Airworthiness Directive · Amendment 39-11496 · General Electric Company GE90 Series Turbofan Engines
General Electric Company GE90 Series Turbofan Engines
Superseded. A later AD replaced this one: AD 2001-21-03. Comply with the one in force.
General Electric Company (GE) Models GE90-76B, - 77B, -85B, -90B, and -92B turbofan engines, installed on but not limited to Boeing 777 series airplanes.
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.
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
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.
