From: Brad Sparks <RB47x.nul>
Date: Thu, 22 Nov 2007 17:50:33 EST
Archived: Fri, 23 Nov 2007 09:44:41 -0500
Subject: Re: Pilots & UAP


>From: Don Ledger <dledger.nul>
>To: ufoupdates.nul
>Date: Wed, 21 Nov 2007 15:26:21 -0400
>Subject: Re: Pilots & UAP

>>From: Brad Sparks <RB47x.nul>
>>To: ufoupdates.nul
>>Date: Tue, 20 Nov 2007 21:55:23 EST
>>Subject: Re: Pilots & UAP

<snip>

>Brad, I'd like to ask you and David Rudiak to address this
>problem that has bothered me for some time; this being reports
>by pilots - or explanations by the FAA, TC, CAA etc. of them
>encountering/reporting a weather balloon.

>Weather ballons usually explode once they expand to a given
>diameter of 8-10 feet which occurs at an altitude of about
>40,000 feet.

>My question is: If an aircraft at 40,000 feet is flying at
>approx. .87 Mach what are the chances that the pilots can
>acquire it as an object long enough to identify it at these
>closing speeds given the size of 10 feet. This is assuming that
>the pilot was looking in the right place at the time.

Don, as your experience with 6 or 7 such weather balloons shows,
the weather balloon generally cannot be spotted until it is
about 1/2 Full Moon in apparent size. The tiniest little dot at
maximum resolution range just doesn't catch anyone's attention
(see calcs below). If we apply that acquisition range data from
your experiences to the 600 mph aircraft and a weather balloon
expanded to max size of around 10 feet, then maybe the crew
inside the 600 mph aircraft could see such a balloon for 2-3
seconds before they overtake it. Doesn't seem long enough and
significant enough to incite anyone to report it.

>I bring up this question because of my own experiences with
>weather ballons while flying my Cessna 172. My typical cruise
>speed was 120 mph. My typical altitude would be around 2,500 to
>3,000 feet depending on circumstances [could range as high as
>9,500 feet]. For the most part private pilots in the 172 sized
>aircraft has his or her eyes out the window with the occassional
>instrument glance then back outside.

>Each of the weather balloons [it's either 6 or 7] I observed
>first appeared as a dot through the windscreen. It took usually
>a couple of seconds to make sure it wasn't a bug on the
>windscreen [by moving my head around to a different angle]. The
>weather balloon would quickly expand in size and I either had to
>maneuver to avoid it or it passed under, above or on either side
>of me. The whole thing would be over in 5 to 6 seconds from the
>acquired dot to the passing of the balloon.

>The speed of the thing was of course my aircraft's closing
>speed. At the nominal 2,500-3,000 foot altitudes the weather
>balloon would be about 4 feet in diameter.

At your typical airspeed of 120 mph (about 180 fps) you travel
about 1,000 feet in 5-6 seconds hence that is the initial
distance to the balloon. At that distance a 4-foot balloon
subtends about 4 milliradians (14 arcminutes) in angular size or
almost 1/2 Full Moon. This is not a pinpoint or point source.
Apparently when the balloons are so far away that they are mere
pinpoints you don't spot them. They have to get close enough to
be almost 1/2 of a Full Moon in apparent size before they get
your attention, even though they would have been visible well
before that point if only you had known exactly where to look
and when to start looking.

Now once spotted if you were foolish enough to turn your head
around backwards and keep watching the balloon until it
disappeared at maximum resolution range then you could see the
balloon out to a much greater distance than the distance when
you acquired it, because you have already fixed on it and
followed it. Since typical 20/20 Minimum Angle of Resolution is
1 arcminute you might be able to follow that 4-foot balloon out
to around 14,000 feet (almost 3 miles) distance.

If we apply these numbers to 600 mph aircraft, flying 5x faster
than you in your Cessna, then they would have 5x shorter time to
see the balloons than your 5-6 second duration (hence about 1
sec), but because the balloons would expand to about 2.5x larger
diameter at typical operating altitudes of 600 mph jets (see
your 10-foot figure below) then you would multiply that factor
to yield a duration of
about 2.5 seconds to spot and watch a balloon. Not very long.

>Because this happened
>so quickly in my own cases I question the ability of pilots at
>35,000 to 40,000 feet at .87 Mach [typical] to acquire or even
>see one of these. Even at say 10 feet in diameter the speed of
>about 600 mph would make it extremely difficult to spot the
>balloon before it was passed by the aircraft in a matter of a
>couple of seconds.

See above.





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