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Safety Advisory Notice issued to: Federal Aviation Administration

Recommendation details
Output No: SAN20000027
Date issued: 22 February 2000
Safety action status: Closed
Background: Why this Safety Advisory Notice was developed

Output text

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


As a result of investigation into this occurrence, the Bureau simultaneously issues the following recommendations:


R20000025

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.


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.

Initial response
Date issued: 21 July 2000
Response from: Federal Aviation Administration (FAA)
Response text:

The FAA has reviewed the evaluation performed by GE and concurs with the following conclusions regarding the nature of the casting defect and the manufacturing process:

- The casting anomaly is dross-like in nature. A dross inclusion is defined as a string or cluster of oxidized particles that form in metal during melting. Dross is an oxide that forms as a result of oxygen combining with the reactive elements in the alloy while in a molten state.

- Scanning Electron Microscopy, Optical Microscopy and Energy Dispersive Spectroscopy revealed Titanium and Aluminum-rich oxides present. Both of these elements are typically found in oxides of the HPT S2 blade alloy, Rene'80.

- Dross formation is possible during production of the ingot master heat manufacture and/or the blade casting process.

- Due to the unusual, internal location of this defect (i.e. the center of an internal shank rib - most dross-like inclusion are connected to an external surface) FPI was not able to detect this anomaly. X-ray inspection was also not capable of detecting this particular defect due to the significant mass in the rib location.

- Cleanliness of the manufacturing process is relied on to prevent defects of this nature.

- High time blades without internal coatings are susceptible to IGO.

Audits of the current ingot master heat and blade casting processes have been conducted at the two HPT S2 blade manufacturers. All current procedures were found to conform to GE specifications to minimize the likelihood of blades containing casting defects being released to service.

GE also released blades with internal coatings in 1992 to reduce the likelihood of IGO.

The Engine & Propeller Directorate believes that no further action is necessary regarding this issue and asks that FAA Safety Recommendation 00.058 be closed.

 
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Last update 05 April 2012