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Safety Recommendation Details

Safety Recommendation A-98-091
Details
Synopsis: On January 9, 1997, an Empresa Brasileira de Aeronautica, S/A (Embraer) EMB-120RT, operated by COMAIR Airlines, Inc., crashed during a rapid descent after an uncommanded roll excursion near Monroe, Michigan. The flight was a scheduled, domestic passenger flight from the Cincinnati/Northern Kentucky International Airport, Covington, Kentucky, to Detroit Metropolitan/Wayne County Airport, Detroit, Michigan. The flight departed Covington with 2 flightcrew, 1 flight attendant, and 26 passengers on board. There were no survivors. The airplane was destroyed by ground impact forces and a postaccident fire. IMC prevailed at the time of the accident, and the flight was operating on an IFR flight plan.The probable cause of this accident was the FAA's failure to establish adequate aircraft certification standardds for flight in icing conditions.
Recommendation: TO THE FEDERAL AVIATION ADMINISTRATION: 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. (Superseded by A-07-14)
Original recommendation transmittal letter: PDF
Overall Status: Closed - Unacceptable Action/Superseded
Mode: Aviation
Location: MONROE, MI, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA97MA017
Accident Reports: In-Flight Icing Encounter and Uncontrolled Collision with Terrain, Comair Flight 3272, Embraer EMB-120RT, N265CA
Report #: AAR-98-04
Accident Date: 1/9/1997
Issue Date: 11/30/1998
Date Closed: 2/27/2007
Addressee(s) and Addressee Status: FAA (Closed - Unacceptable Action/Superseded)
Keyword(s): Icing, Weather

Safety Recommendation History
From: NTSB
To: FAA
Date: 2/23/2010
Response: Notation 7903A: The National Transportation Safety Board (NTSB) has reviewed the Federal Aviation Administration (FAA) notice of proposed rulemaking (NPRM), “Part 121 Activation of Ice Protection,” published at 74 Federal Register 61055 on November 23, 2009. The NTSB evaluated the proposed rule in light of open safety recommendations related to aircraft operations in icing and in regard to other pertinent concerns identified during the course of its investigations. The proposed rule applies to operators of certain airplanes that are used in Title 14 Code of Federal Regulations (CFR) Part 121 operations and that are certificated for flight in icing conditions. Specifically, the proposed rule would require the affected airplane operators to use one of the following means of ensuring that airframe ice protection systems (IPS) are operated continuously at the first sign of ice accretion: installing a primary ice detection system, installing an advisory ice detection system, or requiring continuous operation of the airframe IPS whenever the airplane is operating in conditions conducive to airframe icing. The NPRM states that the proposed rule is based on recommendations to the FAA from the Aviation Rulemaking Advisory Committee (ARAC) Ice Protection Harmonization Working Group (IPHWG). The NPRM also states that the proposed rule will address NTSB Safety Recommendation A-07-14, issued as a result of the NTSB investigation of the February 16, 2005, Cessna Citation 560 accident at Pueblo, Colorado. This recommendation asked the FAA to take the following action: 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. To that end, the proposed regulation requires that the aircraft flight manual (AFM) address initial activation of the IPS, operation of the IPS after initial activation, and deactivation of the airframe IPS. In comments on adopted Amendment 25-129, the NTSB noted that although some manufacturers advise their operators to delay activation of deice boots as a way of preventing ice bridging, research shows that ice bridging does not occur on modern airplanes. In addition, tests conducted by the National Aeronautics and Space Administration have shown that thin, rough ice accumulations on the wing leading edge deice boot surfaces can, depending on distribution, be as aerodynamically detrimental to an airplane’s performance as larger ice accumulations. The NTSB therefore agrees with the FAA that airframe ice protection systems, including deice boots, should be operated at the first sign of ice accretion. Delays intended to prevent deice boot ice bridging are potentially hazardous, and manufacturers’ guidance to operators must be revised accordingly. The proposed rule also addresses the fact that neither current operating regulations nor icing certification regulations in effect before the recent adoption of Amendment 25-149 require a means to ensure timely activation of the IPS. The NTSB is pleased that the FAA is taking steps to ensure that AFMs are revised so that they no longer require IPS activation only after a substantial accumulation of ice. Further, the NTSB is pleased that the proposed rule would require the installation of ice detection systems or the activation of ice protection systems in conditions conducive to icing in most phases of flight. In the cruise phase of flight, the airframe IPS would be activated at the first sign of ice accumulation anywhere on the airplane. Although the NTSB agrees with the FAA stance on the above issues, it disagrees with the proposed rule in two important areas: first, that the rule would apply only to airplanes with a certificated maximum takeoff weight (MTOW) of less than 60,000 pounds and second, that the proposed rule applies to Part 121 operations only. As stated in Safety Recommendation A-07-14, the NTSB believes that, for deice boot-equipped airplanes, the IPS should be operated as soon as the airplane enters icing conditions, regardless of the size or MTOW of the airplane. However, by limiting the new requirements to aircraft of less than 60,000 pounds, the proposed rule excludes a number of aircraft models for which the new requirements would be beneficial. For example, the Bombardier Q400 involved in the February 12, 2009, Colgan Airlines accident in Clarence Center, New York (NTSB accident number DCA09MA027) has an MTOW slightly greater than 60,000 pounds and would therefore not be affected by the proposed rule. While the Bombardier Q400 is equipped with a deice boot and an ice detection system, operation of this aircraft under the requirements of the proposed rule would provide additional protection for safe operation—not only in the icing conditions for which it has been certificated (that is, 14 CFR 25, Appendix C), but also if the airplane inadvertently encounters icing conditions that exceed the atmospheric conditions for which it has been certificated. Such conditions include supercooled large droplets, which were not considered in the Bombardier Q400’s certification for flight in icing conditions and may generate aerodynamic degradation with only small amounts of ice accretion. At the time this response was written, NTSB investigators had determined that icing was not a factor in this accident. Nevertheless, the NTSB believes that the MTOW weight limit in the proposed rule should be expanded to include all deice boot-equipped airplanes currently in service, as stated in Safety Recommendation A-07-14. The second issue with which the NTSB disagrees regards limiting the proposed rule to Part 121 operations only. In the NPRM, the FAA offers several reasons for this decision. One reason is that aircraft operated under Parts 91 and 135 are typically smaller than those operated under Part 121, and this smaller scale allows pilots to monitor ice accretions more easily. The FAA states further that Part 91 and Part 135 aircraft are often operated in a lower air traffic density, which results in fewer holding delays and significantly more routing options in icing conditions. Additionally, the FAA states that most aircraft operated under Parts 91 and 135 have been subjected to airworthiness directives (AD) that specify when to activate the airframe IPS—that is, at the first sign of ice accretion on the airplane. However, the FAA also correctly notes that identifying ice accumulations can be difficult for crews of aircraft subject to these ADs: Activation of the pneumatic deicing boots is still subject to the flightcrew’s observation of ice accretions, and such observations can be difficult during times of high workload, during operations at night, or when clear ice has accumulated. The difficulties associated with observing ice accretions are applicable to any airframe IPS that relies on the flightcrew’s observation for activating the system, not just pneumatic deicing boots, so these AD’s are not adequate to address the safety concern that is the focus of this proposed rulemaking. A case in point is the airplane involved in the February 16, 2005, Pueblo, Colorado, Circuit City Citation 560 accident, which was operating under Part 91, had its AD for activation of the deice boots withdrawn, and relied on the flight crew to observe a prescribed amount of ice before activating the deice boots. These facts were the main impetus for superseding Safety Recommendation A-98-91 with A-07-14, which recommended that, for all deice boot-equipped airplanes, and for all operations including Parts 91 and 135, the FAA require manufacturers and operators to revise guidance and training programs to specify that the IPS be turned on as soon as the airplane enters icing conditions. If the proposed rule is implemented as is and does not apply to Part 91 and 135 operations, the circumstances regarding the deice boot operation on the Citation 560 that existed prior to the Pueblo accident will still exist. To summarize, the NTSB supports issuance of the Part 121 regulatory revisions proposed in this NPRM. However, the NTSB continues to believe that the issues outlined above—applying the requirements to aircraft with an MTOW greater than 60,000 pounds to include all currently in service, deice boot-equipped airplanes and applying the requirements to all Part 121, 91, and 135 operations—should be addressed in the proposed rule. Aside from these reservations, the NTSB believes that the proposed rulemaking is an essential step in improving the safety of flight in icing conditions for airplanes operating under Part 121 and directly addresses the intent of our recommendations. The NTSB appreciates the opportunity to comment on this NPRM.

From: NTSB
To: FAA
Date: 7/23/2007
Response: 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.

From: NTSB
To: FAA
Date: 2/27/2007
Response: In May 2002, the FAA issued an icing test report that recommended an "early and often" approach to deice boot usage to limit the size of residual and intercycle ice accretions. Further, in January 2003, an Aviation Rulemaking Action Committee (ARAC) Ice Protection Harmonization Working Group (IPHWG) recommended revisions to Parts 25 and 121 to require that deice systems be activated as soon as an airplane enters icing conditions. However, since that time, the FAA has taken no action to issue a final rule adopting the regulatory changes proposed by the ARAC IPHWG. Although the accident airplane most likely accumulated less than 1/4-inch-thick ice while operating in the lower cloud layer, the pilots’ failure to activate the deice boots during the approach led to the continued accumulation of thin, rough ice on the protected surfaces, which can severely degrade an airplane’s performance. The circumstances of this accident, information gathered during the Comair flight 3272 accident, and reports issued by the FAA and the ARAC IPHWG clearly demonstrate that existing guidance instructing pilots to delay activation of the deice boots until they observe 1/4- to 1/2-inch-thick ice accumulation is not adequate because it does not protect against the detrimental effects caused by thin, rough ice accumulation on or aft of the protected surfaces. If pilots continue to adhere to guidance about delaying deice boot activation, similar accidents could still occur. The Safety Board concludes that activating the deice boots as soon as an airplane enters icing conditions provides the greatest safety measure. On the basis of this accident and the Board’s continued concerns in this area, the Board believes that the FAA should 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. The new recommendation [A-07-14] will supersede Safety Recommendation A-98-91 and will be classified Open Unacceptable Response. A-98-091 is classied CLOSED--UNACCEPTABLE ACTION/ SUPERSEDED.

From: NTSB
To: FAA
Date: 5/10/2006
Response: The FAA previously wrote to the Safety Board about this recommendation on May 19, 2003. At that time, the FAA provided information on two draft proposed rules for the activation of ice protection systems that the ARAC had sent to the FAA in September 2002. The proposed rules were applicable to airplanes with takeoff weights less than 60,000 pounds, and addressed when to activate the ice protection system and when to exit icing conditions. It was proposed that activation of the airframe ice protection system be based on one of the following: "a primary ice detector "visual cues and an advisory ice detector "visible moisture and a temperature conducive to airframe icing On September 15, 2003, the Safety Board responded that the ice protection system should be activated based on icing conditions regardless of whether the airplane is equipped with an ice detector; this would increase the probability that if the ice detector failed, the flightcrew would notice and activate the ice protection system. In its current letter, the FAA states that it does not agree with the Board's position. The FAA notes that operation of the ice protection system based only on visible moisture and a temperature conducive to icing will result in operation of the ice protection system when there is no ice accretion on the airframe, leading to a decreased life of the system and a decrease in airplane performance. The FAA's position is that operation of the ice protection system when there is no ice accretion is not necessary, providing there are alternatives to alert the crew to the start of icing. The FAA believes that a primary ice detector system and visual cues with an advisory ice detector provide equivalent levels of safety to the operation of an ice protection system based only on potential icing conditions such as visible moisture and an appropriate temperature. In its current letter, the FAA provided the basis for this belief. The Safety Board has considered and accepts the FAA's arguments. In January 2003, the ARAC forwarded recommendations to the FAA to revise Part 25 and Part 121 to address the issues in this recommendation. In the intervening 3 years, the FAA has not taken any further action such as preparing necessary regulatory analyses, issuing an NPRM, or issuing the final rule. With regard to Part 23 airplanes, the FAA indicates that this rulemaking will be included in the regulatory revisions planned in response to Safety Recommendation A-96-54. However, in the interim, the FAA added guidance to AC 23.1419 2C that addresses this recommendation. The regulatory revisions suggested by the ARAC in January 2003 appear to be responsive to this recommendation. The Board notes that this recommendation is now 7 years old. It is not acceptable that in the past 3 years, the FAA has taken no further action to implement these needed changes. Pending issuance of an NPRM and a final rule adopting the regulatory changes proposed by the ARAC in response to this recommendation, Safety Recommendation A-98-91 is classified "Open-Unacceptable Response."

From: FAA
To: NTSB
Date: 10/26/2005
Response: Letter Mail Controlled 10/27/2005 2:12:40 PM MC# 2050501 Marion C. Blakey, Administrator, FAA, 10/26/05 On May 19, 2003, the FAA provided the Board with information on two draft proposed rules for the activation of ice protection systems. These proposed rules would require activation of the of ice protection systems based on one of the following: "a primary ice detector; "visual cues and an advisory ice detector; or "visible moisture and a temperature conducive to airframe icing On September 15, 2003, the Board responded that the ice protection system should be activated based on icing conditions regardless of whether the airplane is equipped with an ice detector. The Board reasoned that if the ice detector fails the flightcrew would probably notice and activate the ice protection system. The FAA does not agree with the Board's position. Operation of the airframe ice protection system based on visible moisture and a temperature conducive to airframe icing will result in the operation of the ice protection system during times where there are no ice accretions on the airframe. This can lead to a decreased life of the ice protection system and a decrease in airplane performance. The FAA's position is that operation of the ice protection system when there are no ice accretions present is not necessary providing there are acceptable alternatives. We find that a primary ice detector system and visual cues with an advisory ice detector provide equivalent levels of safety to the operation of an ice protection system based only on potential icing conditions (i.e., visible moisture and temperature). Primary ice detector systems must be designed to be highly reliable to meet the requirements of 14 CFR 25.1309. This means the combination of system failure to detect ice that is hazardous to the airplane's operation and failure to annunciate the failed condition to the flightcrew must be extremely improbable. This degree of reliability is commensurate with a catastrophic failure case. Therefore, the FAA does not find that it is necessary to require activation of the ice protection system based on visible moisture and temperature in addition to a primary ice detector system. With regard to the option of certificating visual cues and an advisory ice detector, an ARAC working group examined accidents and incidents and found a history of problems with the flightcrew knowing when they should activate the ice protection system. The working group reasoned that the flightcrew's observation of ice accumulations can be difficult during times of high workload, operations at night, or when clear ice has accumulated. Therefore, the working group concluded that an advisory ice detection system in conjunction with substantiated visual cues would provide a much higher level of safety than visual cues alone. This device would mitigate the effects of high workload and of human sensory limitations in detecting ice. The working group has developed improved certification advisory material on an acceptable means of substantiating visual cues. The advisory ice detector along with the improved guidance provides an equivalent level of safety to operation of the airframe ice protection system based only on visible moisture and temperature. The FAA has accepted the working group recommendations. The ARAC forwarded their recommendation for rulemaking to the FAA in January 2003. The next step is for the FAA to prepare a regulatory evaluation of the two rules. Due to the higher priority of other safety-related rulemaking activities the regulatory evaluations have been delayed. The FAA anticipates publishing the NPRMs this year. The need to include similar rulemaking for 14 CFR Part 23 airplanes will be assessed when the 14 CFR Part 23 SLD rule is developed in response to Safety Recommendation A-96-54. In the interim, the FAA added guidance to AC 23.1419-2B that addressed the following: "Recommended the Airplane Flight Manual procedure for boot operation should be to operate the boots in an appropriate continuous mode at the first sign of ice and not to wait for a specific amount of ice to accumulate; "For applicants that choose to recommend a measurable ice accumulation prior to activation of the boots, stated that flight tests in simulated or natural icing conditions should be accomplished to verify that the crew could detect and recognize the specified ice accumulation thickness under all operation conditions; and "For applicants that choose to recommend a measurable ice accumulation prior to boot activation, stated that this preactivation ice accretion must be considered when determining critical ice accretions for performance, stability, control, and stall testing.

From: NTSB
To: FAA
Date: 9/15/2003
Response: The Safety Board notes that, before the end of this year, the FAA plans to issue a notice of proposed rulemaking (NPRM) to revise 14 Code of Federal Regulations (CFR) Part 121. The NPRM will be applicable to airplanes with takeoff weights less than 60,000 pounds and will address when to activate the ice protection system and when to exit icing conditions. We also note that the FAA is working on a revision to 14 CFR Part 25 that addresses when to activate the ice protection system. For the Part 121 and Part 25 revisions, activation of the ice protection system will be based on one of the following: · a primary ice detector; · visual cues and an advisory ice detector; or · visible moisture and a temperature conducive to airframe icing. The Safety Board believes that activation of the ice protection system should be triggered by any of these conditions, rather than just by one. Thus, if there is a failure of the ice detection system or the airplane accretes ice not detected by the ice detector, the crew will probably notice and activate the ice protection system. The recommendation asks that the FAA require the crew to turn on the ice protection system whenever flying in conditions conducive to icing. An automatic system that is activated by an ice detection system will be working even if the crew does not notice accumulating ice. Pending issuance of a rule requiring activation of the ice protection system as soon as the airplane enters icing conditions, Safety Recommendation A-98-91 remains classified "Open--Acceptable Response."

From: FAA
To: NTSB
Date: 5/19/2003
Response: Letter Mail Controlled 5/28/2003 2:49:05 PM MC# 2030264 In September 2002, the Aviation Rulemaking Advisory Committee's Transport Airplane and Engine Issues Group voted to forward a proposed revision to 14 CFR Part 121 and advisory material to the FAA for consideration. The proposed rule is applicable to airplanes with takeoff weights less than 60,000 pounds, and addresses when to activate the ice protection system and when the flightcrew should exit icing conditions. The latter aspect is limited to airplanes with unpowered roll controls. The FAA is processing a 14 CFR Part 25 proposed rule that addresses when to activate the ice protection system for all 14 CFR Part 25 airplanes. It is proposed that the activation of the airframe ice protection system be based on one of the following: · a primary ice detector; · visual cues and an advisory ice detector; or · visible moisture and a temperature conducive to airframe icing. The Board expressed concern in previous correspondence over airworthiness directives that require the activation of deicing boots based on the visual observation of ice accretions. The Board believes the deicing boots should be activated based on icing conditions. This is option number three in the proposed rule. The other two options require either a primary ice detector or visual cues supplemented by an advisory ice detector. Each of the options provides an acceptable means of knowing when the airframe ice protection system must be activated. The FAA anticipates publishing the notices of proposed rulemaking this year. I will keep the Board informed of the FAA's progress on this safety recommendation.

From: NTSB
To: FAA
Date: 7/11/2002
Response: The FAA reports that the Aviation Rulemaking Advisory Committee (ARAC) is considering a proposed revision to Title 14 Code of Federal Regulations (CFR) Part 121 and advisory material. Although the FAA's actions continue to be responsive to the recommendation, the Safety Board reiterates the point made in its March 12, 2001, letter to the FAA concerning the airworthiness directives (AD) that the FAA planned to issue in response to this recommendation: The Safety Board is concerned because these ADs require activation of the deicing boots at the first sign of ice accretions anywhere on the aircraft; the recommendation asks for deicing boot activation as soon as the airplane enters icing conditions. The Board notes that the accident that prompted this recommendation is a lesson in the potentially catastrophic consequences of small, imperceptible ice accumulations. Therefore, the Board continues to believe that deicing boots should always be activated as soon as icing conditions are encountered. The Safety Board urges the FAA and the ARAC Working Group to consider this important distinction. Pending the FAA's issuance of a rule that requires manufacturers and operators of modern turbopropeller-driven airplanes, for which ice bridging is not a concern, to include updated icing information and to emphasize that leading edge deicing boots should be activated as soon as the airplane enters icing conditions, Safety Recommendation A-98-91 remains classified "Open--Acceptable Response."

From: FAA
To: NTSB
Date: 9/21/2001
Response: Letter Mail Controlled 10/22/2001 11:44:27 AM MC# 2010866: The Aviation Rulemaking Advisory Committee (ARAC) is considering a proposed revision to 14 CFR Part 121 and advisory material. The proposed rule is applicable to airplanes operated under 14 CFR Part 25 with takeoff weights less than 60,000 pounds. The proposed rule addresses when to activate the ice protection system and when the flightcrew should exit icing conditions. The latter aspect is limited to airplanes with unpowered roll controls. The ARAC is also considering a similar certification standard for transport-category airplanes under 14 CFR Part 121. I will keep the Board informed of the FAA's progress on this safety recommendation.

From: NTSB
To: FAA
Date: 3/12/2001
Response: Although these actions are responsive to Safety Recommendation A-98-91, the Safety Board is concerned because these ADs require activation of the deicing boots at the first sign of ice accretions anywhere on the aircraft; the recommendation asks for deicing boot activation as soon as the airplane enters icing conditions. The Board notes that the accident that prompted this recommendation is a lesson in the potentially catastrophic consequences of small, imperceptible ice accumulations. Therefore, the Board continues to believe that deicing boots should always be activated as soon as icing conditions are encountered. The Safety Board urges the FAA and the ARAC Working Group to consider this important distinction. Pending the FAA’s issuance of a rule that requires manufacturers and operators of modern turbopropeller-driven airplanes for which ice bridging is not a concern to include updated icing information and to emphasize that leading edge deicing boots should be activated as soon as the airplane enters icing conditions, Safety Recommendation A-98-91 remains classified “Open--Acceptable Response.”

From: FAA
To: NTSB
Date: 9/25/2000
Response: Letter Mail Controlled 10/02/2000 3:16:36 PM MC# 2001437 The Federal Aviation Administration (FAA) gathered and evaluated information regarding the initial operation of deicing boots. The FAA received information in response to its letter dated October 1, 1998, that requested information from manufacturers of turbopropeller-powered aircraft on the safe operation of its aircraft with ice accretions on the protected surfaces. The FAA also gathered information at an FAA-sponsored conference in February 1999. Based on the evaluation, the FAA concluded the following: · Activation of the deicing boots at the first sign of ice accretions anywhere on the aircraft should be mandated through the airworthiness directive (AD) process. · Deicing boots should continue to be either cycled in the automatic mode, if available, or operated manually to minimize the ice accretions on the airframe. · Mandatory action should be applicable to all aircraft equipped with deicing boots rather than limiting the action to turbopropeller-powered aircraft as the Board suggested. The FAA issued 19 notices of proposed rulemaking (NPRM) during July and August 1999 that were applicable to 14 CFR Part 25 airplanes equipped with pneumatic deicing boots to propose the following requirements: · Activating the deicing boots at the first sign of ice accretions anywhere on the aircraft. · Cycling the boots in the automatic mode, if available, or manually operating to minimize the ice accretions on the airframe. The FAA withdrew 2 of the 19 NPRM's based on data received during the comment period. These data substantiated that the affected aircraft have safe operating characteristics with ice accreted on the protected surfaces. The FAA issued 20 similar NPRM's in October 1999, applicable to 14 CFR Part 23 airplanes equipped with pneumatic deicing boots and issued 1 additional 14 CFR Part 23 NPRM in March 2000. The FAA is in the process of withdrawing 5 of these NPRM'S. Between November 1999 and March 2000, 27 NPRM's for 14 CFR Parts 23 and 25 airplanes became final rules. During the comment period for the remaining NPRM'S, it was brought to the FAA's attention that McDonnell Douglas DC-3 and DC-4 aircraft and Gulfstream G-159 aircraft were initially certificated with older style boots that may be susceptible to ice bridging. Therefore, six supplemental NPRM's were issued proposing to require activation of the boots at the first sign of ice accretion if an aircraft had been retrofitted with modern style boots. Two supplemental NPRM's were issued to address McDonnell Douglas DC-3 and DC-4 aircraft and Gulfstream G-159 aircraft that may be equipped with either modern or older style deicing boots. The McDonnell Douglas and Gulfstream supplemental NPRM's became final rules in February 2000 and May 2000, respectively. The FAA is evaluating the comments for the Gulfstream G-159 supplemental NPRM and three 14 CFR Part 23 NPRM'S. I have enclosed copies of a sample AD that has been issued for the Board's information. The Aviation Rulemaking Advisory Committee's (ARAC) Ice Protection Harmonization Working Group is addressing the issue of the flightcrew having an adequate means to know when to operate the ice protection system. Therefore, the AD's should be viewed as interim actions to the committee's Ice Protection Harmonization Working Group's activities. I will keep the Board informed of the FAA's progress on this safety recommendation.

From: NTSB
To: FAA
Date: 3/9/2000
Response: THE SAFETY BOARD CONCURS WITH THE ACTION TAKEN IN RESPONSE TO THIS RECOMMENDATION AND CLASSIFIES A-98-91 "OPEN--ACCEPTABLE RESPONSE."

From: FAA
To: NTSB
Date: 2/26/1999
Response: ON 10/1/98, THE FAA ISSUED LETTERS REQUESTING MANUFACTURERS OF TURBOPROPELLER-POWERED TRANSPORT-CATEGORY AIRCRAFT TO PROVIDE DATA SHOWING THAT THEIR AIRCRAFT HAVE SAFE OPERATING CHARACTERISTICS WITH ICE ACCRETED ON THE PROTECTED SURFACES. AIRCRAFT MANUFACTURERS WERE REQUESTED TO CONSIDER ICE ACCRETION BEFORE ACTIVATION OF THE DEICE SYSTEM AND INTERCYCLE ICE. THE LETTERS INFORMED THE MANUFACTURERS THAT THE FAA IS CONSIDERING MANDATORY ACTION TO REQUIRE THAT DEICING SYSTEMS BE ACTIVATED AT THE FIRST INDICATION OF ICING CONDITIONS AND OPERATED THEREAFTER SO AS TO MINIMIZE ICE ACCRETION. IN JANUARY 1999, FAA SPECIALISTS MET TO ENSURE THE USE OF CONSISTENT REVIEW CRITERIA AND TO REACH A PRELIMINARY POSITION ON WHETHER OR NOT MANDATORY ACTIONS ARE WARRANTED. FEBRUARY 2-4, 1999, THE FAA HELD A CONFERENCE WITH AIRFRAME MANUFACTURERS, AIRLINE OPERATORS, WORLDWIDE CIVIL AVIATION AUTHORITIES, AND OTHER AVIATION ORGANIZATIONS. AT THE CONFERENCE, INFORMATION WAS EXCHANGED ON VARIOUS TOPICS INCLUDING THE ACCEPTABILITY OF ACTIVATING THE AIRFRAME DEICING SYSTEMS AT THE FIRST SIGN OF ICING CONDITIONS. THE FAA WILL EVALUATE THE INFORMATION OBTAINED AT THE CONFERENCE TO DETERMINE IF MANDATORY ACTION NEEDS TO BE TAKEN FOR TRANSPORT-CATEGORY AIRCRAFT. THE FAA WILL REVIEW THAT POSITION FOR APPLICABILITY TO SMALL AIRPLANES AND IMPLEMENT AS APPROPRIATE. ONE ELEMENT OF THE FAA IN-FLIGHT AIRCRAFT ICING PLAN PUBLISHED IN APRIL 1997 CALLS FOR THE DEVELOPMENT OF ADVISORY INFORMATION RELATED TO ICE BRIDGING. THE FAA'S IN-FLIGHT ICING NATIONAL RESOURCE SPECIALIST IS PREPARING A PAPER ON ICE BRIDGING AND ANTICIPATES RELEASING THE PAPER IN FEBRUARY 1999.