Airworthiness Directives; Boeing Model 737 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-148-AD; Amendment 39-11048; AD 99-04-23]

RIN 2120-AA64

Airworthiness Directives; Boeing Model 737 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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

SUMMARY: This amendment adopts a new airworthiness directive (AD),

applicable to certain Boeing Model 737 series airplanes, that requires

repetitive ultrasonic inspections to detect broken bolts that attach

the terminal support fittings to the upper part of the Body Station

1088 bulkhead, and corrective actions, if necessary. This amendment

also requires eventual replacement of the existing bolts with new,

improved bolts, which, when accomplished, terminates the repetitive

inspection requirements of this AD. This amendment is prompted by

reports that bolts that attach the terminal support fittings to the

upper part of the bulkhead were found broken. The actions specified by

this AD are intended to prevent such broken bolts, which could result

in reduced structural integrity of the vertical fin installation and

possible loss of the vertical fin.

DATES: Effective March 29, 1999.

The incorporation by reference of certain publications listed in

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

of March 29, 1999.

ADDRESSES: The service information referenced in this AD may be

obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle,

Washington 98124-2207. This information may be examined at the

[[Page 8501]]

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: Rick Kawaguchi, Aerospace Engineer,

Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle

Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,

Washington 98055-4056; telephone (425) 227-1153; 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 certain Boeing Model 737 series

airplanes was published in the Federal Register on July 15, 1998 (63 FR

38116). That action proposed to require repetitive ultrasonic

inspections to detect broken bolts that attach the terminal support

fittings to the upper part of the Body Station 1088 bulkhead, and

corrective actions, if necessary. That action also proposed to require

eventual replacement of the existing bolts with new, improved bolts,

which, when accomplished, would terminate the requirements of the AD.

Comments Received

Interested persons have been afforded an opportunity to participate

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

the comments received.

Several commenters support the proposed rule.

Request to Revise Applicability of the AD

One commenter requests that the applicability of the proposed AD be

revised to list the affected airplanes by specific model number. The

commenter states that the proposed applicability could cause undue

confusion because the next generation (737-600/-700/-800) series

airplanes will start over with line number 001, and the proposal does

not apply to these next generation airplanes.

The FAA concurs with the commenter's request. The FAA has verified

that the cumulative line numbering of the next generation airplanes

(737-600/-700/-800) will be reset to begin with line number 001.

Additionally, the Model 737-400 and -500 series airplanes begin with

line number 1486 and have a design change implemented that specifies

installation of the Inconel bolts; therefore, those airplanes are not

subject to the identified unsafe condition. The applicability section

of the final rule has been revised to specify Model 737-100, -200 and -

300 series airplanes only, line numbers 1 through 1485.

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 change previously

described. The FAA has determined that this change will neither

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

the AD.

Cost Impact

There are approximately 1,485 airplanes of the affected design in

the worldwide fleet. The FAA estimates that 630 airplanes of U.S.

registry will be affected by this AD.

It will take approximately 3 work hours per airplane to accomplish

the required inspection, at an average labor rate of $60 per work hour.

Based on these figures, the cost impact of the inspection required by

this AD on U.S. operators is estimated to be $113,400, or $180 per

airplane, per inspection cycle.

It will take approximately 9 work hours per airplane to accomplish

the required replacement, at an average labor rate of $60 per work

hour. Required parts will cost approximately $471 per airplane. Based

on these figures, the cost impact of the replacement required by this

AD on U.S. operators is estimated to be $636,930, or $1,011 per

airplane.

The cost impact figures discussed above are 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:

99-04-23 Boeing: Amendment 39-11048. Docket 98-NM-148-AD.

Applicability: Model 737-100, -200, and -300 series airplanes,

line numbers 1 through 1485 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 (c) 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 broken bolts that attach the terminal support

fittings to the upper part of the Body Station (BS) 1088 bulkhead,

which could result in reduced structural integrity of the vertical

fin installation and possible loss of the vertical fin, accomplish

the following:

(a) Within 18 months after the effective date of this AD,

perform an ultrasonic inspection to detect broken bolts that attach

the terminal support fittings to the upper part of the BS 1088

bulkhead, in accordance with Boeing Service Bulletin 737-53-1107,

Revision 3, dated August 26, 1993; as revised

[[Page 8502]]

by Notice of Status Change 737-53-1107 NSC 3, dated June 9, 1994,

and Notice of Status Change 737-53-1107 NSC 4, dated September 22,

1994; or Boeing Service Bulletin 737-53-1107, Revision 4, dated

February 8, 1996.

(1) If no broken bolt is found, repeat the ultrasonic inspection

thereafter at intervals not to exceed 18 months.

(2) If any broken bolt is found, prior to further flight,

perform the actions specified in paragraph (b) of this AD.

(b) Prior to the accumulation of 20 years since date of

manufacture of the airplane, or within 18 months after the effective

date of this AD, whichever occurs later, remove all 16 H-11 steel

alloy bolts that attach the terminal support fittings to the upper

part of the bulkhead, and perform an eddy current inspection to

detect cracking or corrosion of the bolt holes, in accordance with

Figure 2 of Boeing Service Bulletin 737-53-1107, Revision 3, dated

August 26, 1993; as revised by Notice of Status Change 737-53-1107

NSC 3, dated June 9, 1994, and Notice of Status Change 737-53-1107

NSC 4, dated September 22, 1994; or Boeing Service Bulletin 737-53-

1107, Revision 4, dated February 8, 1996.

(1) If no cracking or corrosion is found, prior to further

flight, oversize all 16 bolt holes and install new Inconel bolts, in

accordance with Figure 2 of the service bulletin. Accomplishment of

this installation constitutes terminating action for the repetitive

inspection requirements of this AD.

(2) If any corrosion is found, prior to further flight, oversize

the bolt hole within the limits specified in Figure 2, Step 4, of

the service bulletin, and install a new Inconel bolt, in accordance

with Figure 2 of the service bulletin. Accomplishment of the

installation for all 16 bolt holes constitutes terminating action

for the repetitive inspection requirements of this AD. If corrosion

does not clean up within the limits specified in Figure 2, Step 4,

of the service bulletin, prior to further flight, repair in

accordance with a method approved by the Manager, Seattle Aircraft

Certification Office (ACO), FAA, Transport Airplane Directorate.

(3) If any cracking is found, prior to further flight, oversize

the bolt hole within the limits specified in Figure 2, Step 5, of

the service bulletin, and perform another eddy current inspection to

ensure cracks have been removed, in accordance with Figure 2 of the

service bulletin.

(i) If, after oversizing, no cracking is found, prior to further

flight, oversize the bolt hole again, and install a new Inconel

bolt, in accordance with Figure 2 of the service bulletin.

Accomplishment of the installation for all 16 bolt holes constitutes

terminating action for the repetitive inspection requirements of

this AD.

(ii) If, after oversizing, any cracking is found, prior to

further flight, repair in accordance with a method approved by the

Manager, Seattle ACO.

Note 2: Replacement of all H-11 steel alloy bolts accomplished

prior to the effective date of this AD, in accordance with Boeing

Service Bulletin 737-53-1107, dated October 15, 1987; Revision 1,

dated June 22, 1989; or Revision 2, dated September 10, 1992; is

considered acceptable for compliance with the applicable actions

specified in paragraph (b) of this AD.

(c) 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 ACO. 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 3: Information concerning the existence of approved

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

obtained from the Seattle ACO.

(d) 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.

(e) Except as provided by paragraphs (b)(2) and (b)(3)(ii) of

this AD, the actions shall be done in accordance with Boeing Service

Bulletin 737-53-1107, Revision 3, dated August 26, 1993; as revised

by Notice of Status Change 737-53-1107 NSC 3, dated June 9, 1994,

and Notice of Status Change 737-53-1107 NSC 4, dated September 22,

1994; or Boeing Service Bulletin 737-53-1107, Revision 4, dated

February 8, 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 Boeing

Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-

2207. 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.

(f) This amendment becomes effective on March 29, 1999.

Issued in Renton, Washington, on February 11, 1999.

John J. Hickey,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 99-3935 Filed 2-19-99; 8:45 am]

BILLING CODE 4910-13-U