TYPES OF LANDING GEAR

TYPES OF LANDING GEAR

        The basics of the landing gear was explained in the before posts.(https://sabaeroline.blogspot.com/2020/06/aircraft-landing-gear.html) Landing gear types would clearly explain in the present post. As pilot tries, Not Every Aircraft landing is perfect due to Bad weather conditions, short landing etc., Landing gear play important role at time of rough landing, handles the aircraft smoothly and safely landing without breaking or collapsing the aircraft into pieces. 

TYPES OF LANDING GEAR

There are many types of Landing gear. The types of landing gear used in the aircraft depend on two things design of the aircraft (like military, civil purpose) and its intended use (like Cargo, commercial).There are three main types of landing gears used.

Tail wheel Landing Gear

Tail wheel Landing Gear is also known as Conventional or traditional type landing gear because this was milestone for majority of the aviation history, used in the other legendary fighters of WW2. The main gear are located forward to centre of gravity of flight, which makes the tail to get support  from the third wheel assembled in the tail of the aircraft. In some aircraft skid replaces the third wheel which helps slow the aircraft while landing and provide direction stability in earlier aircraft.

By raising the angle of fuse large when fitted with conventional gear allows to fix long propeller in front of engine for older aircraft, It also provide increase ground clearance of the forward fuse large with is also a advantage in using Conventional Landing Gear.

Directional stability is controlled by different breaking system until the aircraft speed comes under the control of the Rudder. Steerable tail wheel connected to the rudder and rudder pedals by cables. For smooth and easy landing springs fixed for damping.

Tandem landing gear

Most of the aircraft using tandem landing gear are military planes and spy planes. This type of landing gear has a main gear and tail gear aligned on the longitudinal axis of the aircraft. 

The main advantage of Tandem landing gear design reduces drag when deployed they are retractable.

Tricycle-type landing gear

The most common type landing arrangement used in modern aircraft is the Tricycle-type landing gear consist of a nose gear and main gear. Larger and small aircraft today used this gear arrangement.

Benefits

• Allows more forceful application of the breaks without noise created over when Breaking which increases high landing speed.
• Provides better visibility from the flight while landing and ground maneuvering.
• Weights are equally spread over large area and are equally distributer each Gears provide a better safety margin.
• Aircraft centre of gravity lies forward of the main gear, force act on CG point makes the aircraft moving forward avoiding looping which prevents groung-looping.

Landing Gear Design

Depend on the Aircraft usage and operation the landing been designed either Fixed Gear (immovable) Retractable Gear (movable).

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Fuel System

          

Fuel system in aircraft is designed to deliver uniform flow of clean fuel from the tank to the propulsion system of the aircraft without any interruption to power system during continuous flight at high altitude, during all approved maneuvers.  Each fuel tank is equipped with internal fuel pumps, valves and plumbing to feed fuel to the engine to produce thrust.

          Fuel system consist multiple fuel tanks located in the wing or fuselage base on aircraft design, intended use and as well as age aircraft determine which fuel tank to be installed. The tanks are made of non corrosive materials that are non reactive aviation fuel. Aluminium alloy are more commonly used in modern aircraft fuel tank of its light weight and corrosive resistant, Synthetic rubber coated type fuel cells are also used.

                     

        In high wing aircraft there is no need of any pumps to feed the fuel. Gravity propels the fuel from tank to the engine. In lighter Aircraft and low wing aircraft fuel tanks are located inside the wing. Have filler opening at the top of the wing through which fuel can be filled and drains in the bottom by which any moisture can be removed, to drain fuel sample for inspection. Electrical Pump been used to pass the fuel from the tank to the Carburetor, and pressure gauge will be attached to the pump show weather the pumps are working properly. Vent (Duct) placed to equalise the internal pressure. Fuel selector valve are used to avoid imbalance fuel flow and allow to choose from which tank the fuel should flow to the Engine. Before the fuel enters the engine fuel will passes through the Strainer where the water and other contaminated particles are removed to avoid improper quality fuel to flow leads to Failure of Fuel system.

Common fuel system issues  

   

Pressurization of Fuel Tank

During maneuvering, rolling and yawing motion of the aircraft Centrifugal force will be created due to which pressure acts on fuel tank. During design fuel tank will undergo analyse applying different pressure load at pitch yaw roll motion to calculate natural frequency and resonance which may leads to the vibration of the fuel Tank which are more effective.

Failure of Fuel pump

Pumps have automatic bypass valves. If one valve fails other pumps will continue normal flow to pass the failed pump. A failure pump can causes several of problems. Fuel pump is a non serviceable part means it needs to be replaced.

Imbalance fuel flow

On flight the usage and the movement of the fuel in the fuel tank keeps changing which would change center of gravity of the aircraft. Many air craft have pump to pass the fuel from one tank in the wing to another to balance level equally on both as not to get heavier on onside. This happens because of unequal usage of fuel by the engines. Imbalance fuel flow affects the stability of the aircraft during flight.

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Aircraft landing Gear

        Landing gear is an undercarriage part of the flight landing system. Aircraft landing gear has wheels equipped with shock absorbers on light planes and Hydraulic or pneumatic oleo struts on larger aircraft. The main function of the landing gear is undercarriage to the primary structure of the aircraft to enable the aircraft for a taxi, safe landing and takeoff, and to support the aircraft in the rest of the ground operation.

 

     

Landing-Gear Components

To support and stabilize the aircraft during landing and Ground taxing Landing gear assemblies are made of various components

 

Trunnion

It a component used in the landing gear attached to the airframe at one end other end supports by a bearing, which allows the gear to move to and fro during retraction and extension. Landing gear strut attached approximate to the center of the trunnion in downward direction.

Strut (outer Cylinder)

Is a vertical member consisting of shock absorbing mechanism, form a cylinder for the air-oleo shock absorber. Strut is also called as outer Cylinder.

Piston (Inner Cylinder)

Is a component moving to and fro inside the air-oleo shock absorber, Bottom of the piston is attached to the axle connecting truck Piston is also named as Inner Cylinder or Piston rod.

Seal

Seals are placed on the piston, which seals the air pressure in the upper part of the strut keep the inner cylinder aligned with the outer cylinder

Orifice Rod

Permits rate of hydraulic fluid flow from the inner cylinder to the upper side of the piston.

Torque Links

This connects the strut cylinder to the pistons and axle. Torque links protect the strut avoiding the extension of the piston during gear retraction and holds the wheel and axle in proper and correct aligned position in corresponding to the Strut.

Truck (bogle)

Truck is located to the bottom of the Strut piston, to which one of the axles attached to it. Truck is cylinder structure cylinder connected used when one wheel is placed behind another. Truck can tilt fore and aft at the piston connections which allows for the direction change in aircraft altitude during takeoff, landing and taxing.

Drag Link (drag strut)

To stabilize the landing gear, support the gear assembly longitudinally drag link are used. When the gear retracts forward or aft drag link will be hinged at middle allows the gear to retract.

LANDING GEAR TYPES detail are available in next Post

Click here

TYPES OF LANDING GEAR 

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Forces Acting on an Aircraft

How Does an Aircraft Fly’s?

            This question everyone ask when seeing an aircraft (Airplane) flying in Sky. Concept is there are four forces acting on the airplane during Flying. Forces which act on aircraft are

          Lift,    Drag,    Thrust,    Weight

Forces Acting on an Aircraft

Lift and Drag are Aerodynamic force “Aero” stands for the Air and “Dynamic” denotes motion, as they are created due to the movement of the Airplane through Air.

Lift- To overcome the weight force, Lift is an upward force created on the aircraft wing to make the aircraft move upward. Lift is produced by the motion of the Airplane through the Air.

Lift is produced due Pressure Gradient created on the Wing surface, Where lower pressure created on the upper surface of the airplane wing than to the pressure on the wings lower surface causing the wing to Lifted upward.

 Lift will be always perpendicular airplane moving direction, which opposes the Gravity Force.

Drag- Drag is always opposite to Thrust. It is an opposing force created on an airplane, while the airplane moves in forward direction. Air resist the motion of the aircraft the resisting force is called as Drag. Drag force is mainly created by skin friction and Displacement of the air.

Thrust- In order start moving an airplane Thrust should be greater than the Drag. To overcome drag thrust force is generated on the airplane using engine powered propulsion system. Thrust is man-made force.

Magnitude of the Thrust depends factors based propulsion systems includes Throttle capacity

• Number of engine used
• Type of Engine

 Weight-Weight is opposite to Lift. It is a force always acting vertically downward to the center of gravity. The magnitude of weight include total of (Mass of all the airplane parts + Amount of fuel + payload on board includes people, baggage, luggage) Weight is acting towards the center of gravity of earth.

TOTAL WEIGHT = (Mass of all the airplane parts + Amount of fuel + payload on board includes people, baggage, luggage or cargo)

Flight Directions and Controls

Flight control is Aerodynamics devices allows pilot to adjust and maintain the airplane in stable path during flight.

ROLL - Ailerons controls motion along longitudinal axis. The pilot create Roll by changing bank angle by (increasing the lift on one wing and decreasing the lift on other) lift difference causes rotation motion.

PITCH   -  Elevator controls rotational motion along lateral axis. The pilot creates pitch by changing the angle of the Elevator, Aircraft moves up and down direction with reference to the Nose.

YAW  -  Rudder controls motion along Vertical axis. The pilot creates pitch by changing Rudder angle located on the Tail, Aircraft moves left and Right direction with reference to the Nose.

 

Longitudinal axis - The line of axis passes through aircraft from Nose to Tail

Lateral axis - The line of axis passes through aircraft From Wing tip to Wing tip.

Vertical axis - The line of axis passes through aircraft from Top to Bottom.

 

The combination of this force and controls makes the aircraft Fly.

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