On Sat, 22 Sep 2007 23:01:54 -0400, "Kyle Boatright"
wrote in
:


What is your threshold for landing (or departing) downwind?

That is dependent on the length of the runway(s), its gradient/slope,
surface, and the performance of the particular aircraft.

And what is the correct radio phraseology to say: "Fellas, it is time to
reverse the pattern - you're taking off and landing downwind.." ?

The correct radio phraseology for operating at an uncontrolled field
is, Podunk airport traffic, Cessna 123 entering left downwind for
runway 18, Podunk traffic. Nothing changes. You self-announce your
intentions, keep your eyes open for conflicting traffic, and give
right of way in accordance with CFR 14 § 91.113 Right-of-way rules:
http://ecfr.gpoaccess.gov/cgi/t/text... .1.3.10.2.4.7

The tricky part of downwind landings is the necessity to extend your
traffic pattern's Downwind Leg (actually against the wind in the case
of a downwind landing) WELL BEYOND (perhaps double or more) what you
are accustomed to in a normal into-the-wind landing. If you fail to
do this, you will overshoot.

There's also the issue of whether to takeoff into or with the wind on
runways that aren't level....
http://groups.google.com/group/rec.a...5?dmode=source
An average force derivation gives the following formula for
the "breakeven headwind," i.e., the headwind of such speed that
it's a wash whether you take off into the headwind up hill or
take off with that tailwind down hill:

Vhw,breakeven = Slope in degrees * distance to lift off with
no wind, no slope / (5*speed at lift off in KTAS)

where Vhw,breakeven is in knots and the distance to lift off
is in feet.

With the same "constant" average force assumption the same
should be true for landing, making obvious changes. In actual fact
the above formula is a slight "simplification" of a somewhat more
complicated one.

The thing that messes up a lot of people is that you can have
three airplanes ready to take off on the same strip under the same
conditions and one of them (higher powered) is best off to go
uphill into the wind, one of them best off downhill with the wind,
and with the third it makes no difference (unless there are other
considerations like terrain clearance, etc.)

Hope this helps more than it confuses.
John T. Lowry