021 04 00 00 LANDING GEAR, WHEELS, TYRES, BRAKES

Last Updated on 4 years by teboo

021 04 01 00 Landing gear
021 04 01 01 Types

(01) X Name, for an aeroplane, the following different landing-gear configurations:
— nose wheel; Less chance of ground loop and higher landing speeds.
— tail wheel. Main wheels ahead go c.g.

021 04 01 02 System components, design, operation, indications and warnings, on-ground/in-flight protections, emergency extension systems

(01) Explain the function of the following components of a landing gear:
— oleo leg/shock strut;

Absorbs compressive loads.

— axles;

The shaft that the wheels are attached.

— bogies and bogie beam;

A set of axles connected by a bogie beam.

— drag struts;

Braces the gear against forward and read loads.

— side stays/struts;

Same as drag struts but resists side ways forces like crosswinds.

— torsion links;

Keeps the piston in the cylinder.

— locks (over centre);

Geometric or over centre, the weight of the landing gear, with the help of a spring in some cases, locks the gear down with gravity.

— gear doors.

To keep the fuselage and wings aerodynamically quiet.

(03) Name the different components of a landing gear, using the diagram appended to these LOs (021).

(04) Describe the sequence of events during normal operation of the landing gear.

Doors open, the gear is unlocked from its up position, it extends, locks in place then some of the doors may close again.

(05) State how landing-gear position indication and alerting is implemented.

Green is down and locked, red is unlocked, traveling or lever selection does not match the actual gear position. No lights is up and locked.

(06) Describe the various protection devices to avoid inadvertent gear retraction on the ground and explain the implications of taking off with one or more protection devices in place:
— ground lock (pins);

Physical pins with big red ‘remove before flight’ tags.

— protection devices in the gear retraction mechanism.

Solenoids in the gear leaver liked to ‘weight on wheels’.

(07) Explain the speed limitations for gear operation (VLO (maximum landing gear operating speed) and VLE (maximum landing gear extended speed)).

Easy peasy…

(08) Describe the sequence for emergency gear extension:
— unlocking; — operating; — down-locking.

(09) Describe some methods for emergency gear extension including:
— gravity/free fall; — air or nitrogen pressure; — manually/mechanically.

021 04 02 00 Nose-wheel steering
021 04 02 01 Design, operation

(01) Explain the operating principle of nose-wheel steering.

(03) Describe, for an aeroplane, the functioning of the following systems:
— differential braking with free-castoring nose wheel; — tiller or hand wheel steering; — rudder pedal nose-wheel steering. (04) Explain the centring mechanism of the nose wheel.

Two cams that centre the wheel prior to retraction – smaller aircraft. Upstream hydraulic pressure can be used too.

(05) Define the term ‘shimmy’ and the possible consequences of shimmy for the nose- and the main-wheel system and explain the purpose of a shimmy damper to reduce the severity of shimmy.

Quick oscillation of the nose wheel and reduce directional control on the ground. Shimmy damper, eh, damps shimmy.

(06) Explain the purpose of main-wheel (body) steering.

Enables tighter turns and reduces wear on the rubber of the main gear. Acts in the opposite way to the nose.

021 04 03 00 Brakes
021 04 03 01 Types and materials

(01) Describe the basic operating principle of a disc brake.

Creates friction and therefore slows the wheel down.

(02) State the different materials used in a disc brake (steel, carbon).

(03) Describe the characteristics, advantages and disadvantages of steel and carbon brake discs with regard to:
— weight;

A multi disc system gets heavy.

— temperature limits;

Carbon can absorb twice as much heat as steel so is less prone to brake fade.

— internal-friction coefficient;

Much better for carbon than steel for all the reasons here.

— wear.

Carbon brakes last longer.

021 04 03 02 System components, design, operation, indications and warnings

(01) Explain the limitation of brake energy and describe the operational consequences.

A lot of kinetic energy needs to be absorbed which is translated into heat causing brake fade.

(02) Explain how brakes are actuated:
— hydraulically, — electrically.

(03) Explain the purpose of an in-flight wheel brake system.

To stop the wheels spinning in the fuselage.

(04) Describe the function of a brake accumulator.

An emergency means of using the brakes, can give about six brake applications.

(05) Describe the function of the parking brake.

Well, no idea at all…. Some parking brakes can disable anti-skit or touchdown protection. May also not be advisable to apply parking brakes when they are excessively hot;

(06) Explain the function of brake-wear indicators.

A physical bar or rod that shows how worn they are.

(07) Explain the reason for the brake-temperature indicator.

I would have thought this obvious.

021 04 03 03 Anti-skid

(01) Describe the operating principle of anti-skid where excessive brake pressure applied is automatically reduced for optimum breaking performance.

(02) Explain that the anti-skid computer compares wheel speed to aeroplane reference speed to provide the following:
— slip ratio for maximum braking performance;
— locked-wheel prevention (protection against deep skid on one wheel);
— touchdown protection (protection against brake-pressure application during touchdown);
— hydroplane protection.

(03) Give examples of the impact of an anti-skid system on performance, and explain the implications of anti-skid system failure.

021 04 03 04 Autobrake

(01) Describe the operating principle of an auto brake system.

An automatic system.which operates on landing and disengages when certain parameters agree.

(02) Explain why the anti-skid system must be available when using autobrakes.

Because it is important because at maximum braking skid protection is required.

(03) Explain the difference between the three modes of operation of an autobrake system:
— OFF (system off or reset);

— Armed (the system is ready to operate under certain conditions);

Anti skid ON, power levers at a certain place, hydraulics working brake pedals not depressed.

— Activated/Deactivated (application of pressure on brakes).

Above.

(04) Describe how an autobrake system setting will either apply maximum braking (RTO or MAX) or result in a given rate of deceleration, where the amount of braking applied may be affected by:
— the use of reverse thrust;

The amount of braking will be less if reverse thrust is sensed and is being used.

— slippery runway.

More brake pressure may be used but only up until the anti-skid system kicks in.

021 04 04 00 Wheels, rims and tyres
021 04 04 01 Types, structural components and materials, operational limitations, thermal plugs

(01) X Describe the different types of tyres such as:
— tubeless;

Airtight liner is vulcanised (hardened) to form an airtight gas seal, reduces weight and allows the wheels to cooler overall

— diagonal (cross ply);

Or bias, adjacent cords are at 90degrees to each other.

— radial (circumferential bias).

(02) X Define the following terms:
— ply rating;

The strength of the tyre, high is high.

— tyre tread;

Made from rubber and provides grip, channels help disperse water.

— tyre creep;

The movement of the tyre relative to the wheel. Greatest after new fitting, can shear the valve off.

— retread (cover).

Can be done to extend the life of a tyre with heat bonding.

(03) Explain the function of thermal/fusible plugs.

The plugs will pop before the tyre does allowing a controlled deflation.

(04) Explain the implications of and how to identify tread separation and wear or damage with associated increased risk of tyre burst.

Damage or incorrect pressure can lead to separation or tyre failure. Basically, check everything is within limits…

(05) Explain why the ground speed of tyres is limited.

Exceeding the rating has obvious consequences.

(06) Describe the following tyre checks a pilot will perform during the pre-flight inspection and identify probable causes:
— cuts and damages; — flat spots.