Carb ice

I was flying with an instrument student yesterday (she is almost done) and
she noted that the engine was running rough and turned on the carb heat.
Sure enough, the engine began running so rough that the cowl was shaking. I
hoped it would go away as we continued toward Tacoma Narrows, but it did not
and we decided to just proceed direct and land instead of flying another
approach. The temperature was in the low 70s and (this being Puget Sound)
the humidity was high.

By the time we landed the engine was just barely rough, probably because the
carb heat had made the mixture a little too rich. We had managed to get two
hours of practice in, though, so it was still a good flight. I expect to put
the student up for a check ride as early as next week if we can get her
partial panel work to acceptable levels (still a little rusty after the
cross countries).

I have seen carburetor icing in temperatures approaching 100 degrees in this
area. This has to be one of the worst places in the world for it. This was a
172M. These airplanes seem especially susceptible anyway, but I have never
understood the reason for it. Maybe they have Freon cooled carburetors or
something. :-)

--
Christopher J. Campbell
World Famous Flight Instructor
Port Orchard, WA


If you go around beating the Bush, don't complain if you rile the animals.