Turbine Technology: Brazing Repair

by William Hui Ma
Created: February 10, 2010

For CF6-80 gas turbine engine HPT shroud support

Table 2: EASA Classification

Major Repair Substantiation Sheet	Yes	No
1. Structural performance
Static Strength		X
Fatigue		X
Damage Tolerance		X
Flutter		X
Stiffness Characteristics		X
2. Weight and Balance
Weight Change		X
C.G. Location		X
Control Surface Stiffness		X
Control Surface Mass Distribution		X
Control Surface Profile		X
Flutter and Controllability		X
3. System
Effect on Complete System		X
Effect on System Redundancy		X
Effect on adjacent or remote systems parts		X
4. Operational Characteristics
Stall Characteristics		X
Handling		X
Performance and Drag		X
Vibration		X
5. Other Characteristics
Changes to Load Path and Load Sharing		X
Change to Noise and Emissions		X
Fire Protection / Resistance		X
6. Continued Airworthiness
Additional Inspection		X
Life Limited or Critical Parts		X
Changes to Aircraft Flight Manual		X
7. Extensive static, fatigue and damage tolerance strength justification and/or testing		X
8. Unusual methods, techniques or practices (unusual material selection, heat treatment, material processes, jigging diagrams, etc)		X
IIf all above items are checked ‘NO”, the action may be considered MINOR.
If any above item is checked “YES”, the action is considered MAJOR.

Table 3

FAR Sec. 33.4 Instructions for Continued Airworthiness The applicant must prepare Instructions for Continued Airworthiness in accordance with Appendix A to this part that are acceptable to the Administrator. Appendix A. The Instructions for Continued Airworthiness for each engine must include the Instructions for Continued Airworthiness for all engine parts. If Instructions for Continued Airworthiness are not supplied by the engine part manufacturer for an engine part, the Instructions for Continued Airworthiness for the engine must include the information essential to the continued airworthiness of the engine. The Instructions for Continued Airworthiness must contain the following ma nuals or sections, as appropriate, and information: (a) Engine Maintenance Manual or Section. (b) Engine Overhaul Manual or Section. The Instructions for Continued Airworthiness must contain a section titled Airworthiness Limitations that is segregated and clearly distinguishable from the rest of the document. This section must set forth each mandatory replacement time, inspection interval, and related procedure required for type certification.	Continued airworthiness requirements for OEM part as published in Engine Overhaul Manual will apply to the repaired part without changes. All inspection and repair procedures applicable to OEM part may also be performed on the repaired part. The part is inaccessible during engine maintenance thus it is not necessary to add supplements to Engine Maintenance Manual. Another MRO facility can use current engine maintenance manual to perform inspection, repair, and overhaul for the repaired part. It is concluded that Engine Maintenance Manual and Engine Overhaul Manual is not affected by the repair scheme.
FAR Sec. 33.15 Materials. The suitability and durability of materials used in the engine must: (a) Be established on the basis of experience or tests; and (b) Conform to approved specifications (such as industry or military specifications) that ensure they have the strength and other properties assumed in the design data	All materials are as specified for CF6 HPT shroud support by TC holder. This repair is very similar to a brazing repair in OEM manual which is currently being applied on the same part. There is no change for function and operating condition except repair location. Previous experience indicates that no repaired parts have been returned to our facility during normal service therefore it is anticipated that the component repaired by the repair process will react similar to the stated approved repaired component through intended use. So suitability and durability of used materials conform to approved specifications that ensure they have the strength and other properties assumed in the design data.
FAR Sec. 33.19 Durability. (a) Engine design and construction must minimize the development of an unsafe condition of the engine between overhaul periods.	The durability of CF6 HPT shroud support stage 1 repaired by the process will not have adverse effect on engine durability. This repair is very similar to a brazing repair in OEM manual which is currently being applied on the same part to restore similar defects. The methods, techniques and practices utilized during the repair process are as stated by TC holder and therefore it is anticipated that the repaired part will react similarly to TC holder approved repaired part through its intended use. Therefore the repair techniques minimize the development of an unsafe condition between overhaul periods.
FAR Sec. 33.75 Safety Analysis. (a) (1) The applicant must analyze the engine, including the control system, to assess the likely consequences of all failures that can reasonably be expected to occur.	Safety is not affected because part is returned to original condition.

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