AD Amdt-39-10888

[Federal Register Volume 63, Number 222 (Wednesday, November 18, 1998)]
[Rules and Regulations]
[Pages 63975-63977]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 98-30536]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-141-AD; Amendment 39-10888; AD 98-24-01]
RIN 2120-AA64


Airworthiness Directives; British Aerospace (Jetstream) Model 
4101 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 British Aerospace (Jetstream) Model 4101 
airplanes, that requires repetitive detailed visual inspections to 
detect cracking or other damage of certain diaphragm support structures 
of the forward equipment compartment; and repair, if necessary. This 
amendment is prompted by the issuance of mandatory continuing 
airworthiness information by a foreign civil airworthiness authority. 
The actions specified by this AD are intended to detect and correct 
failure of the two diaphragms that support the upper structure of the 
forward equipment compartment, which could accelerate fatigue damage in 
adjacent structure and result in reduced structural integrity of the 
airframe.

DATES: Effective December 23, 1998.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of December 23, 1998.

ADDRESSES: The service information referenced in this AD may be 
obtained from AI(R) American Support, Inc., 13850 Mclearen Road, 
Herndon, Virginia 20171. 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 
Office of the Federal Register, 800 North Capitol Street, NW., suite 
700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Norman B. Martenson, Manager, 
International Branch, ANM-116, FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
227-2110; fax (425) 227-1149.

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 British Aerospace 
(Jetstream) Model 4101 airplanes was published in the Federal Register 
on January 8, 1998 (63 FR 1074). That action proposed to require 
repetitive detailed visual inspections to detect cracking or other 
damage of certain diaphragm support structures of the forward equipment 
compartment; and repair, if necessary.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Request To Allow Flight With Known Cracks

    One commenter, the manufacturer, requests that the proposed AD be 
revised to allow operators to continue operation of an unrepaired 
airplane for up to 300 flight cycles following detection of cracking of 
certain diaphragm support structures of the forward equipment 
compartment. The commenter states that, during full-scale fatigue 
testing, failure of both diaphragms occurred, and the test continued 
for another 24,000 flight cycles before either of the diaphragms was 
replaced. The commenter further states that, during the period between 
detection of the cracking and replacement of the diaphragms, no damage 
was detected that would cause concern regarding the structural 
integrity of the airplane. In light of these fatigue testing data, the 
commenter notes that the compliance time of 300 flight cycles after 
detection of cracking, as specified in the service bulletin, is already 
a very conservative threshold.
    The FAA does not concur. It is the FAA's policy to require repair 
of known cracks prior to further flight, except in certain cases of 
unusual need, as discussed below.
    This policy is based on the fact that such damaged airplanes do not 
conform to the FAA-certificated type design and, therefore, are not 
airworthy until a properly approved repair is incorporated. The FAA's 
policy regarding flight with known cracks does allow deferral of 
repairs in certain cases, if there is an unusual need for a temporary 
deferral. Unusual needs include such circumstances as legitimate 
difficulty in acquiring parts to accomplish repairs. Because the FAA is 
not aware of any unusual need for repair deferral in regard to this AD, 
the FAA has determined that any subject diaphragm that is found to be 
cracked must be repaired prior to further flight in accordance with a 
method approved by the FAA. However, operators may request approval of 
an alternative method of compliance if data are

[[Page 63976]]

provided to substantiate that such a method would provide an acceptable 
level of safety.

Request To Remove Requirement for Repetitive Inspections After 
Repair

    One commenter, the manufacturer, requests that the requirement to 
continue the repetitive inspections following the installation of an 
improved diaphragm be removed from the proposal. The commenter states 
that, during full-scale fatigue testing, no new cracking of the 
diaphragms was detected following repair of the diaphragms until 65,700 
total flight cycles. Based on these data, the commenter states that an 
inspection threshold of 20,000 landings after installation of a new 
diaphragm, and a repetitive inspection interval thereafter of 6,000 
landings, would be adequate to ensure that any cracking would be 
detected in a timely manner. The commenter further states that such an 
inspection threshold and repetitive interval will be added to the 
Airworthiness Limitations specified in Chapter 5 of the Jetstream 4100 
Airplane Maintenance Manual (AMM).
    The FAA does not concur with the commenter's request to remove the 
requirement for repetitive inspections of the diaphragm following 
replacement. First, the commenter implies that an improved diaphragm is 
available; however, the FAA is not aware of any such improved part. 
Further, the lack of specific data in the service bulletin regarding 
the repair prevents the FAA from determining whether elimination of the 
repetitive inspection requirement is warranted. Also, though the FAA 
acknowledges the manufacturer's intent to incorporate a program of 
repetitive inspections into the Airworthiness Limitations specified in 
Chapter 5 of the AMM, the FAA would have to engage in further 
rulemaking in order to require such an inspection program.
    Although the FAA does not concur with the request to remove the 
repetitive inspection requirement following accomplishment of a repair, 
paragraph (b) of this AD contains a provision for requesting approval 
of an alternative method of compliance to address operators' unique 
circumstances. In accordance with paragraph (b) of this AD, an operator 
may submit a repair method, along with a proposed repetitive inspection 
program or data to support elimination of the repetitive inspection 
requirement, for consideration by the FAA. No change to the final rule 
is necessary.

Conclusion

    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule as proposed.

Interim Action

    This is considered to be interim action until final action is 
identified, at which time the FAA may consider further rulemaking.

Cost Impact

    The FAA estimates that 55 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 that the average 
labor rate is $60 per work hour. Based on these figures, the cost 
impact of the AD on U.S. operators is estimated to be $3,300, or $60 
per airplane, per inspection cycle.
    The 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.

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:

98-24-01  British Aerospace Regional Aircraft [Formerly Jetstream 
Aircraft Limited British Aerospace (Commercial Aircraft) Limited]: 
Amendment 39-10888. Docket 97-NM-141-AD.

    Applicability: Jetstream Model 4101 airplanes, constructors 
numbers 41004 through 41098 inclusive; 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 detect and correct failure of the two diaphragms that support 
the upper structure of the forward equipment compartment, which 
could accelerate fatigue damage in adjacent structure and result in 
reduced structural integrity of the airframe, accomplish the 
following:
    (a) Prior to the accumulation of 4,500 total landings, or within 
300 landings after the effective date of this AD, whichever occurs 
later: Perform a detailed visual inspection to detect cracking or 
other damage of the diaphragms installed between station 4 and 
station 8 of the forward fuselage, in accordance with Jetstream 
Alert Service Bulletin J41-A53-023, dated December 2, 1996.
    (1) If no cracking or other damage is detected, repeat the 
inspection thereafter at intervals not to exceed 3,000 landings.
    (2) If any cracking or other damage is detected, prior to 
further flight, repair the diaphragm in accordance with a method 
approved by the Manager, International Branch, ANM-116, FAA, 
Transport Airplane Directorate. Thereafter, repeat the inspection at 
intervals not to exceed 3,000 landings.
    (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,

[[Page 63977]]

International Branch, ANM-116. Operators shall submit their requests 
through an appropriate FAA Principal Maintenance Inspector, who may 
add comments and then send it to the Manager, International Branch, 
ANM-116.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the International Branch, ANM-116.

    (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.
    (d) The inspections shall be done in accordance with Jetstream 
Alert Service Bulletin J41-A53-023, dated December 2, 1996. 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 AI(R) American Support, Inc., 13850 
Mclearen Road, Herndon, Virginia 20171. Copies may be inspected at 
the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., 
Renton, Washington; or at the Office of the Federal Register, 800 
North Capitol Street, NW., suite 700, Washington, DC.

    Note 3: The subject of this AD is addressed in British 
airworthiness directive 007-12-96.

    (e) This amendment becomes effective on December 23, 1998.

    Issued in Renton, Washington, on November 9, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-30536 Filed 11-17-98; 8:45 am]
BILLING CODE 4910-13-P