11.11 Pressure Generation

Question 1

what are the two clasifications of pumps?

Answer 1

• positive displacement
• non-positive displacement ( variable displacent )

Question 2

what is a constant delivery pump?

Answer 2

a constant amount of displacement is forced through the outlet per rotation

Question 3

what are gear type power pumps?

Answer 3

positive displacement pump that consists of two meshed gears that rotate in opposite ways

Question 4

what is a gerotor pum

Answer 4

another positive displacement displacement pump with a smaller star shaped placed in an eccentric position, which drives an exterior housing

Question 5

what is the most common type of main system pump?

Answer 5

piston pumps

Question 6

what sort of displacement does a piston pump provide?

Answer 6

constant or variable displacement

Question 7

a pump drive shaft is usually paired with a pump drive coupling, what is the purpose of this?

Answer 7

a short shaft with a set of male splines on the other and engage with the female splines in the pump shaft

Question 8

what other benifit does a drive coupling give?

Answer 8

if the pump becomes unusually hard to turn or jammed, the coupling will shear, as a safety mechanism, to prevent damage to surrounding systems and itself

Question 9

what are the two types of piston pump ?

Answer 9

• bent axis pump
• inline piston pump

Question 10

what is a bent axis piston pump?

Answer 10

a constant displacement type pump that has an angular housing causing cylinders to dispce fluid

Question 11

in an inline piston pump, what determines the displacement?

Answer 11

determined by the size and number of pistons, aswell as their stroke length

Question 12

how is a vane type pump comstructed?

Answer 12

rotor is positioned off-centre within the sleeve, the vanes are mounted in the slots of the rotor, dividing the chamber into sections, when the pump rotates, the spring loaded vanes compress decreasing volume and expand increasing volume , allowing fluid to travel through the pump

Question 13

what is special about a variable displacement pump?

Answer 13

allows flow rate and outlet pressure to be changed during operation

Question 14

what causes pressure in a hydraulic system ?

Answer 14

restriction of fluid flow

Question 15

what is the most common type of pump used in modern aircraft?

Answer 15

variable delivery or compensator controlled type

Question 16

what is the term used to describe the generation of primary hydraulic power?

Answer 16

main pressurisation

Question 17

where are the pumps providing primary pressure generation mounted?

Answer 17

generally on the accessory gearbox and is rotated by a shaft

Question 18

what sort of displacement does the EDP provide ?

Answer 18

variable displacement

Question 19

what is different between the ACMP and the EDP?

Answer 19

generally the same pump, however the pump is driven by an electrical motor instead of the engine gearbox

Question 20

why might an aircraft have an ACMP installed?

Answer 20

installed as primary pumps and for use in emergencies or during ground operation when engines are not running

Question 21

when are air driven pumps usually used?

Answer 21

used as demand pumps to supplement the primary pumps

Question 22

what sort of displacement does an ADP provide?

Answer 22

variable displacement

Question 23

where are hand pumps used?

Answer 23

in older aircraft or in newer aircraft incase of an emergency

Question 24

why might a hand pump be installed?

Answer 24

intalled for testing purposes, emergencies and to service the reservoirs from a single refilling station

Question 25

what types of hand pumps are there and what sort of flow do they provide ?

Answer 25

• single-action only provies fluid on one stroke
• double-action provides fluid on both strokes
• rotary continuous output while the handle is i operation