[Federal Register Volume 61, Number 175 (Monday, September 9, 1996)]
[Proposed Rules]
[Pages 47459-47462]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-22919]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-NM-194-AD]
RIN 2120-AA64


Airworthiness Directives; de Havilland, Inc., Model DHC-8-100 and 
-300 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Supplemental notice of proposed rulemaking; reopening of 
comment period.

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SUMMARY: This document revises an earlier proposed airworthiness 
directive (AD), applicable to de Havilland Model DHC-8-100 and -300 
series airplanes. That proposal would have superseded a previously-
issued AD that currently requires repetitive inspections to detect 
cracks of the upper drag strut trunnion fittings of the nose landing 
gear and to verify tightness of the fitting attachment bolts. It also 
would have required the

[[Page 47460]]

installation of a modification to terminate the repetitive inspections. 
This new action revises the proposed rule by proposing to require a 
different terminating modification.
    This action is prompted by data indicating that the previously 
proposed terminating modification is not effective.
    The actions specified by the proposed AD are intended to prevent 
failure of the upper drag strut trunnion fittings of the nose landing 
gear, which could lead to collapse of the nose landing gear.

DATES: Comments must be received by September 30, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 93-NM-194-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 Bombardier, Inc., Bombardier Regional Aircraft Division, 
Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada. This information 
may be examined at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT: Jon Hjelm, Aerospace Engineer, 
Airframe Branch, ANE-172, FAA, Engine and Propeller Directorate, New 
York Aircraft Certification Office, 181 South Franklin Avenue, Room 
202, Valley Stream, New York 11581; telephone (516) 256-7523; fax (516) 
568-2716.

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 93-NM-194-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. 93-NM-194-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to add an airworthiness directive (AD), applicable to 
certain de Havilland Model DHC-8-100 and -300 series airplanes, was 
published as a notice of proposed rulemaking (NPRM) in the Federal 
Register on February 7, 1994 (59 FR 5554). That NPRM would have 
superseded AD 93-08-03, amendment 39-8550 (58 FR 25549, April 27, 
1993), which currently requires repetitive inspections to detect cracks 
of the upper drag strut trunnion fittings of the nose landing gear and 
to verify tightness of the fitting attachment bolts. It also requires 
replacement of the fittings or fasteners, if necessary. AD 93-08-03 was 
prompted by reports of cracks detected in two trunnion fittings which 
retain and support the nose landing gear upper drag link. The 
requirements of AD 93-08-03 are intended to prevent failure of the 
upper drag strut trunnion fittings of the nose landing gear, which 
could lead to collapse of the nose landing gear.
    The NPRM would have added a requirement to the AD to modify the 
upper drag strut trunnion fittings and fasteners of the nose landing 
gear. Once the modification was installed, the repetitive inspections 
could be terminated.

Actions Since Issuance of Previous Proposal

    Since the issuance of that NPRM, Transport Canada Aviation, which 
is the airworthiness authority for Canada, has advised the FAA that the 
modification proposed as terminating action for AD 93-08-03 has been 
determined to be ineffective. Data indicate that installation of 
Modification 8/1880, which is described in de Havilland Service 
Bulletin S.B. 8-53-45, dated July 12, 1993, may recreate the original 
problem that the AD intends to correct.

Explanation of New Relevant Service Information

    De Havilland has issued Service Bulletin S.B. 8-53-49, dated June 
30, 1995, that describes procedures for installing Modification 8/2139. 
This modification entails the installation of strengthened drag link 
trunnion fittings and adjacent right-angled support fittings, both of 
which will reduce premature fatigue. Additionally, the modification 
involves the installation of fasteners with larger diameters to attach 
the fittings, and installation of a new sensor support bracket.
    Transport Canada Aviation approved the technical content of this 
service bulletin and issued Revision 3 of Canadian airworthiness 
directive CF-92-18, dated August 2, 1995, in order to assure the 
continued airworthiness of these airplanes in Canada. That revised 
Canadian airworthiness directive specifies that Modification 8/2139 is 
an optional terminating action for the repetitive inspections required 
of the drag strut trunnion fittings (required by the original issue of 
CF-92-18).
    Additionally, de Havilland has issued Revision ``D'' of Service 
Bulletin S.B. A8-53-40, dated June 30, 1995. This revision is 
essentially identical in its technical content to the previous 
revisions of the service bulletin, but contains updated effectivity 
information and new references to Modification 8/2139.

FAA's Conclusions

    This airplane model is manufactured in Canada 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, Transport Canada Aviation has kept 
the FAA informed of the situation described above. The FAA has examined 
the findings of Transport Canada Aviation, reviewed all available 
information, and determined that similar AD action is necessary for 
products of this type design that are certificated for operation in the 
United States.

Explanation of the New Proposed Requirements of the 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, this new proposed AD would

[[Page 47461]]

supersede AD 93-08-03 to continue to require inspection to detect 
cracks of the upper drag strut trunnion fittings of the nose landing 
gear, inspection to verify tightness of the fitting attachment bolts, 
and replacement of the fittings or fasteners, if necessary. 
Additionally, this new proposed AD would require the installation of 
Modification 8/2139. When accomplished, this modification would 
terminate the need for the currently required inspections. The 
modification would be required to be accomplished in accordance with de 
Havilland Service Bulletin S.B. 8-53-49, described previously.
    The proposed AD also would limit the applicability of the rule to 
exclude those airplanes on which Modification 8/2139 has been installed 
previously. The manufacturer has installed Modification 8/2139 prior to 
delivery of airplanes having serial numbers 396 and subsequent. 
Airplanes so modified are not subject to the unsafe condition addressed 
by this proposed AD.
    Paragraph (a) of the proposed AD has been revised to reference 
Revision ``D'' of de Havilland Service Bulletin S.B. A8 53-40, dated 
June 30, 1995, as an additional appropriate source of service 
information.

Differences Between the Proposed Rule and Related Canadian AD

    Operators should note that, whereas the Canadian AD allows 
installation of Modification 8/2139 as an optional action, this 
proposed AD would mandate its installation as terminating action. 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 modification requirement is in consonance with these 
considerations.

Reopening of Period for Public Comment

    Since the changes made to this proposal expand the scope of the 
originally proposed rule, the FAA has determined that it is necessary 
to reopen the comment period to provide additional opportunity for 
public comment.

Cost Impact

    The FAA estimates that 146 airplanes of U.S. registry would be 
affected by this proposed AD.
    Accomplishment of the currently required inspections takes 
approximately 1 work hour per airplane, at an average labor rate of $60 
per hour. Based on these figures, the cost impact of the currently 
required inspection actions on U.S. operators is estimated to be 
$8,760, or $60 per airplane, per inspection.
    The proposed modification action would take approximately 18 work 
hours per airplane to accomplish the proposed actions, at an average 
labor rate of $60 per work hour. Required parts would cost 
approximately $3,325 per airplane. Based on these figures, the cost 
impact of the proposed AD on U.S. operators is estimated to be 
$638,725, or $4,405 per airplane.
    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. However, based on the 
effective date and compliance time of AD 93-08-03, it can be reasonably 
assumed that the majority of affected U.S. operators already have 
initiated and are currently conducting the inspections required by that 
AD.

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:

De Havilland, Inc.: Docket 93-NM-194-AD. Supersedes AD 93-08-03, 
amendment 39-8550.

    Applicability: Model DHC-8-102, -103, -301, -311, and -314 
series airplanes; having serial numbers 003 through 395, inclusive, 
but excluding serial numbers 011, 362, and 391; on which 
Modification 8/2139 (as described in de Havilland Service Bulletin 
S.B. 8-53-49, dated June 30, 1995) has not been accomplished; 
certificated in any category.

    Note 1: 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 (d) 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 failure of the upper drag strut trunnion fittings of 
the nose landing gear, which could lead to collapse of the nose 
landing gear, accomplish the following:
    (a) Within 500 landings after May 27, 1993 (the effective date 
of AD 93-08-03, Amendment 39-8550), unless accomplished within the 
last 500 landings, conduct a visual inspection of both upper drag 
strut trunnion fittings of the nose landing gear to detect cracks; 
and conduct an inspection of the fitting attachment bolts to verify 
tightness; in accordance with de Havilland DHC-8 Alert Service 
Bulletin S.B. A8-53-40, Revision `A', dated June 12, 1992; or 
Revision `B', dated February 24, 1993; or Revision `D', dated June 
30, 1995.
    (1) If no crack is detected in the upper drag strut trunnion 
fittings of the nose landing

[[Page 47462]]

gear, and no looseness is detected in the fitting attachment bolts, 
repeat the inspections at intervals not to exceed 1,000 landings 
until the modification required by paragraph (b) of this AD is 
accomplished.
    (2) If any crack is detected on either fitting, prior to further 
flight, replace both fittings with confirmed crack-free fittings in 
accordance with the service bulletin. After such replacement, the 
inspections required by this paragraph must continue at intervals 
not to exceed 1,000 landings until the modification required by 
paragraph (b) of this AD is accomplished.
    (3) If any fitting attachment bolt is found to be loose during 
the initial inspection, prior to further flight, replace the 
fasteners (nut, washer, and bolt) that secure the fitting, in 
accordance with the service bulletin. After such replacement, the 
inspections required by this paragraph must continue at intervals 
not to exceed 1,000 landings until the modification required by 
paragraph (b) of this AD is accomplished.
    (4) If any fastener is found to be loose during any repetitive 
inspection required by this AD, prior to further flight, tighten the 
bolt to the value specified in the service bulletin.
    (b) Within 6 months after the effective date of this AD, install 
Modification 8/2139 in accordance with de Havilland Service Bulletin 
S.B. 8-53-49, dated June 30, 1995. Installation of this modification 
constitutes terminating action for the inspection requirements of 
this AD.
    (c) Installation of Modification 8/2139, in accordance with de 
Havilland Service Bulletin S.B. 8-53-49, dated June 30, 1995, 
constitutes terminating action for the inspections required by this 
AD.
    (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, New York Aircraft Certification 
Office (ACO), ANE-170, FAA, Engine and Propeller Directorate. 
Operators shall submit their requests through an appropriate FAA 
Principal Maintenance Inspector, who may add comments and then send 
it to the Manager, New York ACO.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the New York 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.

    Issued in Renton, Washington, on September 3, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-22919 Filed 9-6-96; 8:45 am]
BILLING CODE 4910-13-U