[Federal Register Volume 59, Number 86 (Thursday, May 5, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-10394]


[[Page Unknown]]

[Federal Register: May 5, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 91-ANE-47; Amendment 39-8878; AD 94-08-06]

 

Airworthiness Directives; Pratt & Whitney JT9D-7R4 Series 
Turbofan Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to Pratt & Whitney JT9D-7R4 series turbofan engines, that 
requires initial and repetitive fan blade leading edge inspections, and 
either installation of fan blade sets with modified fan blade shrouds 
or rework of the fan blade shrouds as a terminating action to the 
inspections. This amendment is prompted by reports of flutter-induced 
fan blade fractures. The actions specified by this AD are intended to 
prevent fan blade fracture and uncontained engine failure, resulting in 
possible damage to the aircraft.

DATES: Effective July 5, 1994.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of July 5, 1994.

ADDRESSES: The service information referenced in this AD may be 
obtained from Pratt & Whitney, 400 Main Street, East Hartford, CT 
06108. This information may be examined at the Federal Aviation 
Administration (FAA), New England Region, Office of the Assistant Chief 
Counsel, 12 New England Executive Park, Burlington, MA; or at the 
Office of the Federal Register, 800 North Capitol Street, NW., suite 
700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: John Fisher, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone (617) 
238-7149, fax (617) 238-7199.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations to include an airworthiness directive (AD) that is 
applicable to Pratt & Whitney (PW) JT9D-7R4 series turbofan engines was 
published in the Federal Register on June 2, 1993 (58 FR 31356). That 
action proposed to require initial and repetitive on-wing or shop fan 
blade leading edge inspections to check for leading edge damage in 
accordance with PW Service Bulletin (SB) No. 72-255, Revision 5, dated 
January 8, 1990; and to require fan blade set replacement or optional 
rework of the fan blade shrouds in accordance with PW SB No. 72-309, 
Revision 9, dated June 12, 1991. Though the NPRM referenced PW SB No. 
72-309, Revision 9, dated June 12, 1991, this final rule incorporates 
the later Revision 10, dated September 2, 1993, which is substantially 
unchanged from Revision 9. Rework of the fan blade shrouds in 
accordance with PW SB No. 72-309, Revision 9, dated June 12, 1991, is 
an acceptable alternate means of compliance for paragraphs (c) and (d) 
of this AD.
    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 comment states that the proposed 90-day requirement for 
initializing the inspection program poses a significant hardship and 
economic impact due to difficulty in scheduling engine maintenance. 
This comment requests extending the initializing period to 180 days. 
The Federal Aviation Administration (FAA) agrees that the proposed 
initial 90-day eddy current inspection requirement may be burdensome to 
some operators. The FAA has therefore added a visual inspection as an 
option to the eddy current inspection in this final rule. This visual 
inspection offers greater flexibility in scheduling as it can easily be 
performed in the field. The FAA does not concur, however, in extending 
the initializing period to 180 days, as this time period does not offer 
an adequate level of safety based on risk analysis results. This final 
rule establishes an interval of 200 cycles in service (CIS) before 
visual or eddy current inspection that should enable operators to 
initialize the inspection program with minimum disruption to scheduling 
without reducing flight safety. Also, the FAA has added guidance 
emphasizing the manner in which the visual inspection should be 
performed.
    One comment requests eliminating the reference in paragraphs (a) 
and (b) of the proposed rule to the leading edge refurbishment 
described in PW Service Bulletin (SB) No. 72-117, as the determining 
factor for beginning the inspection program. The comment further states 
that a previous AD, 90-14-08, already requires the leading edge 
refurbishment described in PW SB No. 72-117, and therefore meets the 
intent of paragraphs (a) and (b) of the proposed rule. The FAA concurs. 
Repetitive leading edge refurbishment as described in PW SB No. 72-117 
is already required by AD 90-14-08. The compliance section of this AD 
has been changed from the wording in the NPRM to eliminate reference to 
leading edge refurbishment, and combines paragraphs (a) and (b) of the 
proposed rule into a new paragraph (a) which has the same inspection 
requirements and interval of 200 CIS as the repetitive inspections of 
paragraph (c) of the proposed rule.
    One comment states that the mandatory incorporation of the fan 
blade shroud angle rework to 52 degrees as described in PW SB No. 72-
309 should be relaxed from within two years after the effective date of 
this AD to the next engine shop visit, thereby reducing the potential 
for on-wing maintenance induced error. The FAA does not concur. The FAA 
has determined that it is necessary to expeditiously remove fan blades 
with the 62 degree shroud configuration, thereby reducing the potential 
for operating the fan blade in flutter. The FAA has reviewed a risk 
analysis study that indicates that a two-year time period for 
incorporating this modification is required to lower the risk 
sufficiently to avert future potential uncontained fan blade failures.
    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 described 
previously. 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 730 PW JT9D-7R4 series engines of the 
affected design in the worldwide fleet. The FAA estimates that 220 
engines installed on aircraft of U.S. registry would be affected by 
this AD, and that the average labor rate is $55 per work hour. The 
inspections required by this AD will take approximately 1.6 work hours 
per engine. The blade rework will cost approximately $15,600 per 
engine. Based on these figures, the total cost impact of the AD on U.S. 
operators is estimated to be $3,451,360.
    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:

94-08-06 Pratt & Whitney: Amendment 39-8878. Docket 91-ANE-47.

    Applicability: Pratt & Whitney (PW) JT9D-7R4 series turbofan 
engines installed on but not limited to Boeing Models 747 and 767 
aircraft, and Airbus Models A300 and A310 aircraft.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent fan blade fracture and uncontained engine failure, 
resulting in possible damage to the aircraft, accomplish the 
following:
    (a) Perform an initial visual or eddy current inspection of the 
fan blade set leading edges for leading edge damage within 200 
cycles in service (CIS) after the effective date of this AD, and 
rework or replace fan blades as necessary, in accordance with the 
Accomplishment Instructions of PW Service Bulletin (SB) No. 72-255, 
Revision 5, dated January 8, 1990. Perform the fan blade leading 
edge visual inspections using a strong white light, as well as 
fingernails and fingertips when inspecting for nicked, eroded, or 
blunt leading edges.
    (b) Thereafter, perform repetitive visual or eddy current fan 
blade leading edge inspections, at intervals not to exceed 200 CIS, 
and rework or replace fan blades as necessary, in accordance with 
the Accomplishment Instructions of PW SB No. 72-255, Revision 5, 
dated January 8, 1990. Perform the fan blade leading edge visual 
inspections using a strong white light, as well as fingernails and 
fingertips when inspecting for nicked, eroded, or blunt leading 
edges.
    (c) For PW Model JT9D-7R4H1 engines, install a new or reworked 
fan blade set with a 52 degree shroud angle, in accordance with PW 
SB No. 72-309, Revision 10, dated September 2, 1993, within 1 year 
after the effective date of this AD.
    (d) For PW Models JT9D-7R4D, D1, E, E1, G2, and E4 engines, 
install a new or reworked fan blade set with a 52 degree shroud 
angle, in accordance with PW SB No. 72-309, Revision 10, dated 
September 2, 1993, within 2 years after the effective date of this 
AD.
    (e) Installation of a new or reworked fan blade set with a 52 
degree fan blade shroud angle, in accordance with paragraphs (c) or 
(d) of this AD, constitutes a terminating action to the inspection 
requirements of paragraphs (a) and (b) of this AD.
    (f) 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, Engine Certification Office. The 
request should be forwarded through an appropriate FAA Principal 
Maintenance Inspector, who may add comments and then send it to the 
Manager, Engine Certification Office.

    Note: Information concerning the existence of approved 
alternative methods of compliance with this airworthiness directive, 
if any, may be obtained from the Certification Office.

    (g) Special flight permits may be issued in accordance with 14 
CFR 21.197 and 21.199 to operate the airplane to a location where 
the requirements of this AD can be accomplished.
    (h) The modification and inspections shall be done in accordance 
with the following service bulletins:

----------------------------------------------------------------------------------------------------------------
                       Document No.                             Pages          Revision             Date        
----------------------------------------------------------------------------------------------------------------
PW SB No. 72-255..........................................             1-2               5  Jan. 8, 1990.       
                                                                       3-4               4  Aug. 25, 1988.      
                                                                         5               5  Jan. 8, 1990.       
                                                                       6-8               3  Aug. 17, 1987.      
                                                                                                                
Total Pages: 8.                                                                                                 
                                                                                                                
PW SB No. 72-309..........................................               1              10  Sept. 2, 1993.      
                                                                         2               8  Apr. 5, 1989.       
                                                                       3-4               9  Jun. 12, 1991.      
                                                                         5           (\1\)  Oct. 2, 1986.       
                                                                         6               1  Nov. 7, 1986.       
                                                                         7               5  Jul. 22, 1987.      
                                                                      8-10               8  Apr. 5, 1989.       
                                                                        11              10  Sept. 2, 1993       
                                                                     12-18               8  Apr. 5, 1989        
                                                                     19-20              10  Sept. 2, 1993       
                                                                        21               8  Apr. 5, 1989        
Total Pages: 21.                                                                                                
                                                                                                                
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\1\Original.                                                                                                    

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 Pratt & Whitney, 400 Main Street, 
East Hartford, CT 06108. Copies may be inspected at the FAA, New 
England Region, Office of the Assistant Chief Counsel, 12 New 
England Executive Park, Burlington, MA; or at the Office of the 
Federal Register, 800 North Capitol Street, NW., suite 700, 
Washington, DC.
    (i) This amendment becomes effective on July 5, 1994.

    Issued in Burlington, Massachusetts, on April 5, 1994.
Jay J. Pardee,
Manager, Engine and Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 94-10394 Filed 5-4-94; 8:45 am]
BILLING CODE 4910-13-P