Airworthiness Directives; Learjet Model 35, 35A, 36, 36A, 55, 55B, and 55C Airplanes

[Federal Register Volume 60, Number 94 (Tuesday, May 16, 1995)] [Proposed Rules] [Pages 26003-26004] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 95-11975]

======================================================================== Proposed Rules Federal Register ________________________________________________________________________ This section of the FEDERAL REGISTER contains notices to the public of the proposed issuance of rules and regulations. The purpose of these notices is to give interested persons an opportunity to participate in the rule making prior to the adoption of the final rules. ========================================================================

Federal Register / Vol. 60, No. 94 / Tuesday, May 16, 1995 / Proposed Rules

[[Page 26003]]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-NM-25-AD]

Airworthiness Directives; Learjet Model 35, 35A, 36, 36A, 55, 55B, and 55C 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 Learjet Model 35, 35A, 36, 36A, 55, 55B, and 55C airplanes. This proposal would require installation of a placard on the instrument panel in the cockpit to advise the flightcrew that the Omega navigation system may be inoperative at certain engine speeds. This proposal is prompted by reports of loss of certain navigation signals during extended over water operation. The actions specified by the proposed AD are intended to prevent excessive deviation from the intended flight path due to loss of navigation signals, which could result in a potentially low- fuel condition or a traffic conflict.

DATES: Comments must be received by June 26, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 95-NM-25-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays. The service information referenced in the proposed rule may be obtained from Gates Learjet, Mid-Continent Airport, P.O. Box 7707, Wichita, Kansas 67277. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT: C. Dale Bleakney, Aerospace Engineer, ACE-130W, Systems and Equipment Branch, FAA, Wichita Aircraft Certification Office, Small Airplane Directorate, 1801 Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas 67209; telephone (316) 946-4135; fax (316) 946-4407.

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 95-NM-25-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. 95-NM-25-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received reports of loss of the Omega navigation signal from certain global navigation systems (GNS) manufactured by Flight Management Systems and installed on various Learjet airplane models. These systems, GNS-500, GNS-1000, and GNS-X, have been shown to be susceptible to generator noise at approximately 92.5% N2. This generator noise has the potential to render the Omega navigation signal inoperative. GNS-500, GNS-1000, and GNS-X systems all rely on a single Omega frequency of 13.6 KHz. This is the same frequency as the noise created by the Bendix generator used on Model 35, 36, and 55 airplanes when operated near 92.5% N2. If alternate suitable navigation signals such as VOR, VOR/DME, GPS, and VLF, are deselected and the GNS- 500, -1000, or -X system is used exclusively, the aircraft may enter a ``dead reckoning'' mode until a suitable navigation signal is obtained. Use of the GNS-500, -1000, or -X navigation system exclusively during extended overwater operation with the Omega signal rendered inoperative due to generator noise, could result in excessive deviation from the intended flight path, and may lead to a potential low-fuel condition or a traffic conflict. 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 installation of a placard on the instrument panel in the cockpit to advise the flightcrew that the Omega navigation system may be inoperative when engine speed reaches 92.5% N2. Additionally, the FAA has reviewed and approved Gates Learjet Airplane Accessory Kit Model 55 AAK 55-85-2 (for Model 55 airplanes) dated January 14, 1986, as revised by Airplane Accessory Kit Change Notice AAK No. AAK55-85-2, Change 1 (undated). The FAA has also reviewed and approved Gates Learjet Airplane Accessory Kit Model AAK 85-1, dated January 14, 1986 (for the Model 35 and 36 airplanes), as revised by Airplane Accessory Kit Change Notice AAK-85-1, Change 1 (undated). These kits describe procedures for installation of a generator band reject filter on certain Model 35, 36, and 55 series airplanes. This noise filter will prevent generator noise from reaching the 13.6 KHz frequency. This proposed AD also would provide operators with the option of installing the applicable modification as [[Page 26004]] terminating action for the required placard. As a result of recent communications with the Air Transport Association (ATA) of America, the FAA has learned that, in general, some operators may misunderstand the legal effect of AD's on airplanes that are identified in the applicability provision of the AD, but that have been altered or repaired in the area addressed by the AD. The FAA points out that all airplanes identified in the applicability provision of an AD are legally subject to the AD. If an airplane has been altered or repaired in the affected area in such a way as to affect compliance with the AD, the owner or operator is required to obtain FAA approval for an alternative method of compliance with the AD, in accordance with the paragraph of each AD that provides for such approvals. A note has been included in this notice to clarify this long-standing requirement. There are approximately 710 Learjet Model 35, 35A, 36, 36A, 55, 55B, and 55C airplanes of the affected design in the worldwide fleet. The FAA estimates that 177 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 actions, and that the average labor rate is $60 per work hour. The cost of required parts (local manufacture of a placard) is negligible. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $10,620, or $60 per airplane. Should an operator elect to accomplish the optional terminating action that would be provided by this AD action, it would take approximately 14 work hours to accomplish it, at an average labor rate of $60 per work hour. The cost of required parts would be approximately $3,050 per airplane. Based on these figures, the total cost impact of the optional terminating action would be $3,890 per airplane. The total cost impact figure discussed above is 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. 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. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

Sec. 39.13 [Amended] -

2. Section 39.13 is amended by adding the following new airworthiness directive:

Learjet: Docket 95-NM-25-AD.

Applicability: Model 35, 35A, 36, 36A, 55, 55B, and 55C airplanes; equipped with Global Wulfsburg GNS 500, GNS-1000, and GNS-X Flight Management Systems; certificated in any category.

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) 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 excessive deviation from the intended flight path which, if the aircraft is on an extended overwater operation, may lead to a potential low-fuel condition or a traffic conflict operation, accomplish the following: (a) Within 60 days after the effective date of this AD, install a placard in a prominent location on the instrument panel that states:

``VLF/OMEGA MAY BE INOPERATIVE AT 92.5% N2''

(b) For Model 35 airplanes, serial numbers 35-001 through 35-603 inclusive; and Model 36, serial numbers 36-001 through 36-053 inclusive: Installation of a GNS 500/1000 generator band reject filter in accordance with Gates Learjet Airplane Accessory Kit Model AAK 85-1, dated January 14, 1986, as revised by Airplane Accessory Kit Change Notice AAK-85-1, Change 1 (undated), constitutes terminating action for the placard requirement of paragraph (a) of this AD. Following installation of the filter, the placard required by paragraph (a) of this AD may be removed. (c) For Model 55 airplanes, serial numbers 55-003 through 55-124 inclusive: Installation of a GNS 500/1000 generator band reject filter in accordance with Gates Learjet Airplane Accessory Kit Model 55 AAK 55-85-2, dated January 14, 1986, as revised by Airplane Accessory Kit Change Notice AAK No. AAK55-85-2, Change 1 (undated), constitutes terminating action for the placard requirement of paragraph (a) of this AD. Following installation of the filter, the placard required by paragraph (a) of this AD may be removed. (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, Wichita Aircraft Certification Office (ACO), FAA, Small 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, Wichita ACO.

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

Issued in Renton, Washington, on May 10, 1995. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 95-11975 Filed 5-15-95; 8:45 am] BILLING CODE 4910-13-U