Received: from opus.hpl.hp.com by jr.hpl.hp.com with ESMTP (1.37.109.24/15.5+ECS 3.3+HPL1.1) id AA209910206; Fri, 2 Jul 1999 00:23:26 -0700 Return-Path: <seven@mechsys2.me.berkeley.edu-DeleteThis> Received: from hplms26.hpl.hp.com by opus.hpl.hp.com with ESMTP (1.37.109.24/15.5+ECS 3.3+HPL1.1) id AA125540199; Fri, 2 Jul 1999 00:23:19 -0700 Received: from mechsys2.me.berkeley.edu (mechsys2.ME.Berkeley.EDU [128.32.141.18]) by hplms26.hpl.hp.com (8.9.1a/HPL-PA Relay) with ESMTP id AAA13058 for <wind_talk@opus.hpl.hp.com-DeleteThis>; Fri, 2 Jul 1999 00:23:19 -0700 (PDT) Received: from mechsys2.me.berkeley.edu (mechsys2.ME.Berkeley.EDU [128.32.141.18]) by mechsys2.me.berkeley.edu (8.8.7/8.8.7) with ESMTP id WAA31507 for <wind_talk@opus.hpl.hp.com-DeleteThis>; Thu, 1 Jul 1999 22:49:14 -0700 Sender: seven@mechsys2.me.berkeley.edu-DeleteThis Message-Id: <377C6363.AD69A7F@mechsys2.me.berkeley.edu-DeleteThis> Date: Fri, 02 Jul 1999 06:59:47 +0000 From: "J.R. Ridgely" <seven@mechsys2.me.berkeley.edu-DeleteThis> Organization: Cal X-Mailer: Mozilla 4.5 [en] (X11; U; Linux 2.2.2 i686) X-Accept-Language: en To: wind_talk@opus.hpl.hp.com-DeleteThis Subject: Re: "Twisters" (Wingtip vortices) References: <199907020355.AA081497727@jr.hpl.hp.com-DeleteThis> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit
> One of the things Ken Poulton added to the list of impacts of the SFO
> Airport exansion was:
>
> > Occasional violent turbulence (small 40+ knot "twisters") at water
> >level.
>
> I have witnessed these several times at Coyote and not everyone even
> believes me when I tell them. Basically, the twister just leaves the airport
> area and works it's [sic] way downwind -- a swirl of blasting winds, probably
> 40-50 mph, maybe more.
They should believe it...I would expect more than 50 mph when the vortices are
generated, decreasing as they dissipate, but that's just a guess with no
supporting evidence.
> A friend of mine flies 747's, and claims that vortex generated by each
> wing can knock down wind surfers.
Heck, they can knock down small airplanes (see below).
> It is a little like bowling, only a
> lot more fun.
Except that by the time the vortices reach the windsurfers a mile or two
away, the plane should be taxiing up to the terminal...
> My guess is these vortex's (vortices?) are generated from the wing tips
> of large planes, and I'm pretty sure they are a well documented hazard.
> Any small plane pilot should be able to give more information.
Tip vortices from large aircraft are indeed a well documented hazard. Every
small plane pilot learns how to avoid them; they can easily cause loss of
control and a crash of a smaller aircraft. In one pilot training movie, we
were shown video of a small plane flown into the wake of a C-5 at landing
speed (at a safely high altitude, as a demonstration). The small plane was
flipped completely over. Given what it can do to a 2500 pound airplane, the
vortex could reasonably be considered a significant safety issue for a 250
pound windsurfer.
JR
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