Topic 3: Wheels, Tires, and Breaks

Question 1

Since the correct operation of the landing gear is of the utmost importance, a number of ________ are included in the retraction and extension systems to ensure its correct operation under all conditions.

Answer 1

safety features

Question 2

Since the correct operation of the landing gear is of the utmost importance, a number of safety features are included in the ________ and ________ systems to ensure its correct operation under all conditions.

Answer 2

retraction; extension

Question 3

built-in to stop the gear being retracted when it’s not safe to do so and to warn the crew if they are attempting to land with the gear not
extended.

Answer 3

safety features

Question 4

To avoid damage to the airframe structure, the ________ must always be aligned in the fore and aft direction prior to retraction.

Answer 4

nosewheel

Question 4

A number of methods are used to ensure that safety features happen automatically. These are:

Answer 4

1. hydraulic nose wheel centering on aircraft with powered steering; and
2. self-centering cam system.

Question 5

To prevent inadvertent retraction of the
landing gear when it’s not safe to do so, a ________ is incorporated which prevents the landing gear selector lever being selected up. This consists of a ________ which retains the selector in the down position and is released by the operation of an electrically operated solenoid.

Answer 5

safety device; mechanical lock

Question 6

On smaller aircraft, electrical power to the solenoid is controlled by ________ mounted on the main gear shock absorber struts. When the struts are compressed, switches are ________ but as the struts extend after takeoff switch contacts ________ and the electrical supply to the solenoid is completed thus releasing the selector lever lock and allowing the landing gear to be selected up.

Answer 6

switches; open; close

Question 7

On larger aircraft, a number of additional criteria have to be met before it is safe to raise
the gear. For instance, the ________ may have to be tilted to the correct angle and for the aircraft with body gear steering, the gear will have to be aligned ________ and ________. Only
then will the lever lock be released.

Answer 7

main gear trucks; fore; aft

Question 8

A means of overriding the lock such as by _________ is provided for use in the event of _________ and for ________.

Answer 8

mechanical means; solenoid failure; maintenance purposes

Question 9

A means of overriding the lock such as by mechanical means is provided for use in the event of solenoid failure and for maintenance purposes. Flight crews should exercise great care in using this bypass facility. Normally, it should only be used when called for in a checklist as raising the gear hydraulically when parts of it are incorrectly positioned can cause catastrophic damage to both the ________ and the _________.

Answer 9

gear; airframe

Question 10

further safety features which are intended to prevent inadvertent retraction of the gear when the aircraft is on the ground.

Answer 10

landing gear ground locks or locking pins

Question 11

They will usually consist of pins or metal sleeves which interfere with the operation of the gear in such a way that it is impossible for the gear to move when they are in position.

Answer 11

landing gear ground locks or locking pins

Question 12

They are fitted with warning flags which help prevent the crew from inadvertently getting airborne with them still in position on the gear.

Answer 12

landing gear ground locks or locking pins

Question 13

To guard against landing with the landing gear not locked down an _________ is incorporated in the system.

Answer 13

aural warning

Question 14

often provided to allow certain flight exercises
to be carried out without unnecessary warnings.

Answer 14

aural warning isolation switch

Question 15

Different aircraft types use different criteria for the operation of the aural warning and isolation switch. These normally involve a combination of _________ positions.

Answer 15

flap and throttle

Question 15

If fitted, this will give a “too low” gear warning when passing a specified radio altitude with the gear not locked down.

Answer 15

enhanced ground proximity warning system or EGPWS

Question 16

A means of lowering the landing gear and locking it in the down position is provided to cater for the possibility of _________.

Answer 16

failure in the normal system

Question 17

In most modern aircraft, the up locks may be released ________ as in the case of the Boeing 747 where the switches control electric motors which operate up locks or ________ as in the case of the Boeing 737 where the handles in the cockpit are connected by cables to the up-lock release mechanisms.

Answer 17

electrically; mechanically

Question 18

once the up locks have been released, the _________ lowers or free falls under its own weight and the _________ are engaged mechanically by springs.

Answer 18

landing gear; down locks

Question 19

pulling the handle to the _________ detent releases the door up lock allowing the door to fall open.

Answer 19

first

Question 20

Pulling the handle to the _________ detent
releases the gear up lock which allows
the gear to drop to the down position.

Answer 20

second

Question 21

A _________ in the down lock actuator forces the over center mechanism into the locked down position.

Answer 21

heavy spring

Question 22

If the gear has been lowered by the free fall method, there will be _________ available to close the ________ after extension so they will remain open, and the door open light will remain illuminated.

Answer 22

no power; hydraulically operated doors

Question 23

The ________ and ________ of an aircraft support it when on the ground and to provide it with a means of mobility for takeoff, landing, and taxiing.

Answer 23

wheels; tires

Question 24

help to cushion the aircraft from shocks due to irregularities in the ground surface (bumps) and take some of the shock on landing.

Answer 24

pneumatic tires

Question 25

The ________ and in a small number of cases, the ________, house brake units which control the movement of the aircraft on the ground and provide a means of deceleration on landing.

Answer 25

main wheels; nose wheels

Question 26

Because aircraft tires are usually _________ and _________ than the tires found on cars, they also have to be specially designed to facilitate _________.

Answer 26

larger; stiffer; tire replacement

Question 27

two types of wheels in common use:

Answer 27

1. loose or detachable flange type
2. divided wheel

Question 28

Both wheel types are made with one flange integral with wheel body and the other a separate removable part which is machined to fit over the wheel rim.

Answer 28

loose and detachable flange type

Question 29

The difference between the loose and the detachable flange tires is the method by which the removable flange is ________. In the ________, the flange is retained by a locking device on the wheel rim and held in place by the tire pressure. In the ________ of wheel, the flange is secured to the wheel body by nuts and bolts.

Answer 29

secured; loose flange type; detachable flange type

Question 30

this maybe a single piece or two or three pieces bolted together.

Answer 30

detachable flange

Question 31

advantage of the loose or the detachable flange type of wheel:

Answer 31

the tire can be changed without removing the wheel from the aircraft.

Question 32

The type of wheel most usually found on aircraft.

Answer 32

divided wheel

Question 33

It consists of two half wheels matched up and joined together by bolts which passed through the two halves.

Answer 33

divided wheel

Question 34

an example of a divided wheel is having a _________ to prevent abrasion between the two halves and provide an airtight fit.

Answer 34

seal incorporated at the joint

Question 35

When in service, particularly during heavy braking, there is a tendency for the tire to rotate or ________ around the wheel.

Answer 35

creep

Question 36

this, if excessive, will tear out the inflation valve on a wheel fitted with an inner tube causing the tire to burst.

Answer 36

creep

Question 37

less likely to occur if the tire gas pressure is correctly maintained.

Answer 37

creep

Question 38

In prevention of creep, one method is that wheels are often produced with a _________. The ________ of the wheel flange is milled so that the side pressure of the tire locks the tire walls to the flange.

Answer 38

knurled flange; inner face

Question 39

Other method involves making wheel rim _________ so that the flange area has a greater diameter than at the center of the rim. When the tire is inflated, the _________ forces the tire outwards to grip the rim.

Answer 39

tapered; side pressure

Question 40

Under extra hard braking conditions, the heat generated in the wheel tire and brake assembly can be sufficient to cause the pressure to rise to a level that the tire cannot withstand causing it to split with possible catastrophic consequences for the aircraft. This is commonly known as a ________.

Answer 40

tire blowout

Question 41

To prevent a sudden blow out, these are fitted in some wheels.

Answer 41

fusible plugs or thermal plugs

Question 42

These plugs are screwed into holes in the wheel rim.

Answer 42

fusible plugs or thermal plugs

Question 43

They are sealed by a piston which is held in position in the plug by a fusible alloy.

Answer 43

fusible plugs or thermal plugs

Question 44

Under these conditions, the alloy melts allowing the piston to escape this causes the tire to deflate in a controlled manner.

Answer 44

excessive heat conditions

Question 45

aircraft wheels are fitted with ________ which may be tubeless or have an inner tube.

Answer 45

pneumatic tires

Question 46

Tires fitted with inner tubes tend to be used on some _________ and on _________. Most _________ have tubeless tires fitted.

Answer 46

light aircraft; older aircraft; modern aircraft

Question 47

Tires are usually inflated with _________ which absorb shocks and supports the weight of the aircraft while the _________ maintains the shape of the tire, transmits braking, and provides a wearing surface. If a tube is fitted, the _________ also restrains the tube and protects it from damage.

Answer 47

nitrogen; tire cover; tire

Question 48

The tire is divided into regions or sections. The tread of the tire is situated in the ________ and _________ section.

Answer 48

crown; shoulder

Question 49

The _________ allows the tire to be flexible and the _________ is seated inside the flange of the wheel.

Answer 49

sidewall; bead

Question 50

There are two types of tires in common use. The names originating from the way the tires are constructed. These are known as:

Answer 50

1. radial ply; and
2. bias or cross ply tires

Question 51

The _________ consists of a casing made of plies of cotton, rayon, or nylon cords. The cords are not woven but arranged parallel in _________ layers and held together by a thin film of _________ which prevents cords of adjacent plies from cutting one another as the tire flexes in use.

Answer 51

tire; single; rubber

Question 52

During construction of the tire, the plies are fitted in _________ and set out so that the cords of adjacent plies are at _________ to one another in the case of bias or cross ply tires.

Answer 52

pairs; 90 degrees

Question 53

The plies are fitted _________ at approximately __________ to the centerline of the tire in radial tires.

Answer 53

bead to bead; 90 degrees

Question 54

The tire manufacturer gives each tire a _________. This rating does not relate directly to the number of plies in the tire but is the index of the ________ of the tire.

Answer 54

ply rating; strength

Question 55

The ply rating is shown on the _________ of the tire.

Answer 55

sidewall

Question 56

The ________ hold the tire on its wheel. They are made of high tensile wire strands. Each wire strand is coated with ________ and is spiral-wound into a coil of the specified _________ for the tire. The ________ are wrapped around the beads and turned out back on to themselves.

Answer 56

tire beads; rubber compound; diameter; plies

Question 57

To absorb and distribute load shocks and protect the casing from concussion damage, some tires have _________ narrow plies embedded in thick layers of rubber between the casing and the tread. These special plies are termed _________.

Answer 57

two; breaker strips

Question 58

The most popular tread pattern.

Answer 58

ribbed type

Question 59

It is formed from circumferential grooves around the tire to assist in water dispersion and to help prevent aquaplaning or
hydroplaning.

Answer 59

ribbed type

Question 60

help to improve contact grip between the tread and the runway surface.

Answer 60

grooves

Question 61

_________, particularly those fitted to aircraft with the engines mounted on the rear fuselage, may have a _________ or _________ molded onto the shoulder.

Answer 61

Nosewheel tires; chine or chines

Question 62

These are rubber extensions designed to direct water away from the engine intakes and so prevent flameouts due to water ingestion.

Answer 62

chine or chines

Question 63

A nosewheel tire fitted to a ________ wheel installation will have a chine molded onto both sides of the tire, whilst on a ________ nosewheel, installations in the chines are fitted only to the outer edge of each tire.

Answer 63

single; double

Question 64

Whether the tire is fitted with a tube or is
tubeless, an ________ is required.

Answer 64

inflation valve

Question 65

In the case of the ________, the valve form is part of the tube installation.

Answer 65

tire with a tube

Question 66

On a ________, inflation valve is fitted directly onto the wheel rim with a rubber sealing gasket.

Answer 66

tubeless tire

Question 67

Each inflation valve is fitted with a _________.

Answer 67

non-return valve

Question 68

The ________ is not considered to be a perfect seal, therefore, the inflation valve must always be fitted with the _________.

Answer 68

valve core; valve cap

Question 69

This also prevents dirt from entering the valve.

Answer 69

valve cap

Question 70

It is important when doing the external check of the aircraft that the valve caps are checked, which are normally colored ________, are fitted.

Answer 70

yellow

Question 71

They will slow down the loss of pressure in the event of a valve failure.

Answer 71

valve caps

Question 72

The differences in landing speeds, loading, landing gear surfaces, and landing gear construction of aircraft make it necessary to provide a wide range of:

Answer 72

tire sizes, types of tire construction, and inflation pressures

Question 73

In terms of inflation pressures, tires are split into four main groups identified as:

Answer 73

low, medium, high, and extra high-pressure tires

Question 74

tires designed to operate at a pressure of 25 to 35 pounds per square inch or psi.

Answer 74

low pressure tires

Question 75

These tires are fitted to aircraft using grass surfaces for takeoff and landing.

Answer 75

low pressure tires

Question 76

low pressure tires are designed to operate at a pressure of _________.

Answer 76

25 to 35 psi

Question 77

these tires operate at a pressure of 35 to 70 psi.

Answer 77

medium pressure tires

Question 78

medium pressure tires operate at a pressure of _________.

Answer 78

35 to 70 psi

Question 79

tires used on grass surfaces or on medium firm surfaces without a consolidated base.

Answer 79

medium pressure tires

Question 80

these tires operate at a pressure of 70 to 90 psi.

Answer 80

high pressure tires

Question 81

high pressure tires operate at a pressure of _________.

Answer 81

70 to 90 psi

Question 82

tires suitable for concrete runways

Answer 82

high pressure tires; extra high-pressure tires

Question 83

tires fitted to most large modern airliners.

Answer 83

extra high-pressure tires

Question 84

They operate at pressures of over 90 psi with some tires of this type being inflated to 350 psi.

Answer 84

extra high-pressure tires

Question 85

extra high-pressure tires operate at pressures of over _________ with some tires of this type being inflated to _________.

Answer 85

90 psi; 350 psi.

Question 86

Tires in use must be kept inflated to the correct pressure using ________ or other inert gas with less than _________ oxygen content.

Answer 86

nitrogen; 5%

Question 87

_________ tires may move or creep around the wheel and _________ tires will cause other types of failure such as loss of control due to reduced traction and contact with the road surface.

Answer 87

Under inflated; overinflated

Question 88

It is estimated that _________ of all tire failures can be attributed to incorrect gas pressure.

Answer 88

90%

Question 89

_________ will cause excessive wear to the crown of the tires whilst _________ is the cause of excessive shoulder wear and creep.

Answer 89

Over inflation; under inflation

Question 90

On some modern aircraft, real-time tire pressures can be displayed on the _________.

Answer 90

flight deck

Question 91

The manufacturer will set a _________ to which a tire can be subjected. This will be marked on the _________ of the tire. It is important that this speed is not exceeded as damage, including possible _________, may occur.

Answer 91

maximum ground speed; side; tread separation

Question 92

a phenomenon caused by a wedge of water building up under the tread of the tire and breaking its contact with the ground.

Answer 92

aquaplaning or hydroplaning

Question 93

the speed, measured in nautical miles per hour or knots, at which the tire loses contact with the ground.

Answer 93

aquaplaning speed

Question 94

aquaplaning speed is measured in what?

Answer 94

nautical miles per hour or knots

Question 95

The possibility of aquaplaning increases as the depth of the tread is _________. It is therefore important that the __________ remaining is accurately assessed.

Answer 95

reduced; amount of tread

Question 96

When _________, neither nosewheel steering nor braking will be effective.

Answer 96

aquaplaning

Question 97

The _________ generated between the tire and the water, if the brakes are applied during aquaplaning, may be sufficient to melt the _________ of the tire.

Answer 97

heat; tread

Question 98

During _________, tires must be examined for cuts, bulges, embedded stones, metal, or glass, signs of wear, creep, and local sponginess.

Answer 98

pre-flight inspection

Question 99

_________ in the tire penetrating the chords
render the tire unserviceable. The ________ will be recognizable as pieces of white fibrous material embedded in the rubber of the tire. Whether the tie can be repaired or must be renewed is governed by the ________ of the cut.

Answer 99

cuts; cords; depth

Question 100

_________ may indicate a partial failure of the casing. If the casing has failed (fabric is fractured), the tire must be _________.

Answer 100

bulges; replaced

Question 101

Any _________ on the tire tread, especially those caused by skidding or aquaplaning, must be examined with great care to determine if the fabric of the tire has been weakened unduly.

Answer 101

flat spots

Question 102

Foreign bodies such as _________ or _________ or _________ embedded in the tire must be removed and the _________ probed with a blunt tool by a technician to ascertain their depths.

Answer 102

pieces of metal; glass; stones; cuts

Question 103

it is governed by the extent of the damage of the tire.

Answer 103

Repair or renewal

Question 104

The amount of wear that a tire can be subject varies with different tire types. Some tires have _________ in the center groove. On others, the center groove or the two grooves on the either side of the center are used as _________.

Answer 104

marker tie bars; wear indicators

Question 105

Generally, patterned tread covers worn to the base of the marker grooves or to the marker tie bars must _________.

Answer 105

not be used

Question 106

For special high-speed applications, some tires have a layer of fabric woven into the tread which are ________.

Answer 106

reinforced tread

Question 107

This fabric may become visible during normal wear.

Answer 107

reinforced tread

Question 108

With the increased size of modern airports, taxi distances have also _________, thus, increasing the amount of tire wear and risk of damage.

Answer 108

increased

Question 109

To minimize tire wear, it is recommended that a speed of no more than _________ should be reached during the taxi run.

Answer 109

25 miles or 40 km/h

Question 110

When a tire is first fitted to a wheel, it
tends to move slightly around the rim. This
phenomenon is called _________ and at this
stage, it is considered _________.

Answer 110

creep; normal

Question 111

After the tire settles down, its slight movement around the rim should cease. In ________, the tire may tend to continue to creep around the wheel. If this creep is excessive on a tire fitted with an inner tube, it would tear out the _________ and cause the _________ to burst.

Answer 111

service; inflation valve; tire

Question 112

Creep is less of a problem with _________ as long as the tire bead is undamaged, and any pressure drop is within limits.

Answer 112

tubeless tires

Question 113

Creep is less likely to occur if the tire _________ is correctly maintained.

Answer 113

gas pressure

Question 114

Provided that the marks overlap each other, the tire can remain _________. If the marks become completely misaligned, then the tire must be _________.

Answer 114

in service; changed

Question 114

In order to detect creep, two white lines known as ________ are painted one on the wheel and a matching one on the tire. If the lines become misaligned, then the tire is suffering from _________.

Answer 114

creep marks; creep

Question 115

function by using friction between a fixed surface and a moving one to bring an aircraft to rest converting kinetic energy into heat energy.

Answer 115

aircraft wheel brakes

Question 116

The amount of _________ generated in stopping a large modern aircraft is enormous. The problem of dissipating this has been a challenge to aircraft designers and scientists for many years. Breaking systems have been improved but aircraft have got faster and heavier making _________ a constant problem.

Answer 116

heat; heat dissipation

Question 117

The use of _________ on propeller driven aircraft and _________ on jet engine aircraft plus the use of _________ has helped reduce the work the brakes need to do but even with these, the need for powerful brakes still exists.

Answer 117

reverse pitch; reverse thrust; ground spoilers

Question 118

to which is reverse pitch used to help reduce the work the brakes need to do?

Answer 118

propeller driven aircraft

Question 119

to which is reverse thrust used to help reduce the work the brakes need to do?

Answer 119

jet engine aircraft

Question 120

All modern aircraft now use _________ operated by hydraulic systems as their means of slowing down or stopping.

Answer 120

plate brakes

Question 121

use a series of fixed friction pads, bearing on or gripping one or more rotating plates, similar in principle to disc brakes on a car.

Answer 121

Plate brakes operated by hydraulic systems

Question 122

The number of friction pads and rotating plates that are used is a matter of _________ and ________.

Answer 122

design; wheel size

Question 123

A light aircraft would be able to utilize a _________ disc brake whereas a typical arrangement on a large aircraft would be a _________.

Answer 123

single plate; multi-plate unit

Question 124

consist of a pair of fixed friction pads bearing on or gripping a metal disc which rotates with the wheel.

Answer 124

light aircraft brakes

Question 125

With no pressure applied to the toe brake
pedal, the ________ are knocked away from the
disk by the action of it ________.

Answer 125

pads; rotating

Question 126

If pressure is applied to the toe brake pedal, __________ will build up in the slave cylinder behind the piston.

Answer 126

hydraulic pressure

Question 127

_________ will cause the piston to move over within the caliper unit pushing the brake pad against the disk. The reaction of the right-hand brake pad pushing against the disc will cause the caliper unit to move in the _________ direction carrying the left-hand pad with it until the disc is squeezed between the two pads.

Answer 127

hydraulic pressure; opposite

Question 128

On larger aircraft, the pressure required to operate the brakes is _________ than can be generated by the pilot’s feet, so _________ is used.

Answer 128

greater; aircraft hydraulic system pressure

Question 129

In aircraft brakes, the braking surface is increased by using multiple break plates known as _________.

Answer 129

rotors

Question 130

In aircraft brakes, layers of friction materials are mounted on assemblies known as _________.

Answer 130

stators

Question 131

The braking surface is increased by using
multiple break plates known as rotors. Also, layers of friction materials are mounted on assemblies known as stators. This greatly increases the surface area, thus, _________ the braking ability and helping to _________ the brake temperature.

Answer 131

increasing; reduce

Question 132

In this sort of construction of aircraft brakes, the _________ are key to revolve with the outer rim of the wheel and the ________ carrying the friction material are key to remain stationary with the axle.

Answer 132

rotating brake plates or rotors; stationary pad assemblies or stators

Question 133

In aircraft brakes, these are housed in a fixed
torque plate.

Answer 133

actuating pistons

Question 134

In aircraft brakes, they push on the sliding pressure plate

Answer 134

actuating pistons

Question 135

The _________ and _________ assemblies are fitted between the pressure plate and a fixed thrust plate.

Answer 135

stator; rotor

Question 136

When the brake is applied, _________ pushes the actuating pistons squeezing the _________ and _________ between the pressure plate and the thrust plate.

Answer 136

hydraulic pressure; rotors; stators