[Federal Register Volume 69, Number 26 (Monday, February 9, 2004)]
[Rules and Regulations]
[Pages 5918-5920]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-2585]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2001-NM-366-AD; Amendment 39-13452; AD 2004-03-08]
RIN 2120-AA64


Airworthiness Directives; Learjet Model 31, 31A, 35, 35A (C-21A), 
36, and 36A 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 31, 31A, 35, 35A (C-21A), 36, and 
36A airplanes, that requires modification of the drag angles of the 
fuselage and engine pylons to gain access to the shear webs of the 
forward engine beams; repetitive inspections of the shear webs of the 
forward engine beams for cracks; follow-on actions; and modification/
repair of the shear webs of the forward engine beams, as necessary, 
which terminates the repetitive inspections. This action is necessary 
to prevent significant structural damage to the engine pylons, possible 
separation of the engines from the fuselage, and consequent reduced 
controllability of the airplane. This action is intended to address the 
identified unsafe condition.

DATES: Effective March 15, 2004.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 15, 2004.

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, 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: Steven Litke, Aerospace Engineer, 
Airframe Branch, ACE-118W, FAA, Wichita Aircraft Certification Office, 
1801 Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas 
67209; telephone (316) 946-4127; fax (316) 946-4107.

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 31, 31A, 35, 
35A (C-21A), 36, and 36A airplanes was published in the Federal 
Register on November 13, 2003 (68 FR 64283). That action proposed to 
require modification of the drag angles of the fuselage and engine 
pylons to gain access to the shear webs of the forward engine beams; 
repetitive inspections of the shear webs of the forward engine beams 
for cracks; follow-on actions; and modification/repair of the shear 
webs of the forward engine beams, as necessary, which would terminate 
the repetitive inspections.

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

    We have determined that air safety and the public interest require 
the adoption of the rule as proposed.

Cost Impact

    There are approximately 893 airplanes of the affected design in the 
worldwide fleet. We estimate that 673 airplanes of U.S. registry will 
be affected by this AD.
    It will take between 2 and 3 work hours per airplane to accomplish 
the required modification, at an average labor rate of $65 per work 
hour. Required parts will cost approximately $243 per airplane. Based 
on these figures, the cost impact of the required modification on U.S. 
operators is estimated to be between $251,029 and $294,774, or between 
$373 and $438 per airplane.
    We estimate that it will take 3 work hours to perform the required 
inspections, and that the average labor rate is $65 per work hour. 
Based on this figure, the cost impact of the required inspections on 
U.S. operators is estimated to be $131,235, or $195 per airplane, per 
inspection cycle.
    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 cost impact figures discussed 
in AD rulemaking actions represent only the time necessary to perform 
the specific actions actually required by the AD. These figures 
typically do not include incidental costs, such as the time required to 
gain access and close up, planning time, or time necessitated by other 
administrative actions. The manufacturer may cover the cost of 
replacement parts associated with this AD, subject to warranty 
conditions. Manufacturer warranty remedies may also be available for 
labor costs associated with this AD. As a result, the costs 
attributable to this AD may be less than stated above.

Regulatory Impact

    The regulations adopted herein will not have a substantial direct 
effect on the States, on the relationship between the national 
government and the States, or on the distribution of power and

[[Page 5919]]

responsibilities among the various levels of government. Therefore, it 
is determined that this final rule does not have federalism 
implications under Executive Order 13132.
    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

0
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

0
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]

0
2. Section 39.13 is amended by adding the following new airworthiness 
directive:

2004-03-08 Learjet: Amendment 39-13452. Docket 2001-NM-366-AD.

    Applicability: The following airplanes, certificated in any 
category, as applicable:

                         Table 1.--Applicability
------------------------------------------------------------------------
                               As Listed in Bombardier Service Bulletin--
           Model--
------------------------------------------------------------------------
31 and 31A Airplanes.........  31-51-2, dated February 1, 2001; and 31-
                                51-3, Revision 1, dated August 2, 2001.
35, 35A (C-21A), 36 and 36A    35/36-51-3, dated February 1, 2001; and
 Airplanes.                     35/36-51-4, Revision 1, dated August 2,
                                2001.
------------------------------------------------------------------------

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent significant structural damage to the engine pylons, 
possible separation of the engines from the fuselage, and consequent 
reduced controllability of the airplane, accomplish the following:

Inspections

    (a) At the later of the times specified in paragraphs (a)(1) and 
(a)(2) of this AD: Do a detailed inspection (using a probe) and a 
general visual inspection of the shear webs of the forward engine 
beams (including modification of the drag angles) for cracking in 
accordance with the Accomplishment Instructions of Bombardier 
Service Bulletin 31-51-2 (for Model 31 airplanes) or 35/36-51-3 (for 
Model 35 and 36 airplanes), both dated February 1, 2001; as 
applicable.
    (1) Prior to the accumulation of 3,000 total flight hours; or
    (2) Within 1,200 flight hours or 1 year after the effective date 
of this AD, whichever occurs first.

    Note 1: For the purposes of this AD, a general visual inspection 
is defined as: ``A visual examination of an interior or exterior 
area, installation, or assembly to detect obvious damage, failure, 
or irregularity. This level of inspection is made from within 
touching distance unless otherwise specified. A mirror may be 
necessary to enhance visual access to all exposed surfaces in the 
inspection area. This level of inspection is made under normally 
available lighting conditions such as daylight, hangar lighting, 
flashlight, or droplight and may require removal or opening of 
access panels or doors. Stands, ladders, or platforms may be 
required to gain proximity to the area being checked.''


    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.''

Detailed Probe Inspection Follow-On Actions

    (b) Following the detailed probe inspection required by 
paragraph (a) of this AD, do the follow-on actions specified in 
paragraphs (b)(1), (b)(2), or (b)(3) of this AD, as applicable, in 
accordance with the Accomplishment Instructions of Bombardier 
Service Bulletin 31-51-2 or 35/36-51-3, both dated February 1, 2001; 
as applicable.
    (1) If the resistance measured during the inspection is less 
than 0.110 milliohm: Repeat the inspections required by paragraph 
(a) of this AD thereafter at intervals not to exceed 1,200 flight 
hours.
    (2) If the resistance measured during the inspection is 0.110 
milliohm or more, but less than 0.150 milliohm: Within the next 
1,200 flight hours, repair and modify the forward engine beam shear 
web in accordance with the Accomplishment Instructions of Bombardier 
Service Bulletin 31-51-3, Revision 1 (for Model 31 airplanes) or 35/
36-51-4, Revision 1 (for Model 35 and 36 airplanes), both dated 
August 2, 2001; as applicable.
    (3) If the resistance measured during the inspection is 0.150 
milliohm or more: Before further flight, repair and modify the 
forward engine beam shear web in accordance with the Accomplishment 
Instructions of Bombardier Service Bulletin 31-51-3, Revision 1, or 
35/36-51-4, Revision 1; as applicable.

General Visual Inspection Follow-On Actions

    (c) Following the general visual inspection required by 
paragraph (a) of this AD, do all of the applicable follow-on actions 
at the times specified in the Accomplishment Instructions of 
Bombardier Service Bulletin 31-51-2 or 35/36-51-3, both dated 
February 1, 2001; as applicable; except as specified in paragraph 
(d) of this AD.
    (d) If any crack opening is found that is more than 0.03 inch 
during the general visual inspection required by paragraph (a) of 
this AD: Before further flight, do the actions specified in 
paragraphs 2.C.(16)(a) and 2.C.(16)(b) of Bombardier Service 
Bulletin 31-51-2 or 35/36-51-3, both dated February 1, 2001; as 
applicable; repair per a method approved by the Manager, Wichita 
Aircraft Certification Office (ACO), FAA; and do the terminating 
action specified in paragraph (e) of this AD.

Terminating Action

    (e) Modification of the shear webs by accomplishing all of the 
actions specified in the Accomplishment Instructions of Bombardier 
Service Bulletin 31-51-3, Revision 1, or 35/36-51-4, Revision 1, 
both dated August 2, 2001; as applicable; terminates the initial 
inspections required by paragraph (a) and the repetitive inspections 
required by paragraph (b)(1) of this AD.

Repair Approval

    (f) Where any service bulletin identified in this AD specifies 
that the manufacturer may be contacted for disposition of certain 
repair conditions, repair per a method approved by the Manager, 
Wichita ACO, FAA.

Submission of Inspection Results Not Required

    (g) Although the service bulletins identified in this AD specify 
to submit information to the manufacturer, this AD does not include 
such a requirement.

Alternative Methods of Compliance

    (h) In accordance with 14 CFR 39.19, the Manager, Wichita ACO, 
is authorized to approve alternative methods of compliance for this 
AD.

[[Page 5920]]

Incorporation by Reference

    (i) Unless otherwise specified in this AD, the actions shall be 
done in accordance with Bombardier Service Bulletin 31-51-2, dated 
February 1, 2001, and Bombardier Service Bulletin 31-51-3, Revision 
1, dated August 2, 2001; or Bombardier Service Bulletin 35/36-51-3, 
dated February 1, 2001, and Bombardier Service Bulletin 35/36-51-4, 
Revision 1, dated August 2, 2001; 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, 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.

Effective Date

    (j) This amendment becomes effective on March 15, 2004.

    Issued in Renton, Washington, on January 29, 2004.
Kalene C. Yanamura,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 04-2585 Filed 2-6-04; 8:45 am]
BILLING CODE 4910-13-P