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98 knots at 1,500 feet – 62 knots slower in the same atmospheric conditions. The accident crew failed to reference ice accumulation speeds provided by Cessna during a truncated approach briefing. The first officer on the acci- dent f light made an ambiguous refer- ence to both the icing conditions and the decaying airspeed seven seconds before the aircraft entered a sharp roll. Six seconds following the initiation of the roll, the aircraft crashed.
At the time of the accident, deice boot procedures were on the NTSB’s ten most wanted list for aviation safety. As such, it was not surprising to see the final report spend a substantial amount of time on the topic. In the end, the failure to activate the boots was not the primary cause of the ac- cident. The failure to carry proper airspeed was. The appropriate ice reference speeds would have afford- ed the crew a 20-knot safety margin throughout the approach. On a long runway, a few excess knots would have
been permissible as well. Although icing speeds are established to pro- tect against max continuous ice ac- cretion, the margins above stall may be less than what pilots are normally afforded. An additional fudge factor for a difficult approach can be appropriate in some circumstances.
When encountering ice, pilots must maintain a psychological balance be- tween terror and boredom. There is no reason to be intimidated by ice. Still, a healthy dose of respect is called for. In truth, most ice encounters are relatively benign and can be safely traversed even in non-FIKI equipped aircraft. You should obviously not f ly into icing conditions without properly functioning equipment, but do not panic if you find yourselves in those conditions inadvertently (or following equipment failure). Find a safe exit while maintaining sufficient airspeed.
Though fear can be a debilitating emotion when dealing with airborne threats, a blasé attitude is no better.
Even properly certificated aircraft are not capable of managing anything more than light ice indefinitely. It is always a good idea to find another altitude when ice is encountered, no matter the intensity. A few thousand feet up or down is generally enough to exit the conditions. It does not take a ton of ice to be dangerous. A mini- mal amount of ice accumulation can dramatically increase stalling speeds, decrease propeller efficiency and in- crease drag. There is no such thing as a safe amount of ice, only a safe margin of airspeed. Be brave, but also be fast.
Covington
Stan Dunn is an airline captain and check airman. He has 7,000 hours in turbine powered aircraft, with type ratings in the BE-1900, EMB-120, EMB- 145, ERJ-170, and ERJ-190. Stan has been a professional pilot for 14 years, and has been flying for two decades. You can contact Stan at stan@bell- manmultimedia.com.
November 2021 / TWIN & TURBINE • 13