Since the beam forms an isosceles triangle your formula in column C
should be 2*tan(radians(angle/2)). The widths are
somewhat different for wider angle beams.
I use a 12V 100W Halogen MR16 EMC (can't find the angle info) on the
left leg for landing/taxiing and a GE quartz 12V 100W (Q4509?, 7 -
10 degree spread) cowling mounted lamp for approach/taxiing. The GE
provides good lighting of the runway on approach but disappears from
view on flare (can't see over the nose) and the leg light
beautifully illuminates the area I can see down and to the
left. I had pictures taken at night, but I can't find them at this
time.
Scott
Krueger AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL
(KARR)