Ron Rosenfeld wrote:
On Tue, 08 Nov 2005 17:13:07 GMT, Jose wrote:


2. If the purpose of night flying regulations is to require the currency
of special skills when it is "dark", then the times should be adjusted to
reflect local topography. For example, ridges and mountains may cause
darkness to be present earlier than the official sunset time.

I think this is one of those places where judgement comes into play.
We're not talking about much of a temporal difference.

Jose


Well, there are legal, practical and safety issues also. On 29 March 2001
there was a fatal accident involving a Gulfstream at Aspen. They were
executing an approach that was not authorized "at night". "Official"
sunset occurred 33 minutes prior to the accident, so "official" night would
have occurred 3 minutes prior to the accident.

However, according to the NTSB calculations, the sun would have set below
the mountainous terrain about 25 minutes BEFORE official sunset time; and
the shadow for the ridge immediately to the west of the accident site would
have crossed the site 79 minutes earlier than official sunset.

Among the NTSB conclusions was "that the aeronautical definition of “night”
does not adequately describe the conditions under which darkness exists in
mountainous terrain and, therefore, use of this term may not adequately
restrict potentially hazardous flight operations".

The NTSB recommended revisions in this regulatory area, to adequately
address these issues.

The trouble is that you can NEVER write enough regulations to alleviate
poor judgement.


Matt