Airworthiness Directives; Boeing Model 737-100, -200, -300, -400, and -500 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-251-AD; Amendment 39-11314; AD 99-19-27]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 737-100, -200, -300, -400,

and -500 Series 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 Boeing Model 737-100, -200, -300, -400, and -500

series airplanes, that requires a one-time inspection of the main

landing gear (MLG) wheel assemblies to determine whether certain parts

are installed, and follow-on corrective actions, if necessary. For

certain airplanes, this amendment also requires eventual modification

of MLG wheel assemblies, which terminates the requirements of this AD.

This amendment is prompted by incidents of multiple tie bolt failures

on certain BFGoodrich wheel assemblies. The actions specified by this

AD are intended to prevent failure of multiple tie bolts of MLG wheel

assemblies, which could result in failure of the wheel rim, rapid

release of tire pressure, and possible consequent damage to the

airplane and injury to passengers and flightcrew.

DATES: Effective October 20, 1999.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of October 20, 1999.

ADDRESSES: The service information referenced in this AD may be

obtained from BFGoodrich Aerospace, Aircraft Wheels and Brakes, P.O.

Box 340, Troy, Ohio 45373. 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: Don Kurle, Senior Aerospace Engineer,

Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane

Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue,

SW., Renton, Washington 98055-4056; telephone (425) 227-2798; fax (425)

227-1181.

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 all Boeing Model 737-100, -200, -

300, -400, and -500 series airplanes was published in the Federal

Register on November 18, 1998 (63 FR 64013). That action proposed to

require a one-time inspection of the main landing gear (MLG) wheel

assemblies to determine whether certain parts are installed, and

follow-on corrective actions, if necessary. For certain airplanes, that

action also proposed to require eventual modification of MLG wheel

assemblies, which would terminate the requirements of this AD.

Comments

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comments received.

Support for the Proposal

One commenter has no objection to the proposed AD.

Explanation of Change Made to Proposal

The FAA has clarified the inspection requirement contained in the

proposed AD. Whereas the proposed specified a visual inspection, the

FAA has revised paragraphs (b)(2)(i) and (b)(2)(ii) of this final rule

to clarify that its intent is to require a detailed visual inspection.

Additionally, Note 2 has been added to the final rule to define that

inspection.

Request to Revise Applicability

One commenter requests that the applicability of the proposed AD be

revised to read, ``All Model 737-100, -200, -300, -400, and -500 series

airplanes certificated in any category, having wheel assemblies

manufactured by BFGoodrich installed.'' In support of its request, the

commenter states that the current applicability does not exclude

airplanes that do not have BFGoodrich wheel and brake assemblies

installed.

The FAA does not concur. The purpose of the AD is to assure that

all operators verify part numbers, determine if BFGoodrich wheel

assemblies are installed, and if so, take appropriate action. No change

to the applicability section of the AD is made in this regard. However,

the FAA recognizes that a records review can verify part numbers, and

as discussed below, paragraph (a) of the AD has been revised to

essentially accomplish the result sought by the commenter.

Request to Revise Inspection Procedures

Several commenters request that the proposed inspection procedures

of the main landing gear (MLG) wheel assemblies be revised to allow for

a records review in lieu of a visual inspection to determine whether

certain parts are installed. In support of this request, the commenters

noted that other wheel assemblies (AlliedSignal) are not

interchangeable with BFGoodrich wheel assemblies, and since it is not

necessary to determine the type of wheel assemblies that are installed,

a review of records would be less expensive than a visual inspection.

The FAA concurs with the commenters' request to revise the

inspection procedures required by paragraph (a) of this AD. The FAA

recognizes that a visual inspection is not necessary to determine the

type of wheel assemblies that are installed. In light of this, the FAA

has revised paragraph (a) of this final rule to

[[Page 49972]]

require, ``an inspection of the MLG wheel assemblies or perform other

verifications (such as a records review) to determine the part number

(P/N) of each assembly.''

Request for Clarification of Discussion Section

One commenter requests that the FAA clarify the description in the

Discussion Section of the proposed AD of the tie bolt failures to

indicate that they occurred only on certain BFGoodrich wheel assemblies

that are installed on the main landing gear (MLG) of Boeing Model 737-

300 and -400 series airplanes.

The FAA agrees that the Discussion section of the proposed rule may

have been unclear regarding the incidents of tie bolt failures on

certain BFGoodrich wheel assemblies. The FAA acknowledges that no

reports of failures have been reported for Boeing Model 737-100, -200,

or -500 series airplanes. However, because the Discussion section is

not restated in the final rule, no change to this final rule is

necessary in this regard.

Request for Revision of Cost Impact Information

One commenter requests that the cost impact information of the

proposed AD be revised to clarify the usage of parts should an operator

elect to accomplish the replacement. The commenter requests adding a

phrase to clarify that if the same part number steel tie bolt fasteners

were used, such replacement will require no additional work hours if

accomplished during a regularly scheduled tire change.

The FAA concurs with the commenter's request. The cost impact

information, below, has been revised accordingly.

The same commenter requests that the cost impact information of the

proposed AD be revised to clarify the types of parts to be used. The

commenter requests adding a phrase to clarify that the modification of

the wheel assembly be accomplished by installing improved, Inconel tie

bolt fasteners, and that it would require no additional work hours per

airplane if the modification is accomplished during a regularly

scheduled tire change.

The FAA concurs with the commenter's request. The cost impact

information, below, has been revised accordingly.

Request for Clarification of Requirements

One commenter requests that the proposed rule be revised to clarify

certain requirements. The commenter suggests that additional

information be provided to clarify the visual inspections,

replacements, and terminating action.

The FAA does not concur. The FAA acknowledges the comment, however,

the commenter did not make any specific recommendations. Therefore, no

change to the final rule in this regard 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 with the changes previously

described. The FAA has determined that these changes will neither

increase the economic burden on any operator nor increase the scope of

the AD.

Cost Impact

There are approximately 460 Model 737-100, -200, -300, -400, and -

500 series airplanes of the affected design in the worldwide fleet. The

FAA estimates that 118 airplanes of U.S. registry will be affected by

this AD.

It will take approximately 1 work hour per airplane to accomplish

the required one-time inspection, at an average labor rate of $60 per

work hour. Based on these figures, the cost impact of the one-time

inspection required by this AD on U.S. operators is estimated to be

$7,080, or $60 per airplane.

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.

Should an operator elect to accomplish the repetitive visual

inspection, it would take approximately 1 work hour per airplane to

accomplish, at an average labor rate of $60 per work hour. Based on

these figures, the cost impact of the repetitive inspections, if

accomplished, is estimated to be $60 per airplane, per inspection

cycle.

Should an operator elect to accomplish the replacement using the

same part number steel tie bolt fasteners, such replacement would

require no additional work hours if accomplished during a regularly

scheduled tire change. Required parts would cost $2,840 per airplane

($710 per wheel). Based on these figures, the cost impact of the

replacement, if accomplished, is estimated to be $2,840 per airplane,

per replacement cycle.

Should an operator elect to accomplish the revisions to the FAA-

approved maintenance program, it would take approximately 1 work hour

per airplane to accomplish, at an average labor rate of $60 per work

hour. Based on these figures, the cost impact of the maintenance

program revision, if accomplished, is estimated to be $60 per airplane.

Should an operator be required to accomplish the necessary

modification of the wheel assembly by installing improved Inconel tie

bolt fasteners, it would require no additional work hours per airplane,

if the modification is accomplished during a regularly scheduled tire

change. Required parts would cost $4,848 per airplane ($1,212 per

wheel). Based on these figures, the cost impact of any necessary

modification is estimated to be $4,848 per airplane.

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:

[[Page 49973]]

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:

99-19-27 Boeing: Amendment 39-11314. Docket 98-NM-251-AD.

Applicability: Model 737-100, -200, -300, -400, and -500 series

airplanes, 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 (e) 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 multiple tie bolts of main landing gear

(MLG) wheel assemblies, which could result in failure of the wheel

rim, rapid release of tire pressure, and possible consequent damage

to the airplane and injury to passengers and flightcrew, accomplish

the following:

(a) Within 60 days after the effective date of this AD, perform

an inspection of the MLG wheel assemblies or perform other

verifications (such as a records review) to determine the part

number (P/N) of each assembly. If no wheel assembly manufactured by

BFGoodrich Aerospace and having P/N 3-1398-1, 3-1439-2, or 3-1439-3

is installed on the airplane, no further action is required by this

AD.

(b) Except as provided by paragraph (d) of this AD, if any MLG

wheel assembly manufactured by BFGoodrich Aerospace and having P/N

3-1398-1, 3-1439-2, or 3-1439-3 is installed on the airplane, within

60 days after the effective date of this AD, accomplish the actions

specified by paragraph (b)(1) or (b)(2) of this AD.

(1) Accomplish the actions specified by (b)(1)(i) or (b)(1)(ii)

of this AD.

(i) Replace all tie bolts, nuts, and washers of the MLG wheel

assembly with parts having the same P/N's, in accordance with the

BFGoodrich component maintenance manual. Thereafter, repeat the

replacement of tie bolts, nuts, and washers, at intervals not to

exceed 5 tire changes, until the actions specified by paragraph

(b)(2) or paragraph (c) of this AD have been accomplished. Or

(ii) Perform a detailed visual inspection to detect fractures of

any of the 16 tie bolts on each MLG wheel assembly, in accordance

with the Boeing 737 airplane maintenance manual. Thereafter, repeat

the inspection at intervals not to exceed 100 flight cycles until

the actions specified by paragraph (b)(2) or paragraph (c) of this

AD have been accomplished. If any fracture of any tie bolt is found

during any inspection performed in accordance with this requirement,

prior to further flight, replace the tie bolt, nut, and washer, in

accordance with the BFGoodrich component maintenance manual, with

new parts having the same P/N's.

Note 2: For the purposes of this AD, a detailed visual

inspection is defined as: ``An intensive visual examination of a

specific structural area, system, installation, or assembly to

detect damage, failure, or irregularity. Available lighting is

normally supplemented with a direct source of good lighting at

intensity deemed appropriate by the inspector. Inspection aids such

as mirror, magnifying lenses, etc. may be used. Surface cleaning and

elaborate access procedures may be required.''

(2) Revise the FAA-approved maintenance program as specified in

paragraph (b)(2)(i) or (b)(2)(ii) of this AD.

(i) Revise the FAA-approved maintenance program to require

replacement of all tie bolts, nuts, and washers of the MLG wheel

assembly with parts having the same P/N's, in accordance with the

BFGoodrich component maintenance manual, at intervals not to exceed

5 tire changes. Or

(ii) Revise the FAA-approved maintenance program to require a

detailed visual inspection to detect fractures of any of the 16 tie

bolts on each MLG wheel assembly, in accordance with the Boeing 737

airplane maintenance manual, at intervals not to exceed 100 flight

cycles. If any fracture of any tie bolt is found during any

inspection performed in accordance with this requirement, prior to

further flight, replace the tie bolt, nut, and washer, in accordance

with the BFGoodrich component maintenance manual, with new parts

having the same P/N's.

Note 3: After the maintenance program has been revised to

include the procedures specified in paragraph (b)(2)(i) or

(b)(2)(ii) of this AD, operators are not required to subsequently

record AD compliance each time the replacement or inspection is

performed.

(c) If any MLG wheel assembly manufactured by BFGoodrich

Aerospace and having P/N 3-1398-1, 3-1439-2, or 3-1439-3 is

installed on the airplane: Except as provided by paragraph (d) of

this AD, within 2 years after the effective date of this AD, modify

any BFGoodrich Aerospace wheel assembly, having P/N 3-1398-1, 3-

1439-2, or 3-1439-3; by replacing all existing tie bolts, nuts, and

washers, with new, improved parts; and by converting the P/N of the

MLG wheel assembly to 3-1398-2 (for BFGoodrich wheel assemblies

having the old P/N 3-1398-1), 3-1439-5 (for BFGoodrich wheel

assemblies having the old P/N 3-1439-2), or 3-1439-6 (for BFGoodrich

wheel assemblies having the old P/N 3-1439-3), as applicable; in

accordance with BFGoodrich Aerospace Service Bulletin 3-1439-32-13,

or BFGoodrich Aerospace Service Bulletin 3-1398-32-16, both dated

August 20, 1993, as applicable. Such modification constitutes

terminating action for the requirements of this AD, and the FAA-

approved maintenance program procedures specified by paragraph

(b)(2) of this AD may be removed following accomplishment of the

requirements of this paragraph.

(d) Airplanes on which the modification required by paragraph

(c) of this AD is accomplished within the compliance time specified

in paragraph (b) of this AD are not required to accomplish the

actions required by paragraph (b).

Alternative Methods of Compliance

(e) 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, Seattle Aircraft Certification

Office (ACO), 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, Seattle ACO.

Note 4: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Seattle ACO.

Special Flight Permits

(f) 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.

Incorporation by Reference

(g) The modification shall be done in accordance with BFGoodrich

Aerospace Service Bulletin 3-1439-32-13, dated August 20, 1993; or

BFGoodrich Aerospace Service Bulletin 3-1398-32-16, dated August 20,

1993, as applicable. 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 BFGoodrich

Aerospace, Aircraft Wheels and Brakes, P.O. Box 340, Troy, Ohio

45373. 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.

(h) This amendment becomes effective on October 20, 1999.

Issued in Renton, Washington, on September 2, 1999.

Dorenda D. Baker,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 99-23474 Filed 9-14-99; 8:45 am]

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