[Federal Register Volume 61, Number 166 (Monday, August 26, 1996)] [Proposed Rules] [Pages 43692-43694] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 96-21594] ----------------------------------------------------------------------- DEPARTMENT OF TRANSPORTATION 14 CFR Part 39 [Docket No. 96-NM-40-AD] RIN 2120-AA64 Airworthiness Directives; British Aerospace Model BAe 146 Series Airplanes and Model Avro 146-RJ Series Airplanes AGENCY: Federal Aviation Administration, DOT. ACTION: Notice of proposed rulemaking (NPRM). ----------------------------------------------------------------------- SUMMARY: This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain British Aerospace Model BAe 146 and Model Avro 146-RJ series airplanes. This proposal would require repetitive tests of the integrity of the electrical circuit between the windshear computer and the flap position sensor, and repair of the electrical wiring, if necessary. This proposal also would require replacement of certain windshear computers with new computers, which, when accomplished, terminates the repetitive tests. This proposal is prompted by a report indicating that the existing windshear computer is not capable of detecting a signal indicating loss of flap position; this could result in the flightcrew following erroneous computer-generated guidance. The actions specified by the proposed AD are intended to prevent the incapability of the windshear computer to detect the true flap position, which, if not corrected, could result in the inability of the flightcrew to avoid a windshear encounter, and consequent reduced controllability of the airplane. DATES: Comments must be received by October 4, 1996. ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 96-NM-40-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. The service information referenced in the proposed rule may be obtained from British Aerospace Regional Aircraft Limited, Avro International Aerospace Division, Customer Support, Woodford Aerodrome, Woodford, Cheshire SK7 1QR, England. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. FOR FURTHER INFORMATION CONTACT: Tim Backman, Aerospace Engineer, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 227-2797; fax (206) 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 [[Page 43693]] 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 96-NM-40-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-103, Attention: Rules Docket No. 96-NM-40-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Discussion The Civil Aviation Authority (CAA), which is the airworthiness authority for the United Kingdom, recently notified the FAA that an unsafe condition may exist on certain British Aerospace Model BAe 146 and Model Avro 146-RJ series airplanes. The CAA advises that it received a report indicating that the windshear computer installed on these airplanes is not capable of detecting a signal indicating loss of flap position. During a windshear encounter, the windshear computer displays guidance on the flight directors. This guidance indicates to the flightcrew to avoid windshear. The recommended flight maneuver in such cases depends upon many factors, including flap position. However, if the windshear computer is unable to detect the true flap position because the signal that indicates loss of flap position is not detected, the flightcrew could follow erroneous computer-generated guidance. This condition, if not corrected, could result in inability to avoid a windshear encounter and consequent reduced controllability of the airplane. Explanation of Relevant Service Information Avro International Aerospace has issued Alert Inspection Service Bulletin S.B. 34-A155, Revision 2, dated August 9, 1995, which describes procedures for repetitive tests of the integrity of the electrical circuit between the windshear computer and the flap position sensor, and repair of the electrical wiring, if necessary. The CAA classified this service bulletin as mandatory in order to assure the continued airworthiness of these airplanes in the United Kingdom. Additionally, British Aerospace has issued Modification Service Bulletin SB.34-160-70548A, dated November 21, 1994, which describes procedures for replacement of existing windshear computers with new Safe Flight windshear computers. The new computer is capable of detecting an open circuit failure in the flap position input circuit. Accomplishment of the replacement also involves changing the polarity of the polarizing keys to preclude installation of lesser standard computers. Accomplishment of the replacement eliminates the need for the repetitive tests described previously. The CAA has approved the technical content of this service bulletin. FAA's Conclusions These airplane models are manufactured in the United Kingdom and are type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, the CAA has kept the FAA informed of the situation described above. The FAA has examined the findings of the CAA, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States. Explanation of Requirements of Proposed Rule Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design, the proposed AD would require repetitive tests of the integrity of the electrical circuit between the windshear computer and the flap position sensor, and repair of the electrical wiring, if necessary. The proposed AD also would require replacement of existing windshear computers with new Safe Flight windshear computers. Accomplishment of the replacement would constitute terminating action for the repetitive tests. The actions would be required to be accomplished in accordance with the service bulletins described previously. Differences Between FAA's Proposed Action and the CAA's Action Operators should note that, although the CAA did not classify the modification service bulletin as mandatory, this proposed AD would require accomplishment of the replacement described in that service bulletin within 6 months after the effective date of the AD. The FAA finds that accomplishment of continued repetitive tests could increase the likelihood of other failures. In addition, tests in accordance with the inspection service bulletin only verify the condition of the system at the time the tests are performed, and may not reliably predict future system performance. The FAA has determined that long term continued operational safety will be better assured by replacement of the windshear computers to remove the source of the problem, rather than by repetitive tests. Long term testing may not be providing the degree of safety assurance necessary for the transport airplane fleet. This, coupled with a better understanding of the human factors associated with numerous repetitive tests, has led the FAA to consider placing less emphasis on special procedures and more emphasis on design improvements. The proposed replacement requirement is in consonance with these considerations. Explanation of Proposed Compliance Time for Replacement In developing an appropriate compliance time for the proposed replacement, the FAA's intent is that it be performed during a regularly scheduled maintenance visit for the majority of the affected fleet, when the airplanes would be located at a base where special equipment and trained personnel would be readily available, if necessary. The FAA finds that 6 months corresponds closely to the interval representative of most of the affected operators' normal maintenance schedules. The FAA considers that this interval will provide an acceptable level of safety. Cost Impact The FAA estimates that 41 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 1 work hour per airplane to accomplish the proposed test, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the proposed test on U.S. [[Page 43694]] operators is estimated to be $2,460, or $60 per airplane, per test cycle. The FAA estimates that it would take approximately 4 work hours per airplane to accomplish the proposed replacement, at an average labor rate of $60 per work hour. Required parts would be supplied by the manufacturer at no cost to operators. Based on these figures, the cost impact of the proposed replacement on U.S. operators is estimated to be $9,840, or $240 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: British Aerospace: Docket 96-NM-40-AD. Applicability: Model BAe 146 and Model Avro 146-RJ series airplanes on which BAe Modification HCM40270A or HCM40270B (Safe Flight Windshear Computer) has been installed; certificated in any category. Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (e) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it. Compliance: Required as indicated, unless accomplished previously. To prevent the inability of the flightcrew to avoid a windshear encounter and consequent reduced controllability of the airplane due to the inability of the windshear computer to detect the true flap position, accomplish the following: (a) Within 300 landings or 60 days after the effective date of this AD, whichever occurs first: Perform a test of the integrity of the electrical circuit between the windshear computer and the flap position sensor, in accordance with Avro International Aerospace Alert Inspection Service Bulletin S.B. 34-A155, Revision 2, dated August 9, 1995. Repeat the test thereafter at intervals not to exceed 300 landings until the actions required by paragraph (c) of this AD are accomplished. (b) If any test required by paragraph (a) of this AD fails, prior to further flight, repair the electrical wiring in accordance with Avro International Aerospace Alert Inspection Service Bulletin S.B. 34-A155, Revision 2, dated August 9, 1995. Thereafter, repeat the test required by paragraph (a) of this AD at intervals not to exceed 300 landings until the actions required by paragraph (c) of this AD are accomplished. (c) Within 6 months after the effective date of this AD: Replace any Safe Flight windshear computer having part number 6508-2 or 6508-4 with a new Safe Flight windshear computer having part number 6508-5; and change the polarity of the polarizing keys; in accordance with British Aerospace Modification Service Bulletin SB.34-160-70548A, dated November 21, 1994. Accomplishment of these actions constitutes terminating action for the repetitive tests required by paragraph (a) of this AD. (d) As of the effective date of this AD, no person shall install a Safe Flight windshear computer having part number 6508-2 or 6508-4 on any airplane. (e) 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, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Standardization Branch, ANM-113. Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Standardization Branch, ANM-113. (f) Special flight permits may be issued in accordance with sections 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 August 19, 1996. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 96-21594 Filed 8-23-96; 8:45 am] BILLING CODE 4910-13-U