AD 95-19-04

This amendment adopts a new airworthiness directive (AD), applicable to certain Learjet Model 35, 35A, 36, 36A, 55, 55B, and 55C airplanes, that requires 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 amendment is prompted by reports of loss of certain navigation signals during extended over water operation. The actions specified by this 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.

Final rule

95-19-04 LEARJET: Amendment 39-9365. 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) 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 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 ChangeNotice 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.

(f) This amendment becomes effective on October 12, 1995.

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 certain Learjet Model 35, 35A, 36, 36A, 55, 55B, and 55C airplanes was published in the Federal Register on May 16, 1995 (60 FR 26003). That action proposed to 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.

Interested persons have been afforded an opportunity to participate in the making of this amendment. No comments were submitted in response to the proposal or the FAA's determination of the cost to the public. The FAA has determined that air safety and the public interest require the adoption of the rule as proposed.

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 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. The cost of required parts (local manufacture of a placard) is negligible. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $10,620, or $60 per airplane.

The total 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.

Should an operator elect to accomplish the optional terminating action that is provided by this AD action, it will take approximately 14 work hours to accomplish it, at an average labor rate of $60 per work hour. The cost of required parts will be approximately $3,050 per airplane. Based on these figures, the total cost impactof the optional terminating action is $3,890 per airplane.

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.

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), 40101, 40113, 44701.

39.13 - [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive