Mountain flying knowledge required?

"Chris W" wrote in message
news:gj%ae.640$zv1.481@lakeread07...
Is there an altitude above the ridge line at which the "mountain wave"
effect isn't significant?

Probably would be pretty negligible at 23,000 miles. For example.

Seriously though, yes...you can sometimes fly high enough to avoid the wave.
But that depends on the height of the terrain, the strength of the wind, and
of course the type of aircraft. There is no reliable way to know ahead of
time how high you need to fly to avoid it.

That said, there's being high enough to get all the way out of any
noticeable effects of the wave, and then there's being high enough to avoid
the wave forcing you too close to the terrain. The former may be
impossible, depending on the situation. The latter is usually possible. I
have rarely experienced altitude excursions of greater than 2000-3000 feet
as a result of mountain wave, so that's a pretty reliable margin for
crossing ridges.

Of course, there is the question of whether mountain wave can actually push
you into the ground. I've never actually heard of that happening, and for
it to do so, the part of the air mass you're flying in would have to hit the
ground as well. That happens in microbursts, or under virga, for example,
but you'd have to be pretty darn close to the ground in the first place for
a mountain wave to push you into it.

From a practical perspective, a couple of things to consider: higher up may
provide less turbulence (though, don't try to fly through a rotor cloud).
Also, if you want to most efficiently use the mountain wave to your
advantage, pitch up and slow down while it's making you go up, and pitch
down and speed up while it's making you go down. This will increase the
magnitude of your altitude changes, but you'll be spending less time during
the "bad" down areas and more time during the "good" up areas. Fighting the
mountain wave is just that: fighting. And no one wins a fight with Mother
Nature.

Of course, in practice you may have upper and lower limits to acceptable
altitudes, and those need to be taken into account. But inasmuch as you can
allow your altitude to vary with the wave, let it.

Pete

Peter Duniho wrote:

Is there an altitude above the ridge line at which the "mountain wave"
effect isn't significant?

There's no reason to be afraid of wave. Wave isn't turbulent at all,
just think of it as a region with strong up or down draft. Stron means
just that: strong. You'll see 20 fpm and more.

No way to fight a downdraft of 20 fpm. So don't fight it, rather fly
perpendicularly to the ridge until you leave that region. Chances are,
you'll find a region with the same amount of updraft there. Throttle
back and enjoy.

Rotors are a completely different story, but you won't encounter them
above the peaks. Of course you may hit some other turbulence, so stay
below the yellow arc.

Stefan

"Stefan" wrote in message
...
Peter Duniho wrote:

Is there an altitude above the ridge line at which the "mountain wave"
effect isn't significant?

Can you please not screw up the quote attributions? You left my name on an
attribution from which you trimmed everything I wrote.

In article , Peter Duniho wrote:
Of course, there is the question of whether mountain wave can actually push
you into the ground.

Wave won't push you into the ground, however, if you're approaching a
ridge from the downwind side and the wind's up, the 'curlover' on the
downwind side may well cause you to impact the ridge. This is why it's
advisable to approach ridges at a 45 deg. angle and with altitude to
spare so you can turn away if there's trouble.

Wave can be a factor way up above FL350 - gliders from Minden regularly
get up in the FL300+ range. Even our little 2000' mountain, Snaefell,
generates wave which reaches over 10,000 ft.

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"

"Peter Duniho" wrote in message
...
"Chris W" wrote in message
news:gj%ae.640$zv1.481@lakeread07...
Is there an altitude above the ridge line at which the "mountain wave"
effect isn't significant?

Probably would be pretty negligible at 23,000 miles. For example.

Seriously though, yes...you can sometimes fly high enough to avoid the
wave. But that depends on the height of the terrain, the strength of the
wind, and of course the type of aircraft. There is no reliable way to
know ahead of time how high you need to fly to avoid it.

That said, there's being high enough to get all the way out of any
noticeable effects of the wave, and then there's being high enough to
avoid the wave forcing you too close to the terrain. The former may be
impossible, depending on the situation. The latter is usually possible.
I have rarely experienced altitude excursions of greater than 2000-3000
feet as a result of mountain wave, so that's a pretty reliable margin for
crossing ridges.

Of course, there is the question of whether mountain wave can actually
push you into the ground. I've never actually heard of that happening,
and for it to do so, the part of the air mass you're flying in would have
to hit the ground as well. That happens in microbursts, or under virga,
for example, but you'd have to be pretty darn close to the ground in the
first place for a mountain wave to push you into it.

From a practical perspective, a couple of things to consider: higher up
may provide less turbulence (though, don't try to fly through a rotor
cloud). Also, if you want to most efficiently use the mountain wave to
your advantage, pitch up and slow down while it's making you go up, and
pitch down and speed up while it's making you go down. This will increase
the magnitude of your altitude changes, but you'll be spending less time
during the "bad" down areas and more time during the "good" up areas.
Fighting the mountain wave is just that: fighting. And no one wins a
fight with Mother Nature.

Of course, in practice you may have upper and lower limits to acceptable
altitudes, and those need to be taken into account. But inasmuch as you
can allow your altitude to vary with the wave, let it.

Pete


Mountain wave systems extend to and often into the stratosphere so it is
unlikely that you can fly above them unless you have a new airplane that we
haven't been told about :-).

Mike
MU-2