Sender: "Marvin Kaye" <marv@lancaironline.net>
To: lml@lancaironline.net
Date: Thu, 30 Sep 2004 22:46:34 -0400
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From: bob mackey <nospam@pure-flight.com>
Subject: [LML] wing incidence indifference (50 fps lift)
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>>    Now our ES, after surviving that encounter slows down to 170 mph.
>> The AoA is 3.88 degrees, the Cl is .3439. Again it encounters that 50 fps
>> vertical gust,

> Robert,
> What kind of vertical tornado are you talking about--- 50fps?
> ciao, Jeff


50 fps = 3000 fpm = 30 kts = 15 m/s

While updrafts of that strength are not common, they are familiar
to soaring pilots. One of the strongest thermals that I've flown
(in a hangglider) pegged my variometer (a type of VSI) at over
2000 fpm for some time. The portion of the climb from 8000
to 17999 MSL took less than four minutes.

Portions of that thermal were certainly well over 3000 fpm.

Typically, strong thermals are also surrounded by sink, so the vertical
shear experienced by a fast aircraft is the difference between the sink
outside and the lift inside. Sink of -1000 fpm with lift of +2000 fpm is
not unusual on a summer day in the western deserts. When that strong lift
and sink is found in a smaller thermal, the distance from the lift to the
sink can be less than 100 m, or less than a second.

Thunderstorms and tornadoes can be several times stronger than described
here.


- bob mackey
  flying a 235
  building a 320
  103MD -at- pure-flight.com
  [use this email address - the one at the top is spam bait]