Turbine Technology: Brazing Repair

For CF6-80 gas turbine engine HPT shroud support

Table 4: EASA Compliance Review

CE-E 25 Instructions for Continued Airworthiness
(a) Manual(s) shall be provided containing instructions which are acceptable to the Agency for continued airworthiness of the Engine. They must be updated as necessary according to changes to existing instructions or changes in Engine definition.

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.
CS-E 70 Materials and Manufacturing Methods
(a) The suitability and durability of materials used in the Engine shall be established on the basis of
experience or tests. The assumed design values of properties of materials shall be suitably related to the
minimum properties stated in the material specification.
(b) Manufacturing methods and processes shall be such as to produce sound structure and mechanisms
which retain the original mechanical properties under reasonable service conditions.
(c) Material specifications, manufacturing methods and processes shall be identified and referenced in the
Engine type design.
Al 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 their having the strength and other properties assumed in the design data.
CS-E 100 Strength
(a) The maximum stresses developed in the Engine shall not exceed values conforming to those established by satisfactory practice for the material involved, due account being taken of the particular form of construction and the most severe operating conditions. Where a new type of material is involved, evidence shall be available to substantiate the assumed material characteristics. For Turbine Engines, due consideration shall be given to the effects of any residual stresses in Engine Critical Parts.
(b) The Engine components which form part of the Engine mounting and any other parts of the Engine liable to be critically affected shall, when the Engine is properly supported by a suitable Engine Certification Specifications for Engines mounting structure, have sufficient strength to withstand the flight and ground loads for the aircraft as a
whole in combination with the local loads arising from the operation of the Engine.
(c) Each Engine must be designed and constructed to function throughout its declared flight envelope and
operating range of rotational speeds and power/thrust, without inducing excessive stress in any Engine
part because of vibration and without imparting excessive vibration forces to the aircraft structure.
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 sated 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.
Environmental Protection
(a), Ensure that products parts and appliances comply with the applicable requirements for environmental protection.
(b), Issue the appropriate environmental certificates i.e. the type-certificate data sheet for noise.
Environmental and operational design requirements for engine are not affected as the part is returned to original condition.

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