Safer Flying in Icing Conditions

Reprinted with permission from FAA Aviation News

If you’ve watched TV forecasters struggle to correctly predict winter weather, you probably realize that understanding icing—whether on the ground or in the air—is difficult and complex.

Aircraft icing is a continuing concern in all parts of aviation, from small planes to jumbo jets. It is an insidious hazard to aircraft. Wings, stabilizers, and control surfaces are carefully shaped to produce “lift”—the aerodynamic force that makes airplanes fly. Ice on these surfaces can make it hard for the pilot to control the airplane or even keep it airborne. Ice shedding off the wings also can damage the tail or be sucked into the engines.

The FAA has a multi-pronged approach to icing issues, using both immediate safety actions and longer-term rule changes.

Targeting Specific Airplanes

On October 31, 1994, an American Eagle ATR 72 airplane crashed near Roselawn, Indiana, after encountering icing conditions. The accident prompted the FAA to review aircraft in flight icing safety and implement a comprehensive in flight icing program that increases the level of safety.

Since 1994, we have issued more than 100 airworthiness directives to address icing safety issues on more than 50 specific aircraft types. These orders cover safety issues ranging from crew operating procedures in the icing environment to direct design changes. We also have changed airplane flight manuals and other operating documents to address icing safety, and issued bulletins and alerts to operators emphasizing icing safety issues.

In 1999 and 2000, the FAA addressed activation of pneumatic deicing boots on many models by requiring activation of boots at the first sign of ice accumulation. We have issued airworthiness directives on aircraft, such as the Mitsubishi MU-2 and more recently the Cessna 208 given their history of icing-related accidents and incidents.

Broad Transport Category Rule Changes for Greater Safety

In 2007, the FAA has taken major steps to change certification regulations applying to a wide range of icing-related standards.

Current FAA regulations do not require a way to warn pilots of ice buildup. A rule change proposed in April would require an effective way to detect ice buildup or let pilots know that icing conditions exist, and produce timely activation of the ice protection system. It will help avoid accidents and incidents where pilots are either completely unaware of ice accumulation or think it isn’t significant enough to warrant turning on their ice protection equipment.

The proposed rule would mandate one of three methods to detect icing and activation the ice protection system:

• An ice detection system that automatically activates or alerts pilots to activate the ice protection system.
• A definition of visual signs of ice buildup on a specified surface (e.g., windshield wiper post or wings) combined with an advisory system that alerts the pilots to activate the ice protection system.
• Identification of temperature and moisture conditions conducive to air-frame icing that would tip off pilots to activate the ice protection system.

The proposed rule would further require that after initial activation of the ice protection system, the system must operate continuously, automatically turn on and off, or there must be an alert to tell pilots when the system is to be cycled.

On August 8, the FAA published in the Federal Register (volume 72, number 152, and page 44655) a final rule that introduces new airworthiness standards for the performance and handling characteristics of transport airplanes in icing conditions. The new rule will improve the level of safety for new airplane designs when operating in icing conditions, and will harmonize the U.S. and European airworthiness standards for flight in icing conditions. The rule adds a comprehensive set of airworthiness requirements that manufacturers must meet to receive approval for flight in icing conditions, including specific performance and handling qualities requirements, and the ice accretion (size, shape, location, and texture of ice) that must be considered for each phase of flight. These revisions will ensure that minimum operating speeds determined during the certification of all future transport airplanes will provide adequate maneuvering capability in icing conditions for all phases of flight.