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Reduce Dangers to Aircraft Flying in Icing Conditions

Objectives

Use current research on freezing rain and large water droplets to revise the way aircraft are designed and approved for flight in icing conditions.

Give flight crews accurate information to quickly recognize dangers of all types of icing and maintain airspeeds to avoid loss of aircraft control.

Importance

The 1994 in-flight icing encounter, subsequent loss of control and crash of a commuter airliner in Roselawn, Indiana, which took 68 lives, prompted the Safety Board to examine the issue of airframe structural icing and conclude that the icing certification process has been inadequate. The certification process has not required manufacturers to demonstrate the airplane’s flight handling and stall characteristics under a realistic range of adverse ice accretion/flight-handling conditions.  The Federal Aviation Administration (FAA) has not adopted a systematic and proactive approach to the certification and operational issues of turbine-engine driven transport category airplane icing.

The consequences of operating an airplane in icing conditions without first having thoroughly demonstrated adequate handling/controllability characteristics in those conditions are sufficiently severe that they warrant a thorough certification test program, including application of revised standards to airplanes currently certificated for flight in icing conditions.

Summary of Action

Revised Icing Certification Criteria and Testing

As a result of the Roselawn, Indiana, accident, the Safety Board called on the FAA to revise the icing criteria and icing testing requirements necessary for an airplane design to be approved within the United States, and the operational requirements that specify under what icing conditions it is permissible to operate an aircraft. Seven years ago, this work was referred to an industry group that provides input to the FAA on new regulations (the Aviation Rulemaking Advisory Committee or ARAC). The ARAC has recommended to the FAA changes to the regulatory requirements for new airplanes to evaluate performance and handling characteristics in icing conditions. In March 2002, 6 years after it started this work, the ARAC approved a concept to revise the icing criteria in the regulatory requirements for new airplanes. The ARAC’s concept is to develop a rule that includes requirements to demonstrate that an airplane can safely operate in the icing conditions and safely exit from these icing conditions. The ARAC is continuing its work to develop such a rule and associated advisory material. When the ARAC forwards its recommendations, the FAA will then determine the priority for the resulting rulemaking project. In September 2002, the ARAC gave the FAA a proposed regulatory revision that addresses when to activate the ice protection system and when the flight crew should exit icing conditions. The FAA is currently reviewing the appropriate regulations to include these changes, although an NPRM has not yet been published.

Thus, more than 7 years after the Safety Board issued these recommendations, the FAA has yet to issue any of the operational, design or testing requirement revisions recommended. Although the FAA has indicated that an NPRM for a testing requirement to evaluate susceptibility to ice contaminated tailplane stall may be out by June 2004, the Safety Board believes it likely that any resulting final rule will require at least another year, and perhaps several years more before completion and implementation of any changes. The Safety Board also notes that for other needed regulatory reforms related to expansion of the icing certification requirements, the FAA has yet to issue an NPRM, and the FAA has indicated that it will not assign a priority to expansion of the icing certification condition requirements until after the ARAC completes its work. The Board believes these activities are progressing much too slowly and urges the FAA to have the ARAC complete its work sooner, and to assign a high priority to the resulting regulatory revisions.

Apply Revised Icing Requirements to Currently Certificated Aircraft

As a result of the Safety Board’s investigation of the in-flight encounter with icing and subsequent uncontrolled collision with terrain of Comair Flight 3272, an Embraer 120RT, near Monroe, Michigan, on January 9, 1997, in which all 29 persons onboard the airplane were killed, the Safety Board asked the FAA to review the icing certification of all turbopropeller-driven airplanes currently certificated for operation in icing conditions and perform additional testing. This work is contingent on completion of the necessary research, currently being conducted in response to Safety Recommendation A-98-92. Safety recommendation A-98-92 urges the FAA together with NASA to perform the research necessary to support regulatory and testing revisions necessary to ensure safe operations in icing conditions. Although this research has been in progress for several years, and has produced important results, there remain many important issues still in need of study and research. This research forms the basis for needed actions to increase aviation safety. Staff proposes, therefore, adding Safety Recommendation A-98-92 issued to the FAA to the Most Wanted List.

Minimum Maneuvering Airspeeds

Also as a result of the Monroe, Michigan, accident, the Board asked the FAA to require manufacturers of all turbine-engine driven airplanes to provide minimum maneuvering airspeeds for all icing and non-icing conditions.  On July 11, 2002, the Safety Board told the FAA that its actions meet the recommendation's intent with respect to icing conditions, but noted that the recommendation also asks for minimum maneuvering airspeed information for all airplane configurations, phases, and conditions of flight in non-icing conditions. The FAA has not indicated that it is taking any actions for conditions other than icing. Although the recommendation remains open, the FAA has completed its action in response to icing conditions, and therefore, Staff recommends that Safety Recommendation A-98-94 be removed from the Most Wanted List.

Action(s) Remaining

Complete research on aircraft structural icing and continue efforts to revise icing certification criteria, testing requirements, and restrictions on operations in icing conditions.

Safety Recommendations

A-96-54 (FAA)

Issued August 15, 1996

Added to the Most Wanted List: 1997

Status: Open—Acceptable Response

Revise the icing criteria published in 14 [Code of Federal Regulations] CFR Parts 23 and 25, in light of both recent research into aircraft ice accretion under varying conditions of liquid water content, drop size distribution, and temperature, and recent developments in both the design and use of aircraft. Also, expand the Appendix C icing certification envelope to include freezing drizzle/freezing rain and mixed water/ice crystal conditions, as necessary. (Source: Report on the In-flight Icing Encounter and Loss of Control, American Eagle Flight 4184, ATR 72-212, Roselawn, Indiana, and October 31, 1994 [NTSB/AAR-96-01])

A-96-56 (FAA)

Issued August 15, 1996

Added to the Most Wanted List: 1997

Status: Open—Acceptable Response

Revise the icing certification testing regulation to ensure that airplanes are properly tested for all conditions in which they are authorized to operate, or are otherwise shown to be capable of safe flight into such conditions.  If safe operations cannot be demonstrated by the manufacturer, operational limitations should be imposed to prohibit flight in such conditions and flightcrews should be provided with the means to positively determine when they are in icing conditions that exceed the limits for aircraft certification.  (Source: Report on the In-flight Icing Encounter and Loss of Control, American Eagle Flight 4184, ATR 72-212, Roselawn, Indiana, and October 31, 1994 [NTSB/AAR-96-01])

A-98-92 (FAA)

Issued November 30, 1998

Added to the Most Wanted List: New

Status: Open—Acceptable Response

With the National Aeronautics and Space Administration [NASA] and other interested aviation organizations, conduct additional research to identify realistic ice accumulations, to include intercycle and residual ice accumulations and ice accumulations on unprotected surfaces aft of the deicing boots, and to determine the effects and criticality of such ice accumulations; further, the information developed through such research should be incorporated into aircraft certification requirements and pilot training programs at all levels. (Source: Report on the In-flight Icing Encounter and Uncontrolled Collision with Terrain, Comair Flight 3272, Embraer EMB-120RT, Monroe, Michigan, January 9, 1997 [NTSB/AAR-98-04])

A-98-100 (FAA)

Issued November 30, 1998

Added to the Most Wanted List: 1999

Status: Open—Acceptable Response

When the revised icing certification standards and criteria are complete, review the icing certification of all turbopropeller-driven airplanes that are currently certificated for operation in icing conditions and perform additional testing and take action as required to ensure that these airplanes fulfill the requirements of the revised icing certification standards.  (Source: Report on the In-flight Icing Encounter and Uncontrolled Collision with Terrain, Comair Flight 3272, Embraer EMB-120RT, Monroe, Michigan, January 9, 1997 [NTSB/AAR-98-04])

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