Airworthiness Directives; General Electric Company GE90 Series Turbofan Engines

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NE-62-AD; Amendment 39-11496; AD 99-27-15]

RIN 2120-AA64

Airworthiness Directives; General Electric Company GE90 Series

Turbofan Engines

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 General Electric Company GE90 series turbofan

engines. This action requires visually inspecting Ps3 and P3B sense

lines and full authority digital engine control (FADEC) Ps3 and P3B

sensing ports and fittings, cleaning Ps3 and P3B fittings and sensing

ports, purging the Ps3 and P3B systems of moisture, and, if necessary,

blending of high metal, nicks, burrs, or scratches on Ps3 and P3B

fitting threads. This amendment is prompted by seven reports of loss of

thrust control due to corruption of the signals to the FADEC caused by

water freezing in the Ps3 sensing system. The actions specified in this

AD are intended to prevent loss of thrust control due to corruption of

the Ps3 and P3B signals to the FADEC which if it occurs in a critical

phase of flight, could result in loss of aircraft control.

DATES: Effective January 11, 2000.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of January 11, 2000.

Comments for inclusion in the Rules Docket must be received on or

before March 6, 2000.

ADDRESSES: Submit comments to the Federal Aviation Administration

(FAA), New England Region, Office of the Regional Counsel, Attention:

Rules Docket No. 99-NE-62-AD, 12 New England Executive Park,

Burlington, MA

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01803-5299. Comments may also be sent via the Internet using the

following address: ``[email protected]''. Comments sent via the

Internet must contain the docket number in the subject line.

The service information referenced in this AD may be obtained from

General Electric Company via Lockheed Martin Technology Services, 10525

Chester Road, Suite C, Cincinnati, OH 45215; telephone 513-672-8400,

fax 513-672-8422. This information may be examined 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.

FOR FURTHER INFORMATION CONTACT: John E. Golinski, Aerospace Engineer,

Engine Certification Office, FAA, Engine and Propeller Directorate, 12

New England Executive Park, Burlington, MA 01803-5299; telephone 781-

238-7135, fax 781-238-7199.

SUPPLEMENTARY INFORMATION: The Federal Aviation Administration (FAA)

has received seven reports of loss of thrust control (LOTC) on General

Electric Company (GE) Model GE90 turbofan engines installed on Boeing

777 series aircraft. Five LOTC events occurred in-flight and two

occurred on the ground. The five in-flight LOTC events were temporary

in that the engine recovered and continued to operate normally for the

remainder of the flight.

Investigation

The investigation revealed that water can accumulate in the Ps3 and

P3B pressure sensing system, which can freeze in the full authority

digital engine control (FADEC) sensing ports or pressure line. Frozen

water can result in a restriction or a blocked signal to the FADEC.

This blocked signal can cause a corruption of the FADEC signal and

result in abnormal engine start characteristics on the ground or lack

of engine response to commanded thrust levels in flight. Although there

have been no LOTC events attributed to icing of the P3B sensing system

in the field, inspections have identified moisture in this system,

which could freeze and corrupt the P3B signal to the FADEC as well.

This condition, if not corrected, could result in LOTC due to blockage

of the FADEC sense lines, which if it occurs in a critical phase of

flight, could result in loss of aircraft control.

Simultaneous LOTC Events

The FAA is especially concerned about the possibility of

simultaneous LOTC events on both engines installed on the Boeing 777

series aircraft due to common mode threats, such as certain atmospheric

conditions that may result in ice in the Ps3 or P3B pressure sensing

system and causing corrupted signals to the FADEC in both engines.

Interim Action

Both Ps3 and P3B pressure systems incorporate weep holes that

allows drainage of water in the lines that may accumulate from

condensation or ingested water; however, the field events and the

investigation have determined that these design features may not always

be effective in eliminating water from these systems. GE is assessing

design changes that will prevent water from freezing in these systems

and causing corruption of the signals to the FADEC. The requirements of

this AD may change based on the ongoing investigation of the root cause

and field inspection results, and future rulemaking may be necessary.

Service Information

The FAA has reviewed and approved the technical contents of GE

Alert Service Bulletin (ASB) GE90 73-A0060, dated December 23, 1999,

that describes procedures for visually inspecting Ps3 and P3B sense

lines and FADEC sensing ports and fittings, cleaning Ps3 and P3B

fittings and sensor ports, purging the Ps3 and P3B systems of moisture,

and, if necessary, blending of high metal, nicks, burrs, or scratches

on Ps3 and P3B fitting threads.

Difference between ASB and AD

This AD contains provisions for initial actions, and the ASB

assumes that all operators have completed the initial actions based on

field reports. If, however, operators have already accomplished the

required initial actions, they need not repeat those actions, but may

proceed directly to accomplishing the repetitive actions.

Required Actions

Since an unsafe condition has been identified that is likely to

exist or develop on other engines of the same type design, this

airworthiness directive (AD) is being issued to prevent engine LOTC

events. This AD requires:

Visual inspections for high metal, nicks, burrs, or

scratches on Ps3 and P3B fitting threads, and, if necessary, blending.

Visual inspections for moisture, debris, or ice in Ps3 and

P3B FADEC fittings, ports, and open sense lines.

Cleaning of Ps3 and P3B FADEC fittings and sensing ports.

Purging of any moisture from the Ps3 and P3B sense system.

Engine idle leak check run following the maintenance

activity to confirm no Ps3 or P3B sense system faults are present.

Compliance Times

One of the GE90 series engines installed on the Boeing 777 series

airplane must have the initial inspection, cleaning, moisture purging,

and, if necessary, blending of high metal, nicks, burrs, or scratches

on Ps3 and P3B fitting threads, within 10 cycles-in-service (CIS) after

the effective date of this AD. The other engine installed on the

airplane must have the initial inspection, cleaning, moisture purging,

and, if necessary, blending of high metal, nicks, burrs, or scratches,

on Ps3 and P3B fitting threads, within 20 CIS after the effective date

of this AD. Based on concerns over concurrent engine maintenance,

engines installed on the same Boeing 777 series airplane must not have

the inspection, cleaning, moisture purging and, if necessary, blending

of high metal, nicks, burrs, or scratches on Ps3 and P3B fitting

threads performed concurrently.

Credit for Previous Inspections, Cleaning, and Moisture Purging

Engines that have been inspected, cleaned, and moisture purged in

accordance with GE90 All Reps Wire, JSB99-11-24-1, Revision 1, dated

November 25, 1999, may count those inspections, cleaning, and moisture

purging as accomplished and must be inspected, cleaned, moisture

purged, and, if necessary, have high metal, nicks, burrs, or scratches

on Ps3 and P3B fitting threads blended, within 30 CIS since those last

actions. Engines that have accumulated 30 CIS or greater since previous

inspection, cleaning, and moisture purging on the effective date of the

AD must repeat the required procedures within 5 CIS after the effective

date of this AD. Engines that have accumulated less than 30 CIS since

previous inspection, cleaning, and moisture purging on the effective

date of this AD must repeat the required procedures within 30 CIS since

last inspection, or within 5 CIS after the effective date of this AD,

whichever occurs later.

Repetitive Actions

Thereafter, operators must inspect, clean, moisture purge, and, if

necessary, blend high metal, nicks, burrs, or scratches on Ps3 and P3B

fitting threads at intervals not to exceed 30 CIS since last

inspection.

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Immediate Adoption

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 should identify the Rules Docket number and be submitted

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 99-NE-62-AD.'' The postcard will be date stamped and

returned to the commenter.

Regulatory Impact

The regulations adopted herein will 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. Therefore, it

is determined that this final rule does not have federalism

implications under Executive Order (EO) 13132.

The FAA has determined that this regulation is an emergency

regulation that must be issued immediately to correct an unsafe

condition in aircraft, and is not a ``significant regulatory action''

under EO 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:

99-27-15 General Electric Company: Amendment 39-11496. Docket 99-

NE-62-AD.

Applicability: General Electric Company (GE) Models GE90-76B, -

77B, -85B, -90B, and -92B turbofan engines, installed on but not

limited to Boeing 777 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 thrust control due to corruption of the Ps3

and P3B signals to the full authority digital engine control

(FADEC), which if it occurs in a critical phase of flight, could

result in loss of aircraft control, accomplish the following:

Initial Inspection, Cleaning, Moisture Purging, and Blending

(a) Perform the following initial actions in accordance with the

Accomplishment Instructions, Section (3) of GE Alert Service

Bulletin (ASB) No. 73-A0060, dated December 23, 1999:

(1) Inspect, clean, moisture purge, and if necessary, blend any

high metal, nicks, or burrs on fitting threads, on one engine

installed on Boeing 777 series aircraft, within 10 cycles-in-service

(CIS) after the effective date of this AD.

(2) Inspect, clean, moisture purge, and if necessary, blend any

high metal, nicks, or burrs on fitting threads, on the other engine

installed on the Boeing 777 series aircraft, within 20 CIS after the

effective date of this AD.

Credit for Previous Inspections, Cleaning, and Moisture Purging

(b) Engines that have been inspected, cleaned, and moisture

purged in accordance with GE90 All Reps Wire, JSB99-11-24-1,

Revision 1, dated November 25, 1999, may count those inspections,

cleaning, and moisture purging as accomplished and must be

inspected, cleaned, moisture purged, and if necessary, have any high

metal, nicks, or burrs on fitting threads blended, in accordance

with the Accomplishment Instructions, Section (3) of GE ASB No. 73-

A0060, dated December 23, 1999, and the following schedule:

(1) Engines that have accumulated 30 CIS or greater since

previous inspection, cleaning, and moisture purging on the effective

date of the AD must repeat the required procedures within 5 CIS

after the effective date of this AD.

(2) Engines that have accumulated less than 30 CIS since

previous inspection, cleaning, and moisture purging on the effective

date of this AD must repeat the required procedures within 30 CIS

since last inspection, or within 5 CIS after the effective date of

this AD, whichever occurs later.

New and Replacement Engines

(c) For new and replacement engines, perform the initial

inspection, cleaning, and moisture purging, and if necessary, blend

any high metal, nicks, or burrs on fitting threads, prior to

accumulating 30 CIS since entering service in accordance with the

Accomplishment Instructions, Section (3) of GE ASB No. 73-A0060,

dated December 23, 1999.

Repetitive Inspections

(d) Thereafter, inspect, clean, and moisture purge, and if

necessary, blend any high metal, nicks, or burrs on fitting threads

each engine within 30 CIS since last inspection, in accordance with

the Accomplishment Instructions, Section (3) of GE ASB No. 73-A0060,

dated December 23, 1999.

Idle Leak Check

(e) After accomplishing the required actions of this AD, and

prior to entry into

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service, perform an idle leak check to confirm no Ps3 or P3B sense

system faults in accordance with the Accomplishment Instructions,

Section (3), paragraph (14), of GE ASB No. 73-A0060, dated December

23, 1999.

No Simultaneous Actions

(f) Do not perform the actions required by this AD concurrently

on both engines installed on a Boeing 777 series aircraft.

Alternative Methods of Compliance

(g) 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 requests 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 airworthiness directive,

if any, may be obtained from the ECO.

Ferry Flights

(h) 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 aircraft to a location where

the requirements of this AD can be accomplished.

Incorporation by Reference

(i) The actions required by this AD shall be done in accordance

with GE ASB No. 73-A0060, dated December 23, 1999. 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 General Electric Company via

Lockheed Martin Technology Services, 10525 Chester Road, Suite C,

Cincinnati, OH 45215; telephone 513-672-8400, fax 513-672-8422.

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.

(j) This amendment becomes effective on January 11, 2000.

Issued in Burlington, Massachusetts, on December 29, 1999.

Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification

Service.

[FR Doc. 00-134 Filed 1-5-00; 8:45 am]

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