"Gene Seibel" wrote in message
When I was recently sitting on an airliner waiting to take off, we were
told that we couldn't take off because at the time there were both
freezing rain and ice pellets. We were told that they could take off if
either went away, but not as long as both continued. They claimed it
was an FAA requirement.

Every year before the winter season, the FAA publishes an updated Advisory
Circular with data for ground de-icing. The airlines adopt the AC for their
operation and train their personel. The term 'ice pellets' came about after
a crash (IIRC the Montrose, CO, Challenger crash), and after the year's
de-icing data was released. Because that years's data came out before 'ice
pellets' were defined, the airlines didn't have approved data for dealing
with ice pellets. When the ATIS had the words 'ice pellets' in it, there was
no approved data for dealing with ice pellets., and the airlines were
temporarily grounded until the ATIS no longer had the term 'ice pellets' in
it. Then we could start de-icing. This year's ground de-icing data includes
ice pellets, so there shouldn't be as many problems.

D.