UAVs Unmanned Aerial Vehicles

 

UAVs Unmanned Aerial Vehicles

                After the Wright brothers worked so hard to put humans in the air by flying machines, now a day’s some aerospace engineers are working hard to take out of the flying machine. UAVs Unmanned Aerial Vehicles are the Airplanes that have no humans on board which are operated and flown remotely by pilots.

Israel is the first nation to use UAVs in the combat situation arguing that loss of relative inexpensive UAVs was better than the loss of a pilot and a multi-million dollar airplane.

UAVs are mainly used to carry sensors, target designated and electronic transmitters

 Designed to destroy enemy’s target, UAVs are more effective fly at greater range and endurance.

Range – Is the maximum distance an aircraft can fly between takeoff and landing.

Endurance – Is the maximum length of time that an aircraft can spend in cruising flight (level flight).

Aircraft Powerplant Outer Structures

 Aircraft Powerplant Outer Structures

               Aircraft powerplants produces the source of thrust to move the aircraft through the air, at the same time they are also the source of vibration, heat and drag forces. Powerplant Structures includes both the propeller and Engine work in combination to produce thrust. Engine provides the source of power to rotate the propeller.  Propeller is mounted at the front of the engine converts the rotatory force into Thrust in the engine.

Powerplant Outer Structures components

Nacelles

Nacelles encloses the engine provide the streamline flow (uniform flow) of air over the outer surface of the engine to improve the aerodynamics of the aircraft. Protect the engine and its components during flight. Allow the proper flow air to engine for cooling and combustion.

   

Fire walls

Firewalls are normally located near to the engine compartment. Engine, Auxiliary power units, combustion chamber and turbine produces tremendous amount of heat which affect other aircraft component and it functionality, to protect other aircraft component from this heat effect sections of the turbine engine must be isolated from the remainder of the aircraft by means of firewalls. Firewall is used to protect the nacelle strut and systems from the exposure.

Engine Mount

Engine mount is frame structures that support the engine and connect it to the fuselage. Which are designed to distribute the weight of the engine and distribute torque and vibration generate from the engine.

Cowlings and Fairings

Cowlings and Fairings both are similar, which are removable covering for covering the portions of the airplane (Engine, Mounts and other engine components). Design to provide uniform flow of air over the engine surface improve the aerodynamics of the aircraft.

 

 

 

Aircraft engine Firewalls

                      Firewalls are normally located near to the engine compartment.Engine, Auxiliary power units, combustion chamber and turbine produces tremendous amount of heat which affect other aircraft component and it functionality, to protect other aircraft component from this heat effect sections of the turbine engine must be isolated from the remainder of the aircraft by means of firewalls. Firewall is used to protect the nacelle strut and systems from the exposure.

Design

Firewall should design in such a manner that no hazardous quality of air, fluids, or flame can pass from the compartment to other portions of the aircraft.

To be easy access to repair and installation because they normally located in the engine compartment, later there may be need to remove and replace the engine or other components.

 

Material

Material used should provide protection against both heat and corrosion, Base on which following materials been used

• Stainless steel
• Titanium
• Copper or steel based alloy
• Terne plate

Engine Mounts

        Engine mount is frame structures that support the engine and connect it to the fuselage. Which are designed to distribute the weight of the engine and distribute torque and vibration generated by the engine, Vibration that originated in the reciprocating engine are transmitted through the engine mount to the airplane structure for such mounts engine must be attached with some sort of rubber bushing between the engine and mount attachment to control these vibration. 

Maximum vibration from the engines are controlled when tightened so that the engines move slightly with respect to the rubber bushing which limits in a torsion during operating condition, But at the same time if the bolt are too tight the mount structure will tend to vibrate along engine which would transmitted to Airplane wing and fuselage structure which would be undesirable. To avoid over tighten of bolts the technicians should always refer to the manufacture’s service before tightening such bolts.

Material Used

Engine Mount should withstand waste heat released from the engine and ability to carry heavy engines at temperature of up to 500 ⁰ C base on the requirement three alloys types are used

Nickel-Based alloys: Can withstand high extreme temperature

Titanium alloys:  half the weight of steel, used in the place where the light weight material is needed

Steel alloys: Use at the place where high strength needed at very low temperature.

Based On Aircraft

Light Aircraft - Engine mounts made of welded-steel tubing or aluminium alloy sheet metal.

Turbine powered Aircraft - Engine mounts made of forged metal bolted to airframe.

Design and Types

Engine mounts vary widely in appearance and Construction, but basic features of construction are same. Each aircraft differs from other, heat released from the engine differs base on this criteria each new engine mount should also be unique and to be designed that engine and its accessories should be easy for inspection and maintenance.

Most aircraft which exactly from same manufacturer of the engine shall uses the same mount.

Types

Dynafocal engine mount

Protects the vibration and motion from the engine to be transmitted to aircraft structure, Fixing is based on the centre of gravity of the engine.

Shape: Ring-like

Bolt Point: Usually Four points

 

Conical mount

Conical mount are attached parallel to the firewalls, easy for installation simple and easy to fix to aircraft.

Bolt Point: Usually Four points

Drawbacks: Vibration and Torque are transmitted through the Frames

 

Bed mount

Bed mount are attached under the crankcase, which totally differs from the other type of mount (Conical mount and Dynafocal engine mount), Designed for perfect fitting of the engine avoid transmit vibration to the structure

Bolt Point: Usually Four points in modern aircraft

Vibration is more Danger to Aircraft leads to failure, Engine Mount Helps to avoid some sort of Vibration to be transmitted to Aircraft Structure.

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Introduction to Helicopter

Introduction to Helicopter

                 Helicopter is a type of Rotary wing Aircraft that uses rotating wings to provide lift. Rotor blades rotate about a vertical axis generating lift to move the Helicopter upward along with the help of controls and propulsion. Lift is generated by the relative motion of wing surface with respect to the air.

The helicopter can do vertical flight (vertical take-off and landing) where rotor must efficiently supply thrust force to support to support helicopter weight.

Helicopter has two Rotor Blades

Main Rotor Blade

Main rotor is mounted on a vertical mast head over the top of the helicopter connected with a driven shaft and gear box (to control the speed of the rotating blade).

Tail Rotor Blade

Tail rotor is a small rotor mounted at the tail of the helicopter, position and distance from the center of gravity of helicopter to generate needed thrust in same direction with respect to the main rotor rotates. Connected with the shaft powered from main transmission and has gearbox.

Main use of the tail rotor is to counter the torque, In simple words when the main rotor rotates in clockwise direction the helicopter fuselage structure will rotate in anticlockwise direction if the tail rotor is not mounted, So tail rotor is to counter the torque, and maintain the helicopter fuselage structure stable according to the direction it moves or fly.

Single main rotor and tail rotor configuration combating used to provide the torque balance (yaw control) to the helicopter.

 

Use of helicopters

Helicopters are used for both military and civil purpose:

Military

Search and Rescue Operations

Anti-submarine activity

Air observation

Direct support of infantry, These Helicopters are provided with armaments such as missiles machine guns etc.

Civil

Emergency rescue and medical aid purpose

Agricultural operations

Forest patrolling, forest fire extinguishing

Patrolling of highways, oil pipes lines, Electrical supply lines

Commercial use

 

 

 

 

 

Control Surface of airplane

Control Surface of airplane

              Control surface of Aircraft is an aerodynamic device mean by which pilot stabilize aircraft and controls the direction and altitude of an aircraft on flight. Control surface is a movable surface which is lighter in construction has light  spar rod at the front edges to provide strength and rigidity, the spar connect the ribs and covered by the thin skinned sheet. The tabs are attached to the trailing edge of the control surface additional device will be attached based of purpose the control surface is used for transmission of tab loads to the surface.

Sheet Materials used in Control Surface

1. Metal structure                   -        Covered with metal skin
2. Composite Structure          -        Covered with fabric
3. Wooden Structure              -        Covered with Plywood or fabric

Drilling

The hole on the surface made using drain holes to prevent water  trapped inside the structure , which causes the control surface to be thrown out of balance

Jointing

Process involved in jointing the components includes fasteners like adhesive and bonding agents.

Flight Control Surface are sub branched into

• Primary Control Surface
• Secondary Control Surface

Primary Control Surfaceis designed to provide adequate response to controlling device giving a natural feel.

At low speed control will be smooth and sluggish

At high speed control will become increasingly firm

Responding to speed

At low speed the aircraft respond slow to control applied

At high speed the aircraft respond more rapid (faster) to control applied

Primary Control Surface includes:

Ailerons - (ROLL) Control motion along longitudinal axis.

Elevator - (PITCH) Control rotational motion along lateral axis.

Rudder  - (YAW) Control motion along Vertical axis.

Secondary Control Surface are use to improve the aircraft performance characteristics and to release the excessive control loads applied.

Secondary Control Surface includes:

Wing flaps - Used to increase the Lift and Drag increase while Take off.

Slats- Located on the leading edge of the wings. Creates enough lift at high Angle of attack.

Slots- Span wise gap present at each wing allowing air to flow between the wings, which creates lift thus reduces stall.

Trimtabs - Connect trailing edge to large Control Surface, Used to Stabilize the aircraft.

Balancetabs - Control loads on the control surface is significantly reduced, makes aircraft easy to fly.

Anti-Balancetabs - Maintain the stability in the desire position.

Servo tabs- Small Hinged device to assist the movement of the control surface.

The Combination of this Control Surface of Aircraft helps the pilot in controlling and stressing the aircraft during flight .

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Aircraft Wing Structure

Aircraft Wing Structure

          The Wing, in aeronautics are airfoils attached to each side of the fuselage Wings is the primary lifting surface of the aircraft that support the aircraft in flight, The load acting on the aircraft structure are carried the wing structure. So the design of the wing depends on many facts like lift to weight ratio, rate of climb, size, weight and which aircraft it is used, thought its shape may be widely varied its function remains the same.

Basic features of Wing Constructions

The primary structural parts of the wing are spars, ribs, and stringers.

Sparsare also called as wing beams is a main member of the wing structure, it extends from the fuselage to the tip of the wing, all the forces and loads acting on wing are carried and balances by the spars. When the engine or landing gear are mounted on the wing , Spare incorporate structure attached to the components, as spars are designed to have greater bending stress.

Ribsare also called as plain ribs, it’s a chord wise member of the wing structure used to give wing structure it shape, It extends from the leading edge to the trailing edge of the wing It transmits air load from skin to the spars also stabilize the spare against twisting

Stringers are assist to hold shape of wing the span wise called stringers are used. They are attached to the skin usually found fare closed spaced on the upper wing surface, it is used on compression and stiffening of the compression skin to overcome the induced bending loads. But when the wing need of more stiffening where skin is reinforced by panels instead of individual stringers.

Based in this concept, Wing lift the aircraft on air and keeps flying.

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Types of Aircraft Fuselage Structure

Types of Aircraft Fuselage

            The basics of the Aircraft Fuselage was explained in the before posts (https://sabaeroline.blogspot.com/2020/07/aircraft-fuselage-structure.html), Fuselage types would clearly explain in the present post.

    

    In general, fuselage is classified into three major types base on the method by which stress are transmitted to the structure.

There are three most common types of fuselage are:

Truss or Frame Type Fuselage

A truss is a light gauge steel tube assemblage of members forming a frame triangular shape which giver geometric structure to the fuselage. The Primary members of Truss are the four logerons, the longerons are longitudinal member of the fuselage. Lateral bracing are placed at intervals between the longerons. The lateral surface are called as Bulkheads, Space between two bulkheads are called as bays. Lateral and Longitudinal member are made strong stell wires which are design to withstand compression during load applied.

Truss Fuselage are sub-branched into

• Pratt Truss
• Warren Truss

Monocoqne Structure

The word Monocoqne is French word which means “single shell”. In this type the fuselage skin carries all structural stress. The design involves constructing a tube or core which involves no internal structural members which looks like a empty Shell. These types of fuselage are formed by riveting preformed two half together. This Structure carry load effective when the diameter is small. Increasing of the structure diameter depends on the internal cavity.

Semi Monocoqne Structure

It is combination of Truss and Monocoqne type structure together. In Present days Aircraft become large Monocoqne structure not to strong enough. Weight to strength ration is ineffective. Longerons are run length across the monocoqne structure jointing the frame together. Now the Longerons and frame is attached the thin alloy skin shell by rivets and abrasive bonding.

Semi Monocoqne Structure type of fuselage is commonly used both military and commercial aircraft in Modern Days.

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AirCraft Fuselage Structure

Fuselage of Aircraft

    Fuselage is a body of an aircraft to which the wings, tail and Landing Gear units are attached. Spaces from the cockpit cabin, Passenger cabin, Cargo, Controls unit are located inside the fuselage. Design and size of the fuselage varies according to the function to the aircraft. The word fuselage comes from a French word “fusele” means “splindle-shape” Fuselage is a long and vertical spindle hollow tube. The hollow shape design provides maximum strength with minimum weight.

Fuselage are designed to satisfy two major criteria:

• Protect the passengers in the event of crash.

• Efficient in fitting together the wing, tail, landing gear and other control surface in perfect place accomplished with interior space for passenger comfort with minimum frontal area to contour drag for maximum performance.

Fuse large must have a point of attachment for each part such as wings, tail, Landing Gear and Engines to arrange and installed. So that at time of emergency this part can be inspected, removed, repaired and replaced again easily. The fuselage must be very strong at the point of attachment as more loads would be acting on the fuselage and fitted parts during flying and landing.

Outer Design Criteria of Fuselage

Fuselage is the outer shell of the aircraft, the cabin inside are fully pressurized and the pressure inside the aircraft is greater than the pressure outside due to which the fuselage is exposed to different stress, It must be designed with strong durable material. If were any pressure loss occurs. Oxygen levels will drop it can create a dangerous environment to the crew and the passenger inside.

During the time of rotation of the aircraft more torque will be produce fuselage should be designed to withstand this torque force which leads to collapse of the entire structure, as more load will be acting on the outer surface of Fuse large.

Fuselage design base on Aircraft Usage

In fighter jet have a slender and streamline fuselage  to contour drag for maximum performance  and cockpit will only cabin space present large enough only for the controls and pilot. Cockpit is place on the top of the fuselage for ground visualization and the engines and fuel are place at the rear of the fuselage.

In airlines Civil aircraft use to have a wide, long fuselage carry the many number of passenger as well as cargo. The cockpit will have large space and separate desk for passenger cabin and cargo, Cargo space will be located below the passenger cabin and fuel is stored at the wing.

In single engine aircraft the engine is mounted in nose of the fuselage. Cockpit will be place at the top to provide ground visibility.

Fuselage skeleton and skin

Fuselage shielded by a thin sheet of material stiffened by large number of longitudinal stringers running together with transverse frames place between, they carry bending moment, shear force and torsional load which causes axial stresses in the stringers and skin. As shear stress acts on the skin because of the resistance stringers the shear force gets ignored.

(Shear Force: Force acting perpendicular to its longitudinal axis)

Distance between adjacent stringer is usually small due which shear flow in the connecting panel is small.

Material Used

Most airplane uses an Aluminium Fuselage, As Aluminium is strong, corrosive resist to rust and light weight. This characters makes aluminium effect used material for making aircraft component which includes fuselage.

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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 andtail 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 valveare 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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