[Federal Register Volume 61, Number 148 (Wednesday, July 31, 1996)]
[Rules and Regulations]
[Pages 39860-39862]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-19314]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 95-NM-186-AD; Amendment 39-9704; AD 96-16-04]
RIN 2120-AA64


Airworthiness Directives; McDonnell Douglas Model DC-9 and DC-9-
80 Series Airplanes, and C-9 (Military) Airplanes, Equipped With a 
Ventral Aft Pressure Bulkhead

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment supersedes an existing airworthiness directive 
(AD), applicable to certain McDonnell Douglas Model DC-9 and DC-9-80 
series airplanes, Model MD-88 airplanes, and C-9 (military) airplanes, 
that currently requires repetitive inspections to detect fatigue 
cracking in the area of the attach tees of the ventral aft pressure 
bulkhead. This amendment requires revised inspection and repair 
procedures, and provides for terminating action. It also deletes Model 
MD-88 airplanes from the applicability of the rule. This amendment is 
prompted by reports of fatigue cracking found in the subject area. The 
actions specified by this AD are intended to prevent the propagation of 
fatigue cracking, which could lead to structural failure of the ventral 
aft pressure bulkhead and subsequent rapid depressurization of the 
airplane.

DATES: Effective September 4, 1996.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of September 4, 1996.

ADDRESSES: The service information referenced in this AD may be 
obtained from McDonnell Douglas Corporation, 3855 Lakewood Boulevard, 
Long Beach, California 90846, Attention: Technical Publications 
Business Administration, Department C1-L51 (2-60). 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 FAA, Los Angeles Aircraft Certification Office, 
Transport Airplane Directorate, 3960 Paramount Boulevard, Lakewood, 
California; or at the Office of the Federal Register, 800 North Capitol 
Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Brent Bandley, Aerospace Engineer, 
Airframe Branch, ANM-120L, FAA, Los Angeles Aircraft Certification 
Office, 3960 Paramount Boulevard, Lakewood, California 90712; telephone 
(310) 627-5237; fax (310) 627-5210.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) by superseding AD 89-16-12, 
amendment 39-6287 (54 FR 31649, August 1, 1989), which is applicable to 
certain McDonnell Douglas Model DC-9 and DC-9-80 series airplanes, 
Model MD-88 airplanes, and C-9 (Military) airplanes, was published in 
the Federal Register on August 1, 1989 (54 FR 31649). The action 
proposed to require revised inspection and repair procedures, and 
provide for terminating action. It also proposed to delete Model MD-88 
airplanes from the applicability of the rule, since the terminating 
action was installed on those airplanes during production.
    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

    Two commenters support the proposal.

Request To Allow Inspections at Current Intervals

    Several commenters oppose the proposed shorter inspection 
intervals. These commenters request that the proposal be revised to 
permit operators to continue to conduct inspections at the same 
frequency as was mandated previously by AD 89-16-12. The commenters 
contend that the proposed AD is founded on the FAA's statement that 
improved inspection methods are available and should be used. These 
commenters do not object to modernizing the inspection methods, but 
state that nothing supports the proposed increase in inspection 
frequency. The commenters maintain that the increase in the frequency 
of inspections will be disruptive to airline maintenance programs and 
scheduling, and this will have an adverse economic impact on operators.
    The FAA does not concur with the commenters' request. After 
cracking of the ventral aft pressure bulkhead tees was found, the FAA 
issued AD 89-16-12 only as an interim measure to mandate some type of 
inspection on these tees. Because no inspection procedures had been 
developed at that time for inspecting these specific tees, the FAA 
required that operators inspect them using the same inspection 
methods--and inspection intervals--that already had been developed for 
inspecting non-ventral aft pressure bulkhead tees. (Those inspection 
methods and intervals were described in McDonnell Douglas Service 
Bulletin A53-231.) The FAA issued AD 89-16-12 in the absence of any 
specific, pertinent technical data relative to appropriate inspections 
of ventral bulkhead tees, and considered that some type of inspection 
of these tees was better than none at all. Even at the time that AD 89-
16-12 was issued, it was the FAA's intention to revise that AD once the 
manufacturer had developed inspection methods that were specific to 
ventral bulkhead tees. (The FAA explained this in the preamble to AD 
89-16-12.)
    When McDonnell Douglas eventually developed inspections for the 
ventral bulkhead tees, it issued Service Bulletin A53-232, which 
contained the inspection instructions and recommended inspection 
intervals. The inspection intervals were shorter than those that had 
been recommended for non-ventral bulkhead tees. These shorter intervals 
were determined based on the crack growth rate of these specific tees, 
residual strength of uncracked tees, and the detectability of the 
cracking using the inspection method. The FAA reviewed and approved the 
technical material presented in Service Bulletin A53-232.
    Based on that material and other data gathered from the in-service 
fleet, the FAA has determined that:
    1. The structure of the ventral and non-ventral bulkheads differs 
enough to justify the difference in the inspection intervals of the 
associated attach tees;
    2. Using the same inspection interval for both ventral and non-
ventral attach tees cannot be technically justified;
    3. Shorter repetitive inspection intervals are appropriate for the 
ventral attach tees; and
    4. The shorter inspection intervals will ensure that fatigue 
cracking at the attach tees positioned in the ventral aft pressure 
bulkhead is detected and corrected before cracking can grow to a 
critical length and jeopardize the integrity of the bulkhead.
    While operators may incur additional costs because of more frequent 
inspections and maintenance schedule changes, the FAA finds that these 
costs are necessary in order to ensure the continued airworthiness of 
these

[[Page 39861]]

airplanes and the safety of the flying public.

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 as proposed.

Cost Impact

    There are approximately 1,500 Model DC-9 and DC-9-80 series 
airplanes, and C-9 (military) airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 1,000 airplanes of U.S. 
registry will be affected by this proposed AD.
    To accomplish the actions specified as ``OPTION I'' of the AD will 
entail approximately 22 work hours per visual inspection and 12 work 
hours per low frequency eddy current inspection. The average labor rate 
is $60 per work hour. Based on these figures, the cost impact on U.S. 
operators who elect to accomplish OPTION I is estimated to be $2,040 
per airplane per inspection cycle.
    To accomplish the actions specified as ``OPTION II'' of the AD will 
entail approximately 8 work hours per high and low frequency eddy 
current inspection. The average labor rate is $60 per work hour. Based 
on these figures, the cost impact on U.S. operators who elect to 
accomplish OPTION II is estimated to be $480 per airplane per 
inspection cycle.
    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 removing amendment 39-6287 (54 FR 
31649, August 1, 1989), and by adding a new airworthiness directive 
(AD), amendment 39-9704, to read as follows:

96-16-04  McDonnell Douglas: Amendment 39-9704. Docket 95-NM-186-AD. 
Supersedes AD 89-16-12, Amendment 39-6287.

    Applicability: Model DC-9-10, -20, -30, -40, and -50 series 
airplanes; Model DC-9-81 (MD-81), DC-9-82 (MD-82) and DC-9-83 (MD-
83) series airplanes; and C-9 (military) airplanes; equipped with a 
ventral aft pressure bulkhead; as listed in McDonnell Douglas Alert 
Service Bulletin A53-232, Revision 2, dated April 28, 1995; 
certificated in any category.

    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 (d) 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 the propagation of fatigue cracks that could result 
in structural failure of the ventral aft pressure bulkhead, 
accomplish the following:
    (a) Accomplish the requirements of either paragraph (a)(1), 
``OPTION I,'' or (a)(2), ``OPTION II,'' of this AD in accordance 
with McDonnell Douglas Alert Service Bulletin A53-232, Revision 2, 
dated April 28, 1995. The initial inspection of either option must 
be accomplished at the applicable time specified in Table 1 of this 
AD.

                                 Table 1                                
------------------------------------------------------------------------
  Total accumulated landings as of the                                  
       effective date of this AD-               Initial inspection      
------------------------------------------------------------------------
Less than 35,000-......................  Prior to the accumulation of   
                                          36,500 total landings, or     
                                          within 1,500 landings after   
                                          the effective date of this AD,
                                          whichever occurs later.       
35,000 or more.........................  Within 300 landings after the  
                                          effective date of this AD; or 
                                          within 3,500 landings after   
                                          accomplishing the last        
                                          inspection performed in -     
                                          accordance with AD 89-16-12;  
                                          whichever occurs later.       
------------------------------------------------------------------------

    (1) OPTION I: Accomplish the requirements of paragraphs 
(a)(1)(i), (a)(1)(ii), and (a)(1)(iii) of this AD. -
    (i) Conduct a low frequency eddy current inspection to detect 
cracks of the side areas above the floor between longerons 7 and 17 
on fuselage left and right sides. Repeat this inspection at 
intervals not to exceed 1,500 landings.
    (ii) Conduct an optically aided detailed visual inspection to 
detect cracks of the top and lower areas from longeron 7 left side 
to longeron 7 right side, and on the lower fuselage from longeron 17 
to longeron 20 on fuselage left and right sides. Repeat this 
inspection thereafter at intervals not to exceed 1,500 landings.
    (iii) Conduct an optically aided detailed visual inspection to 
detect cracks of the bottom area from longeron 20 left side to 
longeron 20 right side. Repeat this inspection thereafter at 
intervals no to exceed 3,500 landings.
    (2) OPTION II: Conduct both a high frequency and a low frequency 
eddy current inspection for cracks around the entire periphery of 
the fuselage from the forward side of the bulkhead. Repeat these 
inspections at intervals not to exceed 2,500 landings.
    (b) If any cracked tee section is found during any inspection 
required by this AD, prior to further flight, accomplish the 
requirements of either paragraph (b)(1) or (b)(2) of this AD, in 
accordance with the procedures specified in McDonnell Douglas Alert 
Service Bulletin A53-232, Revision 2, dated April 28, 1995:
    (1) Replace the cracked tee section with a new like part. Once 
that replaced part has accumulated 35,000 landings, repeat the 
inspections required by paragraph (a) of this AD. Or
    (2) Replace the cracked tee section with an improved part, as 
specified in the alert service bulletin. Such replacement

[[Page 39862]]

constitutes terminating action for the repetitive inspections of 
that section of the tee only.
    (c) Replacement of all six aft pressure bulkhead tee sections 
with new improved parts, in accordance with McDonnell Douglas Alert 
Service Bulletin A53-232, Revision 2, dated April 28, 1995, 
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, Los Angeles 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, Los Angeles ACO.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Los Angeles ACO.

    (e) 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.
    (f) The inspections and replacements shall be done in accordance 
with McDonnell Douglas Alert Service Bulletin A53-232, Revision 2, 
dated April 28, 1995. 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 McDonnell 
Douglas Corporation, 3855 Lakewood Boulevard, Long Beach, California 
90846, Attention: Technical Publications Business Administration, 
Department C1-L51 (2-60). Copies may be inspected at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington; or at the FAA, Los Angeles Aircraft Certification 
Office, Transport Airplane Directorate, 3960 Paramount Boulevard, 
Lakewood, California; or at the Office of the Federal Register, 800 
North Capitol Street, NW., suite 700, Washington, DC.
    (g) This amendment becomes effective on September 4, 1996.

    Issued in Renton, Washington, on July 24, 1996.

S.R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-19314 Filed 7-30-96; 8:45 am]
BILLING CODE 4910-13-U