[Federal Register Volume 61, Number 49 (Tuesday, March 12, 1996)]
[Proposed Rules]
[Pages 9960-9963]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-5855]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 95-NM-186-AD]


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: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of 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. That AD was prompted by reports of fatigue 
cracking found in that area. This proposed action would require revised 
inspection and repair procedures, and would provide for terminating 
action. It would also delete certain airplanes from the applicability 
of the rule. The actions specified by the proposed 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: Comments must be received by May 6, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-NM-186-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays.
    The service information referenced in the proposed rule 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

[[Page 9961]]
information may be examined at the FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington.

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:

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 95-NM-186-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. 95-NM-186-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On July 24, 1989, the FAA issued AD 89-16-12, amendment 39-6287 (54 
FR 31649, August 1, 1989), which is applicable to McDonnell Douglas 
Model DC-9 and DC-9-80 series airplanes, Model MD-88 airplanes, and C-9 
(military) airplanes, equipped with a ventral aft pressure bulkhead. 
That AD requires repetitive optically aided visual inspections and high 
frequency eddy current inspections to detect fatigue cracking in the 
area of the attach tees of the ventral aft pressure bulkhead, and 
repair or replacement, if necessary. Subsequent inspections are 
required after any repair or replacement. That action was prompted by 
reports of fatigue cracking found in the aft pressure bulkhead attach 
tees. The requirements of that AD are intended to prevent fatigue 
cracking from propagating in this area. If such cracking is not 
detected and corrected in a timely manner, it could result in 
structural failure of the ventral aft pressure bulkhead and subsequent 
rapid depressurization of the airplane.

Service Information Referenced in the Existing AD

    AD 89-16-12 references McDonnell Douglas Service Bulletin A53-231, 
dated February 21, 1989, as the appropriate source for service 
information relative to the required inspection and repair procedures. 
Although AD 89-16-12 was applicable to airplanes equipped specifically 
with a ventral aft pressure bulkhead, the procedures contained in that 
service bulletin applied to airplanes equipped with a non-ventral aft 
pressure bulkhead. At the time that AD 89-16-12 was issued, the 
manufacturer had advised the FAA that it was developing new inspections 
and corrective action that would be pertinent to airplanes with ventral 
aft pressure bulkheads. However, in consideration of the safety 
implications of the unsafe condition presented by fatigue cracking, the 
FAA considered it inappropriate to delay AD action relevant to those 
airplanes until the new inspections were developed. At that time, the 
FAA found that the inspection and repair procedures contained in 
Service Bulletin A53-231 were acceptable, only as an interim measure, 
for addressing fatigue cracks in airplanes with ventral aft pressure 
bulkheads.

New Developments Since Issuance of Existing AD

    Since the issuance of AD 89-16-12, the manufacturer has developed a 
new series of inspection procedures that are specifically designed to 
detect fatigue cracking at the attach tees on airplanes equipped with 
ventral aft pressure bulkheads. These inspections, along with an 
appropriate schedule for conducting them, were developed in order to 
ensure that fatigue cracking in the subject area of these particular 
airplanes is detected and corrected before cracking can grow to a 
critical length. Such fatigue cracking, if allowed to propagate 
unchecked, could result in structural failure of the ventral aft 
pressure bulkhead and subsequent rapid depressurization of the 
airplane.

New Service Information

    The FAA has reviewed and approved McDonnell Douglas Alert Service 
Bulletin A53-232, Revision 2, dated April 28, 1995, which describes 
procedures for conducting various types of repetitive inspections to 
detect cracking in the ventral aft pressure bulkhead web-to-fuselage 
tee sections. It also describes procedures for replacement of cracked 
parts. The inspections can be conducted in either of two ways:
     OPTION I entails repetitive visual and low frequency eddy 
current inspections from the aft side of the bulkhead.
     OPTION II entails repetitive high and low frequency eddy 
current inspections from the forward side of the bulkhead.
    If any cracking is found, the service bulletin calls for 
replacement of the cracked tee section. If it is replaced with new like 
parts, the inspections must continue to be accomplished; if it is 
replaced with a new improved part (that is not susceptible to the 
subject fatigue cracking), the inspections of that tee section may be 
discontinued. When all six aft pressure bulkhead tee sections are 
replaced with the new improved parts, the repetitive inspections can be 
discontinued.

FAA's Findings

    As discussed previously, at the time when AD 89-16-12 was issued, 
the FAA considered that the inspections described in Service Bulletin 
A53-231 were acceptable, as an interim measure only, in detecting 
fatigue cracks before they could grow to a critical size. However, the 
FAA now finds that the new inspection procedures specified in McDonnell 
Douglas Alert Service Bulletin A53-232 are more effective than those 
previously required. They are more effective not only because the 
procedures are tailored specifically for inspecting the ventral 
bulkhead, but because they are more suited for finding (and correcting) 
smaller cracks in the ventral bulkhead.
    Additionally, the FAA finds that the schedule for repetitive 
inspections specified in the service bulletin is appropriate. While 
certain of the repetitive inspection intervals are shorter than those 
of the inspections currently required by AD 89-16-12, the FAA considers 
that these intervals are warranted in order to ensure that fatigue

[[Page 9962]]
cracks are detected before they can propagate.
    In light of these factors, the FAA has determined that the new 
inspection procedures described in McDonnell Douglas Alert Service 
Bulletin A53-232 must be accomplished in order to positively address 
the identified unsafe condition presented by fatigue cracking.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would supersede AD 89-16-12 to completely revise the 
currently required inspection program. This proposed AD would require 
either repetitive visual and low frequency eddy current inspections 
(``OPTION I''), or repetitive high and low frequency eddy current 
inspections (``OPTION II''), to detect cracking in the attach tee area 
of the ventral aft pressure bulkhead. Any cracked tee section would be 
required to be replaced prior to further flight. Replacement of all six 
aft pressure bulkhead tee sections with new improved parts would 
constitute terminating action for the repetitive inspection 
requirements of the AD. The actions would be required to be 
accomplished in accordance with the service bulletin described 
previously.
    While the proposed AD provides for a terminating action, the FAA is 
not proposing to mandate that it be accomplished. The FAA considers 
three criteria for those situations where repetitive inspections of a 
crack-prone area may be permitted to continue indefinitely, even though 
a positive fix to the problem exists: (1) The area is easily 
accessible, (2) the cracking is easily detectable, and (3) the 
consequences of the cracking are not likely to be catastrophic. The FAA 
has determined that the circumstances warranting continual repetitive 
inspections associated with this proposed AD meet these three criteria.
    This proposed AD also would revise the applicability of the rule to 
delete Model MD-88 airplanes. Because the terminating action specified 
in this proposed AD was installed on those airplanes during production, 
those airplanes are not subject to the unsafe condition addressed by 
this action.

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 would be affected by this proposed AD.
    To accomplish the actions specified as ``OPTION I'' of the proposed 
AD would 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 
proposed AD would 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 current or proposed 
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 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 
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), to read as follows:

McDonnell Douglas: 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.

[[Page 9963]]


                                 Table 1                                
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  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.
    (2) Replace the cracked tee section with an improved part, as 
specified in the alert service bulletin. Such replacement 
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.

    Issued in Renton, Washington, on March 6, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-5855 Filed 3-11-96; 8:45 am]
BILLING CODE 4910-13-U