A. The reduction gearbox (RGB) is a module which gives a suitable reduction of the power turbine speed to drive the propeller and accessories shafts. Two identical systems, (one for each engine) are installed. A description of the LH system is given.
A. The RGB includes a spur-type geartrain in four cast housings. The propeller is installed on ashaft at the front of the RGB. Accessories are installed on pads on the housings of the RGB.
A. The RGB has two stages of reduction gears and accessory drive gears. The power turbine drives the input gearshaft which causes the rotation, after speed reductions, of the propeller shaft, alternator drive, overspeed governor and hydraulic pump.
A. The system is fully automatic as soon as theengine turns.
2. Component Information
(Refer to Fig. 72-11-00-990-010-A00)
(Refer to Fig. 72-11-00-990-020-A00)
A. Reduction Gearbox
1. The RGB is made up of a reduction geartrain in two stages in a module including four housings.
2. The RGB is attached to the front flange of the turbomachinery module in Zone 410.
3. The RGB has two stages ofreduction gears, accessory-drive and idler gears. The four castings are the front housing, the rear housing, the input drive housing and the accessory drive cover.
a. The first stage of the reduction geartrain has a helical input gearshaft and two first-stage helical gears. The helical input gear has 23 teeth and the first stage gears 108 teeth each.
b. The second stage hastwo spur gears with 38 teeth and one 135 tooth gear. The two 38-tooth spur gears are on the first-stage helical gearshaft. The 135 tooth-gear is on the propeller shaft.
c. The accessory-drive and idler spur gears in the accessory drive cover are, from left to right :
* The alternator drive gearshaft with 34 teeth
* The idler drive gearshaft with 3 setsof teeth
* The hydraulic-pump drive gearshaft with 59 teeth
* The overspeed-governor drive gearshaft with 30 teeth.
The idler-drive gearshaft has a 32-tooth driven end is a mesh with the large second-stage spur gear. A driving 49-tooth set is a mesh with the 59-tooth set of the hydraulic pump gearshaft. A driving 57-tooth is a mesh with the 34 tooth set of thealternator drive gearshaft. The 30-tooth set of the overspeed governor is a direct mesh with the large second-stage spur-gear.
d. The front housing has mounting pads for the electric feathering pump and the propeller brake with a drive seal. Rivets hold the data plate, of the RGB module, to the front housing. This housing holds the following items :
* The propeller shaftseal and seal runner
* The front roller bearing and ball bearing for the propeller shaft
* The front roller bearing for the two spur gears of the second stage.
Drains are installed at the propeller shaft flange and at the two layshaft covers.
e. The rear housing has three pads for the front mounting of the engine. One is on the top center, the other twoare on each side at the approximate center. The housing has also two torque mounts at the eight and five o'clock positions. Other mounting pads are for the propeller control-unit on the back face, the propeller-speed (NP) sensor on the top and the oil chip-detector on the bottom. The rear housing contains :
* The rear roller bearings of the propeller shaft and of the twosecond-stage spur gears
* The front roller bearings for the two first-stage gears, the input gearshaft, the accessory-drive gears and the accessory idler gear.
f. The input drive housing connects the gearbox to the turbo- machinery module. The RGB torque sensors are installed in a boss on each side of the housing. The housing holds the three rear roller bearings of the input...