Airworthiness Directives; Pratt & Whitney JT8D Series Turbofan Engines

Summary:

This amendment adopts a new airworthiness directive (AD), applicable to Pratt Whitney (PW) JT8D series turbofan engines, that requires inspections of main fuel pump control shafts for excessive spline wear. Additionally, as terminating action to the inspections, this action requires the replacement of the main fuel pump control shaft with parts of improved design, and reworking the main fuel pump impeller, impeller gear train plate assembly, and impeller cover assembly. This amendment is prompted by reports of failed main fuel pump control shafts caused by excessive spline wear. The actions specified by this AD are intended to prevent loss of engine throttle control, uncommanded acceleration, uncommanded deceleration or inflight shutdown, which could result in reduced airplane control during a critical phase of flight.

Table of Contents

Table of Figures

Addresses:

The service information referenced in this AD may be obtained from Pratt Whitney, 400 Main St., East Hartford, CT 06108; telephone (860) 565-8770, fax (860) 565-4503. This information may be examined at the Federal Aviation Administration (FAA), New England Region, Office of the Regional 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:

Christopher Spinney,Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone (781) 238-7175, fax (781) 238-7199.

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 Pratt Whitney (PW) Models JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -15A series turbofan engines was published in the Federal Register on May 5, 2000 (65 FR 26152). That action proposed to require inspections of main fuel pump control shafts for excessive spline wear. Additionally, as terminating action to the inspections, this proposal would require the replacement of the main fuel pump control shaft with parts of improved design, and reworking the main fuel pump impeller, impeller gear train plate assembly, and impeller cover assembly.

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.

Use of PMA Part Number

One comment requests that the FAA clarify the AD to allow the use of a parts manufacturer approved (PMA) part for the new main fuel pump control shaft. The FAA agrees that the addition of specific part number language will clarifiy the requirements of the AD. Specific part number language has been added to paragraph (e) of the AD.

Request To Clarify Gearbox Change Maintenance

One comment asks the FAA to clarify the requirements regarding a gearbox change where the entire gearbox is removed and the hardware, including the fuel pump, is transferred to the replacement gearbox. The FAA does not agree that the inspection requirements need to be clarified. In the case of the gearbox change, the accessibility of the main fuel pump is clearly defined in paragraph (e)(1) of this AD and, therefore, requires the inspections detailed in paragraph (a) of the AD.

Requests for Extension of Inspection and Replacement Limits

Two comments request that inspection and replacement intervals be extended or altered. One comment asks that the FAA extend the overhaul limit for main fuel pumps with more that 12,000 hours TIS since overhaul from 2000 hours TIS to 3000 hours TIS. Another comment requests that the overhaul limit for a main fuel pump with over 12,000 TIS be extended to 6,000 hours if a successful inspection is performed on the pump. Extensions are requested based on the impact the additional fuel pump overhauls will have on an operator's fleet. The FAA agrees in part with these comments. It is not the intent of this AD to place any undue burden on an operator's fleet maintenance. The FAA understands from these comments that some operators would prefer to have an alternative plan that precludes performing the inspections and the associated unplanned maintenance that may result from the inspection program. These operators would prefer to be proactive and to expedite the main fuel pump overhauls on a scheduled basis in order to be fully compliant with the required closing action of the AD, rather than having to perform line maintenance inspections. The FAA has determined that this is an acceptable approach and has added an optional accelerated fleet campaign program that will permit the closing action for the AD to be performed for the entire fleet with the highest time main fuel pumps being addressed first. However, the FAA realizes that the optional plan still may not satisfy the fleet impact concerns of all operators. Operators who believe that the actions required by the AD are a significant burden on their operations and who can show that an alternative plan meets the requirements of paragraph (f) of this AD should submit those plans in accordance with the instructions of paragraph(f).

Request for Extension of the Initial Inspection Threshold

A comment requests that the 1000 hours TIS threshold time for conducting accessibility inspections be extended. The FAA concurs and has extended the initial inspection threshold to 3000 hours TIS for main fuel pumps that have not incorporated the reworked impeller, impeller gear train plate assembly and impeller cover assembly. For main fuel pumps that have incorporated the reworked impeller, impeller gear train plate assembly and impeller cover assembly the initial inspection threshold has been extended to 6000 hours TIS. These changes are reflected in paragraph (a) of this AD.

Change Terminating Action

One comment recommends that the reworked impeller, impeller gear train plate assembly and impeller cover assembly be deemed terminating action to the inspections of paragraphs (a) and (b). This comment asks that the FAA eliminate the replacement of the main fuel pump control shaft as terminating action. The FAA agrees in part. The FAA recognizes that partial incorporation of the terminating actions has some benefit to the main fuel pump control shaft durability. However, the FAA does not agree that it should be terminating action to the inspections. Instead a relaxed inspection and replacement schedule has been added for main fuel pumps that have incorporated the reworked impeller, impeller gear train plate assembly and impeller cover assembly. These changes are reflected in paragraphs (a)(1) and (c)(3)(iii) of this AD.

Modify Definition of Accessibility

One comment suggests that, to be consistent with the alert service bulletin, the words “on the engine” be added to the definition of accessibility.The FAA agrees and has modified the definition in paragraph (e) for clarity.

Typographical Errors in ASB

Two comments point out several typographical errors in ASB A6381. The FAA agrees that some typographical errors may exist in the ASB, however, the errors will not prevent proper execution of the instructions in the ASB. The alleged typographical errors will be forwarded to the manufacturer for possible corrections to later revisions of the ASB.

Require Inspections at Shop Visits only

One comment states that the accessibility inspection requirements place a burden on large complex maintenance operations because of the variety of possible locations and fuel pump exposures. The comment suggests that the FAA limit inspections to a shop visit to reduce the training and tooling required for all of the line maintenance facilities. The FAA agrees and has added an optional accelerated fleet campaign in paragraph (d) of this AD for operators who choose not to equip their line maintenance facilities with the necessary training and tooling to perform the inspections of this AD.

Removal of Engine Models

One comment requests that the FAA remove JT8D-1, -1A and -1B models from the applicability section of the AD. The FAA does not agree. While these particular models are no longer believed to be operating, they are still listed on the type certificate for the JT8D and, as such, must be included in the applicability section of the rule.

Removal of Backlash Inspection

One comment recommends removal of the backlash inspection because of the possibility of missing a worn control shaft. The FAA does not agree. While no inspection program can be 100% effective, this inspection minimizes the possibility of a badly worn main fuel pump control shaft being returned to service prior to being replaced at the next overhaul.

Use of Argo-Tech Parts List Number

One comment recommends that the AD be changed to state that a certain Argo-Tech parts list number should be referenced as terminating action to the inspections of the AD. The FAA does not agree that a change needs to be made to the AD to reference the Argo-Tech parts list number. The certified parts list for an engine build is based on the engine manufacturer's part numbers. There is no top level part number change on the engine manufacturer's top level part number for the main fuel pump assembly, and, therefore, no change in the AD compliance section. An operator may use the Argo-Tech parts list number as long as they can demonstrate by the incorporation of that number that the appropriate maintenance actions required by the AD have been complied with.

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.

Economic Impact

There are approximately 5,800 engines of the affected design in the worldwide fleet. The FAA estimates that 2962 engines installed on aircraft of US registry would be affected by this proposed AD, that it would take approximately 0.3 work hours to perform the required inspections and 0.5 hours per engine to accomplish the replacements proposed at overhaul, and that the average labor rate is $60 per work hour. Required parts would cost approximately $3,996 per engine. Based on these figures, the total cost impact of the proposed AD on US operators is estimated to be $11,978,328.

Regulatory Impact

This rule does not have federalism implications, as defined in Executive Order 13132, because it would not have a substantial direct effect 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. Accordingly, the FAA has not consulted with state authorities prior to publication of this rule.

For the reasons discussed above, I certify that this action (1) is not a “significant regulatory action” underExecutive Order 12866; (2) is not a “significant rule” underDOT 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 RulesDocket. 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.

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

2000-22-06Pratt Whitney: Amendment 39-11952. Docket No. 99-NE-29-AD.

Applicability: Pratt Whitney (PW) Models JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -15A turbofan engines, installed on but not limited to Boeing 727 and 737 series, and McDonnell Douglas DC-9 series airplanes.

Note 1:

This airworthiness directive (AD) applies to each engine 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 engines 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 (f) 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 loss of engine throttle control, uncommanded acceleration, uncommanded deceleration or inflight shutdown, which could result in reduced airplane control during a critical phase of flight, accomplish the following:

Initial Inspection

(a) Inspect and, if necessary, replace the main fuel pump control shaft in accordance with procedures and intervals described in paragraphs 1.B. and 1.C. of the Accomplishment Instructions of PW Alert Service Bulletin (ASB) A6381, dated March 15, 2000, as follows:

(1) For fuel pumps that have incorporated the modifications of paragraph (c)(1) but not the modifications of paragraph (c)(2) as of the effective date of this AD, perform the initial inspection at the next main fuel pump accessibility after accumulating 6000 hours time in service (TIS) since last main fuel pump overhaul.

(2) For fuel pumps that have not incorporated the modifications of paragraph (c)(1) as of the effective date of this AD, perform the initial inspection at the next main fuel pump accessibility after accumulating 3000 hours TIS since last main fuel pump overhaul.

Repetitive Inspections

(b) Thereafter, reinspect the main fuel pump control shaft and remove and replace, if necessary, in accordance with intervals and procedures described in paragraphs 1.B. and 1.C. of the Accomplishment Instructions of PW ASB A6381, dated March 15, 2000.

Installation and Terminating Action

(c) At the next main fuel pump overhaul perform the following:

(1) Install a reworked impeller, impeller gear train plate assembly and impeller cover assembly in accordance with paragraph 2.A of PW ASB A6381, dated March 15, 2000.

(2) Replace the main fuel pump control shaft with a serviceable main fuel pump control shaft.

(3) The next main fuel pump overhaul must occur no later than:

(i) 12,000 hours time in service (TIS) since last fuel pump overhaul; or

(ii) 2000 hours TIS from the effective date of this AD; or

(iii) 3000 hours TIS from the effective date of this AD, provided the main fuel pump has incorporated the modifications of paragraph (c)(1) as of the effective date of this AD and the inspection results from paragraph (a) of this AD are less than or equal to 15 degrees; whichever occurs latest.

(4) Modifications required by paragraph (c)(1) and (c)(2) of this AD constitute terminating action to the inspections required by paragraphs (a) and (b) of this AD.

Optional Fleet Campaign

(d) It is not necessary to perform the inspections required by paragraphs (a) and (b) or to adhere to the schedule of paragraph (c)(3) of this AD if the main fuel control modifications of paragraph (c)(1) and (c)(2) are performed throughout an operator's fleet in accordance with the schedule of Table 1 or Table 2 of this AD as follows:

(1) For fuel pumps that have incorporated the modifications of paragraph (c)(1) but not the modifications of paragraph (c)(2) as of the effective date of this AD, perform modifications in accordance with the schedule of Table 1.

(2) For fuel pumps that have not incorporated the modifications of paragraphs (c)(1) as of the effective date of this AD, perform the modification in accordance with the schedule of Table 2.

Table 1.—Optional Accelerated Fleet Campaign Schedule
Time in service since last main fuel pump overhaul:Perform modifications of paragraph (c)(2) of this AD:
[For engines that have incorporated the modifications of paragraph (c)(1) of this AD but not the modifications of paragraph (c)(2) of this AD as of the effective date of this AD]
Greater than or equal to 15,000 hours TIS on the effective date of this AD Within 1,000 hours TIS from the effective date of this AD.
Greater than or equal to 12,000 hours and less than 15,000 hours TIS on the effective date of this AD Within 2,000 hours TIS from the effective date of this AD.
Greater than or equal to 8,000 hours and less then 12,000 hours TIS on the effective date of this AD. Within 3,000 hours TIS from the effective date of this AD.
Less than 8,000 hours TIS on the effective date of this AD Within 4,000 hours TIS from the effective date of this AD or 8,000 TIS since last main fuel pump overhaul, whichever occurs later.
Table 2.—Optional Accelerated Fleet Campaign Schedule
Time in service since last main fuel pump overhaul:Perform modifications of paragraph (c)(1) and (c)(2) of this AD:
[For engines that have NOT incorporated the modifications of paragraph (c)(1) of this AD as of the effective date of this AD]
Greater than or equal to 12,000 hours TIS on the effective date of this AD Within 1,000 hours TIS from the effective date of this AD.
Greater than or equal to 10,000 hours and less than 12,000 hours TIS on the effective date of this AD Within 2,000 hours TIS from the effective date of this AD.
Greater than or equal to 6,000 hours and less than 10,000 hours TIS on the effective date of this AD Within 3,000 hours TIS from the effective date of this AD.
Less than 6,000 hours TIS on the effective date of this AD Within 4,000 hours TIS from the effective date of this AD or 6,000 hours TIS since last main fuel pump overhaul, whichever occurs later.

Definitions

(e) For the purpose of this AD:

(1) Accessibility of the main fuel pump is defined as removal of the fuel control from the fuel pump on the engine or removal of the fuel pump from the engine.

(2) Main fuel pump overhaul is defined as compliance with the manufacturer's recommended overhaul procedures described in Argo-Tech Overhaul Manual 73-11-1.

(3) A serviceable main fuel pump control shaft is defined as Argo Tech part number 219093 or Rogers Dierks part number RD219093.

Alternative Methods of Compliance

(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 (ECO). Operators shall submit their request through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, ECO.

Note 2:

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the ECO.

Ferry Flights

(g) 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.

Incorporated by Reference

(h) The actions specified in this AD must be done in accordance with the following Pratt Whitney Alert Service Bulletin:

Document no.PagesRevisionDate
JT8D A6381 All Original March 15, 2000

Total pages: 14.

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 St., East Hartford, CT 06108; telephone (860) 565-8770, fax (860) 565-4503. Copies may be inspected at the FAA, New England Region, Office of the Regional 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.

Effective Date of This AD

(i) This amendment becomes effective on December 4, 2000.

Issued in Burlington, Massachusetts, on October 20, 2000. Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification Service.

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