99-17547. Airworthiness Directives; Short Brothers Model SD3-30, SD3-60, SD3-SHERPA, and SD3-60 SHERPA Series Airplanes  

  • [Federal Register Volume 64, Number 136 (Friday, July 16, 1999)]
    [Proposed Rules]
    [Pages 38329-38332]
    From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
    [FR Doc No: 99-17547]
    
    
    
    [[Page 38329]]
    
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    DEPARTMENT OF TRANSPORTATION
    
    Federal Aviation Administration
    
    14 CFR Part 39
    
    [Docket No. 99-NM-154-AD]
    RIN 2120-AA64
    
    
    Airworthiness Directives; Short Brothers Model SD3-30, SD3-60, 
    SD3-SHERPA, and SD3-60 SHERPA Series Airplanes
    
    AGENCY: Federal Aviation Administration, DOT.
    
    ACTION: Notice of proposed rulemaking (NPRM).
    
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    SUMMARY: This document proposes the adoption of a new airworthiness 
    directive (AD) that is applicable to certain Short Brothers Model SD3-
    30, SD3-60, SD3-SHERPA, and SD3-60 SHERPA series airplanes. This 
    proposal would require revising the Airplane Flight Manual (AFM) to 
    include requirements for activation of the airframe pneumatic deicing 
    boots. This proposal is prompted by reports of inflight incidents and 
    an accident that occurred in icing conditions where the airframe 
    pneumatic deicing boots were not activated. The actions specified by 
    the proposed AD are intended to ensure that flightcrews activate the 
    pneumatic wing and tail deicing boots at the first signs of ice 
    accumulation. This action will prevent reduced controllability of the 
    aircraft due to adverse aerodynamic effects of ice adhering to the 
    airplane prior to the first deicing cycle.
    
    DATES: Comments must be received by August 16, 1999.
    
    ADDRESSES: Submit comments in triplicate to the Federal Aviation 
    Administration (FAA), Transport Airplane Directorate, ANM-114, 
    Attention: Rules Docket No. 99-NM-154-AD, 1601 Lind Avenue, SW., 
    Renton, Washington 98055-4056. Comments may be inspected at this 
    location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
    Federal holidays.
    
    FOR FURTHER INFORMATION CONTACT: Norman Martenson, Aerospace Engineer, 
    Manager, International Branch, ANM-116, FAA, Transport Airplane 
    Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; 
    telephone (425) 227-2110; fax (425) 227-1149.
    
    SUPPLEMENTARY INFORMATION:
    
    Comments Invited
    
        Interested persons are invited to participate in the making of the 
    proposed rule by submitting such written data, views, or arguments as 
    they may desire. Communications shall identify the Rules Docket number 
    and be submitted in triplicate to the address specified above. All 
    communications received on or before the closing date for comments, 
    specified above, will be considered before taking action on the 
    proposed rule. The proposals contained in this notice may be changed in 
    light of the comments received.
        Comments are specifically invited on the overall regulatory, 
    economic, environmental, and energy aspects of the proposed rule. All 
    comments submitted will be available, both before and after the closing 
    date for comments, in the Rules Docket for examination by interested 
    persons. A report summarizing each FAA-public contact concerned with 
    the substance of this proposal will be filed in the Rules Docket.
        Commenters wishing the FAA to acknowledge receipt of their comments 
    submitted in response to this notice must submit a self-addressed, 
    stamped postcard on which the following statement is made: ``Comments 
    to Docket Number 99-NM-154-AD.'' The postcard will be date stamped and 
    returned to the commenter.
    
    Availability of NPRMs
    
        Any person may obtain a copy of this NPRM by submitting a request 
    to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
    Docket 99-NM-154-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-
    4056.
    
    Discussion
    
        On January 9, 1997, an Empresa Brazileira de Aeronautica, S.A. 
    (EMBRAER) Model EMB-120RT series airplane was involved in an 
    uncommanded roll excursion and consequent rapid descent that resulted 
    in an accident near Monroe, Michigan. The post-accident investigation 
    conducted by the National Transportation Safety Board (NTSB) concluded 
    that the airplane had accumulated a thin, rough layer of ice on its 
    lifting surfaces. That accumulation of ice, in combination with the 
    slowing of the airplane to an airspeed inappropriate for the icing 
    conditions in which the airplane was flying, resulted in loss of 
    control that was not corrected before the airplane impacted the ground. 
    The NTSB also concluded that the flight crew did not activate the wing 
    and tail pneumatic deicing boots. An NTSB recommendation related to 
    this accident requested that the FAA mandate that pneumatic deicing 
    boots be turned on as soon as the airplane enters icing conditions.
        The FAA has reviewed the icing-related incident history of certain 
    airplanes, and has determined that icing incidents may have occurred 
    because pneumatic deicing boots were not activated at the first 
    evidence of ice accretion. As a result, the handling qualities or the 
    controllability of the airplane may have been reduced due to the 
    accumulated ice. That factor was present in the accident discussed 
    previously and, as such, constitutes an unsafe condition.
    
    Request for Information
    
        On October 1, 1998, the FAA sent letters to certain manufacturers 
    of airplanes certified in accordance with part 25 of the Federal 
    Aviation Regulations (14 CFR part 25). The letters requested certain 
    icing system design information and operational procedures applicable 
    to their airplanes concerning flight during icing conditions. The 
    letters also requested that manufacturers provide data showing that the 
    aircraft has safe operating characteristics with ice accreted on the 
    protected surfaces (boots). The manufacturers were asked to provide 
    data using the following assumptions: The most adverse ice accumulation 
    possible during operation in the icing envelope specified in part 25, 
    Appendix C of the Federal Aviation Regulations (14 CFR part 25), and 
    that recommended procedures for deicing boot operation were used. 
    Additionally, the manufacturers were asked to provide information 
    related to operation of the autopilot during icing conditions, and for 
    information related to appropriate operating speeds for icing 
    operations.
        No information received, as a result of that request, has caused 
    the FAA to reconsider the previous conclusion that an unsafe condition 
    may exist.
    
    Public Meeting
    
        Subsequent to the collection of those design and operational data, 
    the FAA held an international conference on ``Inflight Operations in 
    Icing Conditions'', in Washington, DC, on February 2-4, 1999. The 
    purpose of the conference was to discuss the status of the FAA Icing 
    Plan and other related efforts. Additionally, the conference provided a 
    forum for representatives of industry to express their viewpoints on 
    current information related to activation of deicing boots, minimum 
    airspeeds, autopilot operation in icing conditions, flightcrew 
    information needs, and flightcrew training. Certain information 
    presented at that meeting is discussed in
    
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    this proposed rule in the following section.
    
    Delayed Activation of Pneumatic Deicing Boots
    
        In accordance with manufacturer instructions and FAA-approved 
    airplane flight manual (AFM) procedures, the flightcrews of most 
    airplanes equipped with pneumatic deicing boots delay the initial 
    activation of the boots until a certain quantity of ice has accumulated 
    on the protected surfaces (boots). Some crews routinely wait for \1/4\ 
    to \1/2\ inch of ice to accumulate, and at least one airplane type is 
    routinely flown with up to 1\1/2\ inches of ice on the protected 
    surfaces before the initial activation of the deicing boots.
    
    Ice Bridging
    
        In the past, concern about ``ice bridging'' on early pneumatic 
    deicing boot designs resulted in the common practice of delaying 
    activation of ice protection. Ice bridging of pneumatic deicing boots 
    occurred when a thin layer of ice is sufficiently plastic to deform to 
    the shape of the inflated deicing boot tube without being fractured and 
    shed during the ensuing tube deflation. As the deformed ice hardens and 
    accretes additional ice, the deicing boot becomes ineffective in 
    shedding the ``sheath'' of ice. However, ice accumulation resulting 
    from delayed activation may pose an unsafe condition due to the 
    resultant adverse aerodynamic effects on the airplane's performance or 
    handling qualities.
        In November 1997, the FAA and the National Aeronautics and Space 
    Administration (NASA) co-sponsored an international workshop on 
    aircraft deicing boot ice bridging. The objective of the workshop was 
    to provide an open forum for investigating the existence of deicing 
    boot bridging and other concerns related to activating ice protection 
    systems at the initial detection of inflight icing. Sixty-seven 
    representatives from airframe and deicing boot manufacturers, various 
    airlines, the pilot community, NASA, the National Transportation Safety 
    Board, non-US civil aviation authorities, and the FAA participated. At 
    the workshop no evidence was presented to substantiate that aircraft 
    with modern deicing boot designs experience ice bridging. The general 
    consensus of the workshop participants was that ice bridging is not a 
    problem for modern pneumatic deicing boot designs due to the use of 
    higher air supply pressures, faster boot inflation and deflation 
    cycles, and smaller boot chambers. Icing wind tunnel and flight testing 
    of these newer design features with automatic cycling have demonstrated 
    successful shedding of ice when activated at the onset of ice 
    accretion, with ice not shed on the initial deicing boot cycle 
    continuing to increase in thickness and being shed during subsequent 
    cycles.
        During the previously discussed November 1997 international 
    workshop, the inability of flightcrews to accurately gauge wing and 
    control surfaces ice accretion thickness before activating the deicing 
    boots was recognized. Also, increased airplane drag resulting from ice 
    accretion was recognized as a potential contributing cause of 
    inadvertent airspeed loss that characterized most in-flight icing 
    related accidents and incidents. Two airframe manufacturers, whose 
    products comprise a substantial percentage of the turbopropeller 
    transport fleet, reported that, because of these concerns they 
    recommend activating the automatic airframe deicing system at first 
    onset of airframe icing. Those manufacturers have received no reports 
    of deicing boot ice bridging events for these airplanes.
        The FAA considers that ice accumulation on protected surfaces due 
    to delayed boot activation constitutes a potential safety concern. 
    However, the FAA recognizes that not all airplanes may be equipped with 
    ``modern'' deicing boots (as that term is used in this NPRM). The FAA 
    specifically invites the submission of comments and other data 
    regarding the effects of this proposed AD on airplanes equipped with 
    older pneumatic deicing boots, including arguments for the retention of 
    existing activation delays for these older-style deicing boots.
    
    Residual Ice
    
        During the February conference, the attendees agreed that the 
    airplane is at risk while the airplane is accreting ice, and that the 
    airplane must be adequately protected to ensure that no adverse 
    handling and performance characteristics develop. An additional concern 
    discussed at the conference was the possibility that early activation 
    of the ice protection system might degrade the ice shedding 
    effectiveness of the deicing boots, resulting in increased residual 
    ice, i.e., there would be more ice fragments remaining on the deicing 
    boots than would exist if a more substantial quantity of ice was 
    allowed to form before the first ice shedding cycle. However, the FAA 
    does not concur. No data has been provided that shows that the presence 
    of residual ice following an earlier activation of the deicing boots is 
    more hazardous than delaying cycling of the boots until the ice 
    accretes to a larger, specific thickness. In fact, testing in icing 
    conditions has shown that residual ice remaining on the boots after the 
    initial boot cycle is removed during subsequent cycles.
        As reported during the November 1997 international workshop, 
    manufacturers of a substantial percentage of the turbopropeller 
    transport fleet have reported satisfactory in-flight icing operations 
    of their products with recommended procedures to activate operation of 
    the deicing boots in the automatic mode at the onset of airframe icing.
        Therefore, the FAA considers that the activation of pneumatic wing 
    and tail deicing boots at the first signs of ice accumulation is 
    warranted. The FAA specifically invites the submission of data to 
    substantiate that operating the deicing boots at the first sign of ice 
    accretions is more hazardous than delaying boot activation until a 
    specific thickness of ice has accumulated.
    
    Other Considerations
    
        The FAA recognizes that there may be some phases of flight during 
    which use of the deicing boots may be inappropriate. For example, a 
    deicing boot inflation cycle that begins immediately before or during 
    the landing flare or the takeoff rotation may cause unexpected loss of 
    lift or other adverse aerodynamic events. This proposed AD explicitly 
    does not supersede procedures in the AFM that specify not using deicing 
    boots for certain phases of flight (e.g., during take-off, final 
    approach, and landing).
        The FAA specifically invites the submission of comments and other 
    data regarding adverse effects that may occur during specific phases of 
    flight, including takeoff, final approach, or landing. Any recommended 
    speed restrictions or other operational procedures that would be 
    necessary in order to mitigate any adverse aerodynamic effects of 
    deicing boot inflation during critical phases of flight should be fully 
    explained and documented.
    
    FAA's Determinations
    
        The FAA is aware that, based on previous procedures provided to 
    flightcrews of many airplanes equipped with deicing boots, an 
    historical precedent has been set that permits waiting to activate the 
    deicing equipment. In light of this information and based on reports 
    received, the FAA considers that certain procedures should be included 
    in the Limitations Section of the AFM for Short Brothers SD3-30, SD3-
    60, SD3-SHERPA, and SD3-60 SHERPA series airplanes to require immediate 
    activation of the ice
    
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    protection systems when any ice accumulation is detected on the 
    airplane.
        This proposed action is one of a number of proposed ADs being 
    issued on airplanes that have been determined to be subject to the same 
    identified unsafe conditions. Additionally, certain other airplanes are 
    also being reviewed by the Small Airplane Directorate to determine 
    specifically which airplanes may be subject to the identified unsafe 
    condition. Currently proposed AD's for other airplanes that are 
    equipped with pneumatic deicing boots address the following airplanes:
    
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                   Airplane models                        Docket No.
    ------------------------------------------------------------------------
    Cessna Aircraft Company, Models 500, 550,     99-NM-136-AD.
     and 560 Series Airplanes.
    Sabreliner Corporation, Models 40, 60, 70,    99-NM-137-AD.
     and 80 Series Airplanes.
    Gulfstream Aerospace, Model G-159 Series      99-NM-138-AD.
     Airplanes.
    McDonnell Douglas, Models DC-3 and DC-4       99-NM-139-AD.
     Series Airplanes.
    Mitsubishi Heavy Industries, Model YS-11 and  99-NM-140-AD.
     YS-11A Series Airplanes.
    Frakes Aviation, Model G-73 (Mallard) and G-  99-NM-141-AD.
     73T Series Airplanes.
    Lockheed, Models L-14 and L-18 Series         99-NM-142-AD.
     Airplanes.
    Fairchild, Models F27 and FH227 Series        99-NM-143-AD.
     Airplanes.
    Aerospatiale, Models ATR-42/ATR-72 Series...  99-NM-144-AD.
    Jetstream, Model BAe ATP Airplanes..........  99-NM-145-AD.
    Jetstream, Model 4101 Airplanes.............  99-NM-146-AD.
    British Aerospace, Model HS 748 Series        99-NM-147-AD.
     Airplanes.
    Saab, Model SF340A/SAAB 340B/SAAB 2000        99-NM-148-AD.
     Series Airplanes.
    CASA, Model C-212/CN-235 Series Airplanes...  99-NM-149-AD.
    Dornier, Model 328-100 Series Airplanes.....  99-NM-150-AD.
    Lockheed, Model 1329-23 and 1329-25           99-NM-151-AD.
     (Lockheed Jetstar) Series Airplanes.
    de Havilland, Model DHC-7/DHC-8 Series        99-NM-152-AD.
     Airplanes.
    Fokker, Model F27 Mark 100/200/300/400/500/   99-NM-153-AD.
     600/700/050 Series Airplanes.
    Short Brothers, Model SD3-30/SD3-60/SD3-      99-NM-154-AD.
     SHERPA Airplanes.
    ------------------------------------------------------------------------
    
    Explanation of Requirements of Proposed Rule
    
        Since an unsafe condition has been identified that is likely to 
    exist or develop on other products of this same type design, the 
    proposed AD would require revising the Limitations Section of the AFM 
    to include requirements for activation of pneumatic deicing boots at 
    the first indication of ice accumulation on the airplane.
    
    Cost Impact
    
        The FAA estimates that 138 airplanes of U.S. registry would be 
    affected by this proposed AD.
        The FAA estimates that it would take approximately 1 work hour per 
    airplane to accomplish the proposed AFM revisions, at the average labor 
    rate of $60 per work hour. Based on these figures, the cost impact of 
    the proposed AD on U.S. operators is estimated to be $8,280, or $60 per 
    airplane.
        The cost impact figures discussed above are based on assumptions 
    that no operator has yet accomplished any of the proposed requirements 
    of this AD action, and that no operator would accomplish those actions 
    in the future if this AD were not adopted.
    
    Regulatory Impact
    
        The regulations proposed herein would 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 
    proposal would not have sufficient federalism implications to warrant 
    the preparation of a Federalism Assessment.
        For the reasons discussed above, I certify that this proposed 
    regulation (1) is not a ``significant regulatory action'' under 
    Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
    Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
    and (3) if promulgated, 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 copy of the draft 
    regulatory evaluation prepared for this action is contained in the 
    Rules Docket. A copy of it may be obtained by contacting the Rules 
    Docket at the location provided under the caption ADDRESSES.
    
    List of Subjects in 14 CFR Part 39
    
        Air transportation, Aircraft, Aviation safety, Safety.
    
    The Proposed Amendment
    
        Accordingly, pursuant to the authority delegated to me by the 
    Administrator, the Federal Aviation Administration proposes to amend 
    part 39 of the Federal Aviation Regulations (14 CFR part 39) as 
    follows:
    
    PART 39--AIRWORTHINESS DIRECTIVES
    
        1. The authority citation for part 39 continues to read as follows:
    
        Authority: 49 U.S.C. 106(g), 40113, 44701.
    
    
    Sec. 39.13  [Amended]
    
        2. Section 39.13 is amended by adding the following new 
    airworthiness directive:
    
    Short Brothers PLC: Docket 99-NM-154-AD.
    
        Applicability: Model SD3-30, SD3-60, SD3-SHERPA, and SD3-60 
    SHERPA series airplanes equipped with pneumatic deicing boots, 
    certificated in any category.
        Compliance: Required as indicated, unless accomplished 
    previously.
        To ensure that flightcrews activate the wing and tail pneumatic 
    deicing boots at the first signs of ice accumulation on the 
    airplane, accomplish the following:
        (a) Within 10 days after the effective date of this AD: Revise 
    the Limitations Section of the FAA-approved Airplane Flight Manual 
    (AFM) to include the following requirements for activation of the 
    ice protection systems. This may be accomplished by inserting a copy 
    of this AD in the AFM.
        `` Except for certain phases of flight where the AFM 
    specifies that deicing boots should not be used (e.g., take-off, 
    final approach, and landing), compliance with the following is 
    required.
         Wing and Tail Leading Edge Pneumatic Deicing Boot 
    System, if installed, must be activated:
    
    --At the first sign of ice formation anywhere on the aircraft, or 
    upon annunciation from an ice detector system, whichever occurs 
    first; and
    --The system must either be continued to be operated in the 
    automatic cycling mode, if available; or the system must be manually 
    cycled as needed to minimize the ice accretions on the airframe.
    
         The wing and tail leading edge pneumatic deicing boot 
    system may be deactivated only after leaving icing
    
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    conditions and after the airplane is determined to be clear of 
    ice.''
        (b) An alternative method of compliance or adjustment of the 
    compliance time that provides an acceptable level of safety may be 
    used if approved by the Manager, Manager, International Branch, ANM-
    116, FAA, Transport Airplane Directorate. The request shall be 
    forwarded through an appropriate FAA Operations Inspector, who may 
    add comments and then send it to the Manager, International Branch, 
    ANM-116 ACO.
    
        Note 1: Information concerning the existence of approved 
    alternative methods of compliance with this AD, if any, may be 
    obtained from the International Branch, ANM-116 ACO.
    
        (c) Special flight permits may be issued in accordance with 
    Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 
    21.197 and 21.199) to operate the airplane to a location where the 
    requirements of this AD can be accomplished.
    
        Issued in Renton, Washington, on June 30, 1999.
    D.L. Riggin,
    Acting Manager, Transport Airplane Directorate, Aircraft Certification 
    Service.
    [FR Doc. 99-17547 Filed 7-15-99; 8:45 am]
    BILLING CODE 4910-13-P
    
    
    

Document Information

Published:
07/16/1999
Department:
Federal Aviation Administration
Entry Type:
Proposed Rule
Action:
Notice of proposed rulemaking (NPRM).
Document Number:
99-17547
Dates:
Comments must be received by August 16, 1999.
Pages:
38329-38332 (4 pages)
Docket Numbers:
Docket No. 99-NM-154-AD
RINs:
2120-AA64: Airworthiness Directives
RIN Links:
https://www.federalregister.gov/regulations/2120-AA64/airworthiness-directives
PDF File:
99-17547.pdf
CFR: (1)
14 CFR 39.13