AD 96-1102

[Federal Register Volume 61, Number 17 (Thursday, January 25, 1996)] [Rules and Regulations] [Pages 2095-2099] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 96-1102]

======================================================================== Rules and Regulations Federal Register ________________________________________________________________________ This section of the FEDERAL REGISTER contains regulatory documents having general applicability and legal effect, most of which are keyed to and codified in the Code of Federal Regulations, which is published under 50 titles pursuant to 44 U.S.C. 1510. The Code of Federal Regulations is sold by the Superintendent of Documents. Prices of new books are listed in the first FEDERAL REGISTER issue of each week. ========================================================================

Federal Register / Vol. 61, No. 17 / Thursday, January 25, 1996 / Rules and Regulations

[[Page 2095]]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-NM-55-AD; Amendment 39-9494; AD 96-02-06]

Airworthiness Directives; Boeing Models 727, 737, and 747 Series Airplanes; McDonnell Douglas Model DC-8 and DC-9 Series Airplanes, Model MD-88 Airplanes, and Models MD-11 and MD-90-30 Series Airplanes; Lockheed Models L-1011-385 Series Airplanes; Fokker Models F28 Mark 1000, 2000, 3000, 4000, and 0100 Series Airplanes; and British Aerospace Model Avro 146-RJ Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: This amendment supersedes two existing airworthiness directives (AD), applicable to certain transport category airplanes equipped with certain Honeywell Standard Windshear Detection Systems (WSS). Those AD's currently require a revision to the FAA-approved Airplane Flight Manual (AFM) to alert the flightcrew of the potential for significant delays in the WSS detecting windshear when the flaps of the airplane are in transition. Those AD's were prompted by a report of an accident during which an airplane encountered severe windshear during a missed approach. This amendment requires that the currently- installed line replaceable unit (LRU) be replaced with a modified LRU having new software that eliminates delays in the WSS detecting windshear when the flaps of the airplane are in transition. The actions specified by this AD are intended to prevent significant delays in the WSS detecting hazardous windshear, which could lead to the loss of flight path control.

EFFECTIVE DATE: February 26, 1996.

ADDRESSES: Information concerning this AD may be obtained from or examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Los Angeles Aircraft Certification Office, Transport Airplane Directorate, 3960 Paramount Boulevard, Lakewood, California.

FOR FURTHER INFORMATION CONTACT: J. Kirk Baker, Aerospace Engineer, Systems and Equipment Branch, ANM-130L, FAA, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, California 90712; telephone (310) 627-5345; fax (310) 627-5210.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 95-04-01, amendment 39-9153 (60 FR 9619, February 21, 1995), and AD 95-09-05, amendment 39-9208 (60 FR 20887, April 28, 1995) that was corrected on May 12, 1995 (60 FR 26824, May 19, 1995); was published in the Federal Register on June 13, 1995 (60 FR 31122). The proposed action is applicable to certain transport category airplanes equipped with certain Honeywell Standard Windshear Detection Systems (WSS). The action proposed to require replacement of the currently-installed line replaceable unit (LRU) with a modified LRU having new software that eliminates delays in the WSS detecting windshear when the flaps of the airplane are in transition. Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. - One commenter supports the proposed rule. One commenter requests that the proposal be withdrawn since unmodified WSS's provide the necessary level of safety required for windshear detection. Furthermore, the commenter states that existing AD's 95-04-01 and 95-09-05, which require that specific operational procedures be followed, ensure that the flightcrews are properly trained on the peculiarities of the Honeywell WSS. - The FAA does not concur. The FAA finds that the unsafe condition will be positively addressed by installing new software in the LRU that will eliminate delays in the WSS detecting windshear when the flaps of the airplane are in transition. Additionally, the FAA has determined that long term continued operational safety will be better assured by design changes to remove the source of the problem, rather than by performing special operating procedures. Performing long-term special operating procedures may not be providing the degree of safety assurance necessary for affected airplanes in the fleet. This, coupled with a better understanding of the human factors associated with numerous continual special procedures, has led the FAA to consider placing less emphasis on special procedures and more emphasis on design improvements. This requirement for modification of the software is in consonance with these considerations. One commenter requests a revision to part 121 or part 135 of the Federal Aviation Regulations (FAR) (14 CFR 121 or 135), since the proposal does not address the root problem. The commenter states that the proposal addresses ``reactive'' WSS's but, since ``predictive'' systems are now available, they should be required equipment on all aircraft. The commenter contends that the ultimate solution to the problem would be to require airborne predictive windshear detection equipment, in conjunction with ground-based detection equipment, on all airplanes operating in accordance with FAR part 121 or 135. The FAA does not concur. According to section 39.1 (``Airworthiness directives'') of the FAR (14 CFR 39.1), the issuance of an AD is based on the finding that an unsafe condition exists or is likely to develop in a product of a particular type design. This AD is based on such a finding; it is the result of an investigation into the cause of an accident involving a transport category airplane equipped with Honeywell Standard Windshear Detection System. That investigation revealed that a design feature in the windshear computer delayed detection of windshear when the airplane's flaps were in transition. From this investigation, the FAA determined that an unsafe condition exists with regard to the flightcrew

[[Page 2096]] being unaware of the potential for significant delays in the WSS detecting windshear when the flaps of the airplane are in transition. The issuance of this AD is to correct that unsafe condition. While the commenter's request to require installation of specific equipment for operation of air carriers or air taxis in accordance with part 121 or part 135 has merit, it is clearly beyond the scope of this AD action. One commenter requests a change in the applicability from the proposed manufacturers of the airplanes to Honeywell, the manufacturer of the faulty WSS's. The FAA does not concur in this case. While it is assumed that an operator will know the models of airplanes it operates, there is a potential that the operator will not know or be immediately aware of specific items that are installed on its airplanes. The FAA reasons that, by calling out all of the manufacturers of the airplane models on which the subject item is likely to be installed, it will prevent ``unknowing non-compliance'' with the AD on the part of the operator.- One commenter requests a revision to the proposal to include a requirement to install placards in all airplanes to warn flightcrews of the potential for significant delays in the WSS detecting windshear. This commenter states that, since the WSS's on all airplanes within an operator's fleet will not be modified simultaneously, the flightcrew may not know whether the airplane has a modified or unmodified WSS. This commenter contends that these proposed placards would minimize the possibility for confusion as to the operating characteristics of the specific WSS on the airplane. - The FAA does not concur. The FAA finds that safety of the fleet of affected airplanes will be ensured by the requirements of AD 95-04-01 and AD 95-09-04 [and retained in paragraph (a) of the final rule], which require a limitation to the FAA-approved Airplane Flight Manual (AFM) to alert the flightcrew of the potential for significant delays in the WSS detecting windshear when the flaps of the airplane are in transition. Typically, placards that are used in the cockpit are brief and provide pilots with information that highlights significant changes (i.e., labeling specific equipment inoperative). Longer, more detailed changes to systems, such as that required by paragraph (a) of the final rule, are normally detailed in the AFM. Therefore, the FAA finds that the requiring the installation of a placard in the cockpit to warn pilots of the potential for significant delays in the WSS detecting windshear would not significantly enhance safety. Conversely, the FAA has received comments to other rulemaking actions from operators indicating that an overabundance of placards in the cockpit tends to clutter the cockpit, which would make it easy for the flightcrew to overlook important operational changes that require the pilot to take necessary action. - One commenter requests a revision to paragraph (a) of the proposal, which restates the requirements of AD 95-04-01 and AD 95-09-05. Proposed paragraph (a) requires a revision to the FAA-approved AFM to alert the flightcrew of the potential for significant delays in the WSS detecting windshear when the flaps of the airplane are in transition. The commenter requests the inclusion of references to the roll rate desensitizing feature, which the commenter states would increase flightcrew confidence in the system to detect windshear in all configurations. - The FAA does not concur. During certification testing, the FAA evaluated the effects of bank angles and roll rates, and determined that roll rates high enough to cause desensitization will produce the 15-degree bank angle that is noted in the AFM limitation required by paragraph (a) of the final rule. The FAA has reviewed all currently available data and finds that changes to paragraph (a) of the final rule to incorporate roll rate compensations are not warranted. However, paragraph (b) of the final rule has been changed to recommend revising the AFM limitation [required by paragraph (a) of the final rule] following installation of a modified LRU. The newly revised AFM limitation alerts pilots that sustained banks greater than 15 degrees will desensitize the WSS and that the potential exists for delays in the WSS detecting windshear. - Several commenters object to the proposed requirement of paragraph (b) to replace the currently installed LRU with a modified LRU having new software that eliminates delays in the WSS detecting windshear when the flaps of the airplane are in transition. Several commenters state that the proposed replacement is unnecessary since such replacement would not enhance safety of the affected airplanes. One of these commenters notes that the proposed replacement requirement would result in changes in aircraft configuration that may increase nuisance alerts, since the sensitivity reduction factor would be totally eliminated during flap transition. - The FAA does not concur. The criteria for reactive windshear systems state that a warning shall be issued once the windshear is encountered. The criteria also consider the airplane's available performance and the system's propensity for nuisance alerts due to turbulence. The FAA evaluates compliance with these criteria based upon the system's ability to issue timely warnings in all reasonably expected conditions. The FAA finds that encountering windshear during flap transition is a reasonably expected condition, vis-a-vis the accident during which an airplane encountered severe windshear during a missed approach. - Further, the FAA has determined that conducting missed approaches, prior to encountering windshear, is a reasonably probable scenario. In such a scenario, the pilot would rely on prior knowledge attained in FAA-required training to recognize and recover from a windshear encounter, such as that provided in ``Windshear Training Aid,'' Revision 1, dated February 1990. Therefore, the pilot would likely determine that windshear has been encountered before the detection system actually detects the phenomena since the WSS is intended to be strictly an adjunct system, not a sole or primary system. The windshear training that pilots receive instructs the pilot not to retract the airplane's flaps in this scenario. However, if the pilot does not believe that windshear has been encountered, the pilot may execute a normal go-around and retract the flaps, due to what the pilot perceives to be an unstable approach. Therefore, the FAA considers any delay in windshear detection to be unacceptable while the airplane's flaps are in transition. Consequently, the FAA finds that any improvement in warning time for the pilot will enhance safety for the affected airplanes. - Further, the FAA does not concur that installation of a modified LRU, and consequently, removal of the windshear warning delay during flap transition, would result in an increase in nuisance alerts. The FAA has reviewed all available data and cannot substantiate the commenter's assertion that elimination of the sensitivity reduction factor during flap transition would result in an increase in nuisance alerts. The FAA finds that the flaps are usually extended at altitudes higher than the altitude at which the system is armed. Furthermore, the FAA considers conducting a go-around with strong turbulence (excluding actual windshear conditions) to be a highly unlikely combination of events. Additionally, the FAA will evaluate the modified Honeywell windshear computer to determine compliance with the nuisance alert criteria, discussed above. - Several commenters request an extension to the proposed compliance

[[Page 2097]] time of 24 months for the replacement of the LRU. These commenters suggest that a compliance time of 36 months would be more appropriate to accommodate the time necessary to amend the supplemental type certificate (STC) and revise the parts manufacture approval. One of these commenters states that, since airplanes are prohibited from flying with a mixture of modified and unmodified units, this extension is necessary to ensure that Honeywell will be able to provide an adequate number of modified units to the affected fleet. The FAA concurs. The FAA has verified with the manufacturer that the lead time for developing the required LRU will exceed the proposed compliance time of 24 months. Further, the FAA has determined that extending the compliance time to the suggested 36 months will accommodate the time necessary for the manufacturer to develop, test, and certify these units. The FAA finds that this 12-month extension will not adversely affect safety significantly. Therefore, paragraph (b) of the final rule has been revised accordingly. One commenter requests that the proposed 24-month compliance time for replacement of the LRU be shortened to 12 months. This commenter suggests that the proposed compliance time may be too long, in light of the catastrophic consequences of the identified unsafe condition. The FAA does not concur that a shorter compliance time is appropriate. The proposed 24-month compliance time was based on the time originally estimated as necessary for operators to obtain modified LRU's, plus the time necessary for operators to install that modified LRU on the affected fleet. However, in light of the information received concerning availability of these required parts, as discussed above, the FAA has determined that a more appropriate time for accomplishing the replacement of the LRU is 36 months. The FAA considers that the AFM limitation currently required by AD 95-04-01 and AD 95-09-05 [and retained in paragraph (a) of the final rule] will ensure safety in the interim until the LRU's can be replaced. One commenter requests a revision to paragraph (b) of the proposal to specify that the modified LRU have software that would eliminate the horizontal portion of the flap rate compensation feature only. The commenter contends that removal of the vertical portion of the flap rate compensation feature will increase nuisance alerts and will minimally improve the time it takes for the WSS to detect hazardous windshear when the flaps of the airplane are in transition. The FAA does not concur. Since paragraph (b) of the final rule requires that the FAA approve all replacement LRU's, the FAA approval will include, among other factors, a review of the system's susceptibility to nuisance warnings caused by both horizontal and vertical compensations. Two commenters request an extension to the proposed compliance time of 12 months required by paragraph (c), which prohibits installation of unmodified LRU's. One of these commenters states that a 12-month extension would allow Honeywell, the manufacturer of these WSS's, sufficient time to develop and manufacture an adequate number of modified units. The other commenter suggests that an extension of 6 months would allow operators ample time to remove and return the units to Honeywell to be reprogrammed. The FAA concurs that a 6-month extension to the compliance time is appropriate. The FAA has confirmed that the manufacturer will require 18 months to manufacture an adequate number of units. The FAA has determined that such an extension to the compliance time will not compromise the safety of the affected airplanes, and that the currently required operating limitations will provide an acceptable level of safety in the interim. Therefore, paragraph (c) of the final rule has been revised to prohibit, installation of unmodified LRU's as of 18 months after the effective date of the AD. One commenter supports the proposed rule, but recommends that the proposed 12-month compliance time of paragraph (c), which prohibits installation of unmodified LRU's, be shortened to 6 months. This commenter states that, in light of the accident that prompted this AD action, 12 months may be too long to permit unmodified LRU's to be installed on the affected airplanes. The FAA does not concur. Based upon the information received concerning the new schedule for the availability of required parts, discussed above, the FAA finds it necessary to extend this compliance time to 18 months. After 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 with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD. There are approximately 2,320 airplanes of the affected design in the worldwide fleet. The FAA estimates that 1,618 airplanes of U.S. registry will be affected by this AD. The actions that are currently required by AD's 95-04-01 and 95-09- 05 take approximately 1 work hour per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact on U.S. operators of the actions currently required is estimated to be $97,080, or $60 per airplane. The new actions that are required by this new AD will take approximately 10 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts will be provided by Honeywell at not cost to operators. Based on these figures, the cost impact on U.S. operators of the new requirements of this AD is estimated to be $970,800, or $600 per airplane. The cost impact figures discussed above are 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. The 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. For 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.''

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Safety.

[[Page 2098]]

Adoption of the Amendment

Accordingly, 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:

PART 39--AIRWORTHINESS DIRECTIVES

-1. The authority citation for part 39 continues to read as follows:

Authority: 49 USC 106(g),40113, 44701.

Sec. 39.13 [Amended]

-2. Section 39.13 is amended by removing amendments 39-9153 (60 FR 9619, February 21, 1995) and 39-9208 (60 FR 20887, April 28, 1995), and by adding a new airworthiness directive (AD), amendment 39-9494, to read as follows:

96-02-06 Boeing; McDonnell Douglas; Lockheed; Fokker; and British Aerospace Regional Aircraft Limited, AVRO International Aerospace Division (Formerly British Aerospace, plc; British Aerospace Commercial Aircraft, Limited): Amendment 39-9494. Docket 95-NM-55- AD. Supersedes AD 95-04-01, Amendment 39-9153; and AD 95-09-05, Amendment 39-9208.

Applicability: The following models and series of airplanes, certificated in any category, equipped with Honeywell Standard Windshear Detection Systems (WSS):

---------------------------------------------------------------------------------------------------------------- Manufacturer and model of airplane Type of computer Part Nos. ---------------------------------------------------------------------------------------------------------------- Boeing 727-100 and -200................ Standard Windshear 4061048-902, -903, and -904, 4068054-901, (Honeywell STC). 4068060-901. Boeing 737-100 and -200................ Standard Windshear 4061048-903, -904, and -905, 4068058-903. (Honeywell STC). Boeing 737-200......................... Performance Management 4050730-904 through -911, 4051819-906. (Honeywell STC). Boeing 737-300......................... Standard Windshear 4068060-901. (Honeywell STC). Boeing 747-100 and -200................ Standard Windshear 4061048-904. (Honeywell STC). McDonnell Douglas DC-8-50, -60, and -70 Standard Windshear 4068046-903. (Honeywell STC). McDonnell Douglas DC-9-10, -21, -31, - Standard Windshear 4068046-901, -902, 4068048-901, -902. 41, and -51. (Honeywell STC)-. McDonnell Douglas DC-9-80 and MD-88.... Windshear (OEM TC)........ 4059845-902. McDonnell Douglas MD-90-30............. Windshear (OEM TC)........ 4059845-910. McDonnell Douglas MD-11................ Flight Control (OEM TC)... 4059001-901 through -905 (with windshear option selected). Lockheed L-1011-385-1, -385-1-14, -385- Standard Windshear (OEM 4068044-901. 1-15, and -385-3. TC). Fokker F28 Mark 1000, 2000, 3000, and Standard Windshear 4068052-901. 4000. (Honeywell STC). Fokker F28 Mark 0100................... Flight Management (OEM TC) 4052502-951 (with windshear option selected). British Aerospace Avro 146-RJ70A, - Flight Control (OEM TC)... 4068300-902. RJ85A, and -RJ100A. ----------------------------------------------------------------------------------------------------------------

Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been 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 use the authority provided in paragraph (d) of this AD to request approval from the FAA. This approval may address either no action, if the current configuration eliminates the unsafe condition; or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any airplane from the applicability of this AD.

Compliance: Required as indicated, unless accomplished previously. To prevent significant delays in the Honeywell Standard Windshear Detection Systems (WSS) detecting hazardous windshear, which could lead to the loss of flight path control, accomplish the following: (a) Revise the Limitations Section of the FAA-approved Airplane Flight Manual (AFM) to include the following statement, at the time specified in either paragraph (a)(1) or (a)(2) of this AD, as applicable. This may be accomplished by inserting a copy of this AD in the AFM. ``During sustained banks of greater than 15 degrees or during flap configuration changes, the Honeywell Windshear Detection and Recovery Guidance System (WSS) is desensitized and alerts resulting from encountering windshear conditions will be delayed.'' (1) For all Boeing, McDonnell Douglas, Lockheed, and Fokker airplanes specified in the applicability statement of this AD: Within 14 days after March 8, 1995 (the effective date of AD 95-04- 01, amendment 39-9153). (2) For British Aerospace Model Avro airplanes specified in the applicability statement of this AD: Within 14 days after May 15, 1995 (the effective date of AD 95-09-05, amendment 39-9208). (b) Within 36 months after the effective date of this AD, replace the currently-installed line replaceable unit (LRU) with a modified LRU having new software that eliminates delays in the WSS detecting windshear when the flaps of the airplane are in transition, in accordance with a method approved by the Manager, Los Angeles Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Accomplishment of this replacement constitutes terminating action for the requirements of paragraph (a) of this AD; after the replacement has been accomplished, the AFM limitation required by paragraph (a) of this AD may be revised to read as follows: ``During sustained banks of greater than 15 degrees, the Honeywell Windshear Detection and Recovery Guidance System (WSS) is desensitized and alerts resulting from encountering windshear conditions will be delayed.'' (c) As of 18 months after the effective date of this AD, no person shall install on any airplane an LRU that has not been modified in accordance with paragraph (b) of this AD. An unmodified LRU may be installed up to 18 months after the effective date of this AD, provided that, during that time, the AFM

[[Page 2099]] limitation required by paragraph (a) of this AD remains in effect. (d) 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, Los Angeles ACO. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Los Angeles ACO.

Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Los Angeles ACO.

(e) 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. (f) This amendment becomes effective on February 26, 1996.

Issued in Renton, Washington, on January 18, 1996. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 96-1102 Filed 1-24-96; 8:45 am] BILLING CODE 4910-13-U