A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to all McDonnell Douglas Model DC-3 and DC-4 series airplanes was published in the Federal Register on September 16, 1997 (62 FR 48553). That action proposed to require revising the Limitations Section of the FAA-approved Airplane Flight Manual (AFM) to specify procedures that would: \n\nrequire flight crews to immediately request priority handling from Air Traffic Control to exit severe icing conditions (as determined by certain visual cues); \n\nprohibit flight in severe icing conditions (as determined by certain visual cues); \n\nprohibit use of the autopilot when ice is formed aft of the protected surfaces of the wing, or when an unusual lateral trim condition exists; and \n\nrequire that all icing wing inspection lights be operative prior to flight into known or forecast icing conditions at night. \n\n\tThat action also proposed to require revising the Normal Procedures Section of the FAA-approved AFM to specify procedures that would: \n\nlimit the use of the flaps and prohibit the use of the autopilot when ice is observed forming aft of the protected surfaces of the wing, or if unusual lateral trim requirements or autopilot trim warnings are encountered; and \n\nprovide the flight crew with recognition cues for, and procedures for exiting from, severe icing conditions.\n\nComments \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the following comments received. \n\n\tIn addition to the proposed rule described previously, in September 1997, the FAA issued 24 other similar proposals that address the subject unsafe condition on various airplane models (see below for a listing of all 24 proposed rules). These 24 proposals also were published in the Federal Register on September 16, 1997. This final rulecontains the FAA's responses to all relevant public comments received for each of these proposed rules. \n\n\nDocket Number\nManufacturer/Airplane Model\nFederal Register Citation\n\n\n\n97-CE-49-AD \nAerospace Technologies of Australia\n62 FR 48520\n\nModels N22B and N24A\n\n\n\n\n97-CE-50-AD \nHarbin Aircraft Mfg. Corporation\n62 FR 48513\n\nModel Y12 IV\n\n\n\n\n97-CE-51-AD \nPartenavia Costruzioni \n62 FR 48524\n\nAeronauticas, S.p.A. \n\n\nModels P68, AP68TP 300, AP68TP 600\n\n\n\n\n97-CE-52-AD \nIndustrie Aeronautiche \n62 FR 48502\n\nMeccaniche Rinaldo Piaggio S.p.A.\n\n\nModel P-180\n\n\n\n\n97-CE-53-AD\nPilatus Aircraft Ltd.\n62 FR 48499\n\nModels PC-12 and PC-12/45\n\n\n\n\n97-CE-54-AD \nPilatus Britten-Norman Ltd.\n62 FR 48538\n\nModels BN-2A, BN-2B, and BN-2T\n\n\n\n\n97-CE-55-AD \nSOCATA - Groupe Aerospatiale\n62 FR 48506\n\nModel TBM-700\n\n\n\n\n97-CE-56-AD \nAerostar Aircraft Corporation\n62 FR 48481\n\nModels PA-60-600, -601,\n\n\n-601P, -602P, and -700P\n\n\n\n\n97-CE-57-AD \nTwin Commander Aircraft Corporation\n62 FR 48549\n\nModels 500, -500-A, -500-B,\n\n\n-500-S, -500-U, -520, -560, \n\n\n-560-A, -560-E, -560-F, -680, -680-E,\n\n\n-680FL(P), -680T, -680V, -680W, \n\n\n-681, -685, -690, -690A, -690B, -690C,\n\n\n-690D, -695, -695A, -695B, and 720\n\n\n\n\n97-CE-58-AD \nRaytheon Aircraft Company \n62 FR 48517\n\n(formerly known as Beech \n\n\nAircraft Corporation)\n\n\nModels E55, E55A, 58, 58A, 58P, \n\n\n58PA, 58TC, 58TCA, 60 series, \n\n\n65-B80 series, 65-B-90 series, \n\n\n90 series, F90 series, 100 series, \n\n\n300 series, and B300 series\n\n\n\n\n97-CE-59-AD \nRaytheon Aircraft Company \n62 FR 48531\n\n(formerly known as Beech\n\n\nAircraft Corporation) Model 2000\n\n\n\n\n97-CE-60-AD \nThe New Piper Aircraft, Inc. \n62 FR 48542\n\nModels PA-46 -310P and\n\n\nPA-46-350P\n\n\n\n\n97-CE-61-AD \nThe New Piper Aircraft, Inc.\n62 FR 52294\n\nModels PA-23, PA-23-160, \n\n\nPA-23-235, PA-23-250, PA-E23-250, \n\n\nPA-30, PA-39, PA-40, PA-31,PA-31-300, PA-31-325, PA-31-350, \n\n\nPA-34-200, PA-34-200T, PA-34-220T, \n\n\nPA-42, PA-42-720, PA-42-1000\n\n\n\n\n97-CE-62-AD \nCessna Aircraft Company \n62 FR 48535\n\nModels P210N, T210N, P210R, \n\n\nand 337 series\n\n\n\n\n97-CE-63-AD \nCessna Aircraft Company\n62 FR 48528\n\nModels T303, 310R, T310R, 335, \n\n\n340A, 402B, 402C, 404, F406, 414, \n\n\n414A, 421B, 421C, 425, and 441\n\n\n\n\n97-CE-64-AD \nSIAI-Marchetti S.r.I. (Augusta)\n62 FR 48510\n\nModels SF600 and SF600A\n\n\n\n\n97-NM-170-AD \nCessna Aircraft Company \n62 FR 48560\n\nModels 500, 501, 550, 551,\n\n\nand 560 series \n\n\n\n\n97-NM-171-AD \nSabreliner Corporation\n62 FR 48556\n\nModels 40, 60, 70, and 80 series\n\n\n\n\n97-NM-172-AD \nGulfstream Aerospace\n62 FR 48563\n\nModel G-159 series \n\n\n\n\n97-NM-173-AD \nMcDonnell Douglas\n62 FR 48553\n\nModels DC-3 and DC-4 series \n\n\n\n\n97-NM-174-AD \nMitsubishi Heavy Industries\n62 FR 48567\n\nModels YS-11 and YS-11A series\n\n\n\n\n97-NM-175-AD \nFrakes Aviation\n62 FR 48577\n\nModels G-73 (Mallard) and G-73T series\n\n\n\n\n97-NM-176-AD \nLockheed\n62 FR 48574\n\nModels L-14 and L-18 series\n\n\n\n\n97-NM-177-AD \nFairchild\n62 FR 48570\n\nModels F27 and FH227 series\n\n\n\nComment 1. Unsubstantiated Unsafe Condition for This Model \n\n\tOne commenter suggests that the AD's were developed in response to a suspected contributing factor of an accident involving an airplane type unrelated to the airplanes specified in the proposal. The commenter states that these proposals do not justify that an unsafe condition exists or could develop in a product of the same type design. Therefore, the commenter asserts that the proposal does not meet the criteria for the issuance of an AD as specified in the Federal Aviation Regulations (14 CFR part 39). \n\n\tThe FAA does not concur. As stated in the Notice of Proposed Rulemaking (NPRM), the FAA has identified an unsafe condition associated with operating the airplane in severe icing conditions. Asstated in the preamble to the proposal, the FAA has not required that airplanes be shown to be capable of operating safely in icing conditions outside the certification envelope specified in Appendix C of part 25 of the Federal Aviation Regulations (14 CFR part 25). This means that any time an airplane is flown in icing conditions for which it is not certificated, there is a potential for an unsafe condition to exist or develop and the flight crew must take steps to exit those conditions expeditiously. Further, the FAA has determined that flight crews are not currently provided with adequate information necessary to determine when an airplane is operating in icing conditions for which it is not certificated or what action to take when such conditions are encountered. The absence of this information presents an unsafe condition because without that information, a pilot may remain in potentially hazardous icing conditions. This AD addresses the unsafe condition by requiring AFM revisions that provide the flight crews with visual cues to determine when icing conditions have been encountered for which the airplane is not certificated, and by providing procedures to safely exit those conditions. \n\n\tFurther, in the preamble of the proposed rule, the FAA discussed the investigation of roll control anomalies to explain that this investigation was not a complete certification program. The testing was designed to examine only the roll handling characteristics of the airplane in certain droplets the size of freezing drizzle. The testing was not a certification test to approve the airplane for flight into freezing drizzle. The results of the tests were not used to determine if this AD is necessary, but rather to determine if design changes were needed to prevent a catastrophic roll upset. The roll control testing and the AD are two unrelated actions. \n\n\tAdditionally, in the preamble of the proposed rule, the FAA acknowledged that the flight crew of any airplane thatis certificated for flight icing conditions may not have adequate information concerning flight in icing conditions outside the icing envelope. However, in 1996, the FAA found that the specified unsafe condition must be addressed as a higher priority on airplanes equipped with pneumatic deicing boots and unpowered roll control systems. These airplanes were addressed first because the flight crew of an airplane having an unpowered roll control system must rely solely on physical strength to counteract roll control anomalies, whereas a roll control anomaly that occurs on an airplane having a powered roll control system need not be offset directly by the flight crew. The FAA also placed a priority on airplanes that are used in regularly scheduled passenger service. The FAA has previously issued AD's to address those airplanes. Since the issuance of those AD's, the FAA has determined that similar AD's should be issued for similarly equipped airplanes that are not used in regularly scheduled passenger service. \n\nComment 2. AD is Inappropriate to Address Improper Operation of the Airplane \n\n\tOne commenter requests that the proposed AD be withdrawn because an unsafe condition does not exist within the airplane. Rather, the commenter asserts that the unsafe condition is the improper operation of the airplane. The commenter further asserts that issuance of an AD is an inappropriate method to address improper operation of the airplane. \n\n\tThe FAA does not concur. The FAA has determined that an unsafe condition does exist as explained in the proposed notice and discussed previously. As specifically addressed in Amendment 39-106 of part 39 of the Federal Aviation Regulations (14 CFR part 39), the responsibilities placed on the FAA statute (49 U.S.C., formerly the Federal Aviation Act), justify allowing AD's to be issued for unsafe conditions however and wherever found, regardless of whether the unsafe condition results from maintenance, design defect, or any other reason. \n\n\tThis same commenter considers that part 91 (rather than part 39) of the Federal Aviation Regulations (14 CFR part 91) is the appropriate regulation to address the problems of icing encounters outside of the limits for which the airplane is certificated. Therefore, the commenter requests that the FAA withdraw the proposal. \n\n\tThe FAA does not concur. Service experience demonstrates that flight in icing conditions that are outside the icing certification envelope does occur. Apart from the visual cues provided in these final rules, there is no existing method provided to the flight crews to identify when the airplane is in a condition that exceeds the icing certification envelope. Because this lack of awareness may create an unsafe condition, the FAA has determined that it is appropriate to issue an AD to require revision of the AFM to provide this information. \n\n\tOne commenter asserts that while it is prudent to advise and routinely remind the pilots about the hazards associated with flight into known or forecast icing conditions, the commenter is opposed to the use of an AD to accomplish that function. The commenter states that pilots' initial and bi-annual flight checks are the appropriate vehicles for advising the pilots of such hazards, and that such information should be integrated into the training syllabus for all pilot training. \n\n\tThe FAA does not concur that substituting advisory material and mandatory training for issuance of an AD is appropriate. The FAA acknowledges that, in addition to the issuance of an AD, information specified in the revision to the AFM should be integrated into the pilot training syllabus. However, the development and use of such advisory materials and training alone are not adequate to address the unsafe condition. The only method of ensuring that certain information is available to the pilot is through incorporation of the information into the Limitations Section of the AFM. The appropriate vehiclefor requiring such revision of the AFM is issuance of an AD. No change is necessary to the final rule. \nComment 3. Inadequate Visual Cues \n\n\tOne commenter provides qualified support for the AD. The commenter notes that the recent proposals are identical to the AD's issued about a year ago. Although the commenter supports the intent of the AD's as being appropriate and necessary, the commenter states that it is unfortunate that the flight crew is burdened with recognizing icing conditions with visual cues that are inadequate to determine certain icing conditions. The commenter points out that, for instance, side window icing (a very specific visual cue) was determined to be a valid visual cue during a series of icing tanker tests on a specific airplane; however, later testing of other models of turboprop airplanes revealed that side window icing was invalid as a visual cue for identifying icing conditions outside the scope of Appendix C. \n\n\tThe FAA does not concur with the commenters' request to provide more specific visual cues. The FAA finds that the value of visual cues has been substantiated during in-service experience. Additionally, the FAA finds that the combined use of the generic cues provided and the effect of the final rules in increasing the awareness of pilots concerning the hazard of operating outside of the certification icing envelope will provide an acceptable level of safety. Although all of the cues may not be exhibited on a particular model, the FAA considers that at least some of the cues will be exhibited on all of the models affected by this AD. For example, some airplanes may not have side window cues in freezing drizzle, but would exhibit other cues, (such as accumulation of ice aft of the protected area) under those conditions. For these reasons, the FAA considers that no changes regarding visual cues are necessary to the final rule. However, for those operators that elect to identify airplane-specific visual cures, the FAA would consider a request for approval of an alternative method of compliance, in accordance with the provisions of this AD. Comment 4. Request for Research and Use of Wing-Mounted Ice Detectors \n\n\tOne commenter requests that wing-mounted ice detectors, which provide real-time icing severity information (or immediate feedback) to flight crews, continue to be researched and used throughout the fleet. The FAA infers from this commenter's request that the commenter asks that installation of these ice detectors be mandated by the FAA. \n\n\tWhile the FAA supports the development of such ice detectors, the FAA does not concur that installation of these ice detectors should be required at this time. Visual cues are adequate to provide an acceptable level of safety; therefore, mandatory installation of ice detector systems, in this case, is not necessary to address the unsafe condition. Nevertheless, because such systems may improve the current level of safety, the FAA has officially taskedthe Aviation Rulemaking Advisory Committee (ARAC) to develop a recommendation concerning ice detection. Once the ARAC has submitted its recommendation, the FAA may consider further rulemaking action to require installation of such equipment. \n\nComment 5. Particular Types of Icing \n\n\tThis same commenter also requests that additional information be included in paragraph (a) of the AD that would specify particular types of icing or particular accretions that result from operating in freezing precipitation. The commenter asserts that this information is of significant value to the flightcrew. \n\n\tThe FAA does not concur with the commenter's suggestion to specify types of icing or accretion. The FAA has determined that supercooled large droplets (SLD) can result in rime ice, mixed (intermediate) ice, and ice with glaze or clear appearance. Therefore, the FAA finds that no type of icing can be excluded from consideration during operations in freezing precipitation, and considers itunnecessary to cite those types of icing in the AD. \n\nConclusion \n\n\tAfter careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed. \n\nCost Impact \n\n\tThere are approximately 300 McDonnell Douglas Model DC-3 and DC-4 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 166 airplanes of U.S. registry will be affected by this AD, that it will take approximately 1 work hour per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $9,960, or $60 per airplane. \n\n\tThe cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. \n\n\tIn addition, the FAA recognizes that this action may impose operational costs. However, these costs are incalculable because the frequency of occurrence of the specified conditions and the associated additional flight time cannot be determined. Nevertheless, because of the severity of the unsafe condition, the FAA has determined that continued operational safety necessitates the imposition of the costs. \n\nRegulatory Impact \n\n\tThe regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. \n\n\tFor the reasons discussed above, I certify that this action (1) is not a "significant regulatory action"under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." \n\nList of Subjects in 14 CFR Part 39 \n\n\tAir transportation, Aircraft, Aviation safety, Safety. \n\nAdoption of the Amendment \n\n\tAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows: \n\nPART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1. The authority citation for part 39 continues to read as follows: \n\nAuthority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 (Amended) \n\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: