Headwinds, always

Peter Duniho wrote:

"Larry Dighera" wrote in message
news
[...]
So I appears that my recollection was faulty. But it seems counter
intuitive, that a 90-degree crosswind contributes half its velocity to
a tailwind component.


That's because you need to take into account the application of that
particular resource. Applying that sort of thinking to cruise flight IS
counter-intuitive, because it's not correct in that context.

It's not even literally correct in the context of the article you quoted,
but nevertheless the article you quoted has useful information in it.
First, it's a discussion of landing, not cruising. Second, it's a
collection of rules of thumb, not a precise analysis of reality.

It is easy to show that mathematically, a 90 degree crosswind results in no
tailwind component. Without a correction, it results in no headwind
component as well.

I'd like you to show that since it is easy. And a crosswind is relative
to your track, not your heading. OK, now show us the math! :-)

Matt

"Matt Whiting" wrote in message
...
It is easy to show that mathematically, a 90 degree crosswind results in
no tailwind component. Without a correction, it results in no headwind
component as well.

I'd like you to show that since it is easy.

Including crab, a 90 degree crosswind creates a groundspeed of cos(T) * true
airspeed, where T is the crab angle. cos(T) is always less than or equal to
1, so your groundspeed is always less than or equal to your true airspeed,
and so there is no POSITIVE tailwind component (if my inclusion of the word
"POSITIVE" here makes a difference to your previous post, then you're just
being intentionally obtuse, as my meaning was perfectly clear: a 90 degree
crosswind never increases your groundspeed, no matter how strong).

And a crosswind is relative to your track, not your heading.

A crosswind is relative to whatever you define it to me relative to. If you
don't care about where you are going (as is sometimes the case), a 90 degree
crosswind doesn't affect your speed in the direction of your heading at all
(though it does, obviously, affect your speed along your ground track).

OK, now show us the math! :-)

Done.

Pete

Peter Duniho wrote:
"Matt Whiting" wrote in message
...

It is easy to show that mathematically, a 90 degree crosswind results in
no tailwind component. Without a correction, it results in no headwind
component as well.

I'd like you to show that since it is easy.


Including crab, a 90 degree crosswind creates a groundspeed of cos(T) * true
airspeed, where T is the crab angle. cos(T) is always less than or equal to
1, so your groundspeed is always less than or equal to your true airspeed,
and so there is no POSITIVE tailwind component (if my inclusion of the word
"POSITIVE" here makes a difference to your previous post, then you're just
being intentionally obtuse, as my meaning was perfectly clear: a 90 degree
crosswind never increases your groundspeed, no matter how strong).

My question was about the headwind component, and I read it too quickly
and didn't catch the "without a correction" comment which I assume you
meant to discount the crab angle. Yes, a 90 crosswind will not add a
tailwind component, but it will add a headwind component due to the crab
angle required to stay on track.


Matt

"Matt Whiting" wrote in message
...
[...] Yes, a 90 crosswind will not add a tailwind component, but it will
add a headwind component due to the crab angle required to stay on track.

I've basically said so two posts in a row (not to mention in other posts).
Your point escapes me.