[Federal Register Volume 59, Number 25 (Monday, February 7, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-2658]


[[Page Unknown]]

[Federal Register: February 7, 1994]


-----------------------------------------------------------------------


DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 93-NM-194-AD]

 

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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: This document proposes the supersedure of an existing 
airworthiness directive (AD), applicable to certain de Havilland, Inc., 
Model DHC-8-100 and -300 series airplanes, that currently requires 
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. This action would require a terminating modification that 
would eliminate the need for repetitive inspections; and would limit 
the applicability of the rule. This proposal is prompted by the 
development of a modification that positively addresses the identified 
unsafe condition. 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 April 4, 1994.

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 a.m. and 3 p.m., Monday through Friday, except 
Federal holidays.
    The service information referenced in the proposed rule may be 
obtained from de Havilland, Inc., Garratt Boulevard, Downsview, Ontario 
M3K 1Y5, Canada. This information may be examined at the FAA, Transport 
Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at 
the FAA, Engine and Propeller Directorate, New York Aircraft 
Certification Office, 181 South Franklin Avenue, room 202, Valley 
Stream, New York.

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) 791-6220; fax (516) 
791-9024.

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

    On April 15, 1993, the FAA issued AD 93-08-03, Amendment 39-8550 
(58 FR 25549, April 27, 1993), applicable to certain de Havilland Model 
DHC-8-100 and -300 series airplanes, 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. That action 
was prompted by reports of cracks detected in two trunnion fittings 
which retain and support the nose landing gear upper drag link. Studies 
indicate that these fittings have a low fatigue life. Initial 
investigations revealed that ground handling caused higher loads than 
initially predicted, primarily due to towing of the airplane. Cracked 
trunnion fittings may be further aggravated by loose fasteners (loose 
nuts, washers, and bolts). The requirements of that 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.
    Since issuance of that AD, the manufacturer has designed a 
modification of the nose landing gear drag link trunnion fittings and 
fasteners that will significantly improve the fatigue life of these 
parts and should eliminate the possibility of cracked fittings. De 
Havilland has issued Service Bulletin S.B. 8-53-45, dated July 12, 
1993, that describes procedures for installation of Modification 8/
1880, which entails replacing both currently-installed upper drag strut 
trunnion fittings and fasteners of the nose landing gear with new, 
improved upper drag strut trunnion fittings and new fasteners, and 
installation of a new sensor bracket. Installation of new fasteners 
will secure the fittings. The grease nipple in each new fitting is 
installed at an angle to the horizontal to allow easier access for 
lubrication. Transport Canada Aviation, which is the airworthiness 
authority for Canada, has approved this service bulletin, but it has 
not classified it as mandatory.
    The FAA has reviewed Modification 8/1880 and has determined that 
implementation of this modification will positively address the unsafe 
condition identified as failure of the upper drag strut trunnion 
fittings of the nose landing gear, which could lead to collapse of the 
nose landing gear.
    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 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 AD action is necessary for products of 
this type design that are certificated for operation in the United 
States.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of the same type design registered 
in the United States, the proposed AD would 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, the proposed AD 
would require incorporation of Modification 8/1880. When accomplished, 
this modification would terminate the need for the currently required 
inspections. The actions would be required to be accomplished in 
accordance with the service bulletin described previously.
    Additionally, the proposed AD would limit the applicability of the 
rule to exclude those airplanes on which Modification 8/1880 has been 
accomplished previously. The manufacturer has installed Modification 8/
1880 on airplanes having serial numbers 385 and subsequent prior to 
delivery. Airplanes so modified are not subject to the unsafe condition 
addressed by this proposed AD.
    The FAA estimates that 125 airplanes of U.S. registry would be 
affected by this proposed AD, that it would take approximately 9 work 
hours per airplane to accomplish the proposed actions, and that the 
average labor rate is $55 per work hour. Required parts would cost 
approximately $1,860 per airplane. Based on these figures, the total 
cost impact of the proposed AD on U.S. operators is estimated to be 
$294,375, or $2,355 per airplane.
    The total 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.
    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 14 
CFR part 39 of the Federal Aviation Regulations as follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing amendment 39-8550 (58 FR 
25549, April 27, 1993), and by adding a new airworthiness directive 
(AD), to read as follows:

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 on which Modification 8/1880 (as described in de 
Havilland Service Bulletin S.B. 8-53-45, dated July 12, 1993) has 
not been accomplished; certificated in any category.
    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.
    (1) If no crack is detected in the upper drag strut trunnion 
fittings of the nose landing 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 8/1880 (which entails replacing both of the currently-
installed upper drag strut trunnion fittings and fasteners of the 
nose landing gear with new, improved upper drag strut trunnion 
fittings and new fasteners, and installing a new sensor bracket), in 
accordance with de Havilland Service Bulletin S.B. 8-53-45, dated 
July 12, 1993. Installation of this modification constitutes 
terminating action for the inspection requirements of this AD.
    (c) Installation of Modification 8/1880, in accordance with de 
Havilland Service Bulletin S.B. 8-53-45, dated July 12, 1993, 
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: 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 
Federal Aviation Regulations (FAR) 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 February 1, 1994.
Darrell M. Pederson,
Acting Manager, Aircraft Certification Service.
[FR Doc. 94-2658 Filed 2-4-94; 8:45 am]
BILLING CODE 4910-13-U