Airworthiness Directives; Learjet Model 23, 24, 25, 28, 29, 31, 55, and 60 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-372-AD; Amendment 39-11238; AD 99-16-03]

RIN 2120-AA64

Airworthiness Directives; Learjet Model 23, 24, 25, 28, 29, 31,

55, and 60 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD),

applicable to certain Learjet Model 23, 24, 25, 28, 29, 31, 55, and 60

series airplanes, that requires a one-time detailed visual inspection

of the electrical wire leads of the horizontal stabilizer anti-ice

system to verify that the numbers on the wire leads correctly

correspond to the numbers on the connected airframe wiring;

installation of a wire ID strap on the left-and right-hand sides of

each terminal block; and installation of a warning placard. This

amendment is prompted by a report of severe flight control buffeting of

a Learjet Model 55 series airplane due to a malfunction of the

horizontal stabilizer anti-ice system. The actions specified by this AD

are intended to prevent undetected accretion of ice on the leading edge

of the horizontal

[[Page 41779]]

stabilizer, which could result in the loss of pitch control and

consequent reduced controllability of the airplane.

DATES: Effective September 7, 1999.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of September 7, 1999.

ADDRESSES: The service information referenced in this AD may be

obtained from Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-

2942. This information may be examined at the Federal Aviation

Administration (FAA), Transport Airplane Directorate, Rules Docket,

1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Small

Airplane Directorate, Wichita Aircraft Certification Office, 1801

Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas; or at

the Office of the Federal Register, 800 North Capitol Street, NW.,

suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Jose Flores, Senior Aerospace

Engineer, Systems and Propulsion Branch, ACE-116W, FAA, Small Airplane

Directorate, Wichita Aircraft Certification Office, 1801 Airport Road,

Room 100, Mid-Continent Airport, Wichita, Kansas 67209; telephone (316)

946-4133; fax (316) 946-4407.

SUPPLEMENTARY INFORMATION: 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 23, 24, 25,

28, 29, 31, 55, and 60 series airplanes was published in the Federal

Register on May 17, 1999 (64 FR 26703). That action proposed to require

a one-time detailed visual inspection of the electrical wire leads of

the horizontal stabilizer anti-ice system to verify that the numbers on

the wire leads correctly correspond to the numbers on the connected

airframe wiring; installation of a wire ID strap on the left-and right-

hand sides of each terminal block; and installation of a warning

placard.

Comments

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.

Conclusion

The FAA has determined that air safety and the public interest

require the adoption of the rule as proposed.

Cost Impact

There are approximately 1,010 airplanes of the affected design in

the worldwide fleet. The FAA estimates that 806 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 inspection and

installations, and that the average labor rate is $60 per work hour.

Required parts will be provided by the manufacturer at no cost to the

operators. Based on these figures, the cost impact of the required AD

on U.S. operators is estimated to be $48,360, or $60 per airplane.

The 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.

Regulatory Impact

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, Incorporation by

reference, 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 U.S.C. 106(g), 40113, 44701.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

99-16-03 Learjet: Amendment 39-11238. Docket 98-NM-372-AD.

Applicability: Model 23, 24, 25, 28, 29, 31, 55, and 60 series

airplanes; as listed in Learjet Service Bulletins SB 23/24/25-30-3,

SB 28/29-30-3, SB 31-30-05, SB 55-30-3, and SB 60-30-4, all dated

October 27, 1998; 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 request approval for an

alternative method of compliance in accordance with paragraph (b) 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 undetected accretion of ice on the leading edge of

the horizontal stabilizer, which could result in the loss of pitch

control and consequent reduced controllability of the airplane,

accomplish the following:

One-Time Inspection

(a) Within 100 flight hours after the effective date of this AD:

Perform a one-time detailed visual inspection of the electrical wire

leads of the horizontal stabilizer anti-ice system to verify that

the numbers on the wire leads correctly correspond to the numbers on

the connected airframe wiring, in accordance with Learjet Service

Bulletins SB 23/24/25-30-3, (for Model 23, 24, and 25 series

airplanes), SB 28/29-30-3 (for Model 28 and 29 series airplanes), SB

31-30-5 (for Model 31 series airplanes), SB 55-30-3 (for Model 55

series airplanes), or SB 60-30-4 (for Model 60 series airplanes);

all dated October 27, 1998; as applicable.

Note 2: For the purposes of this AD, a detailed inspection is

defined as: ``An intensive visual examination of a specific

structural area, system, installation or assembly to detect damage,

failure or irregularity. Available lighting is normally supplemented

with a direct source of good lighting at intensity deemed

appropriate by the inspector. Inspection aids such as mirror,

magnifying lenses, etc. may be used. Surface cleaning and elaborate

access procedures may be required.''

[[Page 41780]]

Corrective Action

(1) If no discrepancy is detected during the inspection required

by paragraph (a) of this AD: Concurrent with the inspection, install

a wire ID strap on the left-and right-hand sides of each terminal

block, and install a warning placard on each terminal block, in

accordance with the applicable service bulletin.

(2) If any discrepancy is detected during the inspection

required by paragraph (a) of this AD: Prior to further flight,

repair the discrepancy in accordance with the procedures specified

in Chapter 30 of the Learjet Airplane Wiring Manual. Concurrent with

the repair, install a wire ID strap on the left-and right-hand sides

of each terminal block, and install a warning placard on each

terminal block; in accordance with the applicable service bulletin.

Alternative Methods of Compliance

(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, 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 3: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Wichita ACO.

Special Flight Permits

(c) 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.

Incorporation by Reference

(d) Except as provided by paragraph (a)(2) of this AD, the

actions shall be done in accordance with Learjet Service Bulletin SB

23/24/25-30-3, dated October 27, 1998; Learjet Service Bulletin SB

28/29-30-3, dated October 27, 1998; Learjet Service Bulletin SB 31-

30-5, dated October 27, 1998; Learjet Service Bulletin SB 55-30-3,

dated October 27, 1998; or Learjet Service Bulletin SB 60-30-4,

dated October 27, 1998, as applicable. This incorporation by

reference was approved by the Director of the Federal Register in

accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be

obtained from Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-

2942. Copies may be inspected at the FAA, Transport Airplane

Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the

FAA, Small Airplane Directorate, Wichita Aircraft Certification

Office, 1801 Airport Road, Room 100, Mid-Continent Airport, Wichita,

Kansas; or at the Office of the Federal Register, 800 North Capitol

Street, NW., suite 700, Washington, DC.

(e) This amendment becomes effective on September 7, 1999.

Issued in Renton, Washington, on July 22, 1999.

D. L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 99-19297 Filed 7-30-99; 8:45 am]

BILLING CODE 4910-13-U