[Federal Register Volume 64, Number 146 (Friday, July 30, 1999)]
[Rules and Regulations]
[Pages 41273-41274]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-19296]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-ANE-21-AD; Amendment 39-11233; AD 98-23-07 R1]


Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan 
Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; rescission; request for comments.

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SUMMARY: This amendment rescinds Airworthiness Directive (AD) 98-23-07, 
which is applicable to certain Pratt & Whitney (PW) JT9D series 
turbofan engines. That AD requires a one-time acid etch inspection of 
the turbine exhaust case (TEC) wall between and on either side of the 
``3R'' and ``S'' rails in the engine mount lug area (top quadrant of 
the case) for the presence of weld material, and if weld material is 
detected, removal from service and replacement with serviceable parts. 
The requirements of that AD were intended to prevent TEC structural 
failure under abnormal operating conditions, which could result in 
reduced main mount load capability, engine separation from the wing and 
subsequent loss of control of the airplane. Since the issuance of that 
AD, the FAA received reports from the manufacturer that describe a new 
safety analysis that determines the acid etch inspection for weld 
material is unnecessary.

DATES: Effective July 30, 1999.
    Comments for inclusion in the Rules Docket must be received on or 
before September 28, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Regional 
Counsel, Attention: Rules Docket No. 98-ANE-21-AD, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may also be sent 
via the Internet using the following address: ``9-ane-
[email protected]''. Comments sent via the Internet must contain the 
docket number in the subject line.

FOR FURTHER INFORMATION CONTACT: Tara Goodman, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England

[[Page 41274]]

Executive Park, Burlington, MA 01803-5299; telephone (781) 238-7130, 
fax (781) 238-7199.

SUPPLEMENTARY INFORMATION: On November 5, 1998, the Federal Aviation 
Administration (FAA) issued Airworthiness Directive (AD) 98-23-07, 
amendment 39-10872 (63 FR 63393, November 13, 1998), applicable to 
certain Pratt & Whitney (PW) Models JT9D-7, -7A, -7H, -7AH, -7F, -7J, -
20, -20J, -7Q, -7Q3, -59A, -70A, and -7R4D turbofan engines. That AD 
requires a one-time acid etch inspection of the turbine exhaust case 
(TEC) wall between and on either side of the ``R'' and ``S'' rails in 
the engine mount lug area (top quadrant of the case) for the presence 
of weld material, and if weld material is detected, removal from 
service and replacement with serviceable parts. That action was 
prompted by reports of weld rework performed in the outer case wall of 
the TEC, in the mount lug fillet area, during original production to 
address local under minimum wall thickness conditions which at the time 
was considered to have left the TEC's structural capability 
compromised. That condition, if not corrected, was considered to have 
the potential to result in TEC structural failure under abnormal 
operating conditions, which could result in reduced main mount load 
capability, engine separation from the wing and subsequent loss of 
control of the airplane.
    Since the issuance of that AD, the FAA has reviewed detailed 
analyses for PW JT9D engine installations (excluding the JT9D-7R4 
bulged low pressure turbine/TEC configurations). The analyses show that 
sufficient margin exists for TECs installed in JT9D-3A, -7, -7A, -7H, -
7AH, -7F, -7J, -20, -20J, -7Q, -7Q3, -59A, -70A, and -7R4D engine 
configurations under abnormal operating conditions. The results also 
show that there are no flight safety issues resulting from weld rework 
in the outer case wall of the TEC in the mount lug fillet area.
    Welding in the mount lug area of the TEC was performed on several 
PW JT9D series TECs during original manufacture in order to address 
case wall thickness that was below the minimum. Since original type 
certification and at present, cracking and welding are prohibited in 
the mount lug area in accordance with the Engine Manual, because of 
concern for structural integrity during abnormal operating conditions. 
The results of the analyses show that the area where welding is 
prohibited in the Engine Maintenance Manual can be redefined, such that 
welding would only be prohibited on the mount pads.
    The FAA has reviewed the analytical results and has determined that 
welding in the fillets at the base of the ``R'' and ``S'' rails and the 
shell wall does not compromise the structural integrity of the TEC. 
Therefore, the FAA has determined that it is necessary to rescind AD 
98-23-07 in order to prevent operators from performing an unnecessary 
action. The current AD requires a one-time inspection of the TEC to be 
performed at the next shop visit. Operators are currently facing the 
requirement to perform this unnecessary inspection; therefore, it is 
impractical to provide prior notice and opportunity for public comment 
before rescinding the current AD.
    In addition, since this action rescinds a requirement to perform an 
unnecessary action, it has no adverse economic impact and imposes no 
additional burden on any person. Therefore, notice and public 
procedures hereon are impractical and the rescission may be made 
effective upon publication in the Federal Register.

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 should 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 notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 98-ANE-21-AD.'' The postcard will be date stamped and 
returned to the commenter.

The Rescission

    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 removing amendment 39-10872 and 
adding 98-23-07 R1 to read as follows:

98-23-07 R1: Amendment 39-11233. Docket No. 98-ANE-21-AD. Rescinds 
AD 98-23-07, Amendment 39-10872.

    Applicability: Pratt & Whitney (PW) Models JT9D-7, -7A, -7H, -
7AH, -7F, -7J, -20, -20J, -7Q, -7Q3, -59A, -70A, and -7R4D turbofan 
engines. These engines are installed on but not limited to Boeing 
747 and 767 series, McDonnell Douglas DC-10 series, and Airbus 
Industrie A300 and A310 series airplanes.
    This rescission is effective July 30, 1999.

    Issued in Burlington, Massachusetts, on July 15, 1999.
Mark C. Fulmer,
Acting Manager, Engine and Propeller Directorate, Engine Certification 
Office.
[FR Doc. 99-19296 Filed 7-29-99; 8:45 am]
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