11.14 Flashcards
Are the MLG in a tail wheel ac the forward or aft ones
Fwd
Where’s the c of g located on tricycle type landing gear
Ahead of MLG
Advantages of tricycle landing gear
Ground looping is prevented because the CG is in front of the main gear providing stability and a returning moment that tends to run straight.
It allows more forceful application of the brakes without nosing over when braking.
Forward vision is not obscured and there is reduced drag during take-off.
What are multiple wheeled MLG also known as
Bogie
Where are tandem gear wheels located
Aligned on longitudinal axis with nose gear in front of c of g and the MLG aft
Benefits of NON retractable gear
Simple
lighter
cost less
What does the trunnions link do
connects the top of the leg to the wing structure and allows the leg to rotate into and out of the landing gear bay.
What’s inside the shock strut
Nitrogen and hydraulic fluid
What does the torsion link do ans what’s it also known as
Counteracts wheel shimmy
Shimmy damper
What does the side strut do
Resists lateral or sideways movement
What does the gear down lock do
Ensures the two parts can’t fold together when gears extended
What do the drag struts do
Braces the legs from longitudinal or fore and aft movement
When’s the shortening mechanism used
When retracting the landing gear
Are nose wheel gears steerable
Do they have brakes
No brakes but are steerable
What does the centering cam in the NLG do
Centers the wheels in preparation for retraction
What is wheel shimmy and what causes it
Rapid oscillation of wheels left to right
Caused by uneven tyre pressure, uneven tyre wear or uneven runway surface
What two ways do shock absorbers dampen the impact
The shock energy is altered and transferred throughout the airframe at a different rate and time than the single strong pulse of impact.
The shock is absorbed by converting the energy into heat energy.
What two main classes can shock absorbers be divided into
Solid- steel or rubber springs
Oleo- a fluid spring with a gas or oil or both
What’s the two ways dampening can be utilised by oleo shock absorbers
One utilises the compressibility of oil pressures at above 700 bar
One utilises the compressibility of nitrogen and oil go provide damping d
What’s contained on the outer cyclinder of oleo to help with servicing
A gas charging valve
A oil charging valve
Whats hydraulic dieseling
Occurs when air mixes with hydraulic cycling oil causing and air bubble and when the oleo takes pressure it can cause the shock strut to crack
In a oleo pneumatic strut with a separator how are the oils and gas separated
With a piston in the inner cylinder
What does the flutter plate in an oleo strut do
Acts as a one way restricter
What’s the movement of the leg with a liquid spring restricted by
The slow rate in which the oil can pass through the dampening orfices
What’s dimension X on MLG
What’s it sometimes also referred to as
The measure of the extension of the inner cyclinder
H
What’s in place on the landing gear lever to prevent it from accidentally being moved or moved by vibration
A detent so the handle must be lifted and moved
What 3 positions do the landing gear lever have
Up
Down
Off
What’s in place to prevent the gear from being retracted in the ground
A solenoid operated latch
Is an override if nessecary
What can override the solenoid latch on the landing gear lever
Only done mechanically
Why’s it important that the correct sequencing of the doors and landing gear is done
To prevent gear from jamming
When the gear selector lever is put to up what happens to the selector valve
Opens to provide pressure to the actuators to move the doors up
What may need to be done when retracting gear to wheels
Wheel breaks to stop rotations to prevent gyroscopic forces on the gear
What does the inner cyclinder on the nose wheel do on take off
Fully extend
What system is used for emergency situations of dropping the landing in larger commercially ac
Free fall system by removing uplock
How many emergency T handles are ther
3
One for each keg
What does a green landing gear door light mean
Red
No light
Green - down ans locked
Red - unlocked and travelling
No light - stowed
When are Microswitches used
When physical contact with an objects permissible
When are proximity switches used
instead of normal microswitches where there is a high risk of contact corrosion due to dirt and moisture.
What are the two types of proximity switches
Two different types of proximity switches are used on aircraft:
Reed Switch
Electronic Switch
What are the two types of proximity switches
Two different types of proximity switches are used on aircraft:
Reed Switch
Electronic Switch
What’s done for an indication that the main downluck stirs are locked properly
Red arrows
Where are air ground switches located on most ac
On MLG (MAINLY)
sometimes nose
What do ground air switches also sometimes monitor on 4-6 wheeled ac
Bogie position/tilt is monitored
What do ground air switches also sometimes monitor on 4-6 wheeled ac
Bogie position/tilt is monitored
What needs to be considered about the materials wheels are made of
Lightweight
Strong
Able to resist extremes of temperature
Protective against the elements
What are ac wheels made of
Magnesium or alluminium alloy
What type of comstruction are ac wheels
Two half hubs
What type of bearings are usually used in wheels
Tapered roller bearings
What half of the wheel are the brakes installed on
The inboard half
What half of the wheel are the brakes installed on
The inboard half
What temp can the break risks get up to
1000 c
What do the wheel heat shields do
Protect tyres from heat from the brakes ONLY
What do fusible plugs do
Relieve the pressure when they exceed a a certain level
NOT INSTALLED ON NOSE WHEEL AS THEY DONT GET AS HOT DUE TO NO BRAKES
What loads do taper roller bearings take
Axial and radial
What loads do taper roller bearings take
Axial and radial
When an ac lands what speed does the wheels go to
0 to 240 km/h
How long after heavy breaking for a TRO can breaks be known to fail
More than 30mins
What fire extinguisher should be used for brake fires
Dry powder
How many brake linings or break pucks does a single disk brake have
6
What does the brake calliper housing contain
Bleed point to remove any unwanted air
What are the rotors and statins made of in a heat pack
Carbon or steel
What are the rotors and statins made of in a heat pack
Carbon or steel
What’s advantages of carbon heat packs over steel heat packs
40% lighter
Can withstand temps 50% higher than steel
Last 20-50% longer than steel breaks so cheaper to maintain
What’s a disadvantage of a carbon heat pack
More expensive to make
Why are the steel heat pack rotors segmented
To prevent bending
What’s the brake piston housing made of
Alluminium
What’s the brake piston housing made of
Alluminium
What 3 functions does the brake pistons serve
Apply the pressure onto the brake packs
Compensate for wear of breaks
Auto adjust break clearance
How many wear pins are there per tyre
2
What does the torque tube in the break system do
Transfers the torque of the stator discs to the piston housing
What advantages do e brakes have
Reduction in the mechanical complexity of traditional hydraulic braking systems.
Eliminates potential departure delays due to leaking hydraulic fluids or system failures.
Ability to self-monitor and removes the need for scheduled wear checks as the system will advise when wear is excessive.
Ability, when parked to efficiently auto-adjust the braking pressure as the brakes cool down.
What do power brakes use for breaking
Hydraulics
What do hydraulic fuses in power brake systems do
Stops excessive flow of fluid it detects by shutting to retain the remaining fluid in system
What’s the key element in a power break system
Break control valve
responds to the brake pedal input by directing hydraulic fluid to the brakes. The influx of fluid to the brake is increased in line with the pressure exerted on the brake pedal, therefore, increasing the pressure and enhancing the braking action.
How many sources of pressure does the power breaking have and what’s this provide
2
Redundancy
How many sources of pressure does the power breaking have and what’s this provide
2
Redundancy
What provides the majority of the brake/rudder feel
supplied by the brake control or brake metering valve in a power brake system
What can the accumulator provide
Emergency breaking
What do brake de boosters do
devices that apply force over different-sized pistons to reduce pressure
What do brake de boosters do
devices that apply force over different-sized pistons to reduce pressure
What happens when the parking brakes applied
Brakes are permanently pressurised with a hydraulic accumulator
Where are the break temps displayed on airbus and Boeing
Boeing - ECAM
airbus - EICAS
What temp should a tyre rcexceed for a green arc to appear on the hottest wheel
When above 100 c
What brake temp would cause the hottest wheel to turn Amber
300 c
What do anti skid systems do
Improve braking efficiency and protect tires
What was the first ABS to be widely used
Dunlop maxarets
When does maximum braking efficiency occur
When wheels are decelerating at a max rate but not skidding
After the ac touches down and the rudder pedals are pressed down then the anti skid system kicks in until the ac has dropped to aprox
30km/h
How’s the flywheel attached to the drum on a mech/hyd anti skid system
One way clutch
How many anti skid systems are there on landing gears
1 per brake
What electrical power do wheel speed sensors used
AC or DC
What electrical power do wheel speed sensors used
AC or DC
What’s the brain of the anti skid system and what does it do if it senses a skid condition
Control unit
Signals sent to control valve to relieve the hydraulic pressure to the relevant brake to prevent or relieve the skid
How many anti skid control valves are there per landing gear
1 per break unit
What does the check valve in the anti skid system do
The check valve linking the inlet and brake outlet port prevents outlet pressure from exceeding inlet pressure which can occur during any thermal expansion conditions.
What does the check valve in the anti skid system do
The check valve linking the inlet and brake outlet port prevents outlet pressure from exceeding inlet pressure which can occur during any thermal expansion conditions.
What’s done to retain the pressure of the breaks when the parking break lever is applied
A solenoid operated valve is closed to block the return line
What can applying breaks as soon as the wheels come into contact with the runway on a landing do
What’s in place to prevent this
Tyre blow out
Touch down protection
What’s the comparator circuitry used for
to relieve pressure when one wheel out of a paired group of wheels rotates 25% slower than the other.
When do auto brakes operate
When there’s weight on wheels and when the engines are in idle or thrust reversers deployed
This reduces delay before brakes to approx 1 sec
Each second of delay usually increases the aircraft’s stopping distance by….
60m
How much does the spoilers increase drag
40-80%
How much does the spoilers increase drag
40-80%
How much does the spoilers increase drag
40-80%
What happens to the pressure in auto breaks when speed breaks are applied
Pressure reduces to maintain the deceleration rate
How many modes does the auto brake selection panel have
One for low deceleration
One for medium deceleration
One for maximum deceleration
How many modes does the auto brake selection panel have
One for low deceleration
One for medium deceleration
One for maximum deceleration
What are type. I, III, VII, VIII
Three-Part Nomenclature tyres,
What type of ac are type I wheels used on
Fixed wheel
What landing speeds are type III tyres used for
Speeds over 160 mph
They are relatively lp
What do the two numbers for TYPE III tyres stand for
The first one is the nominal section width of tyre
Second is diameter of rim the tyres mounted on
What’s narrower tyres Type III or type VII
Type VII is narrower
What ac are type VII tyres and why
Jet ac
Bc they are high performance and high pressure
What does the two number identification system stand for on type VII tyres
First num- overall nominal diameter of tyre
Second num- section width
What are the most advanced wheels on jet ac today
Type VIII
What does the three didget number ident for a type VIII tyre used for
First no - tyre diameter
Second no - section width
Third no - rim diameter
What does the three didget number ident for a type VIII tyre used for
First no - tyre diameter
Second no - section width
Third no - rim diameter
What does ply rating mean
Indication of tyres relative strength
What’s the diff between tube or tubeless wheel
Tubeless have a specialised inner liners to effectively prevent air leaks
What are advantages of tubed tyres
Lighter and reduced susceptible to tyre creep
What’s the difference in how tubed and tubeless tyres react to a puncture
Tubed have sudden losses of pressure and cause the wheel to become unstable
What are the two different types of tyre plies
Bias ans radial
What is the purpose of plies
Form the tyre ans give it strength
What’s the angle of the plys in a bias ply tyre
30-60 degrees
From direction of tyre rotation
What does the bias ply allow
Flexibility
What angle are the plys to the direction of wheel rotation on a radial tyre
What characteristics does this give them
90 deg
Strengthening and allow it to carry high loads
What do belt plies do
Strengthen tread area
What do carcass plies do
Strengthen tyre sidewalls
What do chippers do in tyres
Improve the durability in bead area
What’s negatives of radial tyres
More expensive and can’t be re-treaded as frequently as conventional tyres
What are tyre beads
Metal wires that are embedded in the rubber usually ,one two or three of them, they anchor the carcass into the rim to ensure the tyres firmly mounted on the wheel
Takes all breaking forces
What are carcass plies
Give strength and form to carcass body of tyre
Radial has less plies than bias plies
What does the right pattern tread help to minimise
Hydro planing - wedge of water under tyre
How many times can a tyre be retreaded
10;
What does a Rubin tread provide (characteristic)
good traction under different runway conditions.
Improves tread wear.
Improves directional stability.
What does a Rubin tread provide (characteristic)
good traction under different runway conditions.
Improves tread wear.
Improves directional stability.
What can an unbalanced tire cause
Severe vibration, irregular wear
What are awl marks
Indicate area in which small holes were made during manufacturing to let entrapped gasses out
What are awl marks
Indicate area in which small holes were made during manufacturing to let entrapped gasses out
What are rib tread tyres used for
Diamond tread
Smooth tread
Paved surfaces
Unpaved
Old ac without brakes designed for stopping
When should rib tread tyres be replaced
When the tread depth is less than 2mm for more than 25% of tread circumference
When does shoulder wear occur on tyres
When tread shoulders are more loaded than the crown
When does tread strip damage occur
When tyre encounters fod or as a result of mechanical or thermal fatigue
When does tread chunking occur
When taxiing and turning quickly on rough surfaces
What causes a an open tread joint
When the original manufacture of tyre fails to adequately adhere a joint in tread
What causes a tyre burst
Fod or from it operating at a low pressure for a while
What pressure are tyre assemblies usually stored at
20-30 psi
What causes nose wheel to stay straight
Positive caster
What factors cause nose wheel shimmy
Under or over inflated nose wheel tyres.
Unevenly inflated double nose wheel tyres.
Low pressures in the steering hydraulic system (metering valves).
Worn steering mechanism components.
Worn nose landing gear to fuselage attachment fittings.
What helps to self centre the gear
Centering cam
What’s the purpose of MAIN gear steering
Reduce tyre scrub and ac turn radius
What’s the angular movement of MLG steering?
NLG steering?
MLG- 5-8deg
NLG- 70 deg
What should be done before towing
Nose wheel steering should be unpressurised
Towing safety pin in to prevent the summing lever from moving on
