content_image/533308.jpg content_image/533309.jpg
<img src='content_image/533308.jpg'>

all the blades have been numbered. Mark a number 1 on the face of the hub on the turbine disk. The number 1 blade is then installed adjacent to the number 1 on the disk. [Figure 10-68] The remaining blades are then installed consecutively in a clockwise direction, viewed from the rear face of the turbine disk. If there are several pairs of blades having the same code letters, they are installed consecutively before going 

<img src='content_image/533309.jpg'>

to the next code letters. If a blade requires replacement, the diametrically opposite blade must also be replaced. Computer programs generally determine the location for turbine blades for turbine wheels on modern engines. 

## Turbine Nozzle Inlet Guide Vane Inspection 

After removing the required components, the first stage turbine blades and turbine nozzle vanes are accessible for inspection. The blade limits specified in the engine manufacturer’s overhaul and service instruction manual should he adhered to. Figure 10-69  shows where cracks usually occur on a turbine nozzle assembly. Slight nicks and dents are permissible if the depth of damage is within limits. Inspect the nozzle vanes for nicks or cracks. Small nicks are not cause for vane rejection, provided such nicks blend out smoothly. 

Inspect the nozzle vane supports for defects caused by the impingement of foreign particles. Use a stone to blend any doubtful nicks to a smooth radius. Like turbine blades, it is possible to replace a maximum number of turbine nozzle vanes in some engines. If more than the maximum vanes are damaged, a new turbine nozzle vane assembly must be installed. With the tailpipe (exhaust nozzle) removed, the rear turbine stage can be inspected for any cracks or evidence of blade stretch. Additional nozzle stages can also be inspected with a strong light by looking through the rear-stage turbine. 

## Clearances 

Checking the clearances is one of the procedures in the maintenance of the turbine section of a turbine engine. The manufacturer’s service and overhaul manual gives the procedures and tolerances for checking the turbine. Turbine clearances being measured at various locations are shown in  Figures 10-70 and  10-71 . To obtain accurate readings, special tools provided by each manufacturer must be used as described in the service instructions for specific engines. 

## Exhaust Section 

The exhaust section of the turbine engine is susceptible to heat cracking. This section must be thoroughly inspected along with the inspection the combustion section and turbine section of the engine. Inspect the exhaust cone and exhaust nozzle for cracks, warping, buckling, or hotspots. Hotspots on the tail cone are a good indication of a malfunctioning fuel nozzle or combustion chamber. 

The inspection and repair procedures for the hot section of any one gas turbine engine share similarities to those of other gas turbine engines. One usual difference is the nomenclature applied to the various parts of the hot section by the different manufacturers. Other differences include the manner of disassembly, the tooling necessary, and the repair methods and limits. 

