Notation 7903: The National Transportation Safety Board has reviewed the Federal Aviation Administration’s (FAA) Notice of Proposed Rulemaking (NPRM), “Activation of Ice Protection; Proposed Rule,” which was published at 72 Federal Register 20924 on April 26, 2007. The notice proposes to amend Federal Aviation Regulation (FAR) Part 25 to require a means to ensure timely activation of the airframe ice protection system (IPS) on newly certified transport category airplanes for flight in icing conditions. Specifically, the rule would require that airplane manufacturers provide one of the following methods to detect ice and to ensure that the airframe IPS is activated:
• automatic activation, or
• installation of an ice detection system that alerts the crew to activate the IPS, or
• the identification and publication of environmental conditions conducive to icing for use by the crew to activate the IPS.
The NPRM states that the proposed rule will partially address Safety Recommendations A-96-56 and A-98-91 issued by the Safety Board:
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 limitation 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. (A-96-56)
Require manufacturers and operators of modern turbopropeller-driven airplanes in which ice bridging is not a concern to review and revise the guidance contained in their manuals and training programs to include updated icing information and to emphasize that leading edge deicing boots should be activated as soon as the airplane enters icing conditions. (A-98-91)
In reviewing the proposed rule changes, the Safety Board is pleased that the FAA agrees that the regulations regarding flight in icing conditions need to be improved. The NPRM proposes an alerting system for icing conditions that exceed the limits of aircraft certification, as recommended in part by A-96-56, by adding section 25.1419(e). The NPRM proposes to address A-07-14 in part, which supersedes A-98-91 (discussed later in this response), by requiring IPS activation as soon as the airplane enters icing conditions. However, it is only an NPRM and regulatory changes may be years away. It has been almost 11 years since the Safety Board issued Safety Recommendation A-96-56 as a result of the October 31, 1994, in-flight icing encounter and loss of control of American Eagle Flight 4184, an ATR-72, over Roselawn, Indiana (Safety Board accident DCA95MA001), and 9 years have passed since the issuance of A-98-91, issued as a result of the January 9, 1997, Monroe, Michigan, Comair EMB-120 accident (Safety Board accident DCA97MA017). The Safety Board has investigated several more accidents involving in-flight icing since then, including the following:
• March 14, 1997, Detroit, Michigan, Reno Air MD-87 (accident CHI97FA083)
• March 19, 2001, West Palm Beach, Florida, Comair EMB-120 (accident DCA01MA031)
• February 16, 2005, Pueblo, Colorado, Circuit City Citation 560 (accident DCA05MA037)
• September 8, 2006, Santa Maria, California, American Eagle SF340B (accident LAX06IA076)
Ice-related accidents like these are likely to continue unless the airplane certification regulations are updated to include the icing knowledge and research developed over the past decade. The Safety Board therefore encourages the FAA to act expeditiously on ice certification regulations and IPS activation requirements, including guidance materials and training programs. The Safety Board would like to see the following issues also addressed in the proposed rule.
The first issue is the ongoing disconnect between industry’s current guidance on deice boot activation and what the FAA has learned and research has shown about ice bridging and deice boot effectiveness. Information gathered from the FAA’s 1997 Airplane Deice Boot Bridging Workshop, as well as subsequent icing tunnel and flight tests, revealed that ice bridging does not occur on modern airplanes, which is contrary to what has previously been thought and why some manufacturers’ guidance addresses delayed activation of deice boots. In addition, icing tunnel tests conducted by the National Aeronautics and Space Administration have shown that thin, rough ice accumulations on the wing leading edge deice boot surfaces (like the 1/4 inch or less prescribed by some manufacturers before boot activation) can, depending on distribution, be as aerodynamically detrimental to an airplane’s performance as larger ice accumulations. As a result, deice boots should be operated at the first sign of ice. Delays intended to prevent ice bridging are inappropriate, given the results of current research, and manufacturers’ guidance to operators must be revised accordingly. For example, Cessna operating procedures for the 208 Caravan (C-208) instruct crews to wait for 1/4 to 3/4 inch of ice to accrete before activating the C 208 pneumatic boots. The NPRM, on the other hand, prescribes turning on ice protection at the first sign of ice accretion (or even before, if the conditions are right).
As a result of the Safety Board’s investigation of the February 16, 2005, Cessna Citation 560 accident at Pueblo, Colorado, the Safety Board issued Safety Recommendation A-07-14, which superseded A-98-91:
Require manufacturers and operators of pneumatic deice boot-equipped airplanes to revise the guidance contained in their manuals and training programs to emphasize that leading edge deice boots should be activated as soon as the airplane enters icing conditions. (A-07-14)
The Safety Board encourages the FAA to address this recommendation in the final rule by addressing the ice bridging issue directly to ensure that manufacturers revise the guidance in their manuals and training programs so that operators receive clear, complete, and unambiguous guidance on deice boot activation, as set forth in Safety Recommendation A-07-14.
The second issue is the need for more specific guidance with respect to the identification of environmental conditions conducive for icing, the third method of compliance offered in the NPRM. As stated in Safety Recommendation A-07-14, the Safety Board believes that the IPS should be activated “as soon as the airplane enters icing conditions,” which may include visible moisture and the requisite outside air temperature. The FAA, however, has been reluctant to support IPS activation without the presence of ice, citing concerns of reduced IPS life and airplane performance. Most recently, on April 3, 2007, the FAA issued a letter of interpretation for comment in the Federal Register (Docket No. FAA-2007-27758) seeking clarification from industry on the subject of “known icing.” In it, the FAA stated that “Permutations on the type, combination, and strength of meteorological elements that signify or negate the presence of known icing conditions are too numerous to describe….” It is the Safety Board’s position that industry cannot realistically be expected to implement the third method in the proposed rule until the FAA provides a more specific definition of “environmental conditions conducive to icing.” Understandably, industry has concerns about decreased system life and airplane performance and therefore hesitates to direct operators to activate an IPS based solely on icing potential. The FAA should use the research it has commissioned through the Aviation Rulemaking Advisory Committee to provide a more detailed description of conditions conducive to icing. Until the FAA provides specific environmental parameters and prescribed levels, the third method proposed to address activation of the IPS, despite being the most proactive solution, will not be practical.
The third issue is that the proposed rule does not address operations when certain functions of the IPS are known to be inoperable. Since the proposed rule would alert crews to icing conditions, the Safety Board believes that the proposed rule should prohibit crews from operating when certain functions of the IPS are inoperable. This situation occurred on January 2, 2006, when American Eagle flight 3008, a SAAB SF340B, departed San Luis County Regional Airport, San Luis Obispo, California, with a scheduled destination of Los Angeles International Airport. The airplane encountered icing conditions during the en route climb and departed controlled flight at an altitude of about 11,500 feet mean sea level (msl), descending to an altitude of about 6,500 feet msl. During the previous inbound flight and subsequent incident flight, the airplane’s automatic deice control was inoperable due to a deicer timer light failure. According to American Eagle’s Minimum Equipment List, the crew could dispatch the airplane into known or forecast icing conditions with the automatic function of the IPS inoperable. The proposed rule does not address such operations—that is, operations with an inoperable automatic IPS. The Safety Board believes that the proposed rule should prohibit flight into known icing if certain functions of the IPS are inoperable.
Finally, because ice is a major safety issue that affects all airplanes, regardless of age, the Safety Board believes that the proposed rule should be expanded beyond newly certificated airplanes to include deice boot-equipped airplanes currently certified for flight in icing conditions. The Board hopes that the FAA will apply the new certification standards to ensure timely IPS activation, developed as a result of this NPRM, to earlier recommendations related to icing certification criteria (see Safety Recommendations A-96-54 and A-98-92), so that accidents like the EMB-120 accident in Monroe, Michigan, will not reoccur. The Safety Board stated this concern 9 years ago by issuing Safety Recommendation A-98-100, as a result of the accident in Monroe, Michigan:
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. (A-98-100)
This recommendation was classified “Closed–Unacceptable Action/Superseded” with the issuance of Safety Recommendation A-07-16 to the FAA on February 27, 2007, issued as a result of the February 16, 2005, Pueblo, Colorado, Cessna Citation 560 accident. The prior recommendation addressed turbopropeller airplanes; however, the Citation 560 involved in the Pueblo accident was a deice boot-equipped turbojet. The circumstances of the Pueblo accident demonstrated that pneumatic deice boot-equipped turbojet airplanes also require review and testing to meet the expanded icing certification standards. Hence, this new recommendation, A 07-16, reiterates the point that certification requirements should apply to currently certified deice boot-equipped aircraft, as well as new aircraft:
When the revised icing certification standards (recommended in Safety Recommendations A-96-54 and A-98-92) and criteria are complete, review the icing certification of pneumatic deice boot-equipped 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. (A-07-16)
The Safety Board supports issuance of the regulatory revisions proposed in this NPRM. Ice is detrimental to airplane performance and handling qualities, and it represents a serious threat to aviation safety. The Board has investigated many accidents caused by in-flight icing. Operators need to be fully informed before entering icing conditions, and the proposed rule should help do this. However, the Board continues to believe that the issues outlined above—bridging, clearer guidance on deice activation, operation with a known inoperative IPS, and applying revised certification standards to previously certified airplanes—should be addressed in the proposed rule.
The Safety Board appreciates the opportunity to comment on this NPRM.