[Federal Register Volume 61, Number 219 (Tuesday, November 12, 1996)]
[Proposed Rules]
[Pages 58016-58018]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-28868]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-86-AD]
RIN 2120-AA64


Airworthiness Directives; Jetstream Model 4101 Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Jetstream Model 4101 
airplanes. This proposal would require repetitive inspections to detect 
cracking of the offset lightening hole on the drag brace of the left 
and right main landing gear (MLG); and replacement of these braces with 
braces having a centralized lightening hole. This replacement 
terminates the repetitive inspections. This proposal is prompted by a 
report indicating that fatigue cracking was detected on the upper link 
of a drag brace. The actions specified by the proposed AD are intended 
to prevent fatigue cracking of the drag braces of the MLG, which, if 
not corrected, could cause the MLG to fail and consequent reduced 
controllability of the airplane during takeoff, landing, and taxiing.

DATES: Comments must be received by December 23, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-86-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056. Comments may be inspected at this location 
between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal 
holidays.
    The service information referenced in the proposed rule may be 
obtained from Jetstream Aircraft, Inc., P.O. Box 16029, Dulles 
International Airport, Washington, DC 20041-6029. This information may 
be examined at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT: William Schroeder, Aerospace Engineer, 
Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 
227-2148; fax (206) 227-1149.

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 96-NM-86-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. 96-NM-86-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The Civil Aviation Authority (CAA), which is the airworthiness 
authority for

[[Page 58017]]

the United Kingdom, recently notified the FAA that an unsafe condition 
may exist on certain Jetstream Model 4101 airplanes. The CAA advises 
that it has received a report indicating that cracking has been 
detected on the upper link of a drag brace on the main landing gear 
(MLG) of a Model 4101 airplane; this cracking was found adjacent to an 
offset lightening hole. The cause of the cracking has been attributed 
to fatigue. Such fatigue cracking, if not detected and corrected in a 
timely manner, could result in failure of the MLG and consequent 
reduced controllability of the airplane during takeoff, landing, and 
taxiing.

Explanation of Relevant Service Information

    Jetstream has issued Service Bulletin J41-32-049, Revision 1, dated 
January 15, 1996, which describes procedures for conducting repetitive 
visual inspections to detect cracking of the offset lightening hole on 
the drag brace of the left and right MLG. The service bulletin 
recommends, prior to further flight, the replacement of any cracked 
drag brace with a brace having a centralized lightening hole. This 
service bulletin also describes procedures for replacing these drag 
braces with drag braces that have a centralized lightening hole. 
Installation of a drag brace with a centralized lightening hole 
eliminates the need for the repetitive inspections. The CAA classified 
this service bulletin as mandatory and issued British airworthiness 
directive 008-11-95, dated December 29, 1995, in order to assure the 
continued airworthiness of these airplanes in the United Kingdom.

FAA's Conclusions

    This airplane model is manufactured in the United Kingdom and is 
type certificated for operation in the United States under the 
provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 
21.29) and the applicable bilateral airworthiness agreement. Pursuant 
to this bilateral airworthiness agreement, the CAA has kept the FAA 
informed of the situation described above. The FAA has examined the 
findings of the CAA, reviewed all available information, and determined 
that AD action is necessary for products of this type design that are 
certificated for operation in the United States.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other airplanes of the same type design registered 
in the United States, the proposed AD would require repetitive detailed 
visual inspections of the offset lightening hole on the drag brace of 
the left and right MLG to detect cracking. It would also require, prior 
to further flight, the replacement of any cracked brace with a brace 
having a centralized lightening hole. Such replacement would constitute 
terminating action for the repetitive detailed visual inspections. The 
actions would be required to be accomplished in accordance with the 
service bulletin described previously.

Differences between the Proposed Rule and the CAA Airworthiness 
Directive

    Operators should note that the proposed AD would require all drag 
braces that are the subject to the inspections required by this AD to 
be replaced within two years with braces having a centralized 
lightening hole. This action would be considered final, terminating 
action for this proposed AD. The CAA, however, has not mandated a 
similar replacement of the drag braces.
    The FAA has determined that long-term continued operational safety 
will be better assured by modifications or design changes to remove the 
source of the problem, rather than by repetitive inspections. Long term 
inspections may not be providing the degree of safety assurance 
necessary for the transport airplane fleet. This, coupled with a better 
understanding of the human factors associated with numerous repetitive 
inspections, has led the FAA to consider placing less emphasis on 
special procedures and more emphasis on design improvements. The 
proposed replacement requirement is in consonance with these 
considerations.

Cost Impact

    The FAA estimates that 1 Jetstream Model 4101 airplane of U.S. 
registry would be affected by this proposed AD.
    It would take approximately 1 work hour per airplane to accomplish 
the proposed inspection, at an average labor rate of $60 per work hour. 
Based on these figures, the cost impact of the proposed inspection on 
the single U.S. operator is estimated to be $60 per inspection cycle.
    It would take approximately 2 work hours per airplane to accomplish 
the proposed replacement, at an average labor rate of $60 per work 
hour. Required parts would be provided by the manufacturer at no cost 
to the operator. Based on these figures, the cost impact of the 
proposed replacement on the single U.S. operator is estimated to be 
$120.
    The cost impact figures discussed above are 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 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. 106(g), 40113, 44701.

Sec. 39.13  [Amended]

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

Jetstream Aircraft Limited: Docket 96-NM-86-AD.

    Applicability: Model 4101 airplanes having constructors numbers 
41004 through 41009 inclusive, and 41017; equipped with a main 
landing gear (MLG) on which drag braces having Jetstream part 
numbers (P/N) AIR84352-0 through AIR84352-4, inclusive,

[[Page 58018]]

and having offset lightening holes, are installed; certificated in 
any category.

    Note 1: Drag braces having Jetstream part numbers (P/N) 
AIR84352-0 through AIR84352-4 inclusive, can have either offset or 
centralized lightening holes. This AD applies only to those 
airplanes equipped with those drag braces that have the offset 
lightening holes.
    Note 2: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise 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 (c) 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 fatigue cracking of the drag brace of the left and 
right MLG which, if not corrected, could cause the MLG to fail and 
consequent reduced controllability of the airplane during takeoff, 
landing, and taxiing, accomplish the following:
    (a) Within 50 hours time-in-service after the effective date of 
this AD, perform a detailed visual inspection to detect cracking at 
the offset lightening hole on the drag brace of the left and right 
MLG, in accordance with Part 1 of Jetstream Service Bulletin J41-32-
049, Revision 1, dated January 15, 1996.

    Note 3: Accomplishment of the visual inspection in accordance 
with Part 1 of Jetstream Service Bulletin J41-32-049, dated November 
21, 1995, is considered acceptable for compliance with this 
paragraph.

    (1) If no cracking is detected, repeat this inspection 
thereafter at intervals not to exceed 50 hours time-in-service until 
the requirements of paragraph (b) of this AD have been accomplished.
    (2) If any cracking is detected, prior to further flight, 
replace the drag brace with a drag brace that has Jetstream part 
number (P/N) AIR84352-4 and a centralized lightening hole, in 
accordance with Part 2 of Jetstream Service Bulletin J41-32-049, 
Revision 1, dated January 15, 1996. This replacement constitutes 
terminating action for the repetitive inspections and replacement of 
that brace required by paragraphs (a) and (b), respectively, of this 
AD.

    Note 4: Accomplishment of the replacement in accordance with 
Part 2 of Jetstream Service Bulletin J41-32-049, dated November 21, 
1995, is considered acceptable for compliance with paragraphs (a)(2) 
and (b) of this AD.

    (b) Within two years after the effective date of this AD, 
replace any MLG drag brace that has P/N AIR84352-0 through AIR84352-
4, inclusive, and an offset lightening hole, with a drag brace that 
has Jetstream P/N AIR84352-4 and a centralized lightening hole, in 
accordance with Part 2 of Jetstream Service Bulletin J41-32-049, 
Revision 1, dated January 15, 1996. This replacement constitutes 
terminating action for the repetitive inspections required by 
paragraph (a) of this AD.
    (c) 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, Standardization Branch, ANM-113, 
FAA, Transport 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, 
Standardization Branch, ANM-113.

    Note 5: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Standardization Branch, ANM-113.

    (d) 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 November 5, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-28868 Filed 11-8-96; 8:45 am]
BILLING CODE 4910-13-P