No de-icing system allows a pilot to continue flight in icing conditions
when encountered...they provide a safety margin while escaping from the
conditions. The exposure to icing required for known-icing certification
doesn't amount to much...Appendix C to Part 25 (which applies to Part 23 by
reference) requires quite a bit of interpretation, but for convective clouds
it is something like 3.8 miles and for stratus clouds it is something like
17 miles. If the droplets are larger than 40 microns or you stay in the
clouds longer than the distances laid out in the reg, you have exceeded the
known icing requirements and are on your own.

Bob Gardner

"Peter Duniho" wrote in message
...
"Peter R." wrote in message
...
Andrew, I am flying a Bonanza with a "not known icing" TKS system out of
Syracuse, NY. From what I understand about the system, the difference
between the not known icing and the known icing TKS system has to do
with redundancy, not functionality.

There may be functional differences, in that known-ice certification
requires a laundry list of protected surfaces (in addition to the
redundancy
requirements), some of which may not be included in a "not known-ice"
certification. Some "non known-ice" installations meet all the
requirements
except redundancy, but many do not.

That said, I'm not aware of any de-ice system on a single-engine piston
aircraft, known-ice or not, that is suitable for allowing a flight to be
made into reported non-trace icing. All of the systems should be used as
a
"get out of jail free" card, to allow a pilot to take the plane out of the
icing with less hazard than would otherwise be had. From what I
understand,
even on many (all?) light twins, the same is true.

Of course, that's not to say that a de-ice system wouldn't translate into
a
higher wintertime dispatch rate. Just that pilots should be careful to
not
think that having de-ice on their airplane means they can just cruise
along
ignoring existing icing conditions.

Pete