Chapter 8: Brakes System

Question 1

what types of brakes are normally used on aircrafts?

Answer 1

disc brakes

Question 2

what are brakes used with?

Answer 2

power brake control valve / boost master cylinder

Question 3

what does the brake assembly consist of?

Answer 3

pressure cylinder, pistons, reline indicator, pressure plate, rotor & stators

Question 4

what are the 3 basic actuating systems for brakes?

Answer 4

1) independent system
2) booster system
3) power brake system

Question 5

what does the independent system of brakes consist of?

Answer 5

reservoir, brake pedals & assemblies, amster cylinders

Question 6

how does the independent brake system work?

Answer 6

pedal pushed > piston inside cylinder will extend > pressure hydraulic fluid leading to brakes

pedal released > return spring will bring piston back to original

Question 7

where is a boosted brakes actuating system used?

Answer 7

medium size a/c where more braking force can be applied

Question 8

what does the boosted brake master cylinder do?

Answer 8

increase pressure applied on the brakes by pilot

Question 9

where is power brakes system used?

Answer 9

large size a/c

Question 10

what is power brakes system?

Answer 10

pressure supplied from a/c main hydraulic system

Question 11

what is used instead of a master cylinder for power brakes system and why?

Answer 11

power brakes control valve

higher pressure demand from higher speed and payload

Question 12

what is contained in the two chambers in an accumulator?

Answer 12

1) fluid at system pressure
2) nitrogen / air

Question 13

function of accumulator

Answer 13

1) dampen pressure surge
2) provide complement to power pump
3) store and provide power
4) compensate for small leaks

Question 14

2 types of accumulators

Answer 14

1) spherical
2) cylindrical

Question 15

what is a spherical type accumulator?

Answer 15

synthetic rubber diaphragm is installed in a sphere to create 2 chambers

Question 16

spherical type accumulator advantages and disavantages

Answer 16

adv: cost less, holds gas pre-charge longer

disadv: failure is sudden due to rupture of bag

Question 17

why is piston type accumulator preferred in hydraulic system?

Answer 17

less space than spherical accumulator

Question 18

how does an emergency brake system work?

Answer 18

hydraulic failure > pneumatic valve to direct compressed nitrogen in bottle to brakes system

Question 19

where is the brake debooster located?

Answer 19

downstream of control valve and anti-skid valve

Question 20

function of brake debooster

Answer 20

provide effective braking with a lower pressure than a/c hydraulic pressure

Question 21

how does anti skid system work?

Answer 21

detects wheel skid > relieve pressure to brake piston by connecting brake fluid to return line > allows wheel to rotate

Question 22

at what speed does the anti skid system turns off?

Answer 22

20 mph

Question 23

when does maximum braking efficiency occur?

Answer 23

wheels decelerating at maximum rate but not skidding

Question 24

how does a wheel speed sensor work?

Answer 24

AC tachometer generator mounted > sensor will measure wheel rpm > wheel rotating causes output volt proportional to angular velocity > converts AC to DC before going to control box

Question 25

function of control box in anti skid system

Answer 25

generate electric signal to contol:
1) prevent brake pressure before touchdown
2) brake pressure to prevent skid

Question 26

function of solenoid/control valve in antiskid system

Answer 26

will relieve pressure from brakes when it received signals from control box

Question 27

function of squat switch

Answer 27

located in LG, informs control if a/c is airborne or on ground

Question 28

components of the anti skid system

Answer 28

1) wheel speed sensor
2) anti skid control valve
3) control unit

Question 29

2 condition before control valve permit brakes

Answer 29

1) squat switch must signal weight of aircraft is on ground
2) wheel sensor sense wheel speed over 20mph

Question 30

4 functions of anti skid control

Answer 30

1) normal skid control
2) locked wheel skid control
3) touchdown protection
4) fail safe protection

Question 31

what is touchdown protection?

Answer 31

prevents brakes from being applied during landing even if pedals are pressed

Question 32

what is a fail safe protection anti skid system?

Answer 32

auto returns to manual braking in case of system failure

Question 33

anti skid inoperative warning light lights up when?

Answer 33

system is switched off or there is system failure

Question 34

what does the self system test do in the anti skid control box?

Answer 34

test functionality of components, if any isnt working, warning light illuminates

Question 35

where is the anti skid control valve located?

Answer 35

between brakes and brakes control valve, with line connecting to the return manifold

Question 36

auto brake system will disengage when?

Answer 36

any of the following happens:
1) selector switch to DISARM or OFF
2) pilot uses manual braking
3) thrust lever is advanced
4) speed brake level is moved to DOWN

Question 37

how does auto brake system work?

Answer 37

allows pilot to select deceleration rate after touch down

system directs right amount of pressure to brakes to get right deceleration rate