A Flare Seen Off Santa Cruz Island
Memorial Day Weekend, San Diego, CA, 2012
To be told!
Radio transmission overheard on Marine VHF. someone in a boat offshore saw a
flare. The boat offshore couldn't guess how high the flare was, or distance to
the flare. The coast guard radioman on the radio advised the boater to "use
the fist method" then explained the technique. Hold out his fist at arms
length, thumb up, with the bottom of the fist on the horizon. Then report
about how many fists above the horizon would be stacked to approximate the apex
of the flare.
U. S. Coast Guard Addendum to the United States National SAR Supplement,
Appendix I – Flare Incidents,
COMDTINST M16130.2D
(a) A major point to remember is that for any flare sighting with an angle of elevation of more than 8 degrees,
the distance of the flare from the reporting source is less than 1.4 nm.
(b) Closed Fist Method. A closed fist held at arm’s length with the thumb side up represents approximately 8
degrees of arc.
An estimate of three fingers or half a hand can be extremely useful. Obtain the final estimate in terms such as
“not less than ½ hand and not more than 1 ½ hands.” Convert number of fingers or fractions of hands to
degrees based on Figure I-4a above.
The actual height of the observed flare at the top of its trajectory is also subject to a large uncertainty. For
reports of less than 4 degrees (1/2 fist), the range of distances increases very rapidly.
For flares that are fired into the air,
the maximum height is assumed to be 1200 feet for parachute flares and 500 feet for meteor flares. The
minimum height for both types of flare is assumed to be 250 feet or 10 feet above that of the reporting source
for heights of eye greater than 240 feet. A flare that rises only 250 feet must be much closer to a given observer
(e.g. height of eye 20 feet) in order to produce a given observed angle above the horizon (e.g. 1 degree) than a
flare rising to 1200 feet which produces the same angle from the same point of observation. The distance in the
first case is 2.31 nm while the distance in the second case is 10.98 nm.
Click the images for full-size view. |
|
| |
| |