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

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).

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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]

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