From NASA's Aviation Safety Reporting System�
Number 192 May 1995
It's Almost Summertime
Although summer is just around the corner, one winter-type
woe often hangs around long after winter is officially past.
Unforecast or unexpected IMC can turn an otherwise pleasant
flight into a stressful one.
■ The flight was conducted in VMC. Turn to final approach
course was a sharp descending turn from VMC into IMC. I
immediately got disoriented and started hyperventilating.
After a short period of time that felt like forever, I decided to
abandon the approach and advised Tower Controller. I
calmed myself down [subsequently]...and successfully completed
an ILS approach and landing. Though I am legally
current and have a significant amount of “real” instrument
time given my level of experience, I plan to grab an instructor
and go get some more, particularly with the VMC-to-IMC
transition.
Our reporter has the right idea. A springtime “tune-up” is a
good plan for pilots, and for aircraft, too.
Air carrier aircraft are not immune from the perils of
unforecast IMC. The next report illustrates how little
problems can grow into big ones, even for large aircraft.
■ After takeoff, both magnetic compass systems began to
precess. We quickly determined that we could navigate safely
using our VORs and by updating our magnetic compasses
with reference to the standby compass. We were safe and
legal to continue, provided we remained in visual conditions.
As we approached [our destination], the weather deteriorated
and we requested a vector to our alternate. Due to our reduced
reserve fuel from circumnavigating en route weather,
we declared an emergency to receive priority handling.
The Last Icicle
Some pilots may associate icing only with winter flying. As
the following reports illustrate, and as Murphy’s law would
have it, carburetor and fuel system icing can occur anytime.
■ Two tailwheel-qualified CFIs were on board for a training
flight. Carb heat was applied and the throttle closed in
preparation for a power-off stall. As the aircraft approached
a stall attitude, the prop stopped abruptly. The air temperature
and dew point were 53 and 44 degrees Fahrenheit, respectively.
These parameters plot in the region of maximum
carb ice probability. Although full carb heat was applied
prior to closing the throttle, the heat may have been insufficient.
The next reporter, a pilot of a corporate twin, had expected
better performance from his turbocharged engines. He is
now looking into ways of preventing a repeat of this incident:
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