On inspection of JT9D-20J and -7J engine buildup records it was discovered some 4TH stage low pressu...

Attributes
ACN	404280
Time
Date	199806
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : zzz
State Reference	US
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	DC-10 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	other
Flight Plan	None
Person 1
Affiliation	company : air carrier
Function	other personnel other
Qualification	other other : other
ASRS Report	404280
Person 2
Affiliation	company : air carrier
Function	other personnel other
Qualification	other other : other
ASRS Report	404278
Events
Anomaly	aircraft equipment problem : critical non adherence : far non adherence : published procedure other anomaly other
Independent Detector	other other : unspecified
Resolutory Action	other
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

We discovered 4TH stage low pressure turbine disks may have been installed on JT9D-20J and JT9D-7J engines without having their allowable life reduced from 15000 cycles to 13000 cycles. The way air carrier changes the computer tracked life of rotatable parts is to change the company stock number. The basic part #752504 can be used on any of our model JT9D engines but it's up to the individual inspector to know and change the stock number. We discovered several low pressure turbine modules on JT9D-20J and -7J engines with 4TH stage disks that didn't have the allowable life reduced from 15000 cycles to 13000 cycles. 2 of the disks had accumulated more than 13000 cycles making them beyond the allowable life, even though the computer time tracking didn't catch them because the stock number hadn't been changed.

Original NASA ASRS Text

Title: ON INSPECTION OF JT9D-20J AND -7J ENG BUILDUP RECORDS IT WAS DISCOVERED SOME 4TH STAGE LOW PRESSURE TURBINE DISCS MAY HAVE BEEN INSTALLED AND IN SVC WITH LIFE CYCLES EXCEEDED.

Narrative: WE DISCOVERED 4TH STAGE LOW PRESSURE TURBINE DISKS MAY HAVE BEEN INSTALLED ON JT9D-20J AND JT9D-7J ENGS WITHOUT HAVING THEIR ALLOWABLE LIFE REDUCED FROM 15000 CYCLES TO 13000 CYCLES. THE WAY ACR CHANGES THE COMPUTER TRACKED LIFE OF ROTATABLE PARTS IS TO CHANGE THE COMPANY STOCK NUMBER. THE BASIC PART #752504 CAN BE USED ON ANY OF OUR MODEL JT9D ENGS BUT IT'S UP TO THE INDIVIDUAL INSPECTOR TO KNOW AND CHANGE THE STOCK NUMBER. WE DISCOVERED SEVERAL LOW PRESSURE TURBINE MODULES ON JT9D-20J AND -7J ENGS WITH 4TH STAGE DISKS THAT DIDN'T HAVE THE ALLOWABLE LIFE REDUCED FROM 15000 CYCLES TO 13000 CYCLES. 2 OF THE DISKS HAD ACCUMULATED MORE THAN 13000 CYCLES MAKING THEM BEYOND THE ALLOWABLE LIFE, EVEN THOUGH THE COMPUTER TIME TRACKING DIDN'T CATCH THEM BECAUSE THE STOCK NUMBER HADN'T BEEN CHANGED.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

On inspection of JT9D-20J and -7J engine buildup records it was discovered some 4TH stage low pressure turbine discs may have been installed and in service with life cycles exceeded.