[Federal Register Volume 59, Number 21 (Tuesday, February 1, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-1226]


[[Page Unknown]]

[Federal Register: February 1, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 91-NM-65-AD; Amendment 39-8802; AD 94-04-04]

 

Airworthiness Directives; Boeing Model 727 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 all Boeing Model 727 series airplanes, that requires 
inspections of certain fuselage frames for cracks, and modification, if 
necessary; inspections to detect cracks in certain frame gussets, and 
replacement, if necessary; and inspections at certain body stations to 
detect open pilot holes and to detect cracks in any open pilot hole 
found, and repair and modification, if necessary. This amendment is 
prompted by reports of cracked frames and open pilot holes. The actions 
specified by this AD are intended to prevent frame failures and 
consequent rapid decompression of the cabin.

DATES: Effective March 3, 1994.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 3, 1994.

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 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: Phil Forde, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (206) 227-2771; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations to include an airworthiness directive (AD) that is 
applicable to all Boeing Model 727 series airplanes was published as a 
supplemental notice of proposed rulemaking (NPRM) in the Federal 
Register on May 7, 1993 (58 FR 27217). That action proposed to require 
inspections of certain fuselage frames for cracks, and modification, if 
necessary; inspections to detect cracks in certain frame gussets, and 
replacement, if necessary; and inspections at certain body stations to 
detect open pilot holes and to detect cracks in any open pilot hole 
found, and repair and modification, if necessary.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    One commenter supports the proposed rule.
    One commenter, Boeing, requests that the proposed rule be withdrawn 
and suggests that the service bulletin cited in the proposal be 
incorporated into the structural modification and inspection program 
for aging airplanes. Boeing references a similar situation involving 
the overwing stub frames on Model 737 series airplanes. No AD was 
issued in that instance; instead, the preventive modification was made 
part of the aging fleet modification program at life goal. Boeing also 
states that including the service bulletin cited in the proposal in the 
modification program would reduce the number of AD's concerning that 
subject.
    Boeing also believes that the consequence of frame failures was 
overstated in the proposal. Boeing indicates that although dozens of 
cases of basic frame cracking have occurred, only four cases of inboard 
strap cracking and no cases of frame outboard reinforcing strap 
cracking have been reported. Boeing adds that for rapid decompression 
to occur, the skin must crack; and there have been no reports of skin 
cracks in this area as a result of frame cracks. Boeing believes that 
rapid decompression is extremely unlikely because there is ample 
reinforcing structure in this area.
    The FAA does not concur with the commenter's request to withdraw 
the proposal. Although there have been no reports of outboard strap or 
skin cracking, the FAA has determined that the potential exists for 
failure of the frames, which could lead to failure of the straps and 
skin in the absence of the repair and preventive modification or 
inspection program. Such failures would result in rapid decompression 
of the airplane. The FAA finds that it is not warranted to delay the 
proposed repair for inclusion in the aging airplane program.
    The Air Transport Association (ATA) of America, on behalf of two of 
its members, requests that the FAA reconsider the proposed requirement 
of this AD to remove fasteners prior to inspection and, if necessary, 
require another inspection to verify the existence of cracks without 
fastener removal. One commenter suggests that an option should be 
included in the final rule that would allow visual inspections at more 
frequent intervals in lieu of the proposed fastener removal and eddy 
current inspections. Another commenter suggests that fastener removal 
should be required only during the initial inspection, and that 
subsequent inspections should be accomplished using visual and high 
frequency eddy current inspection methods. This commenter states that 
accomplishment of these suggested subsequent inspections will ensure 
that a crack does not reach a critical length. ATA expresses concern 
that continual removal of fasteners may initiate crack development.
    The FAA does not concur with the commenters' requests to revise the 
intervals or procedures specified in this AD for inspections involving 
fastener removal. The FAA has reconsidered various alternatives to the 
inspection methods and intervals specified in this AD in light of 
available crack growth analysis data. The FAA finds that eddy current 
inspections with fasteners in place would be required at intervals of 
1,500 flight cycles, or four times as often as the interval of 6,000 
flight cycles (with fasteners removed) specified in this AD. Further, 
the FAA finds that if fastener removal were only required during the 
initial inspection and subsequent eddy current inspections with 
fasteners in place were required, the first inspection interval would 
be 6,000 flight cycles with subsequent inspection intervals of 1,500 
flight cycles. In light of the safety implications and practical 
aspects of an orderly inspection of the fleet during regular 
maintenance periods, the FAA considers inspections with fasteners 
removed at intervals of 6,000 flight cycles to be the appropriate 
requirement for this AD. However, the FAA would consider a request for 
an adjustment of the inspection methods or intervals, in accordance 
with the provisions of paragraph (e) of this AD, provided that, for 
example, data is submitted to substantiate that such methods or 
intervals ensure that cracks will not reach a critical length.
    One commenter requests that credit be given in paragraph (d) of the 
proposal for inspections to detect open pilot holes performed in 
accordance with the original issue of the service bulletin. The 
commenter asks specifically that the proposal be revised to state that 
repairs accomplished in accordance with the Model 727 Structural Repair 
Manual (SRM) are acceptable, provided repetitive inspections are 
performed thereafter at intervals of 6,000 flight cycles. This 
commenter has inspected the addressed area in accordance with the 
original issue of the service bulletin. The commenter indicates that 
the area targeted for inspection in paragraph (d) of the proposal is 
essentially the same area identified in the original issue of the 
service bulletin. The commenter is confident that any cracks in the 
pilot holes would have been detected during that inspection (and 
subsequently repaired) in accordance with that issue of the service 
bulletin. The commenter adds that airplanes inspected in accordance 
with the original issue of the service bulletin may have been repaired 
in accordance with chapter 51-40-3 of the SRM, as specified in that 
service bulletin. The commenter states that Boeing has not included a 
reference to the SRM repair in Revision 1 of the service bulletin 
because the SRM repair is not easily adapted to the subject frames. 
However, Revision 1 of the service bulletin indicates that repairs 
installed in accordance with the original issue of the service bulletin 
are adequate as long as repetitive inspections are accomplished.
    Similarly, one commenter requests that paragraphs (b) and (c) of 
the proposal, which address (in part) inspections of the fastener 
holes, the frame flange and web, and certain frame gussets, be revised 
to allow credit for inspections accomplished previously in accordance 
with the original issue of the service bulletin in that the proposed 
compliance time should be longer for airplanes that have been inspected 
previously in accordance with the original issue of the service 
bulletin than for those airplanes that have not been inspected. The 
commenter states that any cracks in the pilot holes would have been 
detected during inspections accomplished in accordance with the 
original issue of the service bulletin.
    The FAA does not concur with the commenters' requests to allow 
credit for inspections accomplished in accordance with the procedures 
described in the original issue of the service bulletin. The original 
issue of the service bulletin does not contain procedures for 
inspections to detect cracks in open pilot holes, which is a 
requirement of this AD. Consequently, the FAA cannot be certain that 
operators that accomplished procedures specified in the original issue 
of the service bulletin also inspected for and repaired cracks in open 
pilot holes, as required by this AD.
    Another commenter requests that plugging uncracked pilot holes in 
accordance with Part VII of the service bulletin be considered optional 
terminating action for the repetitive inspections proposed in paragraph 
(d)(2)(i) of this AD. The FAA does not concur. The location of pilot 
holes in the members of the built-up structure has been shown to vary; 
therefore, since all of the open pilot holes may not be visible during 
an inspection, it is possible that ``figure 8 holes'' could exist on 
the inner members of that structure. These figure 8 holes are two holes 
that have not been drilled concentrically. The danger of figure 8 holes 
is that they have been shown to create very high local stress. In light 
of this hazard, the FAA cannot allow plugging uncracked pilot holes to 
be considered terminating action for the repetitive inspections 
discussed previously.
    This commenter also requests that reference to Part VI of the 
Accomplishment Instructions of the service bulletin be removed from 
paragraph (d)(2) of the proposal. The commenter states that the 
procedures described in Part VI of the Accomplishment Instructions of 
the service bulletin are not applicable to this paragraph of the 
proposal.
    The FAA concurs partially. The FAA's intent in referring to Part VI 
of the Accomplishment Instructions of the service bulletin was simply 
to specify that the appropriate inspection technique to be performed is 
a close visual inspection, which is referenced in Part VI of the 
Accomplishment Instructions of the service bulletin. However, the FAA 
recognizes that clarification of this inspection method is necessary. 
Therefore, paragraph (d)(2) of this final rule has been revised by 
removing reference to Part VI of the Accomplishment Instructions of the 
service bulletin and by specifying that a ``close visual inspection'' 
is defined as a close intensive visual inspection of highly defined 
structural details or locations, searching for evidence of structural 
irregularity and using adequate lighting. In addition, inspection aids 
such as mirrors, etc., surface cleaning, and access procedures are 
required, as necessary, to gain proximity.
    The commenter also requests that paragraph (d)(2)(iii) be revised 
to delete the phrase, ``in accordance with * * * the service 
bulletin.'' The commenter states that repair of any crack found in an 
open pilot hole that is located outside any of the shaded areas shown 
in Figures 3, 4, and 5 of the service bulletin cannot be separated from 
the preventive modification.
    The FAA does not concur. Repair of a crack in an open pilot hole 
and installation of the preventive modification are two different 
items. While the service bulletin contains instructions for repairing 
cracks, it does not specify how to install the modification if the 
cracked pilot hole is located outside the shaded area covered by the 
service bulletin. Consequently, operators are required to request 
approval from the FAA of a method of installing the modification.
    The final rule has been revised to correct certain typographical 
errors in regard to paragraph and service information references, as 
follows:
    1. Paragraph (d)(1) has been revised to clarify that if no open 
pilot hole is found, no further action is required by paragraph (d) of 
this AD.
    2. Paragraph (d)(2)(i) of this AD has been changed to refer to 
paragraphs (d)(2)(ii) and (d)(2)(iii), rather than paragraphs 
(d)(1)(ii) and (d)(1)(iii), respectively.
    3. Paragraph (d)(2)(ii) of this AD has been revised to refer to 
paragraph (d)(2)(i), rather than paragraph (d)(1)(i).
    4. Paragraph (d)(2)(iii) of this AD has been changed to refer to 
paragraph (d)(2)(i), rather than paragraph (d)(1)(i).
    Additionally, for consistency with the service bulletin, paragraphs 
(a) and (b) of this AD have been revised to include the word ``repair'' 
where any reference is made to the preventive modification. This word 
is added to clarify the FAA's intent that when cracks are found, 
operators must install the applicable ``repair and preventive 
modification.''
    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.
    There are approximately 1,695 Model 727 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 1,172 
airplanes of U.S. registry will be affected by this AD, that it will 
take approximately 53 work hours per airplane to accomplish the 
required actions, and that the average labor rate is $55 per work hour. 
Based on these figures, the total cost impact of the AD on U.S. 
operators is estimated to be $3,416,380, or $2,915 per airplane. This 
total cost figure assumes that no operator has yet accomplished the 
requirements of this AD.
    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 14 CFR part 
39 of the Federal Aviation Regulations as follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

94-04-04 Boeing: Amendment 39-8802. Docket 91-NM-65-AD.

    Applicability: All Model 727 series airplanes, certificated in 
any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of fuselage frames and depressurization of 
the airplane, accomplish the following:
    (a) For airplanes identified as Group 1 or 2 in Boeing Service 
Bulletin 727-53-0197, Revision 1, dated April 9, 1992: Prior to the 
accumulation of 12,000 flight cycles since manufacture, or within 
3,000 flight cycles after the effective date of this AD, whichever 
occurs later, perform an eddy current inspection of the fastener 
holes and a close visual inspection of the frame flange and web to 
detect cracks at body stations (BS) 760.95, 783.95, 825.95, and 
848.95 in accordance with Part I of the Accomplishment Instructions 
of the service bulletin.
    (1) If any crack is found, prior to further flight, install the 
applicable repair and preventive modification in accordance with 
Part III of the Accomplishment Instructions of the service bulletin. 
Once this repair and preventive modification is installed, no 
further eddy current inspections of the fastener holes or close 
visual inspections of the modified frame flange and web are required 
by this AD.
    (2) If no crack is found, prior to further flight, accomplish 
one of the procedures identified in paragraphs (a)(2)(i), 
(a)(2)(ii), or (a)(2)(iii) of this AD, in accordance with Part I, 
paragraph E., of the Accomplishment Instructions of the service 
bulletin.
    (i) Oversize the hole by \1/32\ inch and install an oversized 
fastener. Prior to the accumulation of 12,000 flight cycles after 
oversizing the hole, and thereafter at intervals not to exceed 6,000 
flight cycles, continue to accomplish the inspections required by 
paragraph (a) of this AD. If any crack is found, prior to further 
flight, install the applicable repair and preventive modification in 
accordance with Part III of the Accomplishment Instructions of the 
service bulletin. Once this repair and preventive modification is 
installed, no further eddy current inspections of the fastener holes 
or close visual inspections of the frame flange and web are required 
by this AD. Or
    (ii) Install the same size fastener that was removed. Thereafter 
at intervals not to exceed 6,000 flight cycles, continue to 
accomplish the inspections required by paragraph (a) of this AD. If 
cracks are found, prior to further flight, install the applicable 
repair and preventive modification in accordance with Part III of 
the Accomplishment Instructions of the bulletin. Once this repair 
and preventive modification is installed, no further eddy current 
inspections of the fastener holes or close visual inspections of the 
frame flange and web are required by this AD. Or
    (iii) Install the applicable repair and preventive modification 
in accordance with Part III of the Accomplishment Instructions of 
the service bulletin. Once this repair and preventive modification 
is installed, no further eddy current inspections of the fastener 
holes or close visual inspections of the frame flange and web are 
required by this AD.
    (b) For airplanes identified as Group 3, 4, or 5 in Boeing 
Service Bulletin 727-53-0197, Revision 1, dated April 9, 1992: Prior 
to the accumulation of 12,000 flight cycles since manufacture, or 
within 3,000 flight cycles after the effective date of this AD, 
whichever occurs later, perform an eddy current inspection of the 
fastener holes and a close visual inspection of the frame flange and 
web to detect cracks at body stations (BS) 760.95 and 783.95 in 
accordance with Part II of the Accomplishment Instructions of the 
service bulletin.
    (1) If any crack is found, prior to further flight, install the 
applicable repair and preventive modification in accordance with 
Part IV of the Accomplishment Instructions of the service bulletin. 
Once this repair and preventive modification is installed, no 
further eddy current inspections of the fastener holes or close 
visual inspections of the frame flange and web are required by this 
AD.
    (2) If no crack is found, prior to further flight, accomplish 
one of the procedures identified in paragraphs (b)(2)(i), 
(b)(2)(ii), or (b)(2)(iii) of this AD, in accordance with Part II, 
paragraph E. of the Accomplishment Instructions of the service 
bulletin:
    (i) Oversize the hole by \1/32\ inch and install an oversized 
fastener. Prior to the accumulation of 12,000 flight cycles after 
oversizing the hole, and thereafter at intervals not to exceed 6,000 
flight cycles, continue to accomplish the inspections required by 
paragraph (b) of this AD. If cracks are found, prior to further 
flight, install the applicable repair and preventive modification in 
accordance with Part IV of the Accomplishment Instructions of the 
service bulletin. Once this repair and preventive modification is 
installed, no further eddy current inspections of the fastener holes 
or close visual inspections of the frame flange and web are required 
by this AD. Or
    (ii) Install the same size fastener that was removed. Thereafter 
at intervals not to exceed 6,000 flight cycles, continue to 
accomplish the inspections required by paragraph (b) of this AD. If 
cracks are found, prior to further flight, install the applicable 
repair and preventive modification in accordance with Part IV of the 
Accomplishment Instructions of the service bulletin. Once this 
repair and preventive modification is installed, no further eddy 
current inspections of the fastener holes or close visual 
inspections of the frame flange and web are required by this AD. Or
    (iii) Install the applicable repair and preventive modification 
in accordance with Part IV of the Accomplishment Instructions of the 
service bulletin. Once this repair and preventive modification is 
installed, no further eddy current inspections of the fastener holes 
or close visual inspections of the frame flange and web are required 
by this AD.
    (c) For airplanes identified as Group 1, 2, 3, or 4 in Boeing 
Service Bulletin 727-53-0197, Revision 1, dated April 9, 1992: Prior 
to the accumulation of 12,000 flight cycles since manufacture, or 
within 3,000 flight cycles after the effective date of this AD, 
whichever occurs later, perform a close visual inspection to detect 
cracks in the frame gussets at BS 825.95 in accordance with Part V 
(for Groups 1 and 2 airplanes) or Part VI (for Groups 3 and 4 
airplanes) of the Accomplishment Instructions of the service 
bulletin. Repeat these inspections thereafter at intervals not to 
exceed 6,000 flight cycles.
    (1) If any crack is found, prior to further flight, replace the 
gusset with a new gusset in accordance with Figure 10 (for Groups 1 
and 2 airplanes) or Figure 11 (for Groups 3 and 4 airplanes) of the 
service bulletin.
    (2) Replacement of the gusset in accordance with paragraph 
(c)(1) of this AD constitutes terminating action for the repetitive 
inspections required by paragraph (c) of this AD.
    (d) For airplanes identified as Group 1, 2, 3, 4, or 5 in Boeing 
Service Bulletin 727-53-0197, Revision 1, dated April 9, 1992: Prior 
to the accumulation of 12,000 flight cycles since manufacture, or 
within 3,000 flight cycles after the effective date of this AD, 
whichever occurs later, perform a close visual inspection of the 
inner flange of the frames and the strap on the inner flange at BS 
760.95 and 783.95 to detect open pilot holes in accordance with Part 
VII of the Accomplishment Instructions of the service bulletin.
    (1) If no open pilot hole is found, no further action is 
required by paragraph (d) of this AD.
    (2) If any open pilot hole is found, perform a close visual 
inspection to detect cracks in that open pilot hole. A ``close 
visual inspection'' is defined as a close, intensive visual 
inspection of highly defined structural details or locations, 
searching for evidence of structural irregularity and using adequate 
lighting. In addition, inspection aids such as mirrors, etc., 
surface cleaning, and access procedures are required, as necessary, 
to gain proximity.
    (i) If no crack is found in any open pilot hole, repeat the 
inspection required by paragraph (d)(2) of this AD thereafter at 
intervals not to exceed 6,000 flight cycles until the preventive 
modification specified in paragraph (d)(2)(ii) or (d)(2)(iii) of 
this AD, as applicable, is installed.
    (ii) If any crack is found in an open pilot hole that is located 
inside any of the shaded areas shown in Figures 3, 4, and 5 of the 
service bulletin, prior to further flight, repair the crack in the 
pilot hole and install a preventive modification in accordance with 
Part III or IV of the Accomplishment Instructions of the service 
bulletin. Installation of a preventive modification constitutes 
terminating action for the repetitive inspections of the open pilot 
holes specified in paragraph (d)(2)(i) of this AD.
    (iii) If any crack is found in an open pilot hole that is 
located outside any of the shaded areas shown in Figures 3, 4, and 5 
of the service bulletin, prior to further flight, repair the crack 
in the pilot hole in accordance with part III or IV of the 
Accomplishment Instructions of the service bulletin, and install a 
preventive modification in accordance with a method approved by the 
Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport 
Airplane Directorate. Installation of a preventive modification 
constitutes terminating action for the repetitive inspections of the 
open pilot holes specified in paragraph (d)(2)(i) of this AD.
    (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 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: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (f) Special flight permits may be issued in accordance with FAR 
21.197 and 21.199 to operate the airplane to a location where the 
requirements of this AD can be accomplished.
    (g) The actions shall be done in accordance with Boeing Service 
Bulletin 727-53-0197, Revision 1, dated April 9, 1992. 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.
    (h) This amendment becomes effective on March 3, 1994.

    Issued in Renton, Washington, on January 12, 1994.
John J. Hickey,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-1226 Filed 1-31-94; 8:45 am]
BILLING CODE 4910-13-P