navigation lights?

"Greg Farris" wrote in message news:dvpchc$15e1

Are you guessing then?

Not really -- just estimating (based on 35 years worth of looking) because I
don't know the exact specification. You can bet that somewhere there is an
FAA spec telling manufacturers *precisely* the number of lumens, the
candlepower, and the distance from which the light must be visible under
specified circumstances of visibility.

......but many other situations where it is not at all clear
from these light which way a plane is going. This applies to airliners as
well, whose position lights often seem scarcely larger or brighter than
those
of light aircraft. Few airliners have a really clear, white light in the
back
to indicate they are moving away from you .......

You don't necessarily need to see the white light to make that call. That's
precisely why the specs call for different types of lights in stipulated
locations -- different colors, some steady, some flashing -- so you won't
have to see all the lights to make a determination.

John Gaquin wrote

You can bet that somewhere there is an FAA spec telling
manufacturers *precisely* the number of lumens, the
candlepower, and the distance from which the light must
be visible under specified circumstances of visibility.

FAR 23.1385 thru 23.1397

Bob Moore

"John Gaquin" wrote in message
. ..
[...] so you won't have to see all the lights to make a determination.

And in fact, which lights you see or don't see is a key part in interpreting
the lights. If you could see all of them at the same time, they would be
less useful.

In article ,
John Gaquin wrote:

"Greg Farris" wrote in message news:dvpchc$15e1

Are you guessing then?

Not really -- just estimating (based on 35 years worth of looking) because I
don't know the exact specification. You can bet that somewhere there is an
FAA spec telling manufacturers *precisely* the number of lumens, the
candlepower, and the distance from which the light must be visible under
specified circumstances of visibility.

Of course there is.

PART 23--AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND
COMMUTER CATEGORY AIRPLANES

23.1385 Position light system installation.
23.1387 Position light system dihedral angles.
23.1389 Position light distribution and intensities.
23.1391 Minimum intensities in the horizontal plane of position lights.
23.1393 Minimum intensities in any vertical plane of position lights.
23.1395 Maximum intensities in overlapping beams of position lights.
23.1397 Color specifications.

Everything you ever wanted to know about nav lights.