On Tue, 7 Jun 2005 11:19:29 -0700, "Peter Duniho"
wrote in
::

[...]

I believe that is the true nature of the article you've quoted: to provide
rules of thumb that offer safe guidance to pilots landing in constrained
areas, especially when the landing area is defined not by prevailing winds
but by terrain restrictions, preventing the pilot from taking best advantage
of the current winds. Where the winds increase the landing distance, they
are assumed to be greater than actual, and where the winds might shorten the
landing distance, they are assumed to be lesser than actual. In neither
case do the estimates provide any assistance in judging the effects of winds
aloft during cruise flight.

Yes. I can see now, that you're right about the article's
inappropriateness in this discussion due to it's intentional bias
toward conservatism. It only serves to further confuse the issue.

Instead, let's look at a Crosswind Correction Table (I hope the
formatting works in your browser):
http://www.auf.asn.au/navigation/wind.html

Table 1: Wind components
Headwind component [for ground speed]
Crosswind component [for WCA]

Wind Speed Wind Speed
WA | 5 10 15 20 25 30 | 5 10 15 20 25 30
----+--------------------------+--------------------
0° | -5 -10 -15 -20 -25 -30 | 0 0 0 0 0 0
15° | -5 -10 -15 -20 -25 -30 | 1 2 4 5 6 7
30° | -4 -9 -13 -17 -21 -25 | 2 5 7 10 12 15
45° | -3 -7 -10 -14 -17 -21 | 3 7 10 14 17 21
60° | -2 -5 -7 -10 -13 -15 | 4 9 13 17 21 25
75° | -1 -2 -4 -5 -6 -7 | 5 10 15 20 25 30
90° | 0 0 0 0 0 0 | 5 10 15 20 25 30
105°| +1 +2 +4 +5 +6 +7 | 5 10 15 20 25 30
120°| +2 +5 +7 +10 +13 +15 | 4 9 13 17 21 25
135°| +3 +7 +10 +14 +17 +21 | 3 7 10 14 17 21
150°| +4 +9 +13 +17 +21 +25 | 2 5 7 10 12 15
165°| +5 +10 +15 +20 +25 +30 | 1 2 4 5 6 7
180°| +5 +10 +15 +20 +25 +30 | 0 0 0 0 0 0
----+--------------------------+--------------------
| 5 10 15 20 25 30 | 5 10 15 20 25 30

ground speed* = TAS + value shown. WCA = value shown / TAS × 60


As an example of the limited increase in ground speed provided by a
quartering tailwind, let's take the case of a 30 knot wind from
135-degrees. The table indicates an increase of +21 knots can be
expected, but that +21 knot increase in forward velocity must be used
to overcome a 21 knot crosswind to track the desired course line,
which results in a net 0 knot increase in ground speed. So it appears
to me, that only those winds within 45-degrees of directly aft (or a
90-degree arc) will actually result in a real increase in ground
speed. Or stated differently, the probability of encountering a
tailwind sufficient to increase ground speed is 1 in 4; only 25% of
the time wind will result in a net increase in ground speed.

Do you agree with that?