|A T700 engine partially disrobed...|
We have regular inspections on our helicopters, many of which are based on flight hours. They range from the 40 hour and 120 hour inspections which get progressively more thorough to the phase maintenance where major disassembly, inspection and repairs take place. This engine was pulled as part of a phase inspection. During the borescope inspection of the compressor some damaged blades were found so the case was split so the blades could be repaired. You can see a very clear picture of the first five stages of compression in our engine - a sixth stage is just out of sight on the left. The inlet side of the engine is to the right, with the accessory module on top of it. Think of all the stuff on your car engine - starter, alternator, oil pump, fuel pump, etc., all that stuff is driven off this module. On the left side of the picture is the hot section of the engine. Those holes around the outside of the casing are where the fuel injectors go. When the engine is running a ring of fire that doesn't touch any of the case or combustion liner (it's way too hot) provides all the energy to power the helicopter, in this case about 1500 horsepower. Not attached at the moment, although you can see it on the bench near the wall to the left is the power turbine section. All the hot air from the hot section spins a couple of turbines that turn the shaft sticking up in the air which is attached to the main transmission in the helicopter. Interestingly enough, 80% of the air that goes through the engine provides cooling, only 20% is used for combustion. That's a lot of energy in a small place.