Rule change mandates better icing protection

 - August 26, 2009, 12:24 PM

The FAA last month amended its certification standards for icing protection on transport-category airplanes. The new rule, which goes into effect September 2, will require new systems to increase pilot situational awareness during icing conditions. “We’re adding another level of safety to prevent situations where pilots are either completely unaware of ice accumulation or don’t think it’s significant enough to warrant turning on their ice-protection equipment,” said FAA Administrator Randy Babbitt.

Under the new rule, Part 25 aircraft must have one of three methods to detect icing and activate the aircraft’s de-icing systems, such as an ice-detection system that automatically activates or alerts pilots to turn on the ice-protection system; a definition of visual signs of ice buildup on a specified surface, combined with an advisory system that alerts the pilots to activate the ice-protection system; or identification of temperature and moisture conditions conducive to airframe icing that would advise pilots to activate the ice-protection system. According to the amendment, any new system after initial activation must operate continuously, automatically turn on and off or alert the pilots when it should be cycled.

Icing Operations

The process for the new ruling–the culmination of nearly 15 years of deliberation and investigation by the agency–began in 1994 after icing was blamed for the October 31 fatal crash of an American Eagle ATR 72 near Roselawn, Ind. The NTSB determined that the pilots of that twin turboprop lost control as a result of “a sudden and unexpected aileron hinge moment reversal that occurred after a ridge of ice accreted beyond the de-ice boots.”

According to the final NTSB report on the accident, “The manufacturer failed to disseminate adequate warnings and guidance to operators about the adverse characteristics of, and techniques to recover from, ice-induced aileron hinge moment reversal events; and failed to develop additional airplane modifications, which led directly to this accident.”

Two years later, the FAA sponsored the International Conference on Aircraft In-flight Icing and formulated a multi-year plan to address icing problems. In accordance with the plan, the FAA tasked the Aviation Rulemaking Advisory Council with weighing the need for ice-detection systems and other means to warn flight crews of ice accretion on critical surfaces. The resulting NPRM was published in April 2007, and the comment period closed that July.

While this certification rule change addresses some issues brought up by the NTSB as a result of the Roselawn and other icing-related accidents, the new rules fail to cover equipment or operational factors during icing conditions outside the criteria used for certification. The FAA is updating these criteria, found in Appendix C of Part 25, but when they will be released is not yet known.