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airport’s AWOS-3 weather report. Unfortunately, this AWOS is…
unreadable until close to airport….We continued originally at
15,000 feet MSL (filed altitude), we stepped down to 14,000 feet
MSL then 13,000 feet MSL per ATC clearance. About the time
AWOS became readable our flight entered solid overcast IMC with
Number 361 January 2010
Entice ments of ice
I would recommend the airport authority treat runways promptly
or close the airport in such conditions while notifying pilots
through NOTAM system, ASOS, or approach controllers to prevent
an accident.
Boxed In,
But a Way Out
A low-time, instrument rated
Cessna 172 pilot demonstrated
good situational awareness and decision skills after encountering
unforecast icing.
n Flight departed after receiving a weather briefing for the route
of flight. Weather was VFR and predicted to remain VFR for the
flight. A shelf of clouds started to develop about 1,000 feet below
the aircraft and ceilings about 2,500 feet above the aircraft. Inbetween
the shelf and base, I could make out airport in the distance,
so I requested VFR clearance on top to airport. I received the
clearance via radar vectors and flew the vector. The temperature
was at 32 degrees F and I requested vectors that would not make
me penetrate visible moisture. At this point the shelf merged with
the bases and prior to continuing, I looked behind the aircraft
and saw a cloud rolling in behind the aircraft, almost as a curtain
drawing, making it impossible to divert. I followed the vectors to
the best of my ability, but was distracted, making it difficult.
After penetrating a cloud, I noticed approximately 1/8 inch of ice
on the leading edge. At this point, I announced my icing condition
to ATC and they gave me priority handling. Shortly after, I declared
an emergency and ATC gave me vectors for the ILS. I tuned
and identified the ILS and tried to track it, but I was unable to
receive the glideslope. I then received vectors for the airport and
descended to 400 feet AGL. At this point I had closer to 1/4 to 1/2
inch of mixed ice on the wings. I had visual on the airport abeam
runway…and circled to land using no flaps and had a smooth, safe
landing. After landing, I proceeded to the FBO with Airport Rescue
following me in. After examining the aircraft, the propeller was
clear and the wings had about 1/3 inch of ice extending about 6
inches aft of the leading edge.
361
severe icing. All de-ice/anti-ice equipment, including boots/hot
props/windscreen protection were functioning normally, but it was
apparent the conditions encountered were rapidly overwhelming
the aircraft capability. The altered flight characteristics, burble,
airframe vibration and general control deterioration from ice buildup
required immediate action. I disconnected the autopilot and
turned 180 degrees while descending to 12,000 feet MSL, the MVA,
in search of warmer air and to fly out of the IMC/icing conditions
we had entered. While turning/descending, I declared an emergency
with Center and apprised the controller of our change in course/
altitude. The aircraft flew out of IMC conditions at 12,000 feet and
we terminated our emergency status with Center…While inbound
Approach Control took down the icing info from our experience and
passed it along, resulting in an icing SIGMET issuance….
It is important to realize that the de-ice/anti-ice capability of propdriven
GA aircraft is inadequate to handle severe icing situations. I
am convinced our immediate change in direction to reverse course
was the correct response to the weather encountered. Always have
an ‘out’ or ‘Plan B’ if weather conditions are different from forecast.
A Flare on the Glare
A potential problem faced
by both GA and air carrier
pilots who fly into Non-Towered
fields is the lack of current NOTAM, automated weather, or ATC
information about adverse airport conditions. Here’s a report from
the pilot of a private turbojet aircraft who encountered a ‘no go’
situation after landing.
n After a normal descent and ILS approach on Runway 21 I landed
with a 20-knot right crosswind. Shortly after touchdown, I realized
the entire airport property was covered with 1/4 inch of glare ice.
Braking action was nil and the aircraft could only be controlled
with rudder, speed brakes, and differential use of thrust reversers.
The ice was not visible on final because of overcast conditions.
Local FBO personnel told us of ‘ice’ on short final but this did not
nearly describe the severity of the situation. The previous night’s
　
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