Question to Mxmanic

writes:

Upon what do you base the assumption your wake should decend 150'?

All wakes descend; they have to, otherwise the aircraft could not stay aloft.
They move at a few knots, which still amounts to some 500 fpm.

I have never heard of any study of the wake properties of GA aircraft
and the wake of a C172 is very different than the wake of a 747 ...

Since you haven't heard of any study of the wake properties of GA aircraft,
you cannot possibly know whether the wake of a C172 is "very different" from
that of a 747 or not. Oops!

In fact, the general principle is the same for all aircraft wakes. They
always move downward gently. You cannot catch them in a turn unless you move
downward, too. If you are in rising air, the wake might remain stationary
relative to the ground, but then your aircraft would be rising, so you'd still
have to descend relative to the surrounding air in order to catch your wake.
And smoothly rising air isn't that common, although it's not that rare.

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mike regish writes:

On a bumpy day you wouldn't be able to tell the wake from the overall
turbulence.

I agree.

On an otherwise smooth day you can.

Probably--if you actually hit it.

It can be done, Tony.

Not without descending. The wake _must_ descend. This means that you cannot
catch it unless you descend, also. If you can explain how this rule can be
broken, I'm listening.

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writes:

Just because you have never experienced it and can't understand it
from your many hours of playing the Flight Simulator game doesn't
mean it doesn't exist.

My study of aerodynamics thus far indicates that it is impossible, unless you
descend to catch your descending wake. Wakes _always_ descend. It's a
consequence of the mechanism that produces the lift that sustains the
aircraft, and it's unavoidable. Every source that I have consulted points
this out, without exception. Your mere assertion to the contrary is
completely unpersuasive in comparison.

It just means you don't know a whole lot about real flying or what
happens in a real airplane.

No, it means that I look at the facts, and I don't depend on the legends.

Have you ever done a short field take off in your Flight Simulator
Cessna with the springy gear and had the mains vibrate for a few
seconds shaking the airplane?

I don't fly the Cessna, and I fly only at airports with hard, smooth runways
that won't bounce the aircraft around.

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"Kev" wrote in message
ups.com...
On Apr 16, 9:41 am, Jose wrote:
I seem to recall recent magazine (web?) articles where the idea that
you can hit your own wake while actually holding altitude, should be
downplayed nowadays. You _have_ to descend a little bit to do so,

How tall is the wake?

Good point. Still, using the calculator at:

http://www.csgnetwork.com/aircraftturninfocalc.html

It's going to take about 30 seconds to fly a 360 steep turn at
100kts. My wake _should_ descend about 150' during that time (300
fpm). I can't imagine a C172 wake being tall enough to stay in my
way unless something else is ocurring (me descending, or the wake
staying up).

Would love to hear a decent explanation. Kev


I am certainly no expert on the subject, but I think most of the data on
wake turbulence comes from studies held at or very near the ground.
Certainly not all, because I recall an old FAA film on landing in wake
turbulence using a 182 to fly into the wake at altitude. But IIRC it was
part of an awareness film on wake turbulence on approach, just demonstrated
at altitude for safe demonstration of its actual effects.

Based on the numbers I recall, they did indeed teach that the wake from a
landing heavy would NORMALLY travel both down and away from the aircraft a 5
kts or so. But they were also quick to mention that a simple 5 kt or so
crosswind componet could leave the vortex in the middle of the runway for
quite some time.

The problem with trying to use this information at altitude is that you
don't have the ground to help stablize the vertical movement of the vortex.
And every pilot knows the air at altitude is very seldom static, especailly
in warm weather. As someone else mentioned, the vortex that started as a
very small column at the wing tip, can grow very large by the time you
complete a 360 turn at even 60 degrees of bank.

The point is, you are dealing with far to many variables to expect absolute
answers your question or even your own in flight results. Wake turbulence is
really only a problem at altitude if you don't avoid the flight path of
heaver aircraft, and understanding it's presence on take off and landing,
because it is much easier to intercept their flight path around runways.

"Mxsmanic" wrote in message
...
writes:

Upon what do you base the assumption your wake should decend 150'?

All wakes descend; they have to, otherwise the aircraft could not stay
aloft.
They move at a few knots, which still amounts to some 500 fpm.

I have never heard of any study of the wake properties of GA aircraft
and the wake of a C172 is very different than the wake of a 747 ...

Since you haven't heard of any study of the wake properties of GA
aircraft,
you cannot possibly know whether the wake of a C172 is "very different"
from
that of a 747 or not. Oops!

In fact, the general principle is the same for all aircraft wakes. They
always move downward gently. You cannot catch them in a turn unless you
move
downward, too. If you are in rising air, the wake might remain stationary
relative to the ground, but then your aircraft would be rising, so you'd
still
have to descend relative to the surrounding air in order to catch your
wake.
And smoothly rising air isn't that common, although it's not that rare.


You butt head. You clearly don't even understand the simplist properties of
an aircraft vortex.

"Mxsmanic" wrote in message
...
Jose writes:

How tall is the wake?

The downwash is at least equal in height to the total wingspan of the
aircraft. Downwash is a large mass of air moving slowly. Still, you
should
not be hitting your own wake in a 360-degree turn unless you are
descending to
catch it. Oddly enough, if you are descending, the wake moves more slowly
(because you are generating less lift).


Priceless bucko!!!!!

It sounds to me like you are experiencing some serious wake tubulence in the
airspace between your ears.

"Mxsmanic" wrote in message
...
mike regish writes:

On a bumpy day you wouldn't be able to tell the wake from the overall
turbulence.

I agree.

On an otherwise smooth day you can.

Probably--if you actually hit it.

It can be done, Tony.

Not without descending. The wake _must_ descend. This means that you
cannot
catch it unless you descend, also. If you can explain how this rule can
be
broken, I'm listening.


Total bull****. You haven't a clue.

"Mxsmanic" wrote in message
...
writes:

Just because you have never experienced it and can't understand it
from your many hours of playing the Flight Simulator game doesn't
mean it doesn't exist.

My study of aerodynamics thus far indicates that it is impossible, unless
you
descend to catch your descending wake. Wakes _always_ descend. It's a
consequence of the mechanism that produces the lift that sustains the
aircraft, and it's unavoidable. Every source that I have consulted points
this out, without exception. Your mere assertion to the contrary is
completely unpersuasive in comparison.

It just means you don't know a whole lot about real flying or what
happens in a real airplane.

No, it means that I look at the facts, and I don't depend on the legends.

Have you ever done a short field take off in your Flight Simulator
Cessna with the springy gear and had the mains vibrate for a few
seconds shaking the airplane?

I don't fly the Cessna, and I fly only at airports with hard, smooth
runways
that won't bounce the aircraft around.


No your haven't. You have never flown anything but your desk, and regardless
of your medications, it never left the floor.

Mxsmanic wrote:
Not without descending. The wake _must_ descend. This means that you cannot
catch it unless you descend, also. If you can explain how this rule can be
broken, I'm listening.

Then listen hard. The wake consists of more than just the downwash you
are fixated on. If you have ever seen a sky-writer at work, you would
know, even without setting foot in a real aircraft, that it is possible
to return to the same parcel of air and pass through the smoke you had
left previously.
On a calm day, no descending or climbing is required.
Your problem is your fixation on your assumptions, and then insisting
that physical reality must be wrong when your limited assumptions don't
square with that reality, a true sign of immaturity and a basic
inability to assimilate the information that your own senses provide.
Anthony, I'm actually beginning to feel sorry for you. I believe that
you have real, diagnosable mental issues.

Rip

On Apr 16, 10:45 am, Mxsmanic wrote:
Kev writes:
On a warm clear day (which is when I've hit my own
wake), I betcha that the wake is being held upward a tiny bit by the
heat from the ground.

Then you must be descending through the rising column of air.

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You are such an idiot! Probably every GA pilot-in-training with a
C152/172 or something similar has experienced hitting their own wake
when performing their first steep turn with an instructor. I know I
did. I routinely show non-flying friends this phenomenon when I take
them flying.

But go ahead...keep arguing with experience that you don't have.

--Jeff