AD Amdt-39-10938

[Federal Register Volume 63, Number 239 (Monday, December 14, 1998)]
[Rules and Regulations]
[Pages 68669-68672]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 98-32793]



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Federal Register / Vol. 63, No. 239 / Monday, December 14, 1998 / 
Rules and Regulations

[[Page 68669]]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-311-AD; Amendment 39-10938; AD 98-25-12]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 757-200 Series Airplanes 
Powered by Rolls-Royce RB211-535E4/E4B Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain Boeing Model 757-200 series airplanes, that 
requires repetitive inspections to detect cracking of the honeycomb 
core of the acoustic panels in the engine inlet, and repair, if 
necessary. This amendment also requires eventual replacement of the 
existing engine inlet with a new or serviceable inlet, which, when 
accomplished, terminates the repetitive inspections. This amendment is 
prompted by reports of cracking of the honeycomb core of the acoustic 
panels in the engine inlet, and incidents of pieces of the panels 
breaking off and being ingested into the engine. The actions specified 
by this AD are intended to detect and correct cracking of the honeycomb 
core of the acoustic panels in the engine inlet, which could result in 
reduced structural integrity of the engine inlet, and consequent engine 
shutdown or surge; or, in the event of a fan blade failure, separation 
of the inlet from the engine.

DATES: Effective January 19, 1999.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of January 19, 1999.

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: Kathrine H. Rask, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-1547; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to certain Boeing Model 757-200 
series airplanes was published in the Federal Register on March 26, 
1998 (63 FR 14652). That action proposed to require repetitive 
inspections to detect cracking of the acoustic panels in the engine 
inlet, and repair, if necessary. That action also proposed to require 
eventual replacement of the existing engine inlet with a new inlet, 
which, when accomplished, terminates the repetitive inspections.

Comments Received

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Support for the Proposed AD

    One commenter supports the proposed rule.

Request To Revise Description of Unsafe Condition

    One commenter states that the cracking problem with acoustic panels 
could more accurately be described as cracking of the honeycomb core of 
the acoustic panels. The commenter also states that the two ingestion 
incidents referred to in the Summary and Discussion sections of the 
proposed AD were not confirmed to be caused by panel cracking. In 
addition, the commenter states that testing was unable to provide 
conclusive evidence that the cause of the panel cracking was a 
resonance of the honeycomb structure of the core of the acoustic panels 
coinciding with the passing frequency of the fan blades. The commenter 
states that the testing indicated that high sound pressure levels can 
potentially damage the acoustic panels. The commenter requests that the 
proposed AD be revised to reflect this information.
    The FAA concurs partially. The FAA concurs with the commenter that 
cracking of the acoustic panels occurred in the honeycomb core and has 
revised the final rule to specifically state that the cracking occurred 
in the honeycomb core of the acoustic panels.
    The FAA concurs with the commenter that the two ingestion incidents 
were not confirmed to be caused by panel cracking. However, the 
proposed AD does not state that the two ingestion events were caused by 
panel cracking; it states that there have been two reported incidents 
in which portions of the acoustic panels were ingested into the engine.
    In addition, the FAA concurs partially with the commenter's 
information regarding the cause of the cracking. The cause of the 
honeycomb cracking stated in the proposed AD was determined by the 
engine manufacturer and is discussed in Rolls-Royce Service Bulletin 
RB.211-71-B480. After further discussion with the airplane 
manufacturer, the FAA now understands that the cause of the cracking is 
most likely a combination of the high sound pressure levels and a 
resonance of the honeycomb structure. This information does not change 
the effect of the cracking; therefore, no change to the rule is 
necessary.

Request To Withdraw the Proposed AD

    One commenter, the manufacturer of the acoustic panels, states that 
the engine inlet has been designed to remain attached to the engine 
during a fan blade failure event even with a 90-degree sector of the 
intake barrel failed or missing. The commenter believes that, because 
the attachment of the inlet attachment ring to the inlet is through the 
inlet backing skin, it is unlikely that failures in the honeycomb core 
would cause separation of the inlet from the engine during a fan blade 
failure event, as suggested in the proposed AD.

[[Page 68670]]

    Although no specific request is made by this commenter, the FAA 
infers that the commenter does not agree that an unsafe condition 
exists and requests that the proposed AD be withdrawn. The FAA does not 
concur. The FAA does not agree with the commenter's assessment. In the 
structural analysis of the engine inlet referenced by the commenter, 
the airplane manufacturer assumes that up to a 90-degree sector of the 
intake barrel is failed or missing. The analysis assumes that all or 
part of the damage may be caused by the fan blade failure itself. 
Additionally, the inlet backing skin is the main load path of the 
engine inlet, but the honeycomb core is still required to maintain 
integrity of the remaining structure. Therefore, failures in the 
honeycomb core increase the likelihood of separation of the inlet from 
the engine in the event of a fan blade failure. The FAA finds that no 
change to the final rule is necessary.

Request To Allow Replacement with Serviceable Engine Inlets

    Two commenters request that the FAA allow operators to replace 
damaged engine inlets with serviceable inlets that incorporate improved 
acoustic panels. The commenters state that new hardware is not 
required, and that production capability does not exist to manufacture 
new engine inlets for all affected Boeing Model 757-200 series 
airplanes within the compliance time of the proposed AD. The FAA 
concurs with the commenters that new hardware is not required. The FAA 
has revised the final rule to allow replacement of an affected engine 
inlet with a ``new or serviceable'' engine inlet that incorporates 
improved acoustic panels.

Request To Reference Latest Service Information

    One commenter requests that the FAA add a reference to Rolls-Royce 
Service Bulletin RB.211-71-B480, Revision 2, dated July 17, 1998, to 
the proposed AD. The FAA concurs. This revision specifies larger areas 
of damage that may be repaired than the areas specified by Rolls-Royce 
Service Bulletin RB.211-71-B480, Revision 1, dated August 15, 1997 
(which is cited in the proposal as the appropriate source of service 
information for accomplishment of the inspection requirements of the 
AD). The FAA has revised paragraph (a) of the final rule to include 
Rolls-Royce Service Bulletin RB.211-71-B480, Revision 2, dated July 17, 
1998, as an additional source of service information.

Request To Allow Engine Manufacturer to Approve Repairs

    One commenter states that repair instructions for damaged areas 
larger than the acceptance criteria have already been approved by 
Rolls-Royce and are currently in service.
    Although no specific request is made by this commenter, the FAA 
infers the commenter request that the FAA allow operators to contact 
the manufacturer for repair instructions for damaged areas larger than 
the acceptance criteria. (For findings of damage outside the acceptance 
criteria, this AD requires replacement of the engine inlet acoustic 
panels, rather than contacting Rolls-Royce.)
    The FAA does not concur with this request, because to do so would 
be delegating its rulemaking authority to the engine manufacturer. 
Furthermore, operators with airplanes that have repairs other than 
those repairs contained in the service bulletins are required to either 
replace those engine inlets with new or serviceable engine inlets that 
incorporate improved acoustic panels, or to obtain approval of an 
alternative method of compliance for the repairs. ``NOTE 1'' of this AD 
clearly states the need for requesting approval of an alternative 
method of compliance if the parts have been modified, altered, or 
repaired so that the performance of the requirements of this AD is 
affected. Requests for approval of an alternative method of compliance 
can be made in accordance with the provisions of paragraph (c) of this 
AD and should include the substantiation data for the structural 
integrity of the repair. No change to the rule is necessary in this 
regard.

Changes to Cost Impact Information

    The FAA has been advised by Boeing that only 5 airplanes operated 
in the U.S. are still equipped with unmodified engine inlets. 
Accordingly, the FAA has revised the cost impact information, below, to 
reflect this information.

Changes to Service Bulletin References

    The final rule has been revised to reference two appendices and a 
supplement to certain service information cited in the AD, as listed 
below. These references were omitted inadvertently from the proposed 
AD.

--Rolls-Royce Service Bulletin RB.211-71-B480, Revision 1, dated August 
15, 1997, including Appendix 1, Revision 1, dated August 15, 1997, and 
Appendix 2, dated November 10, 1995.
--Rolls-Royce Service Bulletin RB.211-71-9958, Revision 1, dated August 
26, 1994, including Supplement, dated March 18, 1994.

Conclusion

    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule 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.

Cost Impact

    There are approximately 52 Model 757-200 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 24 
airplanes of U.S. registry will be affected by this AD.
    Assuming both engines have inlets on which the improved acoustic 
panels have not been installed, it will take approximately 3 work hours 
per airplane (1.5 work hours per engine) to accomplish the required 
inspection, at an average labor rate is $60 per work hour. Based on 
these figures, the cost impact of this inspection required by this AD 
on U.S. operators is estimated to be $4,320, or $180 per airplane, per 
inspection cycle.
    Assuming both engines have inlets on which the improved acoustic 
panels have not been installed, it would take approximately 4 work 
hours per airplane (2 work hours per engine) to accomplish the required 
replacement, at an average labor rate of $60 per work hour. Required 
parts will be provided by the engine manufacturer at no cost to the 
operator. Based on these figures, the cost impact of this modification 
required by this AD on U.S. operators is estimated to be $5,760, or 
$240 per airplane.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the requirements of this 
AD action, and that no operator would accomplish those actions in the 
future if this AD were not adopted. However, the FAA has been advised 
that new or serviceable engine inlets have been installed on 19 U.S.-
registered airplanes in accordance with the requirements of this AD. 
Therefore, the future economic cost impact of the required inspection 
on U.S. operators is now only $900, or $180 per airplane, per 
inspection cycle; and the future economic cost impact of the required 
modification on U.S. operators is now only $1,200, or $240 per 
airplane.

[[Page 68671]]

Regulatory Impact

    The regulations adopted herein will not have substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government.
    Therefore, in accordance with Executive Order 12612, it is 
determined that this final rule does not have sufficient federalism 
implications to warrant the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) will not have a 
significant economic impact, positive or negative, on a substantial 
number of small entities under the criteria of the Regulatory 
Flexibility Act. A final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it may be obtained 
from the Rules Docket at the location provided under the caption 
ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends part 39 of 
the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39--AIRWORTHINESS DIRECTIVES

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

    Authority: 49 U.S.C. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

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

98-25-12  Boeing: Amendment 39-10938. Docket 97-NM-311-AD.

    Applicability: Model 757-200 series airplanes equipped with 
Rolls-Royce RB211-535E4/E4B engines fitted with nose cowls having 
serial numbers 9001 through 9124 inclusive; 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 (c) 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 cracking of the honeycomb core of the 
acoustic panels in the engine inlet, which could result in reduced 
structural integrity of the engine inlet, and consequent engine 
shutdown or surge; or in the event of a fan blade failure, 
separation of the inlet from the engine; accomplish the following:
    (a) Within 60 days after the effective date of this AD, perform 
a detailed inspection to detect cracking of the honeycomb core of 
the acoustic panels in the engine inlet, in accordance with Rolls-
Royce Service Bulletin RB.211-71-B480, Revision 1, dated August 15, 
1997, including Appendix 1, Revision 1, dated August 15, 1997, and 
Appendix 2, dated November 10, 1995; or Revision 2, including 
Appendices 1 and 2, both dated July 17, 1998.
    (1) If no cracking is detected, repeat the inspection thereafter 
at intervals not to exceed 650 hours time-in-service.
    (2) If any cracking is detected, accomplish the requirements of 
paragraph (a)(2)(i) or (a)(2)(ii), as applicable.
    (i) If cracking is within the acceptance standards provided in 
paragraph 2.A. of Appendix 1 of the service bulletin, repair within 
350 hours time-in-service, in accordance with the service bulletin. 
Thereafter, repeat the inspection required by paragraph (a) of this 
AD at intervals not to exceed 650 hours time-in-service.
    (ii) If cracking is outside the acceptance standards provided in 
paragraph 2.A. of Appendix 1 of the service bulletin, prior to 
further flight, replace the engine inlet with a new or serviceable 
engine inlet that incorporates improved acoustic panels, in 
accordance with Rolls-Royce Service Bulletin RB.211-71-9909, 
Revision 1, dated May 26, 1995; and Rolls-Royce Service Bulletin 
RB.211-71-9958, Revision 1, dated August 26, 1994, including 
Supplement, dated March 18, 1994. No further action is required by 
this AD for that engine inlet.
    (b) Within 18 months after the effective date of this AD, 
replace both existing engine inlets with new or serviceable inlets 
that incorporate improved acoustic panels, in accordance with Rolls-
Royce Service Bulletin RB.211-71-9909, Revision 1, dated May 26, 
1995, and Rolls-Royce Service Bulletin RB.211-71-9958, Revision 1, 
dated August 26, 1994, including Supplement, dated March 18, 1994. 
Accomplishment of such replacement constitutes terminating action 
for the requirements of this AD.
    (c) 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 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.

    (d) 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.
    (e) The actions shall be done in accordance with the following 
Rolls-Royce service bulletins, as applicable, which contain the 
following list of effective pages:

----------------------------------------------------------------------------------------------------------------
 Service Bulletin Reference                                 Revision level Shown on
          and Date                    Page Number                    Page                 Date Shown on Page
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RB.211-71-9909 Revision 1,    1, 3......................  1.........................  May 26, 1995
 May 26, 1995.                2, 4, 5...................  Original..................  January 7, 1994.
RB.211-71-9958 Revision 1,    1, 3......................  1.........................  August 26, 1994
 August 26, 1998.             2, 4, 5...................  Original..................  March 18, 1994.
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                                                   Supplement
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                              1.........................  Original..................  March 18, 1994.
RB.211-71-B480 Revision 1,    1-4.......................  1.........................  August 15, 1997.
 August 15, 1997.
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                                                   Appendix 1
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                              1, 4......................  Original..................  November 10, 1995.

[[Page 68672]]

 
                              2, 3......................  1.........................  August 15, 1997.
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                                                   Appendix 2
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                              1-6.......................  Original..................  November 10, 1995.
RB.211-71-B480 Revision 2,    1-3.......................  2.........................  July 17, 1998.
 July 17, 1998.               4.........................  1.........................  August 15, 1997.
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                                                   Appendix 1
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                              1.........................  Original..................  November 10, 1995.
                              2-4.......................  2.........................  July 17, 1998.
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                                                   Appendix 2
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                              1, 3......................  2.........................  July 17, 1998.
                              2, 4-6....................  Original..................  November 10, 1995.
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    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.
    (f) This amendment becomes effective on January 19, 1999.

    Issued in Renton, Washington, on December 3, 1998.
John W. McGraw,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-32793 Filed 12-11-98; 8:45 am]
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