But if you always use a leading zero, then you always know you have received
the entire number. If you're using a mix of single digit and two digit
numbers you can never be assured you received correct information on the
10 numbers.




"Steven P. McNicoll" wrote in message
link.net...

"Tony Cox" wrote in message
ink.net...

Pilot calls "..left base, two". Could be either 2 or 20 & you know there
is an error. But you're none the wiser as to where he is. Worse case you
assume he's just being lazy with the "Jean traffic" bit & think he's on
base for 2.

Pilot calls "..left base, zero". Error detected, but a reasonable
assumption
is that he is heading for 2.

Which is less likely to lead to problems? And safety is no worse because
some people are announcing the leading zero while some aren't, so you
don't need 100% compliance.


Using leading zeros creates the possibility of transposing numbers. A
pilot
might say "zero two" when he means "two zero". With just "two" there's
nothing to transpose.



BTW, how does ATC call vectors? Don't they say things like "Cherokee
blah-blah turn right heading zero-two-zero", rather than just "two-zero"
?
Been a while & I can't remember.


Three numbers are used when issuing headings.