Faculty Of Technical Engineering

Aircraft Mechanical Engineering Department

Graduation Project

Entitled : UNMANNED AERIAL VEHICLES, A SURVEY AND CASE STUDY

BY

Nowara Ahmed Hamed 21162152

Al hussain Ahmed Abuzaid 21162274

Seraj Salem Mohamed 21162255

UNDER SUPERVISION OF ENG. SALEM BELEID ELTAWERGHI ACKNOWLEGMENT

First and foremost, praises and thanks to the God, the Almighty, for His showers of blessings throughout our research work to complete the graduation project successfully.

We would like to express our deep and sincere gratitude to our research supervisor, Eng. Salem Beleid Eltawerghi, for giving me the opportunity to do research and providing invaluable guidance throughout this research. It was a great privilege and honor to work and study under his guidance. We are extremely grateful for what he has offered us.

Also we would like to pay our deep sense of gratitude and thanks to Eng. Jamal Fathallah Alsahli, the head of aircraft mechanical engineering department for his encouragement and follow up. Our completion of this project could not have been accomplished without his support .

We are extremely grateful to our family for their love, prayers, caring, sacrifices and continuing support to complete this research work.

TABLE OF CONTENTS

LIST OF FIGURES

ABSTRACT

Drones or Unmanned Aerial Systems (UAV - Unmanned Aerial Vehicle or UAS - Unmanned Aerial Systems) are the aircrafts, which are able to fly without a pilot and passengers on board. Drone Controlling is performed remotely by radio waves or autonomously (with a predetermined route). The use of drones is growing rapidly across many civilian and military application domains, including real-time monitoring, providing wireless coverage, remote sensing, search and rescue, delivery of goods, surveillance and launching bombs and missiles. In past few years, unmanned aerial vehicles (UAV) or drones has been a hot topic encompassing technology, security issues, rules and regulations globally due to its remarkable advancements and uses in remote sensing and photogrammetry applications. This thesis is composed of two parts. The first part, presents a literature study about different topics related to drones such as types, uses, construction materials. The practical part will be an attempt to carry out one of the emerging applications of the drone which is Automation Of Aircraft Frame Visual Inspection Using Drone Camera, introducing a new promising technique in aircraft maintenance that would help in reducing aircraft downtime, lowering labor effort, and minimizing maintenance cost.

1. Introduction A drone or unmanned aerial vehicle (UAV) is defined as a type of powered aircraft that does not carry a human pilot, uses aerodynamic forces to prove lift, can fly autonomously or be remotely controlled, can be expendable or recoverable, and can carry a lethal or non-lethal payload. In the recent decades, the use of UAVs is increased rapidly both in the military and civil aviation applications. Being more cost effective than manned systems, and being a multi-purpose versatile aircraft are some of the main aspects that can be addressed to the reasons of the increase in the popularity of the use of the UAVs. [8]

UAVs can be used in many civil applications due to their ease of deployment, low maintenance cost, high-mobility and ability to hover. Such vehicles are being utilized for real time monitoring of road traffic, providing wireless coverage, remote sensing, search and rescue operations, delivery of goods, security and surveillance, precision agriculture, and civil infrastructure inspection. [1]

The UAVs differ from the size of a small bird to a commercial airplane with many different mission profiles. Airborne intelligence, surveillance and reconnaissance, close air support, air combat and ground strike, and homeland security are some of the military associated usage areas. In addition to the military usage, search and rescue, disaster and public infrastructure monitoring, meteorological data acquisition, precision farming, remote aerial mapping, habitat inspection can be given as examples of civilian usage areas of the UAVs. [4] The developments in the materials technology made it easy to access and purchase composite materials. Recently, with the advances in the composite manufacturing technology very complex shaped parts can be built effortlessly within a few days. Since, most of the UAVs are built from composite materials, it became possible to manufacture a UAV in a laboratory or a workshop by four or five people within a few week. Moreover, the maintenance and repair processes of the UAVs can be performed very quickly and easily, since they are assembled from small, cheap and easy to manufacture composite parts. [6] Inasmuch as no pilot is inhabited, limitations from the human abilities are disregarded in the design which leads to aircrafts with increased maneuverability, reduced size and weight, and improved control characteristics with the help of autopilot systems. The UAVs can perform dull, dirty and dangerous missions that would be very risky for a pilot to endure like battlefields, enemy territories, atrocious weather and environments with noxious gases or smokes. [2]

2. History Of Unmanned Aerial Vehicle

2.1 Early History Throughout their history, UAV systems have tended to be driven by military applications, as is true of many areas of technology, with civilian applications tending to follow once the development and testing had been accomplished in the military arena[3].

In 1883, an Englishman named Douglas Archibald attached an anemometer to the line of a kite and measured wind velocity at altitudes up to 1,200 ft. Mr. Archibald attached cameras to kites in 1887, providing one of the world’s first reconnaissance UAVs. William Eddy took hundreds of photographs from kites during the Spanish-American war, which may have been one of the first uses of UAVs in combat[11].

2.2 World War I In 1916, occurs the earliest attempt to use an unmanned aerial vehicle powered so-called "aerial target” by Archibald Montgomery Low (1888- 1956), target planes were controlled from the ground by an automatic Hewitt-Sperry known and as the "flying bomb” which is integrated in the control of a gyroscope (1917)[1]. In 1917 November Kettering Bug plane (Fig. 2.1) called "aerial torpedo”, flew in automatic mode for representatives of the US military, though he was not ready to fight in the war. In 1917, after the war aircraft conversion took place, Standard E-1 (Figure 2.2)

Fig. 2.1. The unmanned system- Kettering Bug

Fig. 2.2. Standard E-1

In 1922’s first launch of a target (RAE 1921 - larynx, Figure 2.3) unmanned carried aboard HMS Argus by the US military.

Fig. 2.3. RAE 1921 - Larynx

RAE 1921 for 39 minutes and in 1933 the British fleet used for withdrawals of practice and training drones in the Mediterranean. De Havilland DH target drones 82B Queen Bee (Figure 2.4) were Tiger Moth biplane based ubiquitous[1].

Fig. 2.4. De Havilland DH-82B

In 1935 there were developed a series of RPV (Figure 2.5), projects led by Reginald Denny. (1891-1967). In 1939 the same Reginald Denny introduced a low-cost RC aircraft for training AA gunners. In the same year, he demonstrates another prototype for U.S. Army:RP-RP-3 and 4[1].

Fig.2.5. RP-1 (Reginald Denny)

2.3 The Second World War June 1944 Germany used Fi-103 (V1) (Figure 2.5) during the Second World War known as cruise missiles.

Fig.2.5. Fi-103 (V1)

In October 1944, the first combat mission and use of a UAV is made from Balla islands. Japanese positions were bombed by 10 bombs aboard TDR-1 built by the Interstate Aircraft Company in Los Angeles (Figure 2.5) belonging to US Navy. Also in 1944 held project Aphrodite, a program that converted the US B-17 and PBY-4Y into bomb flying drones. They were used later to nuclear tests in the classical missions "dirty”[6] .

Fig. 2.6. TDR-1

2.4 The postwar period In April 1946 the first aircraft flying unmanned scientific research Northrop: Northrop P-61 Black Widow who have the task of gathering weather data for U.S. Weather Bureau. In 1951 the first jet engines were used (Teledyne Ryan Firebee type I) see Figure 2.7.

Fig. 2.7. Ryan Firebee II

In 1955 takes place the first flight of an unmanned aircraft in reconnaissance (Northrop radioplane SD-1 Falconer/Observer) subsequently used by the US military and the British company Beechcraft. Entered the game with the Model 1001 for the US Navy, see Figure 2.8.

Fig. 2.8. SD-1 / MQM-57 In 1959 takes place the official birthFalconer plan of the on unmanned flights with RPV / UAV, when the USAF is concerned about the loss of US pilots in hostile territories in theaters at the time. In 1960, the launch of the program UAV codenamed "Red Wagon” take places, when Francis Gary Powers piloting a U-2 was shot down over the USSR and in August the same year takes place the first flight of a helicopter unmanned Gyrodine QH-50A in Maryland see Figure 2.9 .

Fig. 2.9. Girodina UAV QH-50A Falconer In August 1964, in Gulf of Tonkin the U.S. used a UAV in the conflict between U.S. Navy and North Vietnamese Navy. Since 1964 until the fall of Saigon in 1975 USAF Strategic Reconnaissance Wing 100 3435 launched Ryan drone reconnaissance over North Vietnam in which they lost 554 unmanned aerial vehicles. In 1966 initiating the project Lone Eagle (later called Compass Arrow) for the design of necessary reconnaissance missions over China, so arises D- 21 (Figure 2.10) following a competition launched by the US Air force which was also attended by North America Ryan Aeronautical. The objective was to perform photo reconnaissance missions at high altitude. In 1976 - the recognition aircraft utility was demonstrated in Vietnam. These are the first steps for use in combat of UAVs at sea and on land[1].

Fig. 2.10. D-21 Tagboard Falconer

3. Classifications Of UAV's

UAVs can be classified by a broad number of characteristics. Performance characteristics and aspects such as weight, endurance, range, speed and wing loading are important specifications that distinguish different types of UAVs and give rise to useful classification systems. The cost, wing span, the engine type and maximum power developed and maximum altitude are also features which can be considered to compare and classify UAVs. [3]

Classification based on performance characteristics is useful for designers, manufacturers and potential customers because it enables these groups to match their needs with the performance aspects of UAVs.

Important Performance Characteristics:

 Weight  Endurance and Range  Maximum Altitude  Wing Loading  Engine Type  Power/Thrust Loading[7].

3.1 Classification according to Weight

UAVs cover a wide range of weights, from micro UAVs which weigh only a few pounds, right up to the massive Global Hawk (Tier III) which weighs over 11 tones. The following graph shows the weights of all the UAVs considered and it can be seen that there are only a few that weigh more than two tones and the majority of UAVs are quite light. [5]

Classification according to Weight Designation Weight Range Example Super Heavy >2000 kg Global Hawk Heavy 200 – 2000 kg A-160 Medium 50 – 200 kg Raven Light 5 – 50 kg RPO Midget Micro <5 kg Dragon Eye Upon examination of the subsequent graphs four classifications are proposed to distinguish UAVs by weight.

1) Super heavy weight UAVs which are those with take-off weight of over 2 tones. This classification will include the X-45, Darkstar, Predator B and Global Hawk. 2) Heavy weight UAV which would be weigh between 200 and 2000 kg. The heavy weight classification would include all UAVs between the Outrider and the Fire. 3) Medium weight UAV which includes weights 50kg up to 200 kg. This includes the Raven up to the Phoenix. Another classification is the ‘light weight’ UAVs which are between 5 and 50 kg. 4) Micro UAV (MAV) classification for UAVs under 5 kg. This included the Dragon Eye, FPASS, Pointer and SilentEyes. Many of the other performance characteristics are related to the weight of the UAV. For example more lift and thrust will be needed for increased weight therefore wingspan will increase and the type of power plant chosen will differ. The light weight UAVs use primarily electric motors while the super heavy weights commonly use turbo jets or turbo fan engines[8].

Fig. 3.1. The Dragon Eye Micro UAV, International Defense Online Magazine (2006).

3.2 Classification According To Endurance and Range Another useful classification method for UAVs is to categorize them by endurance and range. These two parameters are usually interrelated as obviously the longer a UAV can say airborne the larger its radius of operation is going to be. It is important to consider range and endurance because it enables the UAV designer to determine the type of UAV required depending upon how far the mission objective is from the launch site. Also it determines how regularly refueling is required and would affect how much time can be spent with the UAV performing its task and how much time it needs to spend grounded.[6]

Three classifications are proposed and these are long, medium and short endurance/range. 1) The long endurance UAVs are those that can stay airborne for 24 hours or more. The range for these UAVs are also high, starting from 1500 km up to 22000 km for the Global Hawk. 2) The medium endurance UAVs are those with endurance between 5 and 24 hours. These include the shadow 600 up to the Predator. This is the most common type of UAV. 3) The third class is the low endurance UAV which have less than 5 hours endurance. These are used for short missions such as ‘seeing over the next hill’ which is a safer method of reconnaissance than sending troops into unfamiliar territory[9].

Fig. 3.2. The Pointer UAV in use on the battlefield AeroVironement Inc (2006).

Classifications According To Endurance

Category Endurance Range Example

High >24 hours >1500km Predator B

Medium 5 – 24 hours 100 – 400 km Silver Fox

Low < 5 hours < 100 km Pointer Table 3.2 Classifications According To Endurance

3.3 Classification According To Altitude

The maximum operational altitude, or flight ceiling, is another performance measure by which UAVs can be classified. This is also useful for designers or choosing a UAV to purchase so the customer can select a UAV that meets their altitude needs. Some UAVs in military situations are required with low visibility to avoid being detected and destroyed by the enemy therefore high altitude is an important requirement. Also for imaging and reconnaissance a high altitude is required to obtain images of the maximum amount of terrain[2][5].

A low, medium and high altitude classification is proposed for dividing the UAVs by maximum ceiling.

 Low altitude is any UAV that flies up to 1000m. These UAVs are the micro UAVs and include the FPASS, Pointer and Dragon Eye. These UAVs don’t have much use at this stage and are primarily experimental.  Medium altitude is the category of UAVs with maximum altitude between 1000m and 10000m. The majority of UAVs fall into this category.  High altitude is all UAVs that can fly over 10000m. This includes the X-45, predator B, Darkstar and Global Hawk. There is concern that these UAVs may interfere with commercial and military manned aircraft and high tech collision avoidance systems are being developed and integrated into these UAVs that fly in populated airspace[3]. Classification According to Altitude

Category Max Altitude Example

Low < 1000 m Pointer

Medium 1000 – 10000 m Finder

High > 10000 m Darkstar Table 3.3 Classification According to Altitude

Fig. 3.3. The Darkstar on display at a USAF base

3.4 Classification According To Wing Loading

Another useful way of classifying UAVs is using their wing loading ability. To calculate the wing loading of a UAV the total weight of the UAV was divided by the wing area. There are mainly three categories have been created.  The UAVs that have a wing loading above 100kg/m2 are classified to be of high loading.  For the UAVs that have a wing loading less than 100kg/m2 but greater than 50kg/m2, these will be classified as medium loading.  While the remaining UAVs with a wing loading of less than 50kg/m2 will be classified as low loading[13].

Classification According To Wing Loading Category Wing loading kg/m2 Example Low <50 Seeker Medium 50-100 X -45 High >100 Global Hawk Table 3.4 Classification According To Wing Loading

3.5 Classification According to Engine Type As UAVs are used for a variety of different tasks they need different engines to complete these missions.  Some of the different types of engines found in UAVs are Turbofans, Two strike, Piston, Rotary, Turboprop, Push and Pull, Electric, and Propeller.  As with the majority of aeronautical applications as the weight of the plane increases so does the size of the engine, this was found to be the same with UAVs.  The lighter, smaller UAVs tended to use electric motors, while the heavier, battle ready UAV tend to use piston engines.  Other UAV classifications that are affected by the type of engine in the UAV are endurance and range. A properly chosen engine will increase the endurance and range of a UAV[11][13].

3.6 Other Aspects in UAV'S Classification 3.6.1 Based on Aerodynamics A variety of UAV system has been developed and in the advancement phase, some of them includes the Fixed-wing aircraft , chopper, multi- copter, motor parachute and glider, UAV with Vertical takeoff and landing, congregating ready-made part and commercialized UAV. All of them are specified for a specific mission and have their zeros and ones[6]. 3.6.1.1 Fixed Wing Drones Fixed wing drones are very simple but saturated in designing and manufacturing, because of successful generalization of larger fixed-wing planes with slight modifications and improvements. Fixed wings are the main lift generating elements in response to forward accelerating speed. The velocity and steeper angle of air flowing over the fixed wings controls the lift produced. Fixed wing drones require a higher initial speed and the thrust to load ratio of less than 1 to initiate a flight. Rudder, ailerons and elevators are used for yaw, roll and pitch angles to control the orientation of aircraft[6].

Fig. 3.3. Fixed Wing Drone

Fixed wing drones cannot hover at a place, and they cannot maintain their low speed. Subsequently, it can be seen that lift to drug ratio denotes the lift generated by a wing counter to drag generated. Fixed wing drones are more compatible with larger L/D ratio and with higher Reynolds number. Unfortunately, fixed-wing drones are less noticeable for L/D <10 for the reason that Reynolds number and efficiency decreases for smaller drones[10]. 3.6.1.2 Flapping Wing Drones Flapping wing drones are primarily inspired by insects such as small hummingbirds to large dragonflies. The lightweight and flexible wings are inspired from the feathers of insects and birds which demonstrate the utility of weight and flexibility of wings in aerodynamics. However, these flapping wings are complex because of their complicated aerodynamics. Flapping drones can support stable flights in a windy condition, unlike fixed-wing drone. Light, flexible and flapper wings provide the flapper motion with an actuation mechanism. Intensive research on flapping wings has been carrying out by drone community and biologist because of their exclusive maneuverability benefits[5][7] .

Fig. 3.4. Flapping Wing Drones

3.6.1.3 Fixed-flapping-wing Integrated effect of the fixed and flapping mechanism is used where fixed wings are used to generate lift whereas flagging wings are used for generation of propulsion. These type of drones are inspired by Dragonfly which uses two pairs of wings in order to increase the lift as well as thrust forces. Hybridization using fixed and flapping wing increases overall efficiency and aerodynamic balance[7] . 3.6.1.4 Multirotor Drone Main rotor blade produces a forceful thrust, which is used for both lifting and propelling. Multirotor unmanned aerial vehicles are capable of vertical takeoff and Landing (VTOL) and may hover at a place unlike fixed-wing aircraft . Multirotor are designed by number and location of motors and propellers on the frame. Their hovering capability, ability to maintain the speed makes them ideal for surveillance purpose and monitoring. The only concern with multirotor is that they need more power consumption and makes them endurance limited. Abott equations are used for exact calculation of power and thrust requirements in multirotor aircraft.

4 3 −15 푃표푤푒푟 [푊] = 푃𝑖푡푐ℎ 푋 (퐷𝑖푎푚푒푡푒푟) 푋 (푅푃푀) 푋 (5.33 푋 10 ) ……….(1) 3 2 −10 푇ℎ푢푟푠푡 [푂푍] = 푃𝑖푡푐ℎ 푋 (퐷𝑖푎푚푒푡푒푟) 푋 (푅푃푀) 푋 (10 ) ……….(2)

Multicopter is divided into specific categories based on number and positioning of motors, each category belongs to a specific type of mission, and based on the mission requirement they are classified in various configurations such as Monocopter, Tricopter, quadcopter, hexacopter and Octacopter[12].

Fig.3.5. Monocopter (Single Rotor Drone)

Fig.3.6. Quadcopter ( Four Rotors)

Fig.3.7. Hexacopter ( Six Rotor) Drone )

3.6.2 Based on Landing UAV's can be classified based on takeoff and landing mode to Horizontal takeoff and landing (HTOL) and Vertical takeoff and Landing (VTOL). HTOL may be considered as the extension of fixed-wing aircraft. They have high cruise speed and a smooth landing. VTOL drones are efficient in flying, landing and hovering vertically, but they are limited by cruise speed because of the slowing down of retreating propellers[3][8].

Fig. 3.8 Vertical Takeoff And Landing Drone (VTOL)

Fig.3.9. Horizontal Takeoff And Landing Drone (HTOL)

4. Materials Used For UAV's Airframe Construction

UAV airframes refer to the main physical structure of an Unmanned Aerial Vehicle or drone, on which all vital components such as avionics systems, payloads, engines are installed. Quality of airframe is dependent on the nature of mission, the weight of payloads it has to carry, and the takeoff and landing approach of the drone. High strength with minimum possible weight, large payload carrying capacity, excellent maneuverability, and high hover efficiency are the essential requirement of all airframes. Military UAVs require high endurance to stay in the air for a long period[7].

All modern drones are equipped with an array of sensors, and other systems, inevitably increasing the overall weight and reducing the flight time.

Weight reduction, therefore, is critical, and to build the airframes, manufacturers today use non-conventional materials such as composites (generally made using fibers and resins), which reduce the weight of UAVs without compromising on their strength[9].

Here are some examples of the common materials used for UAV airframes manufacturing:

4.1. Plastic

Plastic is easy to mold into solid objects of different sizes and shapes. Lighter than metal alloys, plastic has high malleable properties and offers high resistance to corrosion and chemicals. It also has low electrical and thermal conductivity and excellent durability and high strength-to-weight ratio. Plastic is very cost-effective. Propellers and skids of a drone are usually made of plastic[9].

4.2. Aluminum Alloys

Aluminum is a common metal used to construct drone airframes. Known for its low density and high strength, aluminum alloys can resist corrosion through passivation, making it an ideal choice for the aerospace industry[3]. 4.3. Composite Materials

Composites are, by definition, materials consisting of two or more materials which together produce beneficial properties that cannot be attained with any of the constituents alone.

One of the most common examples, fiber-reinforced composite materials consist of high strength and high modulus fibers in a matrix material. In these composites, the function of the fibers is carrying the load exerted on the composite structure, and providing stiffness, strength, thermal stability and other structural properties. Matrix material carries out several functions in a composite structure, some which are binding the fibers together and transferring the load to the fibers, and providing protection to reinforcing fibers against chemical attack, mechanical damage and other environmental effects like moisture, humidity, etc.

Offering several advantages, composites have drawn the attention of many industries. The aerospace industry was among the first to realize the benefits of composite materials. In aerospace, the demands upon materials are usually greater than in other applications. The four most important requirements are light weight, high strength, high stiffness, and good fatigue resistance. Composites, particularly the high performance types, are the only existing materials efficiently meeting these requirements[6].

The use of composites in aircraft is increasing rapidly, especially in military aircraft, where the pay-off is the greatest. In commercial aircraft, the acceptance of composites as primary structures have been slower, but is now increasing rapidly. The composite components used in the aircraft are mainly, horizontal and vertical stabilizers, wing skins, fin boxes, flaps, and various other structural components as shown in Table 4.1. In spacecraft, where the weight is of the greatest importance, the composites are accepted as primary materials[6].

Figures 4.1a, 4.1b and 4.1c show the typical composite structures used in commercial and military aircrafts. Aircraft Composite Components F-14 Doors, horizontal tail, fairings F-15 Rudder, vertical tail, horizontal tail, speed brake F-16 Vertical tail, horizontal tail F-18 Doors, vertical tail, horizontal tail, wing box, speed brake, fairings B-1 Doors, vertical tail, horizontal tail, flap, slats, inlet AV-8B Doors, rudder, vertical tail, horizontal tail, aileron, flap, wing box, body, fairings 757 Doors, rudder, elevator, aileron, spoiler, flap, fairings 767 Doors, rudder, elevator, aileron, spoiler, fairings Table 4.1: Composite components in aircraft applications for various types of aircraft.

Figure 4.1a: Typical composite structures used in a commercial aircraft

Figure 4.1b: Typical composite structures used in Indian Light Combat aircraft ( Tejas )

Figure 4.1c: The wide spread of Carbon Fiber composite in French Fighter Aircraft ( Rafale ) Table ( 4.2 ) Shows some of aircraft engine components made of composite fiber

Engine Component Material

Carbon Fiber

Engine Nose Cone

Carbon Fiber

Engine Inlet Guide Vane

Carbon Fiber

Engine Inlet Housing

Some of the conventional composites used for airframes are Carbon Fiber Reinforced Polymers (CFRP), Glass Fiber Reinforced Polymers (GFRP), Boron Fiber Reinforced Polymers (BFRP), and Aramid Fiber Reinforced Polymer (AFRP)[6].

4.3.1 Carbon Fiber Reinforced Polymers (CFRP)

Carbon fiber is a combination of carbon fibers and thermosetting resins, offering weight reduction, strength, enhanced durability, and low thermal shrinkage. For creating carbon fiber, carbon atoms are aligned parallel to the main axis of the filament. For commercial use, thousands of filaments are wound together. Carbon fibers are cost-effective, stronger than steel, lighter than aluminum, and stiffer than titanium. It can be easily mass-produced[6].

Polymer (Resin)

Fiber Reinforcement

Fig.4.2 Typical structure of Carbon Fiber Reinforced Polymers (CFRP)

Carbon fibers are very stiff and strong, 3 to 10 times stiffer than glass fibers. Carbon fiber is used for structural aircraft applications, such as floor beams, stabilizers, flight controls, and primary fuselage and wing structure. Advantages include its high strength and corrosion resistance. Disadvantages include lower conductivity than aluminum; therefore, a lightning protection mesh or coating is necessary for aircraft parts that are prone to lightning strikes. Another disadvantage of carbon fiber is its high cost. Carbon fibers have a high potential for causing galvanic corrosion when used with metallic fasteners and structures[6][13]. Hexcel Corporation is one of the leading players developing carbon fibers. They make HexTow carbon fiber by combining all types of thermoset and thermoplastic resins[6].

Fig.4.3. Production of Carbon Fiber Reinforced Polymers (CFRP)

4.3.2 Glass Fiber Reinforced Polymers (GFRP)

The second-most widely used material in airframes, Glass Fiber, offers low material elongation and high material strength. Moreover, it is easy to produce and requires little maintenance. Glass Fiber is suitable for a variety of applications due to its high strength, increased flexibility, long durability, excellent stability, and high resistance to heat, temperature, and moisture. It is lightweight and can be molded to design radomes and antenna substrates[2].

Fig.4.4. Glass Fiber Reinforced Polymers (GFRP)

Owens Corning (US) is one of the leading players developing glass fiber reinforced polymers. Other leading manufacturers are Jushi Group (China), Owens Corning (US), Taishan Fiberglass Inc. (China), CPIC (China), Saint-Gobain Vertex (France), Nippon Sheet Glass (Japan), and Johns Manville (US), among others[4][12].

4.3.3 Boron Fiber Reinforced Polymers (BFRP)

Boron Fiber is the strongest and expensive material commercially available for airframes. BFRP is used in F-15 fighters, B-1 Bombers, Black Hawk helicopters, space shuttles, and Predator, owing to its excellent compressive strength. This polymer is six times more modulus of elasticity as compared to GFRP. Boron fiber is used in the US military aircraft such as F-14 and F-15. The limited application of boron fiber is attributed to its toxic nature, high costs, and increased brittleness as compared to other fibers. It is not preferred for ground and underwater vehicles. Specialty Materials, Inc. is a leading manufacturer of boron fiber products[6].

4.3.4 Aramid Fiber Reinforced Polymer (AFRP)

It is also known as Kevlar is DuPont. Aramid fiber is a synthetic fiber that offers high impact resistance and increased stiffness. Cutting AFRP requires high accuracy and precision, which makes them expensive and difficult to use. Aramid fiber is known in various trade names such as Nomex (a meta-aramid) or Kevlar (a para-aramid). It is widely utilized for military ballistics and body armors, owing to its susceptibility to light, compression, and hygroscopy. Kevlar and Twaron are the two most popular aramid fibers[9].

Fig.4.5. Aramid Fiber Reinforced Polymer (AFRP)

4.3.5 Advantages and Disadvantages Of Composite Materials

Here are some of the advantages of using composites for UAV airframes, instead of metals:

 Light weight, marking the drone energy efficient

 Incredibly strong and very had to break.

 Resistance against corrosion and compression.

 Low machining errors.

 Design flexibility. Easy to fabricate intricate parts.

 Maximum stiffness and strength.

 Less number of assemblies and fasteners.

 Lighter ‘stealth’ capabilities with low radar and microwave absorption.

 Low thermal expansion in high altitude flights.

 Less maintenance required.

Composites also have some disadvantages compared to metals. They are:

 Expensive to build.

 Structural degradation at high temperature and wet conditions

 Delamination

 Low energy absorption, resulting in high impact during hard Landing.

 Labor-intensive and complex fabrication process.

 Higher maintenance cost.

Typical damage to composites that needs to be detected both after fabrication and after UAV flight are: cracks and delamination in the skin; debonding between skin and core; and defects in the core (crushing), of which only a small part is visible from the outside. Ultrasonic detection can indicate internal defects. Detection of damage is essential to proper UAV maintenance and long service life[1].

5. UAV's Main Components

5.1 Power Distribution Board

Drone Power Distribution Board (PDB) is a printed circuit board that is used to distribute the power from the flight battery to all different components of the drone. Prior to PDB’s becoming common it was necessary to connect all the different components using wire and the result often resembled an octopus and weighed a considerable amount due to the amount of copper and solder joints in the wires.

There are many different PDB’s available from various manufacturers, the majority of them provide very similar features. Initially PDB’s were very simple and were just a thick copper PCB with an input and multiple outputs. As the need for regulated voltages for various components has become more common, manufacturers have begun including voltage regulators on the PDB so that voltage sensitive components can be fed reliable, stable, and clean power. This is especially important when dealing with video components that are often sensitive to electrical noise generated by the motors and ESC’s during flight[13].

PDB’s are one of the simplest components on a Multirotor and therefore are one of the easiest to choose. There are 3 main points that should be considered when choosing a PDB for the drone:

 Size and layout  Voltages and Current Capability (on board voltage regulators)  Additional features

It is necessary to have a good idea of what parts you will be using in your multirotor build in order to make sure that you choose a PDB that will have the right features and be able to support the power consumption of all the components[14].

Fig. 5.1 Main Distribution Board PBD

5.2 Flight Controller

A flight controller (FC) is a small circuit board of varying complexity. Its function is to direct the RPM of each motor in response to input.

A command from the pilot for the multi-rotor to move forward is fed into the flight controller, which determines how to manipulate the motors accordingly.

Fig. 5.2 Drone Flight Controller FC The majority of flight controllers also employ sensors to supplement their calculations. These range from simple gyroscopes for orientation to barometers for automatically holding altitudes. GPS can also be used for auto-pilot or fail-safe purposes.

With a proper flight controller setup, a pilot’s control inputs should correspond exactly to the behavior of the craft. Flight controllers are configurable and programmable, allowing for adjustments based on varying multi-rotor configurations. Gains or PIDs are used to tune the controller, yielding snappy, locked-in response. Depending on your choice of flight controller, various software is available to write your own settings. Many flight controllers allow for different flight modes, selectable using a transmitter switch. An example of a three-position setup might be a GPS lock mode, a self-leveling mode, and a manual mode. Different settings can be applied to each profile, achieving varying flight characteristics[16].

Here are some of the accessories that might be connected to the flight controller of the drone.

5.2.1 G. P. S

GPS stands for Global Positioning System. It is an instrument which provides location and time information in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites.

Often combines GPS receiver and magnetometer to provide latitude, longitude, elevation, and compass heading from a single device. GPS is an important requirement for waypoint navigation and many other autonomous flight modes. Without GPS drones would have very limited uses.

5.2.2 Gyro

A gyro is a microchip, secondary to the main processor, which senses the angular velocity or the speed at which a multimotors drones rotate in the roll, pitch and yaw axis. Using calculus mathematics and gyro inputs, the Drone Flight Controller DFC can estimate the distance a drone has rotated and whether its rotation is accelerating or decelerating. This is the only sensor required for the multimotors drone to fly in acro mode (the multimotors drone stays in the same position when sticks are centered) although certain FC softwares will also use the accelerometer in acro mode to stabilize a quadcopter in a crash, enabling quick recovery[16].

5.2.3 Accelerometers

An accelerometer is another separate sensor chip and can detect the acceleration of a quadcopter in the roll, pitch or yaw axis. Because the accelerometer can also detect the constant acceleration of gravity, the Drone Flight Controller DFC is able to use this information to calculate the multimotor drone precise angle from the horizon.

5.2.4 Video Transmitter

A Drone FPV Video Transmitter (VTx) is the workhorse of the FPV experience. Over the last several years, we have seen a huge technological boost in how they perform, and the power output capable of the units, all in an increasingly smaller and smaller form factor.

Being mounted on the multicopter side of the business, they need to be able to fit into the space provided, be able to be connected easily into both the power distribution board and the camera, and be durable enough to withstand the abuse of many, many crashes.

Video transmitters work using similar technology to a radio, albeit in a much shorter range window. Onboard flight camera does the work of turning the images it is capturing into data, which is then sent to the video transmitter. The video transmitter turns that information into a radio signal, outputs it to the attached antenna, which then sends that signal out. The video receiver (VRx), attached to either your goggles or your ground station then captures that signal, converts it back from radio waves into data, which is then shown on your display. The range of your VTx is very dependent on a few different things; the power level of your VTx (rated in terms of milliwatts or mW), the antenna that is attached to your VTx, the antenna attached to your video receiver and the signal frequency that you are operating on[15][16].

Fig.5.4 Typical Video Transmitter

5.2.5 RC Transmitter

Although it is possible for the flight controller to control the UAV autonomously it is generally a good idea to have a RC transmitter so that the UAV can be controlled manually if something goes wrong or just use the RC transmitter instead. In order to choose the best fit for a transmitter depends on how complex the UAV is. Most of the time a handheld transmitter is adequate enough but for larger areal vehicles it is better to have a base station to help with all of the controls[14].

Fig. 5.5 Handheld Transmitter. Transmitters are judged based on how many channels they have. The number of channels a Transmitter has relates to the number of separate signals the transmitter can send. The more complex is the UAV the more channels you are going to need for the transmitter. Usually a 7 channel radio is adequate enough to operate most of UAV’s.

A receiver usually comes with the transmitter and will have to be banded or synced to the transvers. This is usually a very easy process that can be achieved as easy as pressing a button on both of them at the same time[16].

Fig. 5.6 UAV Receiver or Base Station

5.2.6 F. P. V. Camera

The Drone FPV Camera is the key component that allows you to take that ‘First Person View’ . It is responsible for capturing the image and turning it into data and sending it to the video transmitter.

Fig. 5.7 Drone Camera

There are five main points to consider when choosing a camera for the multirotor: 1. Size 2. Aspect ratio 3. Sensor Type 4. Lens Field of View 5. Additional Features[14]

3. UAV'S MOTOR

UAV's motor is part that responsible for the rotation of the propellers in order to produce the lift required for the drone and payload to fly. It has a huge impact on the flight time and how heavy of a load the UAV can carry.

It is highly recommended that the same type of motor be used for all of the rotors so that they all do the same amount of work for the UAV. Even though the motors are the same make and model their speeds may still vary which is the purpose of the flight controller.

There are deferent kinds of motors used in UAV's, but the most common kind used is DC motor.

DC motors can be can classified according to their electromagnetism, to brushed and brushless motors. Both designs intrinsically incorporate the use of an electromagnet, as a means of converting electrical energy into kinetic energy. When an electromagnet is electrically charged, a magnetic field is produced. This temporary magnetic field interacts with that of the permanent magnets located within the motor. The combination of attraction and repulsion of the electromagnet or permanent magnets translates into rotational motion of the motor shaft[13][16].

Fig. 5.8 Electromagnetism of motors

The principle behind brushless and brushed motors is very similar. When an electric current is passed through the windings of the motor, magnets distributed within the motor are attracted or repelled. The repetitive repulsion and attraction of the magnets translates into a revolution of the shaft. This allows the motor to spin an attached propeller at extremely high speeds, in turn, producing thrust[13].

Fig. 5.9 Brushed and Brushless motors 3.1 Brushed Drone Motor

The internal operation of a brushed motor is contrary to that of a brushless drone motor. In the brushed motor, the stator provides a permanent magnetic field that surrounds the rotor. The rotor of the brushed motor is an electromagnet which is influenced by the surrounding stator. A pair of brushes are attached to DC power contact the commutator ring at the base of the rotor. The commutator ring is divided, therefore its rotation will periodically reverse the direction of the current flowing through the rotor, as its rotation causes the commutator to reverse its polarity. The alternation of the commutator ring polarity translates into uninterrupted revolution of the rotor[16].

Fig. 5.10 Brushed Motor

This entire process occurs internally within a motor can, which provides excellent protection for the delicate components. Although, efficiency of the system is reduced due to the greater thermal insulation of the internal mechanics. It is possible to reverse the rotation direction of the motor by inverting the polarity of the DC power input. Due to the contact of the brushes with the commutator, longevity of the brushed motor is greatly reduced in comparison to the brushless motor. In terms of application, a brushed motor is better suited for micro class multicopters, their small size, low weight and simple driving technique improves their suitability for micro flight[13][16].

3.2. Brushless Drone Motor

As the name implies, a brushless drone motor lack brushes. The brushless motor can be effectively divided into two separate components; the rotor and the stator. The stator is the central unit into which the rotor is mounted. The stator is made up of a network of radial electromagnets that alternatively power on and off to produce a temporary magnetic field when a current is passed through the windings. The rotor holds a collection of permanent magnets which are positioned in close proximity to the semi-permanent stator electromagnets. Attractive and repulsive interaction of the stator and rotor magnets is translated into rotational movement. When assembled, the shaft of the rotor is inserted into a pair of ball bearings located in the stator that maintain linear, smooth revolution of the rotor.

Although the brushless motor is powered by DC current, it can’t be driven directly. Instead, the brushless motor is wired to the control electronics, effectively eliminating the need for brushes or a commutator. Longevity of the brushless motor is excellent as there is no physical contact between the rotor and the stator. The brushless motor is also more efficient than the brushed motor. The brushless motor is extensively used in mini and some micro multicopter applications, where high power outputs and efficiency are prioritized[16].

Fig. 5.11 Brushless Motor

The key factor when looking for your motor is the KV rating. The KV rating of a motor relates how fast it will rotate for a given voltage. Most multi rotor UAV’s a low KV is desired for stability like somewhere around 500 – 1000 KV.

Fig.5.12 Pancake DC motor a typical model UAV motor

Each motor has an ESC (though some designs put all on one board). In its most basic form, an ESC regulates power going to the motor with which it is paired. More sophisticated systems can also relay data back to the MC, such as vitals about how the motors are performing. With six or more rotors, active feedback makes it possible to keep flying (enough to land safety) if one motor fails[13].

4. Electronic Speed Controller

Electronic Speed Controller (ESC) on a drone is a hard-working, powerful component. The ESC connects the flight controller and the motor. Given that each brushless motor requires an ESC, a quadcopter will require 4 ESCs. The ESC takes the signal from the flight controller and power from the battery and makes the brushless motor spin.

Brushless motor lacks contacts, or “brushes” inside the motor. The brush acts as a commutator, which uses physical contact of the motor’s windings to spin the motor, , brushless motors use a different way to turn direct current (DC), the one-way flow of electrons, into a type of alternating current (AC). This is performed externally, through the use of an ESC[13][16].

Fig. 5.13a ESC Electronic Speed Controller

Fig. 5.13b ESC Electronic Speed Controller

ESCs play a crucial role in the performance of the drone, therefore the ESCs hardware continues to improve. ESC hardware can be an individual unit, attached on the arm of the drone between the flight controller and the motor, or a 4-in-1 ESC in which all 4 ESCs are combined into one circuit board and mounted in the main stack under the flight controller. For lighter builds, or for a cleaner look, many pilots choose to purchase the 4-in-1 ESCs. Often they come with built-in voltage regulators and can act as a power distribution board (PDB) as well[13].

Fig. 5.14 Individual and 4-in-1 Electronic Speed Controller

5. UAV's Battery

Battery is the foundational component of any drone and must be considerately selected to achieve an ideal balance between performance and flight time. Lithium batteries are the most common battery chemistry used to power drones due to their high energy densities and high discharge capabilities.

The lithium battery packs used to power quadcopters have two common chemistries:

Lithium polymer (LiPO) and lithium polymer high voltage (LiHV). The primary difference between the two is that a LiPO cell has a fully charged voltage of 4.2V compared to a LiHV cell which has a voltage of 4.35V at full charge. A LiPO has a resting or nominal voltage of 3.7V versus a LiHV which has a storage voltage of 3.8V. In regards to the performance of the two packs, a LiHV battery will initially provide more power but abruptly drops in voltage when discharged whereas a LiPO has a more linear discharge making it easier to qualitatively gauge the remaining flight time. LiPO packs are the most commonly used across all sizes of quadcopters [10][13].

5.1. Battery voltage

Battery voltage is the potential energy difference between the positive and negative terminals. A higher battery voltage allows the pack to provide more power without increasing the current or amp draw. A standard lithium polymer cell has a nominal (storage) voltage of 3.7V hence to increase the power that a single LiPO pack can deliver, these cells are grouped together in series (meaning the ground/negative lead from the first cell is connected to the positive lead of the next cell, forming a chain of individual cells) to increase the overall battery pack voltage. The more cells that are grouped together, the more voltage the overall battery pack will have. The battery pack voltage is important as it impacts the maximum motor speed[13].

Fig. 5.15 LIPO and LIHV Batteries

5.2. Battery Capacity Battery capacity is measured in milliamp hours (mAh) which is a unit describing the current a battery can supply for a unit of time. For example, a 1500mAh battery would be able to supply: 1500 milliamps (1.5A) of current for an hour, 3000mA (3A) of current for a total of 30 minutes, 6000 mA (6A) for 15 minutes and so on. A higher milliamp rating on a battery essentially means that it will provide more flight time per charge. When choosing a battery, a balance should be made between the battery size and the weight. A large capacity battery will provide a longer flight times however the added weight will restrict the performance of the drone by increasing the craft momentum thereby making it respond in a more sluggish manner[13].

6. UAV's Propellers

One of the most important parts of the drone is the propeller. These spinning blades are the wings to the craft, the part that responsible for creating the airflow that lifts your machine into the air. Drone propellers come in many different shapes and sizes – they all serve the same overall purpose, but the flight characteristics of each can be dramatically different.

In fixed wing aircrafts the airflow above and below the wing creates areas of high and low pressure, resulting in lift. higher speed air travels over top of the wing, creating low air pressure, the opposite happens underneath the wing , effectively pushing things upward.

The propeller on the drone is a wing, actually, in the physics sense of things, it is multiple wings attached together. Spinning the little wings around in a circle creates the same air pressures, thus causing lift[13].

Fig. 5.16 Drone Propeller

There are some factors that affect the drone propeller performance,

6.1. Rotation Speed

The basic concept of a fixed blade propeller is that the faster the motor runs, the faster the propeller spins and more lift will be created. Basically, more power = more speed.

6.2. Propeller Blade Pitch angle

Pitch refers to the angle of each of the blades on the propeller, the pitch of a propeller is how far forward that propeller would move in one revolution in ideal state ( no drag, loses and etc. ). . A high pitch propeller will respond to inputs slowly, use more power and will only be efficient when the multirotor is moving quickly.

A low pitch propeller will respond quickly to inputs and use less power but will only be efficient at low speeds, fast direction changes are much easier and more responsive with a lower pitch propeller due to the increased low end torque.

Fig. 5.18 Drone Propeller Pitch Angle

6.3 Propeller Size

Propeller size is directly linked to thrust, responsiveness and the amount of swept air. A larger propeller sweeps through more air and therefore takes more energy to get spinning and will respond slower to inputs from the motors and consume more power.

The benefits of a larger propeller are increased thrust, and because it is working over a larger area, it will have a better ‘hold/grip’ in the air and more stability when making direction changes.

Smaller propellers will respond faster to the inputs because they are sweeping though less air and require less power to change speed. If used on the same frame, smaller propellers will in general provide less thrust and have less control authority due to the fact they cannot move as much air but will also consume less power[16].

Fig. 5.18 Different Sizes Of Propeller

6.4 Propeller's Blade Configuration

Blade configuration refers to the number of individual blades on a propeller. The most Efficient propeller is actually single bladed, but due to its imbalance it is not practical for use in most flying aircraft.

Increasing the number of blades on a propeller can compensate increasing the size where space is constrained, and has very similar characteristics.

Originally multirotors UAVs widely use two bladed propellers like planes, they are more efficient for their size because they only have two blades creating drag in the air. But as motors became more powerful, higher performance was required and frames became smaller, there was not enough space to increase the size of the propellers to get the required thrust and power needed. Increasing the number of blades will increase the amount of thrust and grip in the air, at the cost of responsiveness and increased power consumption[13][16].

6.5 Drone Propellers Material

The propeller material has a significant effect on its attributes including efficiency and sound. Generally, the most critical effect for multirotor pilots is durability.

Originally propellers were predominantly manufactured in fibreglass reinforced plastics which are very stiff for their weight and this allows the propeller to keep the correct and most efficient shape regardless of how fast it spins, but when it hits something like the ground or a branch, that stiffness means it will shatter and the quad can no longer fly.

Recently propellers are being made using polycarbonate which is a type of plastic it has a good stiffness and because of its flexibility it will bend rather than break if it hits something hard.

There are other materials used in propellers but polycarbonate or PC as it is often referred to is generally considered to be the best.Generally, choosing the right material of the propeller depends on the climate and weather condition of the operation location[11][13].

7 Drone's Frame

An FPV Drone Frame is like the skeleton for all of the sensitive electrical components that constitute a quadcopter. It is essential that a frame is as durable and rugged as possible, while still accommodating to the needs of the pilot without hindering the flying experience and the inevitable maintenance that will ensue.

Each frame has a designated size class, based upon the longest distance from motor to motor measured in millimetres, typically taken by measuring diagonally across the frame. A frame measuring less than 150mm motor-to-motor is categorized as a micro. A frame larger than 150mm motor-to-motor is considered a mini. When measuring an unconventional multicopter frame, such as a hexacopter or tricopter, the size will always be given by the greatest motor-to-motor distance[13].

Fig. 5.19 Typical Drone Frame

There are many different styles of frame, all related to the stance of the arms and the size and shape of the electronics carriage. The table 5.1 shows the different frame styles and their names

PLUS STYLE TRUE - X

Z-STYLE WIDE - X

H-X STYLE DEAD CAT

VERTICAL ARMS H- STYLE

6. APPLICATIONS OF UAV's

6.1 Using UAV's In, Engineering, Architecture and Construction (AEC) industry

The Architecture, Engineering, and Construction (AEC) industry in particular is primed for a growth in UAV applications. UAVs are an ideal technology for many AEC applications, since they can access spaces that are unsafe, hard-to-reach, or inaccessible by human workers. UAVs are also capable of doing some AEC-related tasks faster and at a lower cost. They can also be equipped with a variety of onboard sensors as needed by the task. Moreover, the new generation of commercial UAVs and flight platforms are inexpensive and require minimal human involvement to conduct the flights which might lead to more usage and fewer safety challenges on site.

These features together with technological advancement in battery life, flight and data collection sensors, and the integration of flight autonomous capabilities, have made UAVs a more popular and reliable platform for AEC-related applications[10][11].

Fig.6.1 Using UAV's In, Engineering, Architecture and Construction (AEC 6.2 Using UAV's In Boarder Surveillance

Monitoring national borders is remarkably one of the major concerns of any country wishing to protect and control its own infrastructure and reinforce public safety and economic wellbeing.

In this context, countries are working to promote security measures in order to control and monitor their country’s borders. A variety of solutions have been used for detecting, tracking and recognizing illegal activities, unwanted infiltrations, and unauthorized trespassers (e.g., smugglers, terrorists, illegal immigrants, or hostile forces) and preventing from unlawful cross-borders activities[10].

All of these approaches such as boarder line police patrols and helicopter flights on boarder line are generally requesting intensive human involvement which is tedious, error-prone, costly, and time- consuming.

Using of UAV's specially Quadcopters offer unique capabilities and are very flexible devices in terms of the advantageous tasks they can perform including hovering (at lower altitudes) above a point of interest in the monitored area (especially in narrow and unreachable areas)[10].

Fig.6.2 Using UAV's In Boarder Surveillance 6.3 Using of UAV's In Traffic Surveillance

The increase in the number of vehicles on roadway networks has led transport management agencies to allow use of technology advances resulting in better decisions.

Traditional technology for traffic sensing, including inductive loop detectors and video cameras, are positioned at fixed locations in the transportation network. Data related to traffic flow is currently obtained from detectors embedded in pavements or pneumatic tubes stretched across roads. Such methods do not prove to be time-efficient or cost effective. While these detectors do provide useful information and data about traffic flows at particular points, they generally do not provide useful data for traffic flows over space. It is not possible to move detectors; further, they cannot provide useful information such as vehicle trajectory, routing information, and paths through the network. Several on-going research projects have been working to come up with technologies that improve surveillance techniques for traffic management. UAVs may be employed for a wide range of transportation operations and planning applications: incident response, monitor freeway conditions, coordination among a network of traffic signals, traveler information, emergency vehicle guidance, track vehicle movements in an intersection, measurement of typical roadway usage, monitor parking lot utilization, estimate Origin-Destination (OD) flows.

Fig.6.3 Using of UAV's In Traffic Surveillance The advantage of UAVs is that they can move at higher speeds than ground vehicles as they are not restricted to traveling on the road network. Unmanned vehicles have advantages over manned vehicles as most of the functions and operations can be implemented at a much lower cost, faster and safer. UAVs may potentially fly in conditions that are too dangerous for a manned aircraft, such as evacuation conditions, or very bad weather conditions[10].

UAVs are programmed off-line and controlled in real-time to navigate and to collect transportation surveillance data. UAVs can view a whole set of network of roads at a time and inform the base station of emergency or accidental sites. It also permits timely view of disaster area to access severity of damage. The base station can then choose the best route and inform the police cars.

Different UAVs have different data collection capabilities. Some of them have real-time data transfer capabilities to the ground station, while the others are capable of storing high quality video or images on-board[11].

6.4 Using UAV's In Precision Agriculture

The use of unmanned aerial vehicles (UAVs), and connected analytics has great potential to support and address some of the most pressing problems faced by agriculture in terms of access to actionable real-time quality data.

Fig.6.4 Using UAV's In Precision Agriculture The agriculture sector is expected to be the second largest user of drones in the world in the next five years. Sensor networks based on the Internet of things are increasingly being used in the agriculture sector to meet the challenge of harvesting meaningful and actionable information from the big data generated by these systems[8][10].

One of the latest developments is the increase in the use of small, unmanned aerial vehicles (UAVs) or drones, for agriculture. These have a huge potential in agriculture in supporting evidence-based planning and in spatial data collection. Despite some inherent limitations, these tools and technologies can provide valuable data that can then be used to influence policies and decisions.

UAV's provide when combined with analytic tools that can interpret the data and images to actionable information have ushered in a new revolution. However, priority in addressing issues related to privacy, safety and security is the key to the sustainable implementation of these technologies.

The usefulness of drones to facilitate quick data collection with greater accuracy together with providing a safer monitoring system in emergencies was a key element in testing this in the field during challenging humanitarian crises[11].

6.5 Using UAV's In Smart Cities and Public Safety

UAVs can serve as flexible mobile platforms for a many of smart city application and, as postulates “could make a remarkable improvement in public safety”. In today’s world, where half of the global population is already living in urban areas , the improvement of services and quality of life in these areas becomes increasingly important.

Due to recent and ongoing advances, UAVs have been able to serve as aerial video surveillance systems , providing unprecedented aerial perspective for ground monitoring, and moreover, doing so in real time . One fundamental aspect of a smart city is its sensing capability, provided through a large number of sensors deployed. But the deployment of these sensors is only part of the required infrastructure, as the generated data has to be collected and aggregated to support informed decision making. UAVs can play an essential role in providing a mobile wireless sensor network, network relay connectivity and situational awareness. They are expected to communicate with many different smart objects, such as sensors and embedded devices. Their mobility, the ability to provide real-time data and the potential to carry hardware for on-board decision making make UAVs the ideal candidate[10][12].

6.6 Using Of UAV's In Intelligence Gathering

The use of Unmanned Aerial Vehicles (UAVs) in civil defense applications has increased due to their portability and low operational costs. To spread the cost for procuring and operating such devices, further multiple agencies can cooperate and share resources and, more importantly, the data collected by these devices (such as imagery or live video feeds)[6].

UAVs can be used to locate civil security units such as fire fighters or policemen if they are equipped with transponders. This would further enhance the situational awareness and could be used between agencies to coordinate operations or to improve the security of the units in the field[11].

The majority of the fastest growing urban areas are in Asia, Africa or the Middle East and many of them are in coastal regions. Port security is a major factor in those cities as ports involve many continuously changing moving objects as well as large commercial and industrial sites and infrastructure. The ability to deploy sensing capabilities at will to identify objects and activities of interest is desirable. UAVs could work together near/over water or the open sea. To further extend the operational reach water-based autonomous vehicles can be included to cooperate with the aerial units[10][12].

6.7 The Use Of Drones In Aircraft Maintenance

On average a commercial aircraft will be struck by lightning at least twice a year and many will also suffer hail stone and foreign object damage which require assessment to ensure any damage is within limits. Every time this occurs an aircraft must undergo a detailed visual inspection before it is allowed to fly again. Inspection process can be carried out without the need for specialized access systems and reduces the time before a decision can be made if the plane can fly again[17].

Recently, some aviation leading companies like Boeing, Airbus, Easy Fly and Air New Zealand have demonstrated the first ever automated drone-based, innovative aircraft maintenance tool. Drone is to be operated inside a hangar, capable of accelerating and facilitating visual checks, considerably reducing aircraft downtime and increasing the quality of inspection reports[18].

The automated drone is equipped with an integral visual camera, a laser- based obstacle detection sensor, flight planner software and an aircraft inspection software analysis tool. The drone-based aircraft inspection system is optimized for the inspection of the upper parts of the aircraft fuselage[17].

Following a predefined inspection path, the automated drone captures all the required images with its on-board camera. High quality pictures are then sent wirelessly to a tablet for the operator’s review in real-time. They are also transferred to a PC database for detailed analysis using a software system. This allows the operator to localize and measure visual damage on the aircraft’s surface by comparing it with the aircraft’s digital mock-up. The software automatically generates an inspection report.

This technology combines flight control, automation and sensor technologies with innovative 3D visualization and damage localization tools that offer aircraft operator and maintenance, repair and overhaul a significant cost saving for their operation[18].

The new system will be available for the industry in the fourth quarter of 2018 following EASA European Aviation Safety Agency approval of the new inspection process, as a valid alternative means to conduct the General Visual Inspection (GVI) process.

Initial demonstrations have been made to several airlines which have expressed interest. It will also be offered to MRO organizations. Since it is designed for use inside maintenance hangars, the drone is equipped with a laser-based sensor capable of detecting obstacles and halting the inspection if necessary. This laser-based technology allows the vehicle to fly automatically without the need for remote piloting.

The new inspection process will take only three hours, including 30 minutes of image capture by the drone and it will vastly improve operator safety. By contrast, traditional aircraft visual inspection is performed from the ground or using a telescopic platform, in particular for the upper parts of the aircraft – a process which could typically last up to one day. Figures 5.5a, 5.5b and 5.5c show some of deferent stages of this innovative process[17][18].

Fig. 6.5a A quadcopter drone is used to carry out an aircraft general visual inspection

Fig. 6.5b. Drone while flying around Airbus A320

Fig. 6.5c A maintenance personnel while inspecting the uploaded images and videos.

The aircraft inspection drone makes examining the fleet for hail, lightning strikes and FPS faster and more efficient than the traditional methods. By conducting the inspections with drones, the unscheduled ground time (UGT) can be reduced and the administrative process through real-time detection and digital processing. By implementing machine learning, drones can perform inspections faster and more accurately.

Easy Fly Company operates and flies aircraft inspection drone which can fly autonomously scanning the aircraft frame and return to its base after achieving its mission.

The data from the aircraft inspection drone is streamed safely to the platform. Ground engineer is immediately informed about damage[18].

Fig. 6.6 Ground engineers are analyzing collected data

Fig.6.7 Real time visualization of the aircraft frame

The New Zealand carrier has teamed up with maintenance, repair and overhaul provider Structure Engineering to trial the concept, called DroScan, at the MRO’s provider’s facility next to Singapore’s Changi Airport.

Air New Zealand AirNZ planes undergo heavy maintenance checks and the unmanned drones developed by ST Engineering are doing a job that would previously be performed by an engineer on a boom lift.

The drone takes a planned route around the outside of an aircraft to inspect its surface and take high definition images. The images are processed using software with smart algorithms to detect and classify defects that can be reviewed by engineers.

Air New Zealand and ST Engineering are also collaborating to manufacture 3D printed replacement interior parts and on data analytics to optimize maintenance activities[17].

Fig.6.8 drone takes a planned route around the outside of an aircraft

This revolutionary technology can increase workplace safety whist maintaining a competitive edge. Traditional survey method are labor intensive, time consuming and often need dedicated facilities and infrastructure to be conducted. Rabid uses no heavy or cumbersome equipment that may further damage the aircraft, or puts engineers into potentially hazardous situations[17].

7. CASE STUDY

AUTOMATION OF AIRCRAFT FRAME VISUAL INSPECTION USING DRONE CAMERA

7.1 Aircraft Visual Inspection

Aircraft visual inspections are the most recurring procedure in aviation maintenance, repair & overhaul (MRO) to ensure the aircraft airworthiness . Over 75 percent of inspections on large transport aircraft are visual. It is the process of using the naked eye to inspect and detect damages or anomalies that might pose a risk to the continued safe operation of the aircraft. Therefore, as the most basic method of assessing the overall condition of an aircraft and its parts, aircraft visual inspections must be accurate and proficient in order to report defects, manufacturing errors, or component fatigue[19].

Depending on their difficulty and degree of effectiveness, aircraft visual inspections can be divided into four different categories:

Walkaround inspection is a general check to assess the overall condition of the aircraft and its compliance with the security standards. It is performed by a human inspector by walking around on the ground below the aircraft, as the name suggests.

General visual inspection is carried out routinely to inspect, locate, and evaluate any damage, failure, or anomaly. For most areas, the human inspector requires additional equipment, such as ladders and cherry pickers.

Detailed visual inspection consists of an intensive examination of a specific area, component, or system for the detection of damages. Usually, some tools are required, including the use of a flashlight, magnifying glass, mirrors, or specialist measuring tools, etc.

Special detailed visual inspection may be required for damage assessment of a specific item, installation, or assembly[19][20]. It has been proven that regularly scheduled inspections and preventive maintenance assure airworthiness. Operating failures and malfunctions of equipment are appreciably reduced if excessive wear or minor defects are detected and corrected early. The importance of inspections and the proper use of records concerning these inspections cannot be overemphasized[19].

7.2 Aircraft Visual Inspection Difficulties

Inspecting and maintaining commercial aviation is organizationally complex. Aircraft maintenance often spans multiple days and multiple shifts, making coordination of activities and information amongst different operators over different shifts very difficult.

Human errors became more and more examined by researchers. While errors resulting in accidents and incidents are most salient, let us not forget about other relevant consequences such as gate returns, delays in aircraft availability, or diversions to alternate airports which negatively impact airline operations .

Visual inspection is basically depending on human factor which in turn can be effected by different factors such as the inspector’s visual acuity, the work-place lighting conditions, or the time available for inspection. Thus, any situation (e.g., tiredness, bad light, time pressure, etc.) that impedes to properly inspect could impact reliable results and, ultimately, a gradual deterioration of an aircraft[20].

7.3 The Objective Of The Case Study

An attempt to automation of aircraft visual inspection. The goal to automate those that require the least technical skills possessed, for instance, by aircraft maintenance technicians. Instead of spending hours moving from station to station, from stringer to stringer, while searching for damage, aircraft engineers can undertake more complex tasks. With the inspection time reduced to minutes, faster and informed decisions can be made with regards to aircraft’s repair and availability. Automation is set to become the new normal across multiple industries, with aviation as its prime candidate. It offers a unique opportunity to mainstream human-oriented processes: the drone solutions are not only immune to the fatigue experienced by humans but also able to perform tasks with sensitivities not possessed by the human eye.

7.4 Case Study Methodology

The methodology of the case study can be summarized in three main tasks : Inspection, Analyzing and reporting and Tracing and Prediction.

Task – 1 :

Inspection In this task UAV's camera automatically scans and collects high resolution images of the complete aircraft structure.  Coverage of the entire external surface, including fuselage, wings, engine nacelles and tail plane.  Inspection of a narrow body in less than 1 hour  One single flight addresses multiple applications. Task – 2 :

Analyzing and Reporting

 Turn data into actionable insights by collecting and analyzing pictures.  Improve efficiency and productivity autonomous diagnostics allows the inspector validate a pre-flight report.  Damages and defects are accurately positioned according to structure elements ( frame, stringers, ribs, etc.)  Automated report is generated for general visual inspection, paint wear, regulatory markings, lighting strikes.  Multiple job cards are completed with a single drone flight to determine the next maintenance action.

Task – 3 : Tracing and Prediction ( Building objective digital history)

 Inspection data and reports are systematically saved. Remote access to inspection reports allowing secured sharing with maintenance team of experts.  Traceability over time to track evolution or run benchmarks across the fleet.  Digital history unlocking the potential for data mining and predictive maintenance.  One – click to technical documentation and support.

7.5 Case Study Plan

In order to achieve high level of efficiency in application the case study methodology , we decided to work in four tracks : Visualization, Paint Quality, Lightning Strike, Markings Check. These four tracks ensure the maximum coverage of the visual inspection activities.

Track – 1 : Visualization Automated drone inspection when aircraft enters the hangar delivers a detailed and objective inspection report. Precise positioning of all defects according to frames & stringers enables reliable damage mapping and objective comparison of aircraft status over time.

Track – 2 : Paint Quality

Excessive loss of paint and gloss can have a direct impact on airflow, leading to more drag and ultimately to higher fuel burn. Today there is no objective data to evaluate paint quality across the fleet and prioritize aircraft repainting. This lack of objective data also makes claims to paint shops more complicated to support.

In less than one hour, Drone automatically collects images of aircraft surface and maps density of rivet & screw rash on airframe. These images for different parts of the aircraft skin can be compared, analyzed and evaluated. This will provide a consistent, objective paint condition assessment to efficiently track excessive loss of skin wear, prioritize aircraft requiring repainting and trigger warranty claims with OEMs/paint shops.

Track – 3 : Lightning Strike When an aircraft is struck by lightning, it has to be grounded for inspection until the entry/exit points are found. This takes several hours and leads to operational losses for operators.

Complete automated inspection and detection of lightning strike impacts (entry and exit points) with drone and image analysis in less than two hours ensuring rapid aircraft availability.

Track – 4 : Markings Check

Checking all placards on a narrow body aircraft takes several hours. Nevertheless, missing or invalid placards can lead to fines or aircraft grounding when detected during ramp inspections.

Using drone camera makes placard checks faster and objective with automated inspection of all markings and placards in less than 1 hour. It helps to identify missing P/Ns for reordering while ensuring compliance with ramp audits.

7.6 Case Study Plan Execution  Using a drone camera, the whole aircraft exterior was inspected . Inspection was started following the usually walkaround route then transferred to different parts on the aircraft that are not accessible by the walkaround inspection.

Fig. 7.1 Aircraft Walkaround Route

 Pictures and videos recorded during this flight will be collected and analyzed in order to see if there any defects, corrosion pits , dents, loose or missed rivets or any anomalies on aircraft frame.  Ten virtual points are located on different places on the wing and the fuselage . See figure (7.2) . These points are considered as defects points.  High definition pictures were taken to these points to be delivered to structure engineers accompanied with a digital report.  In the digital technical report, the points are localized accurately in order to help engineers to save time that would be consumed in localizing and positioning the defect points and the defects are described .  This digital report can be saved to build a digital achieve for the aircraft in order to trace failures and defects for the whole aircraft life span.  During the drone camera scanning of the aircraft frame, the aircraft painting and all the placards of the aircraft were shot, these pictures will be compared with the original pictures of the aircraft markings in the aircraft documents to decide if there are some placards and markings missed or needed to be repainted.  The aircraft was assumed that been struck the lightening and needed to be inspected to find the lightening enter and exit points.  Two virtual points were located and defined on the aircraft frame as enter/exit points of the lightening. Using the drone camera the whole aircraft exterior was objectively inspected searching these two points. The predefined point were shot by the drone camera and precisely localized according to fuselage frame and stringers coordination.  These pictures of the lightening enter/exit points will be attached with a digital technical report describing the lightening strike points and their position.

Fig. 7.2 Location of virtual defects points

Fig. 7.3 Technical report shows defect localization and description

8. CONCLUSIONS

 Technological amelioration has impacted significantly social, economic and personal life, from business approaches to international wars. These transformations can be visualized by getting benefited from these technological advancements. Unmanned aerial vehicle (UAV) also known as remotely operated aircraft is the best example to visualize the change.  The use of UAVs has become ubiquitous in many civil applications. From rush hour delivery services to scanning inaccessible areas, UAVs are proving to be critical in situations where humans are unable to reach or cannot perform dangerous/risky tasks in a timely and efficient manner. In this survey, we reviewed UAV civil applications and their challenges. We also discuss current research trends and provide future insights for potential UAV uses.  Aircraft visual inspection is still a manual process with limited tracking of past damage reports. Analysis can be incomplete or subjective: it is hard to determine how a damage has evolved from a previous check if it was misreported initially.  Combining experience in aircraft maintenance and robotics with state-of-the-art technology, game-changing results can be achieved. Drone-powered inspection tool can be accessed anywhere and anytime, enabling aircraft engineers to perform aircraft inspections in one click. The damage assessment report pinpoints the exact location of anomalies and damages found. This information can be used by structure engineers to add notes on its depth for a faster decision on the additional repairs.  The high mobility and flexible deployment of drone reduce the resources required for manual inspections. With intuitive user interface, performing aircraft inspection and delivering data reports takes less than one hour.  An automated inspection process prevents human exposure to dangerous situations but also complies with high standards for safety and security. By automation, all data and reports from past inspections are stored on a secure cloud platform. It guarantees full traceability of aircraft status over time, building a digital history of each airplane and allowing comparison of defects from one inspection to another.  A case study was carried out as an approach to the automation of the aircraft visual inspection by using a drone camera. Some of the visual inspection activity were conducted by the camera.  All these maintenance activities were successfully accomplished by the drone camera and all the intended objectives like saving time, reducing labor intensity, minimizing aircraft downtime and lowering maintenance cost.

9. Recommendations and future work

 This work could be followed up by other projects using more powerful drone and high definition camera that can be operated in 360o view angle, that will enable inspectors to visualize more narrow places on the aircraft.  By cooperation with computer programmers, a software can be built for this project which helps to prepare the technical report and ease tracing aircraft throughout the whole fleet and tracking the failure history.  All the leading aviation companies that started aircraft inspection automation technology were authorized by the aviation legislation organization like EASA and EATA. There is a necessity to convey this idea to the local aviation authorities to communicate with international aviation organizations in order to evolve and improve it and to include it in the maintenance program.

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[20] https://www.aviationpros.com/home/article/10388909/another- look-at-visual-inspection