BOBTAIT BOOK QUESTION 6 PAGE 53:

An obstacle situated on the extended centre line of an ALA is 45 feet high. The recommended minimum distance from the end of the strip to this obstacle is closest to:

A) 150 M
275 M
C) 200 M
D) 250 M

The answer on the book is 275 metres.
I'm quiet confuse with the answer how it was worked out..

Because if i calculate it following the formular on the book that says every obstacles must be atleast 20 times its own height away from the end of the strip..

which means 45×20= 900 metres..at the it did show the same but i'm abit confuse when 900 is multiplied with 0.305(900×0.305) where does that 0.305 comes from?

Sir can you please clarify this to me..

G'day Jukzizy

The question says 45 feet not metres, so 45x20= 900 feet so then multiply 900 by .305 to convert into metres = 275metres

Cheers

Thank you very much sir..much appreciated

As to 0.305.

The usual conversion factor most folks remember is

1 m = 3.281 ft

inverting this, we get

1 ft = 1 / 3.281
= 0.305 m

Thank you Sir..planing to sit casa exam this week on friday..

Conversion factors are in the ERSA (GEN-CON-2) which you will have in the exam

ERSA (GEN-CON-2)

Quite. However, for the common factors, it really is better for folks to have them tucked into memory (like so many other things) - one doesn't always have the luxury of time to dig about in a document for stuff which one needs right then ....