almost) second nature. Also read
Tom Knauff's fine text or one of the many others on the subject. They
are written by professionals.

9B

On Oct 28, 3:13*am, Andy wrote:
For the circling over the airport problem you can get some indication
of altitude by looking at the path the wingtip traces on the ground
from a known bank angle. *Above a certain height the path will be
counter to the turning direction, below that height it will be in the
same direction. Do the math to convince yourself.

I guess you didn't do the math yourself :-)

The height at which the change from wingtip-goes-backwards to wingtip-
goes-forwards occurs is too low to be used for normal circuit entry.
At 40 knots it's only 140 ft, and at 60 knots it is about 320 ft. If
you want to use this to judge a 700 ft circuit entry then you'll have
to be flying at 90 knots.

On Oct 27, 7:47*pm, Bruce Hoult wrote:
On Oct 28, 3:13*am, Andy wrote:

For the circling over the airport problem you can get some indication
of altitude by looking at the path the wingtip traces on the ground
from a known bank angle. *Above a certain height the path will be
counter to the turning direction, below that height it will be in the
same direction. Do the math to convince yourself.

I guess you didn't do the math yourself :-)

The height at which the change from wingtip-goes-backwards to wingtip-
goes-forwards occurs is too low to be used for normal circuit entry.
At 40 knots it's only 140 ft, and at 60 knots it is about 320 ft. If
you want to use this to judge a 700 ft circuit entry then you'll have
to be flying at 90 knots.

Glad you mentioned this. I did think of this myself also, and tried it
on a simulator many many times before reading these posts and in every
case the wingtip appeared to move backwards over the terrain. Decided
it would not work.

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 27, 4:47*pm, Bruce Hoult wrote:
On Oct 28, 3:13*am, Andy wrote:

For the circling over the airport problem you can get some indication
of altitude by looking at the path the wingtip traces on the ground
from a known bank angle. *Above a certain height the path will be
counter to the turning direction, below that height it will be in the
same direction. Do the math to convince yourself.

I guess you didn't do the math yourself :-)

The height at which the change from wingtip-goes-backwards to wingtip-
goes-forwards occurs is too low to be used for normal circuit entry.
At 40 knots it's only 140 ft, and at 60 knots it is about 320 ft. If
you want to use this to judge a 700 ft circuit entry then you'll have
to be flying at 90 knots.