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encased in ice the size of baseball bats. They maintained 170 knots throughout the approach (40 knots above normal speeds). They only slowed once they were committed to landing. The air- craft touched down without incident. When the cabin door opened, it hit a six-inch cone of rime on the prop spinner. When ice is hanging off the airframe, speed is life.
Severe ice requires an immediate change in altitude to exit the condi- tions (continuing an approach in many cases is better than climbing back into the offending environment). Many aircraft manufacturers publish speed increments to be added during an ap- proach in icing conditions. Technologi- cally advanced aircraft automatically adjust stall margins when ice is de- tected by advancing the AOA of stall alert systems. Many modern aircraft automatically activate ice protection as soon as ice is detected. Certifica- tion guidance has, over time, adapted to ensure better safety margins. For
all of this, many tried-and-true pilot techniques are still applicable.
Maintain sufficient airspeed. Oc- casionally turn off the autopilot in order to “feel” the aircraft. If it feels sloppy, go faster. Do not allow airspeed to degrade in order to maintain alti- tude. If you cannot maintain adequate speed, descend. Consider declaring an emergency to obtain ATC priority. Modern aircraft produce relatively stable stall characteristics when clean. On a contaminated airframe a stall can be sudden, asymmetric, and occur out of the blue. Snap spins can materialize without warning if airspeed degrades below safe ice speeds.
Fly Fast
On February 16, 2005, two Cessna Citations approached Pueblo Memorial Airport in Colorado. The sister ships were owned by Circuit City. They were flying from Richmond, Virginia, to Santa Ana, California. Both aircraft were scheduled for a short fuel stop in Pueblo, where IMC and freezing
drizzle prevailed. Pueblo tower was vectoring inbound traffic for the ILS. The Citations were equipped with stick shakers programmed to alert seven percent in advance of stall speed. The aircraft had been retrofitted with an AOA computer, which added another five knots to stick shaker speed when engine anti-ice was selected to ON. The inboard wings and engine cowlings were protected against ice via heated surfaces. The outboard wings and horizontal stabilizer were protected by deice boots.
Only one deice boot activation was captured on the accident aircraft dur- ing the approach. The sister ship re- corded five separate activations dur- ing their own approach (which took place 30 minutes after the accident). The sister ship carried excess airspeed throughout the approach, hustling through 1,500 feet AGL at 160 knots (they remained above 120 knots until descending below 200 feet). The acci- dent Citation was decelerating through
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