How Low to Spin??

Andy Blackburn wrote:
I guess the question comes down to energy management.
At one extreme, if you come in low and slow on a long
final you run the risk of not being able to extend
your touchdown point should an obstacle become apparent.
At the opposite extreme, a short, high and fast approach
runs the risk of running too long on touchdown, even
with full spoilers.

In between, I suppose there is "high and slow" (perhaps the "normal"
pattern), and "low and fast" (what you seem to be using). I am curious
about how you decided "low and fast" was the best choice: conversations
with other pilots, testing both methods on fields (maybe with a
motorglider?), or ...?


I've opted for being a bit faster in the pattern to
keep some extra margin for wind gusts and to allow
more margin for moments of distraction turning base
or final.

What are you flying "a bit faster" than? The glider handbook
recommendation? The club instructor's opinion? Or just what you used to use?

To keep total energy under control, this
means flying a bit lower pattern. Flying 70 knots instead
of 60 knots means about 50' lower in the pattern for
the same total energy. Obviously you'd start to slow
down before getting to treetops or other obstacles.

What glider are you flying? 60 knots in calm air already sounds "a bit
faster" than most gliders would have to fly. Where is the yellow
triangle on your airspeed indicator?

How much wind would it take before you'd use _more_ than 70 knots? My
glider has the yellow triangle at 50 knots, and normally I wouldn't use
70 knots on final unless the wind was over 30 knots.



In a 'standard' approach you have to lose about 20
knots from final approach to touchdown. I need lose
30 knots, which means starting that process a few seconds
sooner. The flatter glidepath on short final means
that you are, for a brief period, at a lower angle
to your final touchdown point, so you do get a peek
at potential obstacles.

This "fast and low" approach sounds like something easily done at the
home airport, but would be tricky to do right going into a field you've
never seen before. Have you used this method at airports and into fields
you've been landed at before?

I can't say that this has ever
directly benefitted me, but I do know of cases where
pilots have been too slow on final, with bad results.

And there have been cases where pilots have been too fast on final, with
bad results.

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Eric Greenwell
Washington State
USA