VI Scan the text to fill in the gaps with correct prepositions.

1 Because __the fixed number __poles, the only means __fine-tuning the output

frequency is controlling rotor rpm, often done __ using CSDs.

2 CSDs receive drive power __ hydraulic power, pneumatic power, or the

accessory drive section __ an engine.

3 It is __ this reason that __ most aircraft a CSD unit is located __ the aircraft

engine and the ac generator.

4 __ helicopters, the main generators are mounted __ an accessory gearbox that is

driven __ the main transmission.

5 The purpose __the CSD is __transfer and convert aircraft engine variable-speed

rotation __ a constant-speed rotation, which drives the generator.

6 The CSD consists __ a variable-displacement hydraulic pump, constant-

displacement hydraulic motor, and a governing system.

7 The governing system controls the rate __flow __ the pump, thereby controlling

the speed __ the motor.

8 There are several other components __ the CSD that are necessary __ self-

regulating constant-speed operation.

9 A gear __ the CSD output shaft drives these pumps, the limit governor, and basic

governor.

10 The inner race is separated __ the wobbler shell__ bearing rollers.

11 It is free __ turn __ the pump pistons, which are always __ contact __ the race

during operation.

12 The CSD functions __ three different phases __operation: overdrive phase,

straight- __ phase, and __drive phase.

13 When the engine input rpm is less than the rpm required __the generator, the

CSD makes __ the difference __ rpm.

14 The CSD does this __ causing the pump wobbler system __respond __

governor signals.

15 This response causes the pump __ supply more oil __the motor.

16 The difference __ the input and output rpm depends __ the quantity __ oil

pumped __ regulating the wobbler pump.

17 The pump wobbler would, theoretically, be positioned __ the action __ the

governor to be concentric __ the cylinder block assembly.

18 __ this condition, the pump neither sends oil __ the motor nor accepts oil __the

motor.

19 Since the drive starts__ underdrive and operates normally __ overdrive, this

straight-__condition is only temporary.

20 When engine input rpm exceeds the output rpm requirements __ the generator,

the CSD acts to subtract __ the input rotation.

21 The wobbler pump accomplishes this __ response __ the governor signal.

22 The pump-motor action __underdrive is the reverse __the action required __

overdrive.

23 __ the underdrive phase, the pump performs __ a negative pumping action.

24 Excess input torque is dissipated __ the reverse pumping action __the charged

oil system.

25 When the engine overspeeds or if the basic governor fails, the CSD goes __

underdrive __protect the generator __ overspeed.

26 __ some CSDs, aircraft engine oil __ the engine lubricating system is the

hydraulic medium. 27 __ this case, the CSD also functions as a pump

__supplying the generator __ engine oil __ cooling.

28 Due __ cooling capabilities, oil-cooled generators are __ smaller construction

than air-cooled generators having a similar rating.

VII Are these sentences true or false? Discuss with a partner.

1 Because of the fixed number of poles, the only means of fine-tuning the output frequency is controlling rotor rpm, often done by using CSDs.

2 CSD unit is located on the aircraft engine and the ac generator.

3 The purpose of the CSD is to transfer and convert aircraft generetorvariable-speed rotation to a high-speed rotation, which drives the generator.

4 The CSD consists of a variable-displacement hydraulic pumponly.

5 Three control pistons in the CSD housing move the wobbler sideways to vary the output of the pump.

6 The CSD functions in five different phases of operation: overdrive phase, straight-through phase, and underdrive phase.

7 The difference between the input and output rpm doesn`t dependon the quantity of oilpumped by regulating the wobbler pump.

8 When the engine overspeeds or if the basic governor fails, the CSD goes into overdrive to protect the generator from underspeed.

9 The overspeed pressure switch in the governor oil line functions to break the electrical circuit of the ac control system.

10 The system is protected during an underspeed condition.