[Federal Register Volume 61, Number 191 (Tuesday, October 1, 1996)]
[Proposed Rules]
[Pages 51250-51255]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-25040]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-NM-223-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 727 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Supplemental notice of proposed rulemaking; reopening of 
comment period.

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SUMMARY: This document revises an earlier proposed airworthiness 
directive (AD), applicable to all Boeing Model 727 series airplanes, 
that would have superseded a previously issued AD that currently 
requires inspections to detect cracking of the actuator rib fitting of 
the inboard door of the main landing gear (MLG); and rework or 
replacement of any cracked fitting. The proposed action would have 
required inspections to detect cracking in an expanded area of the 
actuator rib fitting, and various follow-on actions. That action was 
prompted a report of a fractured rib fitting that had been reworked in 
accordance with the existing AD. This new proposed action would expand 
the area of inspection even further than what was previously proposed, 
and would supersede another AD that requires actions related to the 
addressed area of the MLG. The actions specified by the proposed AD are 
intended to prevent damage to the airplane caused by a failure of the 
landing gear to extend due to a fractured rib fitting.

DATES: Comments must be received by October 24, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-NM-223-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 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.

FOR FURTHER INFORMATION CONTACT: Walter Sippel, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-2774; 
fax (206) 227-1181.

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-223-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.

[[Page 51251]]

95-NM-223-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to add an airworthiness directive (AD), applicable to all 
Boeing Model 727 series airplanes, was published as a notice of 
proposed rulemaking (NPRM) in the Federal Register on April 1, 1996 (61 
FR 14271). That NPRM would have superseded AD 90-02-19, amendment 39-
6433 (55 FR 601, January 8, 1990), which currently requires inspections 
to detect cracking of the actuator rib fitting of the inboard door of 
the main landing gear (MLG); and rework or replacement of any cracked 
fitting with a reworked or new fitting. That AD was prompted by an 
incident in which the actuator rib fitting of the MLG door on a Model 
727 series airplane fractured and, consequently, the left MLG of the 
airplane failed to extend for landing. The requirements of that AD are 
intended to prevent damage to the airplane caused by a failure of the 
landing gear to extend due to a fractured rib fitting.

Description of Previous Proposal

    The previously issued NPRM proposed to supersede AD 90-02-19 to:
    1. expand the area of the inspections to require either a high 
frequency eddy current or dye penetrant inspection to detect cracking 
in an expanded area of the actuator rib fitting of the MLG, and various 
follow-on actions;
    2. in cases where no cracking was found, first require modification 
of the rib fitting assembly and, after modification, either repetitive 
high frequency eddy current or dye penetrant inspections; and
    3. in cases where cracking was found, require the replacement of 
the currently installed aluminum rib fitting with a new steel rib 
fitting. (This replacement would terminate the repetitive inspections 
of the fitting.)
    That proposal was prompted by an additional report of an MLG on a 
Model 727 series airplane failing to extend for landing, due to a 
fractured rib fitting. The broken rib fitting caused the MLG door and 
MLG to retract improperly (out of sequence), which led to the MLG 
jamming against the MLG door. That airplane had accumulated 34,039 
flight hours and 22,777 landings. The fitting on that airplane had been 
reworked in accordance with the requirements of AD 90-02-19; no follow-
on inspections of the reworked fitting were required by that AD. 
Further, the area of inspection specified by AD 90-02-19 did not 
include the area of the fitting in which this cracking was found.

Actions Since Issuance of Previous Proposal

    Since issuance of the NPRM, the FAA has received another report of 
an operator who experienced a failure of the MLG door actuator rib 
fitting. The fitting failed due to a fracture at the transitional 
radius. The failure occurred at 1,350 flight cycles after the operator 
had inspected a rib fitting that had been modified (reworked) in 
accordance with Boeing Service Bulletin 727-32-0364, which is required 
by AD 90-02-19. Although that AD does not require repetitive 
inspections of modified rib fittings, this operator had elected to 
inspect them regularly on the airplanes in its fleet. The data from 
this latest incident of cracking confirm the FAA's determination that 
repetitive inspections of modified rib fittings are warranted, and that 
those inspections must be conducted at more frequent intervals than 
proposed in the previous NPRM.
    Based on this data, the FAA has revised the proposal to require 
inspections of rib fittings that previously have been modified in 
accordance with Boeing Service Bulletin 727-32-0364 (but not in 
accordance with Boeing Service Bulletin 727-32-0383) at intervals of 
1,000 flight cycles.
    In addition, the FAA has made other changes to this proposal, based 
on comments received in response to the NPRM, as well as in response to 
the NPRM issued as Docket 95-NM-222-AD (61 FR 14269, April 1, 1996). 
These comments and the ensuing changes are discussed below.

Request To Combine Proposals

    Several commenters request that the FAA combine the proposed AD 
with another proposal that was issued as Docket 95-NM-222-AD. That 
action proposed to revise AD 93-01-14, amendment 39-8468 (58 FR 5574, 
January 22, 1993), to continue to require:
    1. repetitive inspections to detect loose attach fitting bolts of 
door actuator of the MLG;
    2. repetitive inspections to determine whether the serrations of 
the attach fitting of the door actuator of the MLG are fully mated; and
    3. various follow-on corrective actions.
    It also proposed to provide operators the option of terminating all 
of the inspections required by AD 93-01-14 either by replacing the 
currently installed aluminum rib fitting with a new steel rib fitting, 
or by modifying the rib fitting assembly in accordance with Boeing 
Alert Service Bulletin 727-32A0399 and accomplishing follow-on actions. 
Such replacement or modification would also terminate the inspections 
currently required by AD 90-02-19.
    Since the actions of both of these proposals are so closely 
related, the commenters suggest that they be combined into one single 
AD action. The commenters maintain that doing so would create less 
confusion for operators.
    The FAA concurs, and has revised this proposal (Docket 95-NM-223-
AD) to include all of the requirements related to inspections of the 
MLG actuator rib fitting assembly. By separate rulemaking, the FAA will 
withdraw Docket 95-NM-222-AD, since its proposed actions are now 
covered by this new supplemental NPRM.

Requests To Revise Initial Inspection Intervals

    Several commenters request that the FAA revise the proposed initial 
interval for the inspection to detect cracking of the actuator rib 
fitting. The proposal would have required that the inspection be 
conducted at the later of the following:

--prior to the accumulation of 20,000 total flight cycles; or
--prior to the accumulation of 1,000 flight cycles after the effective 
date of the AD or within 2,500 flight cycles after the immediately 
preceding inspection performed in accordance with AD 90-02-19, 
whichever is earlier.

    One commenter requests that the inspection be required at intervals 
of 2,500 flight cycles after the effective date, since this would allow 
the inspection to be accomplished during this commenter's regularly 
scheduled ``C'' check. Another commenter states that accomplishing the 
visual inspection at 1,000 flight cycles, and the high frequency eddy 
current or dye penetrant inspection at 2,500 flight cycles, would 
better suit normal maintenance schedules and still provide an 
acceptable level of safety. Another commenter states that the initial 
inspection interval is too restrictive and does not give credit to 
operators who already have been performing repetitive inspections at 
2,500-flight cycle intervals or if the last inspection was performed 
more than 1,500 flight cycles previously. Another commenter states that 
most operators have already accomplished at least a visual inspection 
of the fitting as a result of the issuance of Boeing All Base Telex

[[Page 51252]]

M-7272-94-2747, dated May 19, 1994, and should receive credit for doing 
it.
    The FAA agrees that the initial inspection interval may be changed 
somewhat, although not necessarily for the reasons suggested by the 
commenters. As explained previously in this preamble, because new 
cracking has been found on modified rib fittings, the FAA finds that 
airplanes on which the rib fittings have been previously modified must 
continue to be inspected. The FAA has considered this cracking data and 
the various configurations of airplanes (those having some modified 
fittings, and those having no modified fittings) that will be affected 
by this proposal, and has revised the proposed schedule for inspections 
as follows:
    1. Airplanes equipped with actuator rib fittings that have been 
modified in accordance with Boeing Service Bulletin 727-32-0364, but 
not with Boeing Service Bulletin 727-32-0383, must be inspected within 
1,000 flight cycles.
    2. Airplanes equipped with rib fittings that have been modified in 
accordance with both Boeing Service Bulletin 727-32-0364 and Boeing 
Service Bulletin 727-32-0383, must be inspected at the later of (a) 
1,000 flight cycles from the effective date of the AD or (b) 1,500 
flight cycles after the immediately preceding inspection performed in 
accordance with AD 90-02-19, or within 1,500 flight cycles after 
accomplishment of the ``terminating action'' specified in AD 93-01-14, 
whichever is earlier.
    3. Airplanes equipped with rib fittings that have been modified in 
accordance with Boeing Alert Service Bulletin 727-32A0399 must be 
inspected within 7,500 flight cycles after modification (and thereafter 
at intervals not to exceed 2,500 flight cycles).
    The FAA considers these inspection times to be warranted, based on 
the data available, and they should fit into normally scheduled 
maintenance intervals for most affected operators.

Request To Extend Compliance Time for Modification

    One commenter requests that the proposed rule be revised to provide 
for a 3-year compliance time for modification of the rib fitting 
assemblies (in accordance with Boeing Alert Service Bulletin 727-
32A0399) if no cracking is detected. This commenter points out that the 
repetitive inspections have been shown to be safe, and that the FAA's 
proposal to modify the fittings at 1,000 flight cycles after the 
effective date of the AD is not justified. The commenter contends that 
adoption of the proposed compliance time would require that this 
commenter special schedule its fleet for this modification, at 
considerable expense over what was estimated by the FAA in it's cost 
impact information. As an alternative to modification, this commenter 
suggests that operators be allowed to conduct repetitive visual 
inspections and high frequency eddy current/dye penetrant inspections 
until the fittings are replaced with steel fittings.
    The FAA partially concurs with the commenters request. Upon 
reconsideration, the FAA agrees that modification within 1,000 flight 
cycles may be too restrictive. However, since fatigue fractures such as 
those experienced on the rib attach fitting are cycle-dependent, not 
time dependent, a calendar time of ``3 years'' is not appropriate for 
correcting a fatigue-related problem.
    In reviewing the available data, the FAA finds that repetitive 
inspections alone will not ensure an acceptable level of safety. The 
data also show that the following items are critical in ensuring a safe 
actuator rib fitting:
    1. proper bolt torque;
    2. proper door rigging; and
    3. removal of poor fatigue details.
    In light of this, the FAA has determined that the modification 
interval can be increased, provided that inspections are conducted more 
frequently, the door is properly rigged, and the bolts are properly 
torqued. The proposed rule has been revised to require these 
inspections of bolt torque and door rigging, and to allow more time for 
modification of those rib fittings on which other modifications have 
been accomplished previously in accordance with Boeing Service Bulletin 
727-32-0364 and Boeing Service Bulletin 727-32-0383.

Request To Allow Unmodified Fittings as Replacement Parts

    Several commenters request that the proposal be revised to allow 
operators to install unmodified fittings as replacement parts. The 
commenters point out that the proposed rule would require that all 
replacement parts be steel fittings. However, the commenters fear that 
there may be a parts availability problem in trying to meet this 
requirement.
    The FAA concurs partially. The latest incident of cracking, 
described previously, indicates that inspections alone are not reliable 
in preventing fractures in the aluminum actuator rib fittings. However, 
FAA finds that it is acceptable to use an aluminum fitting as a 
replacement part, provided that:
    1. It is has been inspected in accordance with Figure 2 of Boeing 
Alert Service Bulletin 727-32A0399;
    2. It has been reworked in accordance with Figure 3 of Boeing Alert 
Service Bulletin 727-32A0399 and in accordance with Boeing Service 
Bulletin 727-32-0364;
    3. After rework, it is installed in accordance with Figure 4 of 
Boeing Alert Service Bulletin 727-32A0399; and
    4. After installation, it is repetitively inspected until replaced 
with a steel fitting.
    Paragraph (d) of this supplemental NPRM specifies this.

Request To Make Service Information References More Specific

    One commenter requests that all of the references in the proposal 
to Boeing service bulletins be revised to make them more specific. The 
commenter suggests that these references cite the specific figure in 
the service bulletins where procedural instructions are found. The 
commenter states that this will provide more clarity to the 
requirements and minimize the chances for errors.
    While the FAA concurs that additional specificity is necessary, it 
does not agree that citing only the ``figure'' in the service bulletin 
is adequate in all cases. A reference to only the figure could 
inadvertently omit important compliance instructions that are necessary 
to accomplish the task. For actions in accordance with Boeing Alert 
Service Bulletin 727-32A0399, the FAA finds that it is more appropriate 
to reference ``Part I,'' ``Part II,'' or ``Part III'' of the 
Accomplishment Instructions, rather than to reference only the figures 
related to those Parts; by doing this, operators will be required to 
consider all steps of the pertinent actions when accomplishing the 
task, and not just the steps listed in the figures. The FAA has revised 
the final rule to include references to these ``Part'' numbers where 
appropriate.

Request To Provide an Option to Certain Steps in Modification 
Requirement

    One commenter requests that the proposed rule provide an option to 
the specific modification procedures called out in Step 1 of Figure 3 
of Boeing Alert Service Bulletin 727-32A0399. That step requires the 
machining of a 0.42-inch, plus/minus 0.03-inch, transition radius. 
According to the service bulletin, this modification is to be 
accomplished with the doors still installed on the airplane. However, 
the commenter states that several machinists have expressed concern 
over their ability to machine such a tight tolerance radius, under 
these

[[Page 51253]]

conditions, on a rib fitting that has already been modified by AD 90-
02-19. The commenter has examined the costs of removing the door and 
sending it to a machine shop for rework, but found this process to be 
cost-prohibitive. Based on this experience, the commenter requests that 
the proposal allow operators, in lieu of the specific instructions in 
Step 1 of Figure 3, the option of blending out the existing machine 
cuts using a .38-inch minimum transition radius to create a smooth 
transition between the adjacent surfaces.
    The FAA concurs that an option to the procedures specified in the 
service bulletin should be provided. This supplemental NPRM would allow 
operators to machine a .39 inch minimum transitional radius. A minimum 
radius of .39 inch will be used since it is the minimum dimension now 
allowed.

Request To Allow Reinstallation of Attaching Hardware

    One commenter requests that the proposal be revised to allow 
operators to inspect and reinstall serviceable attaching hardware 
(i.e., nuts, bolts, and washers) after modifying the rib fitting. This 
commenter states that it routinely disassembles the rib fitting during 
a regularly scheduled ``C'' check and heavy maintenance visit, and 
replaces any corroded hardware found during this process.
    The FAA does not consider that any change to the proposal is 
necessary based on this commenter's request. The proposed rule does not 
mandate the use of new attaching hardware every time the rib fitting is 
disassembled; it only requires the use of the attaching hardware that 
is included as part of the modification described in Boeing Alert 
Service Bulletin 727-32A0399. In addition, that service bulletin 
specifies that fasteners may be substituted in accordance with Chapter 
51 of the 727 Structural Repair Manual.

Conclusion

    Since the change described above expand the scope of the originally 
proposed rule, the FAA has determined that it is necessary to reopen 
the comment period to provide additional opportunity for public 
comment.

Cost Impact

    There are approximately 1,631 Boeing Model 727 series airplanes of 
the affected design in the worldwide fleet. The FAA estimates that 
1,166 airplanes of U.S. registry would be affected by this proposed AD.
    The inspections proposed in this AD action would take approximately 
10 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 
proposed inspections on U.S. operators is estimated to be $699,600, or 
$600 per airplane, per inspection.
    The modification proposed in this AD action would take 
approximately 6 work hours per airplane to accomplish, at an average 
labor rate of $60 per work hour. The cost of required parts would be 
negligible. Based on these figures, the cost impact of the proposed 
modification on U.S. operators is estimated to be $376,560, or $360 per 
airplane.
    These cost impact figures are based on assumptions that no operator 
has yet accomplished any of the proposed requirements of this AD 
action, and that no operator would accomplish those actions in the 
future if this AD were not adopted.
    Should an operator elect to accomplish the proposed terminating 
action (installation of steel fittings), it would take approximately 4 
work hours per airplane, at an average labor rate of $60 per work hour. 
Required parts would cost approximately $428 per airplane. Based on 
these figures, the cost impact of this proposed optional terminating 
action on U.S. operators is estimated to be $668 per airplane.

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 39-6433 (55 FR 
601, January 8, 1990); and by removing amendment 39-8368 (58 FR 5574, 
January 22, 1993); and by adding a new airworthiness directive (AD), to 
read as follows:

Boeing: Docket 95-NM-223-AD. Supersedes AD 90-02-19, amendment 39-
6433; and supersedes AD 93-01-14, amendment 39-8368.

    Applicability: All Model 727 series airplanes, 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 (g) 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 failure of the main landing gear (MLG) to extend for 
landing and subsequent damage to the airplane, accomplish the 
following:
    (a) For airplanes equipped with rib fittings that have been 
modified (reworked) in accordance with Boeing Service Bulletin 727-
32-0364, dated December 15, 1988, or Revision 1, dated October 19, 
1989; but have not been modified in accordance with Figure 2 of 
Boeing Service Bulletin 727-32-0383, Revision 1, dated January 30, 
1992: Accomplish the following:
    (1) Prior to the accumulation of 1,000 flight cycles after the 
effective date of this AD, accomplish the actions specified in both 
paragraphs (a)(1)(i) and (a)(1)(ii):
    (i) Perform either a high frequency eddy current or dye 
penetrant inspection to detect cracking of the actuator rib fitting 
of the

[[Page 51254]]

MLG, in accordance with Part I of the Accomplishment Instructions of 
Boeing Alert Service Bulletin 727-32A0399, dated July 13, 1995. And
    (ii) Inspect the actuator rib fitting of the MLG to ensure that 
serrations are fully mated, and to detect loose bolts, in accordance 
with Figure 1 of Boeing Service Bulletin 727-32-0383, Revision 1, 
dated January 30, 1992.
    (2) If the inspections required by paragraph (a)(1) of this AD 
reveal no cracking or loose bolts, and reveal that the serrations 
are fully mated, accomplish the actions specified in paragraphs 
(a)(2)(i), (a)(2)(ii), and (a)(2)(iii) of this AD:
    (i) Prior to further flight, re-rig the door in accordance with 
the maintenance manual procedures referenced in Boeing Alert Service 
Bulletin 727-32A0399, dated July 13, 1995, to ensure proper door 
rigging. And
    (ii) Thereafter, repeat the inspections required by paragraph 
(a)(1) of this AD at intervals not to exceed 1,000 flight cycles 
until the modification required by paragraph (a)(2)(iii) of this AD 
is accomplished. And
    (iii) Prior to the accumulation of 3,000 flight cycles after the 
effective date of this AD, modify the actuator rib fitting in 
accordance with Part II of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 727-32A0399, dated July 13, 1995. As an 
option to the action specified in Step 1 of Figure 3 of that alert 
service bulletin, operators may layout a .39-inch minimum radius.
    (3) If the inspections required by paragraph (a)(1) of this AD 
reveal no cracking, but do reveal loose bolts or serrations that are 
not fully mated, prior to further flight accomplish either paragraph 
(a)(3)(i) or (a)(3)(ii) of this AD:
    (i) Modify the actuator rib fitting in accordance with Part II 
of the Accomplishment Instructions of Boeing Alert Service Bulletin 
727-32A0399, dated July 13, 1995. As an option to the action 
specified in Step 1 of Figure 3 of that alert service bulletin, 
operators may layout a .39-inch minimum radius. Or
    (ii) Replace the currently-installed aluminum rib fitting with a 
new steel rib fitting, in accordance with Part III of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 727-
32A0399, dated July 13, 1995. After this replacement, no further 
action is required by this AD for that rib fitting.
    (b) For airplanes equipped with rib fittings that have been 
modified in accordance with Boeing Service Bulletin 727-32-0364, 
dated December 15, 1988, or Revision 1, dated October 19, 1989; and 
have been modified in accordance with Figure 2 of Boeing Service 
Bulletin 727-32-0383, Revision 1, dated January 30, 1992: Accomplish 
the following:
    (1) Perform either a high frequency eddy current or dye 
penetrant inspection to detect cracking of the actuator rib fitting 
of the MLG, in accordance with Part I of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 727-32A0399, dated 
July 13, 1995, at the later of the times specified in either 
paragraph (b)(1)(i) or (b)(1)(ii) of this AD.
    (i) Prior to the accumulation of 1,000 flight cycles after the 
effective date of the AD; or
    (ii) Within 1,500 flight cycles after the immediately preceding 
inspection performed in accordance with AD 90-02-19, or within 1,500 
flight cycles after accomplishing the terminating action in 
accordance with AD 93-01-14, whichever is earlier.
    (2) If no cracking is detected during the inspection required by 
paragraph (b)(1) of this AD, accomplish the actions specified in 
paragraphs (b)(2)(i), (b)(2)(ii), and (b)(2)(iii) of this AD:
    (i) Prior to further flight, re-rig the door in accordance with 
the maintenance manual procedures referenced in Boeing Alert Service 
Bulletin 727-32A0399, dated July 13, 1995, to ensure proper door 
rigging. And
    (ii) Thereafter, repeat the inspection required by paragraph 
(b)(1) at intervals not to exceed 2,500 flight cycles until the 
modification required by paragraph (b)(2)(iii) of this AD is 
accomplished. And
    (iii) Prior to the accumulation of 6,000 flight cycles after the 
effective date of this AD, modify the actuator rib fitting in 
accordance with Part II of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 727-32A0399, dated July 13, 1995. A s an 
option to the action specified in Step 1 of Figure 3 of that alert 
service bulletin, operators may layout a .39-inch minimum radius.
    (c) For airplanes equipped with rib fittings that have not been 
modified in accordance with Boeing Service Bulletin 727-32-0364, 
dated December 15, 1988, or Revision 1, dated October 19, 1989: 
Accomplish the following:
    (1) Prior to the accumulation of 1,000 flight cycles after the 
effective date of this AD, accomplish the actions specified in both 
paragraphs (c)(1)(i) and (c)(1)(ii) of this AD:
    (i) Perform either a high frequency eddy current or dye 
penetrant inspection to detect cracking of the actuator rib fitting 
of the MLG, in accordance with Part I of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 727-32A0399, dated 
July 13, 1995. And
    (ii) Inspect the actuator rib fitting of the MLG to ensure that 
serrations are fully mated, and to detect loose bolts, in accordance 
with Figure 1 of Boeing Service Bulletin 727-32-0383, Revision 1, 
dated January 30, 1992.
    (2) If the inspections required by paragraph (c)(1) of this AD 
reveal no cracking or loose bolts, and reveal that the serrations 
are fully mated, prior to further flight, accomplish the actions 
specified in either paragraph (c)(2)(i), (c)(2)(ii), or (c)(2)(iii) 
of this AD:
    (i) Modify the actuator rib fitting in accordance with Part II 
of the Accomplishment Instructions of Boeing Alert Service Bulletin 
727-32A0399, dated July 13, 1995; and in accordance with Boeing 
Service Bulletin 727-32-0364, dated December 15, 1988, or Revision 
1, dated October 19, 1989. As an option to the action specified in 
Step 1 of Figure 3 of Boeing Alert Service Bulletin 727-32A0399, 
operators may layout a .39-inch minimum radius. Or
    (ii) Replace the currently-installed aluminum rib fitting with a 
new steel rib fitting, in accordance with Part III of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 727-
32A0399, dated July 13, 1995. After this replacement, no further 
action is required by this AD for that fitting. Or
    (iii) Replace the fitting with a like fitting that has been 
inspected in accordance with Part I of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 727-32A0399, dated 
July 13, 1995; and modified in accordance with Part II of the 
Accomplishment Instructions of that service bulletin and in 
accordance with Boeing Service Bulletin 727-32-0364, dated December 
15, 1988, or Revision 1, dated October 19, 1989.
    (d) If any cracking is detected during the inspections required 
by paragraphs (a)(1), (b)(1), or (c)(1) of this AD, prior to further 
flight, accomplish the actions specified in either paragraph (d)(1) 
or (d)(2) of this AD:
    (1) Replace the cracked fitting with a like fitting that has 
been inspected in accordance with Part I of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 727-32A0399, dated 
July 13, 1995; and modified in accordance with Part II of the 
Accomplishment Instructions of that service bulletin and in 
accordance with Boeing Service Bulletin 727-32-0364, dated December 
15, 1988, or Revision 1, dated October 19, 1989. As an option to the 
action specified in Step 1 of Figure 3 of Boeing Alert Service 
Bulletin 727-32A0399, operators may layout a .39-inch minimum 
radius. Or
    (2) Replace the cracked fitting with a new steel rib fitting in 
accordance with Part III of the Accomplishment Instructions of 
Boeing Alert Service Bulletin 727-32A0399, dated July 13, 1995. This 
replacement constitutes terminating action for the requirements of 
that AD for that fitting.
    (e) For all airplanes on which modification of the actuator rib 
fitting has been accomplished in accordance with Part II of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 727-
32A0399, dated July 13, 1995; and Boeing Service Bulletin 727-32-
0364, dated December 15, 1988, or Revision 1, dated October 19, 
1989: Within 7,500 flight cycles after accomplishing the 
modification, accomplish the following:
    (1) Perform either a high frequency eddy current or dye 
penetrant inspection to detect cracking of the modified actuator rib 
fitting, in accordance with the alert service bulletin.
    (2) Repeat the inspection thereafter at intervals not to exceed 
2,500 flight cycles until the fitting is replaced with a new steel 
rib fitting, in accordance with Part III of the Accomplishment 
Instructions of the alert service bulletin. This replacement 
constitutes terminating action for the requirements of this AD for 
that fitting.
    (f) Replacement of aluminum actuator rib fittings with new steel 
actuator rib fittings in accordance with Part III of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 727-
32A0399, dated July 13, 1995, constitutes terminating action for the 
requirements of this AD.
    (g) 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 Aircraft Certification 
Office (ACO), FAA, Transport Airplane Directorate. Operators shall 
submit their requests through an

[[Page 51255]]

appropriate FAA Principal Maintenance Inspector, who may add 
comments and then send it to the Manager, Seattle ACO.

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

    (h) 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 September 24, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-25040 Filed 9-30-96; 8:45 am]
BILLING CODE 4910-13-U