Question to Mxmanic

On 04/17/07 11:40, Judah wrote:
Mxsmanic wrote in
:

Many of the MSFS developers are pilots, for better or for worse.

Name 3

It's funny. Anthony's always said that real pilots don't know what they
are talking about, yet he seems to feel the ones that worked on the MSFS
game do.

On Apr 17, 12:24 am, "Maxwell" wrote:
"Kev" wrote in message
http://www.airpower.maxwell.af.mil/a...ew/1971/jul-au...

"Cruise altitude vortices usually level off at about 1000 feet below
the altitude of the aircraft as their density comes into equilibrium
with that of the surrounding air. Decay processes then take over. "

Don't underestimate the value of the words "usually" and "about" in that
sentence. You are still trying to absolutely describe something that is very
dynamic.

True. So I guess we could all agree that where the wake goes, depends
on the surrounding atmosphere and aircraft profile...

Still... if it stayed at the same altitude most of the time (contrary
to NASA reports), or was over 100' tall (as some tried to claim at
first), then EVERY student pilot could hit their own wake all the time
grin.

Kev

writes:

Water is not breathable; only the oxygen (or other gases) contained in
it is.

The same can be said of air. And you may have forgotten water vapor.

--
Transpose mxsmanic and gmail to reach me by e-mail.

"Kev" wrote in message
ups.com...
On Apr 17, 12:24 am, "Maxwell" wrote:
"Kev" wrote in message
http://www.airpower.maxwell.af.mil/a...ew/1971/jul-au...

"Cruise altitude vortices usually level off at about 1000 feet below
the altitude of the aircraft as their density comes into equilibrium
with that of the surrounding air. Decay processes then take over. "

Don't underestimate the value of the words "usually" and "about" in that
sentence. You are still trying to absolutely describe something that is
very
dynamic.

True. So I guess we could all agree that where the wake goes, depends
on the surrounding atmosphere and aircraft profile...

Still... if it stayed at the same altitude most of the time (contrary
to NASA reports), or was over 100' tall (as some tried to claim at
first), then EVERY student pilot could hit their own wake all the time
grin.



But if "ifs" and "buts" were candy and nuts, it would be Christimas every
day.

If you can hit your own wake doing 60/360s and holding altitude, keep
practacing. You are more than likely doing something wrong.

"Maxwell" wrote in message
...

If you can hit your own wake doing 60/360s and holding altitude, keep
practacing. You are more than likely doing something wrong.


Correction, if you CAN'T hit your own wake

On 16 Apr 2007 19:26:17 -0700, Kev wrote:

On Apr 16, 3:59 pm, Tom L. wrote:
The big question is "why does the wake turbulence descend?"
Is the air volume inside the vortices denser than surrounding air?

Found it, Tom. Ref:

http://www.airpower.maxwell.af.mil/a...ug/carten.html

"Cruise altitude vortices usually level off at about 1000 feet below
the altitude of the aircraft as their density comes into equilibrium
with that of the surrounding air. Decay processes then take over. "

Regards, Kev


Great! Thanks for the effort.

Now I have a new question -- where is this extra air coming from, and
how?
The vortices grab some additional air molecules and then take them
down. Theere is now a volume of air with missing molecules (if I'm
allowed to speak in K-grade language). These molecules have to be
replaced, and the only source is lower -- in the more dense air that
is in addition getting the extra particles. So there must exist an
additional upward moving air flow outside the vortices.

The pictures showing jets right on top of clouds do seem to indicate
this. The vortices seem to suck in clouds from below and then spin
them.
So there is this secondary air movement starting at 1000' below an
aircraft, moving upwards on both sides of the aircraft and filling the
low density areas left by the vortices and wing downwash.
Interesting.

- Tom

Ahah! This is great information. If it is not qualified with "on
certain days" or "at low altitudes" it would mean that rising air has
nothing to do with it. Inclusion of the phenomenon in the simulators
tends to indicate the same thing.

Now, if we combine this with the information from the article that Kev
found that lists descent rates and vortex radii, we have a reason to
be really puzzled!
(The article is he
http://www.airpower.maxwell.af.mil/a...ug/carten.html)

According to that article, the vortex descent rate for B-2707 (is it
the same as 707?) is over 700 fpm and the vortex radius is only 11'.
If this is true, by the time the arcraft finishes it's full turn the
vortices are hundreds of feet away.
So what causes the bump? What else is going on here?
Or are the vortices data incomplete or wrong?

- Tom


On Tue, 17 Apr 2007 16:46:16 GMT, rq3
wrote:

Yes, they do. I just asked a friend with 26,000 hours. He confirmed that
DC-8's and 707's do get a bump as they cross their own wake in a 360
degree constant altitude turn. He also said that some Category D
simulators include this effect in their motion repertoire.

Rip

Tom L. wrote:
...
Does anyone know whether big aircraft experience the bump at the
conclusion of their steep 360s?

- Tom

In rec.aviation.piloting Mxsmanic wrote:
writes:

Water is not breathable; only the oxygen (or other gases) contained in
it is.

The same can be said of air. And you may have forgotten water vapor.

Thereby crowning you King of Semantic Word Games.

--
Jim Pennino

Remove .spam.sux to reply.

On Tue, 17 Apr 2007 00:19:02 +0200, Mxsmanic
wrote:

Tom L. writes:

It doesn't have to continue to sink forever. It can stabilize its
position at some point.

It will sink indefinitely unless some other force acts to stop it. In theory,
it will sink until it reaches the ground.

This is not happening in vacuum, the force that acts to stop it is
encountered as soon as the disturbance is created. The questions is
how long does it take for that force to stop disturbed air. That would
be related to how much energy is in the vortices (in their rotation).
Smaller aircraft probably creates vortices with less energy.


E.g. if the vertex radius is 15 feet and sink rate 20 fpm, we hit the
wake after a 30 second turn.

Twenty feet per minute is too slow. The downwash will move at at least a few
knots, and even three knots is 300 fpm.

I've seen numbers from flight tests indicating several hundreds feet
per minute for big aircraft, but I've never seen any numbers for small
aircraft nor I've ever seen a theory that could explain or calculate
everything measured in the flight tests.

Can you point to such test results or a complete theory? It seems that
you have access to at least one of them. Thx

- Tom

On Apr 18, 4:45 am, wrote:
In rec.aviation.piloting Mxsmanic wrote:

Thomas Borchert writes:
Can't follow you there. That's as useful a statement as "airplanes tend to
be stationary objects..."
In a turn, a portion of the lift produced by the wings must be used to
accelerate the aircraft laterally, and this portion of the lift is no longer
available to maintain the aircraft's altitude. Thus, without any adjustment
of pitch or power to compensate, any turn will result in a loss of altitude.

Yet another true but worthless statement.

One of the first things real pilots are taught in real training in
real airplanes is how to maintain a constant altitude in a turn.

Ergo any real turns by real airplanes will be constant altitude
unless the PILOT has a reason to do otherwise.

Since most 360 turns are done as practice to establish and maintain
the skill, most 360 turns will be at a constant altitude +/- 100 feet.


Consider the plight of the average ag pilot if he can't maintain
altitude in a steep turn if mad mixedups crazy claim is correct.....
and the brievity of his working life