Chapter 8: Brakes System Flashcards
what types of brakes are normally used on aircrafts?
disc brakes
what are brakes used with?
power brake control valve / boost master cylinder
what does the brake assembly consist of?
pressure cylinder, pistons, reline indicator, pressure plate, rotor & stators
what are the 3 basic actuating systems for brakes?
1) independent system
2) booster system
3) power brake system
what does the independent system of brakes consist of?
reservoir, brake pedals & assemblies, amster cylinders
how does the independent brake system work?
pedal pushed > piston inside cylinder will extend > pressure hydraulic fluid leading to brakes
pedal released > return spring will bring piston back to original
where is a boosted brakes actuating system used?
medium size a/c where more braking force can be applied
what does the boosted brake master cylinder do?
increase pressure applied on the brakes by pilot
where is power brakes system used?
large size a/c
what is power brakes system?
pressure supplied from a/c main hydraulic system
what is used instead of a master cylinder for power brakes system and why?
power brakes control valve
higher pressure demand from higher speed and payload
what is contained in the two chambers in an accumulator?
1) fluid at system pressure
2) nitrogen / air
function of accumulator
1) dampen pressure surge
2) provide complement to power pump
3) store and provide power
4) compensate for small leaks
2 types of accumulators
1) spherical
2) cylindrical
what is a spherical type accumulator?
synthetic rubber diaphragm is installed in a sphere to create 2 chambers
spherical type accumulator advantages and disavantages
adv: cost less, holds gas pre-charge longer
disadv: failure is sudden due to rupture of bag
why is piston type accumulator preferred in hydraulic system?
less space than spherical accumulator
how does an emergency brake system work?
hydraulic failure > pneumatic valve to direct compressed nitrogen in bottle to brakes system
where is the brake debooster located?
downstream of control valve and anti-skid valve
function of brake debooster
provide effective braking with a lower pressure than a/c hydraulic pressure
how does anti skid system work?
detects wheel skid > relieve pressure to brake piston by connecting brake fluid to return line > allows wheel to rotate
at what speed does the anti skid system turns off?
20 mph
when does maximum braking efficiency occur?
wheels decelerating at maximum rate but not skidding
how does a wheel speed sensor work?
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
function of control box in anti skid system
generate electric signal to contol:
1) prevent brake pressure before touchdown
2) brake pressure to prevent skid
function of solenoid/control valve in antiskid system
will relieve pressure from brakes when it received signals from control box
function of squat switch
located in LG, informs control if a/c is airborne or on ground
components of the anti skid system
1) wheel speed sensor
2) anti skid control valve
3) control unit
2 condition before control valve permit brakes
1) squat switch must signal weight of aircraft is on ground
2) wheel sensor sense wheel speed over 20mph
4 functions of anti skid control
1) normal skid control
2) locked wheel skid control
3) touchdown protection
4) fail safe protection
what is touchdown protection?
prevents brakes from being applied during landing even if pedals are pressed
what is a fail safe protection anti skid system?
auto returns to manual braking in case of system failure
anti skid inoperative warning light lights up when?
system is switched off or there is system failure
what does the self system test do in the anti skid control box?
test functionality of components, if any isnt working, warning light illuminates
where is the anti skid control valve located?
between brakes and brakes control valve, with line connecting to the return manifold
auto brake system will disengage when?
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
how does auto brake system work?
allows pilot to select deceleration rate after touch down
system directs right amount of pressure to brakes to get right deceleration rate
