Jump to Content

Recommendation issued to: General Electric Usa

Recommendation details
Output No: R20000025
Date issued: 22 February 2000
Safety action status:
Background: Why this Recommendation was developed

Output text

The Australian Transport Safety Bureau (formerly the Bureau of Air Safety Investigation) recommends that the engine manufacturer General Electric identify the source of the casting defect of the failed HPT blade.


As a result of investigation into this occurrence, the Bureau simultaneously issues the following recommendation and safety advisory notice:


R20000026

The Australian Transport Safety Bureau (formerly the Bureau of Air Safety Investigation) recommends that the engine manufacturer General Electric review the adequacy of turbine blade manufacturing process controls to reduce the likelihood of blades containing casting defects being released into service.


SAN20000027

The Federal Aviation Administration should note the safety deficiency identified in this document and take appropriate action.

Initial response
Date issued: 17 May 2000
Response from: General Electric Usa
Action status: Closed - Accepted
Response text:

The loss of rib cross section area from fatigue that initiated at a casting anomaly, combined with internal surface Intergranular Oxidation (IGO), reduced the shank cross section area and resulted in a tensile separation of the Ansett CF6-80A Stage 2 HPTB S/N: MSCBH987. The loss of load bearing area due to fatigue that initiated at a casting anomaly is considered to be the primary cause of the separation.

The fatigue damage originated at a casting anomaly (dross) located in the center of the 3-4 cavity rib. The dross was introduced during the original casting process in 1983. Due to the location and size of the casting anomaly, detection by nondestructive inspection techniques (FPI and X-Ray) is not considered likely.

The IGO seen resulted from long time engine exposure (31,593 hours, 23,072 cycles) and is not unusual on high time blades that do not have an internal coating. The current part configuration, released in 1992, includes an internal aluminide coating to preclude oxidation.

A retirement recommendation is currently in place to address internal oxidation (IGO) seen in high time Stage 2 CF6-80A HPT Blades without an internal aluminide coating (KTW, TRM and PCM Serial Numbers). Though IGO is not considered to be the primary cause of the separation, a retirement threshold recommendation will be evaluated for high time Stage 2 CF6-80A HPT Blades without an internal aluminide coating (MSC Serial Numbers).

 
Share this page Comment
Last update 05 April 2012