O. Sami Saydjari wrote:
Do Airworthiness Directive Numbers have any meaning and structure? For
example, AD 82-27-3. Does one part mean year issued? Another refer to
type equipment effected? Another, perhaps a serial number of the AD
itself? Just Curious.


Not really. the first 2 digits are the year. The last two(one) digits
are numerical order. The middle two? Ah, this is the fun part. IIRC,
and I may not, this is the week of the year. So AD 82-27-3 is the
3rd AD published in the 27th week of 1982.

I think.