[Federal Register Volume 62, Number 49 (Thursday, March 13, 1997)]
[Rules and Regulations]
[Pages 11760-11763]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-6086]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-23-AD; Amendment 39-9961; AD 97-06-04]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 757-200 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to certain Boeing Model 757-200 series airplanes. This 
action requires inspections to detect cracking on the free edge of the 
tang, if necessary, and of the fastener holes in the lower spar chord; 
and various follow-on actions. This action also provides for optional 
terminating action for the requirements of this AD. This amendment is 
prompted by a report of fatigue cracking in the lower spar chord of two 
Model 757 series airplanes. The actions specified in this AD are 
intended to detect and correct such fatigue cracking, which could 
result in reduced structural integrity of the engine strut.

DATES: Effective March 28, 1997.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 28, 1997.
    Comments for inclusion in the Rules Docket must be received on or 
before May 12, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 97-NM-23-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056.
    The service information referenced in this AD may be obtained from 
Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 
98124-2207. This information may be examined at the FAA, Transport 
Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at 
the Office of the Federal Register, 800 North Capitol Street, NW., 
suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Todd Martin, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-2781; 
fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: The FAA received a report indicating that 
fatigue cracking was found in the lower spar chord on two Boeing Model 
757-200 series airplanes powered by Rolls Royce engines. On one of 
these airplanes, the tang of the chord was cracked completely through. 
The crack had propagated approximately five inches into the vertical 
flange adjacent to the side skins. On the other airplane, a 0.3-inch 
crack was found in the tang of the chord. Such fatigue cracking, if not 
detected and corrected in a timely manner, could result in reduced 
structural integrity of the engine strut.
    An initial analysis conducted by Boeing revealed that the 
stiffening straps, which were installed on the strut midchords of 
twelve airplanes during production, were the primary cause of the 
cracks. Consequently, to prevent cracks in the lower spar chords, the 
stiffening straps were removed from the midchords in accordance with 
Boeing Service Bulletin 757-54-0028. However, results of subsequent 
analysis related to the structural reassessment of the strut structure 
of the Model 757 revealed that cracks can continue to occur after 
removal of the stiffening straps. The analysis also revealed that 
cracks can occur in the same area on struts that are made without 
stiffening straps.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 757-54-
0031, Revision 2, dated December 19, 1996. The service bulletin 
describes procedures for certain inspections and follow-on actions, 
which include the following:
    1. Tang Inspection: The service bulletin describes procedures for 
an eddy current inspection to detect cracking on the free edge of the 
tang. For airplanes on which cracking within certain limits is found, 
the service bulletin describes procedures for removal of the midchord 
channels, stop-drilling of the cracking, and installation of a repair. 
The service bulletin recommends that if any cracking is found that is 
outside specified limits, the lower spar chord must be replaced with a 
new or serviceable chord; however, the service bulletin does not 
provide procedures for such replacement.
    2. Initial Bolt Hole Inspection: The service bulletin also 
describes procedures for an eddy current inspection (bolt hole 
inspection) to detect cracking of the two fastener holes in the lower 
spar chord. For airplanes on which no cracking is found during

[[Page 11761]]

the bolt hole inspection, the service bulletin describes procedures for 
increasing the diameter of the holes by specified dimensions and 
installing new fasteners.
    For airplanes on which cracking is found during this bolt hole 
inspection, and that cracking can be removed by increasing the diameter 
of the hole, the service bulletin describes procedures for increasing 
the diameter of the hole by specified dimensions, and installing new 
fasteners. For airplanes on which cracking that is within certain 
limits is found, but which cannot be removed by increasing the diameter 
of the hole, the service bulletin describes procedures for installation 
of a repair. Additionally, for airplanes on which cracking that is 
outside certain limits is found, the service bulletin recommends that 
the lower spar chord be replaced with a new or serviceable chord. The 
service bulletin does not specify procedures for such replacement.
    3. Repetitive Bolt Hole Inspections: The service bulletin 
recommends that a repetitive bolt hole inspection be accomplished. (The 
procedures for these inspections are the same as those provided for the 
first bolt hole inspection.)
    Installation of a repair eliminates the need for the inspections 
described previously.

Explanation of the Requirements of the Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other Boeing Model 757-200 series airplanes of the 
same type design, this AD is being issued to detect and correct fatigue 
cracking of the lower spar chord, and consequent reduced structural 
integrity of the engine strut.
    This AD requires repetitive eddy current inspections to detect 
cracking on the free edge of the tang; and removal of the midchord 
channels, stop-drilling of cracking, and installation of a repair; if 
necessary. For airplanes on which cracking is found that is outside 
specified limits, this AD requires replacement of the lower spar chord 
with a new or serviceable chord.
    This AD also requires repetitive eddy current inspections (bolt 
hole inspections) to detect cracking of the two fastener holes in the 
lower spar chord. For airplanes on which no cracking is found, this AD 
requires increasing the diameter of the holes by specified dimensions, 
and installing new fasteners. For airplanes on which cracking is found 
that can be removed by increasing the diameter of the hole, this AD 
requires increasing the diameter of the hole by specified dimensions, 
and installing new fasteners. For airplanes on which cracking is found 
that is within certain limits, but which cannot be removed by 
increasing the diameter of the hole, this AD requires installation of a 
repair. Additionally, for airplanes on which cracking that is outside 
certain limits is found, this AD requires replacement of the lower spar 
chord with a new or serviceable chord.
    Accomplishment of the bolt hole inspections terminates the eddy 
current inspections of the free edge of the tang.
    This AD also provides for optional terminating action, which, if 
accomplished, terminates the requirements of the AD.
    Replacement of the lower spar chord, if necessary, is required to 
be accomplished in accordance with a method approved by the FAA. Other 
actions are required to be accomplished in accordance with the service 
bulletin described previously.

Interim Action

    This AD is considered to be interim action. Boeing currently is 
developing a Strut Improvement Program for Model 757 series airplanes, 
which will include installation of a new midchord configuration. The 
FAA may consider further rulemaking to require accomplishment of that 
installation.

Differences Between Service Bulletin and This AD

    Operators should note that, although the service bulletin 
referenced in this AD recommends a ``grace period'' of 120 days for 
accomplishment of the inspections on airplanes that have exceeded 
certain thresholds, this AD specifies a ``grace period'' of 60 days. 
The FAA has been advised that a significant number of the affected 
Model 757 series airplanes have already reached the specified 
thresholds. In developing an appropriate compliance time for this 
action, the FAA considered not only the degree of urgency associated 
with addressing the subject unsafe condition, but the manufacturer's 
recommendation as to an appropriate compliance time, parts 
availability, and the practical aspect of accomplishing the required 
inspections within an interval of time that parallels the normal 
scheduled maintenance for the majority of affected operators.
    In light of this, the FAA has determined that, for airplanes that 
have already reached certain thresholds, a ``grace period'' of 60 days 
is necessary to ensure that the affected airplanes are inspected in a 
timely manner and that an acceptable level of safety is maintained. 
This ``grace period'' is roughly equivalent to 300 flight cycles, which 
the service bulletin specifies as the number of flight cycles that 
should not be exceeded before inspection of the free edge of the tang 
is accomplished on airplanes that have exceeded certain thresholds.
    In addition, the FAA has determined that the eddy current 
inspections of the free edge of the tang must be accomplished on a 
repetitive basis until the bolt hole inspection is accomplished. (The 
service bulletin recommends only a one-time inspection of the free edge 
of the tang.) The FAA finds that these repetitive inspections of the 
tang must be accomplished in the event an initial inspection of the 
tang is performed well before the 15,000 flight cycle threshold.

Determination of Rule's Effective Date

    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must

[[Page 11762]]

submit a self-addressed, stamped postcard on which the following 
statement is made: ``Comments to Docket Number 97-NM-23-AD.'' The 
postcard will be date stamped and returned to the commenter.

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.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, 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 adding the following new 
airworthiness directive:

97-06-04  Boeing: Amendment 39-9961. Docket 97-NM-23-AD.

    Applicability: Model 757-200 series airplanes having line 
numbers 1 through 736 inclusive, powered by Rolls Royce engines, 
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 otherwise 
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 (i) 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 detect and correct fatigue cracking of the lower spar chord, 
and consequent reduced structural integrity of the engine strut, 
accomplish the following:
    (a) Prior to the accumulation of 15,000 total flight cycles, or 
within 60 days after the effective date of this AD, whichever occurs 
later: Perform an eddy current inspection to detect cracking on the 
free edge of the tang, in accordance with the Accomplishment 
Instructions of Boeing Service Bulletin 757-54-0031, Revision 2, 
dated December 19, 1996. Repeat this inspection thereafter at 
intervals not to exceed 3,000 flight cycles until the inspection 
required by paragraph (d) of this AD is accomplished.

    Note 2: The inspection required by paragraph (a) of this AD need 
not be performed on airplanes on which the inspection required by 
paragraph (d) of this AD is performed prior to the compliance time 
specified in paragraph (a) of this AD.

    (b) If any cracking is found during the inspection required by 
paragraph (a) of this AD, and the cracking is within the limits 
specified in the service bulletin: Prior to further flight, remove 
the midchord channels, stop-drill the cracking, and install a repair 
in accordance with the service bulletin. No further action is 
required by this AD.
    (c) If any cracking is found, and the cracking is outside the 
limits specified in the service bulletin: Prior to further flight, 
replace the lower spar chord with a new or serviceable chord in 
accordance with a method approved by the Manager, Seattle Aircraft 
Certification Office (ACO), FAA, Transport Airplane Directorate.
    (d) Perform an eddy current inspection (bolt hole inspection) to 
detect cracking of the two fastener holes in the lower spar chord, 
in accordance with the Accomplishment Instructions of Boeing Service 
Bulletin 757-54-0031, Revision 2, dated December 19, 1996, at the 
time specified in paragraph (d)(1) and (d)(2) of this AD, as 
applicable. Accomplishment of this inspection terminates the 
inspections required by paragraph (a) of this AD.
    (1) For airplanes on which the stiffening straps have been 
removed from the midchord in accordance with Boeing Service Bulletin 
757-54-0028 prior to the effective date of this AD: Accomplish the 
inspection at the time specified in paragraph I.D. of Boeing Service 
Bulletin 757-54-0031, Revision 2, dated December 19, 1996.
    (2) For airplanes other than those identified in paragraph 
(d)(1) of this AD: Accomplish the inspection prior to the 
accumulation of 18,000 total flight cycles, or within 60 days after 
the effective date of this AD, whichever occurs later.
    (e) If no cracking is found during the inspection required by 
paragraph (d) of this AD, prior to further flight, increase the 
diameter of the holes by the dimensions specified in the 
Accomplishment Instructions of Boeing Service Bulletin 757-54-0031, 
Revision 2, dated December 19, 1996, and install new fasteners in 
accordance with the service bulletin.
    (f) If any cracking is found during the inspection required by 
paragraph (d) of this AD, prior to further flight, accomplish 
paragraph (f)(1), (f)(2), or (f)(3) of this AD, as applicable, in 
accordance with the Accomplishment Instructions of Boeing Service 
Bulletin 757-54-0031, Revision 2, dated December 19, 1996.
    (1) If the cracking can be removed by increasing the diameter of 
the hole in accordance with the service bulletin: Increase the 
diameter of the hole by the dimensions specified in the 
Accomplishment Instructions of the service bulletin, and install new 
fasteners in accordance with the service bulletin.
    (2) If the cracking cannot be removed by increasing the diameter 
of the hole in accordance with the Accomplishment Instructions of 
the service bulletin, but the cracking is within the limits 
specified in the service bulletin: Install the repair in accordance 
with the service bulletin. No further action is required by this AD.
    (3) If the cracking is outside the limits specified in the 
service bulletin: Replace the lower spar chord with a new or 
serviceable chord in accordance with a method approved by the 
Manager, Seattle ACO.
    (g) Accomplish either paragraph (g)(1) or (g)(2) of this AD, as 
applicable, in accordance with Boeing Service Bulletin 757-54-0031, 
Revision 2, dated December 19, 1996.
    (1) If any fastener installed as a result of an inspection 
required by paragraph (d) of this AD has a diameter of \5/8\-inch or 
greater: Install the repair prior to the accumulation of the number 
of flight cycles specified in the ``Subsequent Inspection Interval'' 
column of the Threshold Table included in paragraph I.D. of the 
service bulletin.
    (2) If any fastener installed as a result of an inspection 
required by paragraph (d) of this AD has a diameter of less than \5/
8\-inch: Repeat the bolt hole inspection required by paragraph (d) 
of this AD prior to the accumulation of the number of flight cycles 
specified in the ``Subsequent Inspection Interval'' column of the 
Threshold Table included in paragraph I.D. of the service bulletin 
until the repair specified in paragraph (h) of this AD is installed.
    (h) Installation of the repair in accordance with the 
Accomplishment Instructions of Boeing Service Bulletin 757-54-0031, 
Revision 2, dated December 19, 1996, constitutes terminating action 
for the requirements of this AD.

[[Page 11763]]

    (i) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Seattle ACO. Operators shall submit 
their requests through an appropriate FAA Principal Maintenance 
Inspector, who may add comments and then send it to the Manager, 
Seattle ACO.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (j) 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.
    (k) The actions shall be done in accordance with Boeing Service 
Bulletin 757-54-0031, Revision 2, dated December 19, 1996. This 
incorporation by reference was approved by the Director of the 
Federal Register in accordance with 5 U.S.C. 552(a) and 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.
    (l) This amendment becomes effective on March 28, 1997.

    Issued in Renton, Washington, on March 5, 1997.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-6086 Filed 3-12-97; 8:45 am]
BILLING CODE 4910-13-U