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

[Federal Register Volume 65, Number 65 (Tuesday, April 4, 2000)]
[Rules and Regulations]
[Pages 17583-17586]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-7877]



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Federal Register / Vol. 65, No. 65 / Tuesday, April 4, 2000 / Rules 
and Regulations

[[Page 17583]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-84-AD; Amendment 39-11654; AD 2000-06-13]
RIN 2120-AA64


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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment supersedes an existing airworthiness directive 
(AD), applicable to certain Boeing Model 737-200, -200C, -300, and -400 
series airplanes, that currently requires repetitive visual inspections 
to detect cracking of the corners of the door frame and the cross beams 
of the aft cargo door, and corrective actions, if necessary. That AD 
also provides an optional terminating action for certain repetitive 
inspections. This amendment requires repetitive high frequency eddy 
current (HFEC) inspections, and corrective actions, if necessary. This 
amendment also mandates accomplishment of the previously optional 
terminating action. The actions specified by this AD are intended to 
prevent fatigue cracking of the corners of the door frame and the cross 
beams of the aft cargo door, which could result in rapid 
depressurization of the airplane.

DATES: Effective May 9, 2000.
    The incorporation by reference of Boeing Alert Service Bulletin 
737-52A1079, Revision 6, dated November 18, 1999, as listed in the 
regulations, is approved by the Director of the Federal Register as of 
April 19, 2000.
    The incorporation by reference of Boeing Service Bulletin 737-52-
1079, Revision 5, dated May 16, 1996, as listed in the regulations, was 
approved previously by the Director of the Federal Register as of 
December 24, 1998 (63 FR 67769, December 9, 1998).

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 FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington. 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: Nenita Odesa, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-2557; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) by superseding AD 98-25-06, 
amendment 39-10931 (63 FR 67769, December 9, 1998), which is applicable 
to certain Boeing Model 737-200, -200C, -300, and -400 series 
airplanes, was published in the Federal Register on August 12, 1999 (64 
FR 43950). The action proposed to require continuing the current 
repetitive visual inspections to detect cracking of the corners of the 
door frame and the cross beams of the aft cargo door, and corrective 
actions, if necessary. The action also proposed to require repetitive 
high frequency eddy current (HFEC) inspections, and corrective actions, 
if necessary. Additionally, the action proposed to mandate 
accomplishment of the previously optional terminating action.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Concurrence with the Proposal

    One commenter concurs with the proposal.

Request to Reference New Service Information

    One commenter, the manufacturer, states that the proposal should 
reference the latest Alert Service Bulletin, 737-52A1079, Revision 6, 
dated November 18, 1999. That revision adds procedures describing a 
High frequency eddy current (HFEC) inspection for cracks in the frames 
of doors that do not have steel modification angles, inspection for 
cracks in the upper and lower beam outer chord, repair instructions for 
the lower beam outer chord, and other various changes.
    The FAA concurs that Revision 6 of Boeing Alert Service Bulletin 
737-52A1079 may be specified in the final rule as an alternative method 
of compliance with the requirements of this AD. The final rule has been 
changed to specify that addition.

Request to Revise the Compliance Time of Paragraph (d) of the 
Proposal

    One commenter, the manufacturer, requests that the compliance time 
for the high frequency eddy current inspections specified in paragraph 
(d) of the proposal be revised from ``within 4,500 flight cycles or one 
year after the effective date of the AD,'' to within 12,000 flight 
cycles after installation of the door. The commenter states that if an 
operator has an accurate accounting of the history of the cargo door, a 
threshold of 12,000 flight cycles would provide no adverse effect on 
safety.
    The FAA does not concur with the commenter's request to revise the 
compliance time. Because cargo doors are rotable parts, i.e., they may 
be moved from one airplane to another, an airplane's maintenance 
records may not accurately reflect the total number of flight cycles 
accumulated on the door. However, under the provisions of paragraph (f) 
of the final rule, the FAA may approve requests for adjustments to the 
compliance time if data are submitted to substantiate that such an 
adjustment would provide an acceptable level of safety.

Request to Extend the Compliance Time of Paragraph (e) of the 
Proposal

    One commenter, the manufacturer, requests that the compliance time 
for the accomplishment of the required modification be revised to be in 
consonance with the compliance threshold required by AD 90-06-02,

[[Page 17584]]

amendment 39-6489 (55 FR 8372, March 7, 1990). The new compliance time 
would then read, ``prior to the accumulation of 75,000 total flight 
cycles.'' The commenter points out that compliance times should be 
based on flight cycles rather than calendar time. Fatigue crack growth 
rates are a function of pressurization cycles, not elapsed time, and a 
cycle-based compliance threshold would be more appropriate for the 
proposed rule.
    The FAA does not concur that the compliance time should be changed 
to specify a compliance time of 75,000 total flight cycles. Based on a 
recent depressurization event that occurred much earlier than 75,000 
flight cycles, the FAA has determined that a threshold of 75,000 total 
flight cycles does not provide for an adequate level of safety. 
However, the FAA acknowledges that fatigue cracking is a function of 
pressurization cycles and concurs that a compliance time based on 
flight cycles may be added. Based on recent information, the FAA has 
determined that a compliance time of 12,000 total flight cycles is an 
appropriate compliance time and has added this to the compliance time 
specified in paragraph (e) of the final rule.

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 1,636 Model 737 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 707 
airplanes of U.S. registry will be affected by this AD.
    The detailed visual inspections that currently are required by AD 
98-25-06, and retained in this AD, take approximately 2 work hours per 
airplane to accomplish, at an average labor rate of $60 per work hour. 
Based on these figures, the cost impact of the currently required 
inspections on U.S. operators is estimated to be $84,840, or $120 per 
airplane, per inspection cycle.
    The new high frequency eddy current inspections that are required 
by this AD will take approximately 4 work hours per airplane to 
accomplish, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of the new inspections required by this 
AD on U.S. operators is estimated to be $169,680, or $240 per airplane, 
per inspection cycle.
    The modification that is required by this AD action will take 
approximately 144 work hours per airplane to accomplish, at an average 
labor rate of $60 per work hour. Required parts will cost approximately 
$4,530 per airplane. Based on these figures, the cost impact of the 
modification required by this AD on U.S. operators is estimated to be 
$9,311,190, or $13,170 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 a substantial direct 
effect 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, it 
is determined that this final rule does not have federalism 
implications under Executive Order 13132.
    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 removing amendment 39-10931 (63 FR 
67769, December 9, 1998), and by adding a new airworthiness directive 
(AD), Amendment 39-11654, to read as follows:

2000-06-13 Boeing: Amendment 39-11654. Docket 99-NM-84-AD. 
Supersedes AD 98-25-06, Amendment 39-10931.

    Applicability: The following airplane models, certificated in 
any category:
    <bullet> Model 737-200 and -200C series airplanes, line numbers 
6 through 873 inclusive;
    <bullet> Model 737-200, -200C, -300, and -400 series airplanes; 
line numbers 874 through 1642 inclusive; equipped with an aft cargo 
door having Boeing part number (P/N) 65-47952-1 or P/N 65-47952-524; 
excluding:
    1. Those airplanes on which that door has been modified in 
accordance with Boeing Service Bulletin 737-52-1079; or
    2. Those airplanes on which the door assembly having P/N 65-
47952-524 includes four straps (P/N's 65-47952-139, 65-47952-140, 
65-47952-141, and 65-47952-142) and a thicker lower cross beam web 
(P/N 65-47952-157).

    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 (f)(1) 
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 fatigue cracking of the corners of the door frame and 
the cross beams of the aft cargo door, which could result in rapid 
depressurization of the airplane, accomplish the following:

Restatement of the Requirements of AD 98-25-06:

Inspections and Corrective Actions

    (a) Within 90 days or 700 flight cycles after December 24, 1998 
(the effective date of AD 98-25-06, amendment 39-10931), whichever 
occurs later, perform an internal detailed visual inspection to 
detect cracking of the corners of the door frame and the cross beams 
of the aft cargo door, in accordance with Boeing Service Bulletin 
737-52-1079, Revision 5, dated May 16, 1996, or Boeing Alert Service 
Bulletin 737-52A1079, Revision 6, dated November 18, 1999.
    (1) If no cracking is detected, accomplish the requirements of 
either paragraph (a)(1)(i) or (a)(1)(ii) of this AD.
    (i) Repeat the internal visual inspection thereafter at 
intervals not to exceed 4,500 flight cycles. Or

[[Page 17585]]

    (ii) Prior to further flight, modify the corners of the door 
frame and the cross beams of the aft cargo door in accordance with 
the service bulletin. Accomplishment of such modification 
constitutes terminating action for the repetitive inspection 
requirements of paragraph (a)(1)(i) of this AD.
    (2) If any cracking is detected in the upper or lower cross 
beams, prior to further flight, modify the cracked beam in 
accordance with paragraph III.C. of Part I of the Accomplishment 
Instructions of the service bulletin. Accomplishment of such 
modification constitutes terminating action for the repetitive 
inspection requirements of paragraph (a)(1)(i) of this AD for the 
repaired beam.
    (3) If any cracking is detected in the forward or aft upper door 
frame, prior to further flight, repair the frame and modify the 
corners of the door frame of the aft cargo door, in accordance with 
paragraph III.E. of Part I of the Accomplishment Instructions of the 
service bulletin, except as provided by paragraph (b) of this AD. 
Accomplishment of such modification constitutes terminating action 
for the repetitive inspection requirements of paragraph (a)(1)(i) of 
this AD for the upper door frame.

    Note 2: Cracks of the forward or aft upper door frame, 
regardless of length, must be repaired prior to further flight in 
accordance with paragraph III.E. of Part I of the Accomplishment 
Instructions of the service bulletin.

    (4) If any cracking is detected in the forward or aft lower door 
frame, prior to further flight, replace the damaged frame with a new 
frame, and modify the corners of the door frame of the aft cargo 
door, in accordance with paragraph III.F. of Part I of the 
Accomplishment Instructions of the service bulletin. Accomplishment 
of such modification constitutes terminating action for the 
repetitive inspection requirements of paragraph (a)(1)(i) of this AD 
for the lower door frame.
    (b) Where Boeing Service Bulletin 737-52-1079, Revision 5, dated 
May 16, 1996, or Boeing Alert Service Bulletin, 737-52A1079, 
Revision 6, dated November 18, 1999, specifies that certain repairs 
are to be accomplished in accordance with instructions received from 
Boeing, this AD requires that, prior to further flight, such repairs 
be accomplished in accordance with a method approved by the Manager, 
Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane 
Directorate.

New Requirements of This AD

Inspections and Corrective Actions

    (c) If any cracking of the outer chord of the upper or lower 
cross beams of the aft cargo door is detected as a result of any 
inspection required by paragraph (a) of this AD, prior to further 
flight, repair in accordance with a method approved by the Manager, 
Seattle ACO; Boeing Alert Service Bulletin, 737-52A1079, Revision 6, 
dated November 18, 1999; or in accordance with data meeting the type 
certification basis of the airplane approved by a Boeing Company 
Designated Engineering Representative who has been authorized by the 
FAA to make such findings.
    (d) Within 4,500 flight cycles or one year after the effective 
date of this AD, whichever occurs later: Perform a high frequency 
eddy current inspection (HFEC) to detect cracking of the four 
corners of the door frame of the aft cargo door, in accordance with 
the procedures specified in Boeing 737 Nondestructive Test Manual, 
Part 6, Chapter 51-00-00 (Figure 4 or Figure 23), or Boeing Alert 
Service Bulletin, 737-52A1079, Revision 6, dated November 18, 1999;
    (1) If no cracking of the corners of the door frame of the aft 
cargo door is detected, repeat the HFEC inspections thereafter at 
intervals not to exceed 4,500 flight cycles until accomplishment of 
the modification specified in paragraph (e) of this AD.
    (2) If any cracking of the corners of the door frame of the aft 
cargo door is detected, prior to further flight, replace the damaged 
frame with a new frame, and modify the four corners of the door 
frame, in accordance with Parts II and III of the Accomplishment 
Instructions of Boeing Service Bulletin 737-52-1079, Revision 5, 
dated May 16, 1996, or Boeing Alert Service Bulletin 737-52A1079, 
Revision 6, dated November 18, 1999. Accomplishment of such 
modification constitutes terminating action for the repetitive 
inspection requirements of paragraph (d)(1) of this AD for that door 
frame.

Terminating Action

    (e) Prior to the accumulation of 12,000 total flight cycles, or 
within 4 years after the effective date of this AD, whichever occurs 
later: Modify the four corners of the door frame and the cross beams 
of the aft cargo door, in accordance with Part II of the 
Accomplishment Instructions of Boeing Service Bulletin 737-52-1079, 
Revision 5, dated May 16, 1996, or Boeing Alert Service Bulletin 
737-52A1079, Revision 6, dated November 18, 1999. Accomplishment of 
such modification constitutes terminating action for the repetitive 
inspection requirements of this AD.

    Note 3: Accomplishment of the modification required by paragraph 
(a) of AD 90-06-02, amendment 39-6489, is considered acceptable for 
compliance with paragraph (e) of this AD.


    Note 4: Modification of the corners of the door frame and the 
cross beams of the aft cargo door accomplished prior to the 
effective date of this AD in accordance with Boeing Service Bulletin 
737-52-1079, dated December 16, 1983; Revision 1, dated December 15, 
1988; Revision 2, dated July 20, 1989; Revision 3, dated May 17, 
1990; Revision 4, dated February 21, 1991; is considered acceptable 
for compliance with paragraph (e) of this AD.

Alternative Methods of Compliance

    (f)(1) 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.
    (2) Alternative methods of compliance, approved previously in 
accordance with AD 98-25-06, amendment 39-10931, are approved as 
alternative methods of compliance with this AD.

    Note 5: 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

    (g) 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

    (h) Except as provided in paragraphs (b), (c), (d), and (d)(1) 
of this AD, the actions shall be done in accordance with Boeing 
Service Bulletin 737-52-1079, Revision 5, dated May 16, 1996, or 
Boeing Alert Service Bulletin 737-52A1079, Revision 6, dated 
November 18, 1999.
    (1) The incorporation by reference of Boeing Alert Service 
Bulletin 737-52A1079, Revision 6, dated November 18, 1999, is 
approved by the Director of the Federal Register in accordance with 
5 U.S.C. 552(a) and 1 CFR part 51.
    (2) The incorporation by reference of Boeing Service 737-52-
1079, Revision 5, dated May 16, 1996, was approved previously by the 
Director of the Federal Register as of December 24, 1998 (63 FR 
67769, December 9, 1998).
    (3) 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.
    (i) This amendment becomes effective on May 9, 2000.

[[Page 17586]]


    Issued in Renton, Washington, on March 24, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-7877 Filed 4-3-00; 8:45 am]
BILLING CODE 4910-13-P

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