Good image of the activity over Scotland
http://www.sat.dundee.ac.uk/abin/pro...roject.ch2.jpg
(reg required etc etc)

MetO Form215 VT 15Z suggests vertical speeds of up to 400-450FPM (feet per
minute).

If Jack's watching how turbulent would conditions be and at what sort of
thresholds did you become 'interested' from a pilot's perspective ? I ask
because the military charts only include SIGMET-able waves (500FPM+) and the
future combined military/civil charts could use this threshold.

Jon.

Below cloud base, the air is very disturbed and can be extremely
turbulent. Once above cloud base, things normally calm down nicely.
Indeed, the glider pilot struggling to get into the wave proper
realises that the battle has been one once the turbulence is replaced
by amazingly smooth (laminar) air.

But don't forget that an aircraft, even in the "smooth air", if
it is flying at say 400 knots would pass through the up and down
currents in a very short time and would experience the effect as
"turbulence". However an aircraft flying beneath cloud in mountain
wave conditions would experience an altogether much more extreme form
of "chop". When approaching to land at airfields such as Aberdeen,
Newcastle, Teesside and Leeds/Bradford for example could be quite an
entertaining affair in the right (wrong?) conditions.

Glider pilots become interested when the vertical speeds of the wave
exceeds the rate of descent of the glider, roughly 200 ft/min. This is
about the threshold that would become an irritation to the airline
pilot.

Jack

wrote in message
oups.com...
Below cloud base, the air is very disturbed and can be extremely
turbulent.
snip

Thanks for the reply, Jack.

Jon.

"Jon O'Rourke" wrote in message
...
wrote in message
oups.com...
Below cloud base, the air is very disturbed and can be extremely
turbulent.
snip

Thanks for the reply, Jack.

.... this used to be an ongoing discussion when STC used to provide the
military charts : what was significant when forecasting for a wide
variety of a/c? A consequence of the successive mergers between military
formations (the most significant being between Transport/Air Support and
Strike) was that we had 'one size fits all' output - it never works, and
you are going through it again with the merger of civil and military
output. As Jack writes, fast jets etc., whistle through these phenomena
with hardly an impact - the larger/slower types (which are used on
low-level flights for extended periods, e.g. C-130 on para-drops or
battlefield supply) would be interested in turbulence from whatever
cause. The w/e gliding schools/fixed wing 'familiarisation' flights
would also be wary of turbulence from whatever cause.

Martin.


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On Tue, 21 Jun 2005 13:38:25 -0700, jack.harrison wrote:

Glider pilots become interested when the vertical speeds of the wave
exceeds the rate of descent of the glider, roughly 200 ft/min. This is
about the threshold that would become an irritation to the airline pilot.

In the tail end of an expired hurricane, over the Great Glen, even at Vne
with the brakes out we were still going up. 12,000 (-ish :-) feet,
vario pegged, no oxygen on board :-(((

Had to spin the glider to get down, and saw a beautiful Glory as we did
so, and no cameras on board either...


Sadly, flying over East Anglia (from Gransden as does Jack now) the
opportunity never arises...


Mike

In the tail end of an expired hurricane, over the Great Glen, even at
Vne
with the brakes out we were still going up. 12,000 (-ish :-) feet,
vario pegged, no oxygen on board :-(((

Had to spin the glider to get down, and saw a beautiful Glory as we did
so, and no cameras on board either...

AAARRGGHH!

Anne

I wouldn't have spun but used the dwoncurrent some 2 miles downwind of
the up. But maybe that area was too cloudy

Mind you, I did once have a similar experience under a cu nim in South
Africa. Maximum speed, airbrakes out and holding level flight (ASK
21). Of course, once clear of that storm, it was absoutely smooth with
only the merest of gently descending air. Mind you, it was sufficient
to stop me getting back to base. But that's another story.

By the way, GRL ace Phil Jeffery landed out at Banbury yeaterday.
Guess who went to get him?

Jack

On Thu, 23 Jun 2005 05:18:05 -0700, jack.harrison wrote:

I wouldn't have spun but used the dwoncurrent some 2 miles downwind of the
up. But maybe that area was too cloudy

Yup, granite clouds, Ben Nevis to be precise (I assume it is granite).



By the way, GRL ace Phil Jeffery landed out at Banbury yeaterday. Guess
who went to get him?

Did you check that the trailer was empty before setting out? (Vide
Platypus on Cambridge retrieves ;-)


Mike