Help estimating altitude without altimeter?

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.

Thanks - I didn't do the math. I usually do the math but was feeling
lazy. :-(

I would argue that pattern traced by the wingtip changes even if it
doesn't reverse direction at higher elevations - the reverse circle
gets bigger and bigger as you go higher.

I generally enter the pattern at about 75-80 knots. You could
certainly do a circle at 90 knots if you really needed to see the
wingtip rotate the other way and had no idea how high you were - at
that speed your energy would take you back up to 1000' AGL.

The general point is that all the angular rates versus ground
references change as you get closer to the ground and you should be
aware of them. Turning flight likely gives you more cues than flying
straight ahead.

9B