On Sun, 13 Jan 2013 07:59:41 -0800, Mike the Strike wrote:

As an ex hang-glider pilot, I also thought that the story was well
researched and nicely written, without the usual inaccuracies.

One interesting note - the article says that pilots had to land before
half-an-hour after sunset for the record to be valid. Is this true and,
if so, why do they get half-an-hour longer than glider pilots?


In the UK, anyway, a glider flight must take place during the day, i.e.
may not start or finish at night. The following definitions apply:

night ends 1/2 hour before astronomical sunrise
night starts 1/2 hour after astronomical sunset

....where astronomical sunrise and sunset must be calculated for a
specific lat/lon and day of the year. IIRC for the purposes of this
calculation the world is assumed to be a perfect ovoid, i.e. the effect
of nearby mountains between the sun and the required location is not
taken into account.

As this is an aviation definition of the start and end of night time, I'd
assume the same calculation is used in the USA.

This is why the article talked about the need to land before sunset + 30
minutes.


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martin@ | Martin Gregorie
gregorie. | Essex, UK
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