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Gas Turbine Engine, GGXX5 and GGXX6, Borescope Inspected

Gas Turbine Engine, GGXX5 and GGXX6, Borescope Inspected

Description

  1. Overview
    1. Two engines, models GGXX5 and GGXX6, are available.
    2. Borescope and external inspections have been performed on both units.
  2. Borescope Inspection Findings
    1. Hot section components, visible blades and vanes of turbine and compressors are found serviceable with some acceptable findings.
    2. Variable stator vanes on high pressure compressor cases are stuck due to decayed VSV bushings, rust and saltish white accumulation.
    3. Lesser but same conditions are observed inside of the compressor section.
    4. To make the VSVs operative again it is advised to replace bushings and apply cleaning on both HPC rotor and vanes by opening the HPC upper/lower cases.
    5. For carrying out above procedures engine needs to be removed from package and put on prepared stands.
    6. Radial drive shaft is to be removed and accessory gearbox is to be lowered, then HPC cases will be removed and disassembled.
  3. Missing Components
    1. Compressor inlet temperature sensor (CIT).
    2. Electro magnetic pickup speed sensor that is on gearbox.
    3. Resistance temperature detector immersion type (RTDs).
    4. Vibration transducer.
    5. On GGXX6 only: power lever angle transducer.
    6. On GGXX6 only: one of the lube and scavenge pump screens.
  4. Recommended Maintenance and Repairs
    1. Fuel filter element on fuel pump needs to be replaced before operating the unit.
    2. If same package is planned to be used, duplex filter elements of lubrication system are supposed to be replaced.
    3. Major accessories such as lube and scavenge pump, main fuel control, main fuel pump, ignition exciters, VSV actuators would be better to be applied bench test if possible.
    4. GGXX5 right VSV actuator is observed heavily rust.
    5. Both engine’s fuel nozzles, feeder tubes and manifolds had better to be applied ultrasound cleaning.
    6. HPC borescope plugs are observed with heavy rust and allen key holed type.
    7. GGXX5 STG0 and 1 plug could not be removed; it is advised to replace all HPC plugs with new version.
    8. It had better to try to reach engine bearings in order to make sure their conditions; there are 7 bearings on engine and 4 sump areas.
    9. Unit is equipped with air pressurized starter; if the unit is planned to be used in packages that are powered hydraulically, air starter should be replaced with hydraulic starter and clutch.
    10. Oil in the engine sumps and transfer gearbox would be better to drain, flush and apply bearing wetting procedure.
  5. Inspection Activities for Engine GGXX5
    1. High pressure compressor and variable stator vanes: before inspection VSVs were attempted to operate to open position; they were observed stuck.
    2. HPC upper and lower cases were observed with white color accumulation and rust externally.
    3. Between STG0 to STG15 high pressure compressor rotor blades and visible stator vanes were inspected thoroughly.
    4. Inside of cases, stator vane circles and some of blades have white color deposit suggesting salt-calcium accumulation.
    5. Two of blades have small dents.
    6. Combustion chamber: inner outer liners, spark igniters, trumpets, venturis, dome plate, dome cups, fuel nozzles and other components were inspected.
    7. Slight carbon accumulation on trumpets, dome cups, dome plate were observed.
    8. One trumpet was observed with minor burn that is serviceable.
    9. Combustion chamber was old version which has no thermal barrier coating (TBC).
    10. High pressure turbine: HPT STG1 and 2 blades, HPT STG1 and 2 blade shrouds, HPT STG1 and 2 nozzles were inspected.
    11. Stage 1 and 2 blade shrouds have rubbing sign and erosion that are serviceable.
    12. Turbine mid frame, PT stage 1 nozzle and blades: TMF, PT STG1 nozzle and STG1 blade leading edges were inspected; no abnormal condition was detected.
  6. External Inspection Findings for GGXX5
    1. Compressor inlet sensor (CIT) and its gasket are missing on front frame; CIT sensor P/N: L21225P02, gasket P/N: 9643M56P02.
    2. Variable stator system components look very rusty and some white residue accumulations are observed.
    3. VSVs may need to be disassembled (HPC top case procedure); right VSV actuator seems very rusty, it may be replaced; P/N: 9691M29P09.
    4. Electro magnetic pickup speed sensor (compressor speed sensor) is missing; P/N: L21131P02; also RTV compound is needed P/N: A15F6B6.
    5. Resistance temperature detectors (RTDs) P/N: L21103P01 on lube lines of L and S pump are missing; they should be completed; also O-rings will be needed.