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AERO470: Aircraft Design Laboratory Lecture 1: Introduction Lecturer: Dr Rafic Ajaj Office: C01026G, Abu Dhabi Campus Email: [email protected] Fall 2023 What is design? Design (v): to create, fashion, execute, or construct according to plan : devise, contrive. • from Merriam-Webster dictionary...

AERO470: Aircraft Design Laboratory Lecture 1: Introduction Lecturer: Dr Rafic Ajaj Office: C01026G, Abu Dhabi Campus Email: [email protected] Fall 2023 What is design? Design (v): to create, fashion, execute, or construct according to plan : devise, contrive. • from Merriam-Webster dictionary Engineering design: a systematic, intelligent generation and evaluation of specifications for artifacts whose form and function achieve stated objectives and satisfy constraints. • From Engineering Design: A project-based Introduction, Dym and Little Aircraft design is a separate discipline of aeronautical engineering, where the designer spends time creating the geometric description of an artifact to be built, using knowledge of other disciplines such as aerodynamics, structures and propulsion. • Aircraft Design: A Conceptual Approach, Raymer 2 Phases of engineering design A three-stage description of generic engineering design 3 Phases of aircraft design 4 Phases of aircraft design • Conceptual design (primary focus of this course) Basic questions of configuration management, size, weight and performance are answered Configuration arrangement (type of tail, wing etc.) is completed at this stage It is an iterative process, especially with respect to weight and size. • Preliminary design Specialists in various disciplines (structures, controls, landing gear, etc.) analyze the aircraft. Testing performed for some design areas such as aerodynamics and propulsion 5 Phases of aircraft design It ends with a full-scale development proposal. It must establish confidence that the proposed design can be built on time at the estimated cost. •Detail design The actual pieces of the aircraft to be fabricated are designed. Production design is done at this time: experts determine how the aircraft is to be fabricated, starting with the smallest subassemblies building up to the final assembly. More testing is necessary to ensure that the manufactured parts/assemblies behave as anticipated. Detail design ends with the fabrication of the aircraft. 6 Aircraft types Civil types can be: Passenger aircraft Civil cargo aircraft Business or executive aircraft Agricultural aircraft Light aircraft for pleasure, pilot training and very light transport (includes general aviation aircraft) 7 Aircraft types Military aircraft can be: Fighter Bomber Ground attack Trainer Reconnaissance Military cargo 8 Aircraft types Other aircraft types are Rotorcraft Other VTOL/STOL aircraft (Tiltrotor, autogyro etc.) 9 Anatomy of an aircraft : Structure Aircraft structure must: - safely meet maximum expected loads, - be stiff enough to limit distortions under loading, - have fatigue and corrosion resistance, tolerance to change in atmospheric conditions, - be low weight, - have acceptable material and manufacturing costs 10 Structures in an aircraft Flying and stabilizing surfaces: Wings, tails and canards. Wings generate the lift and carry the aircraft, while tails and canards ensure stable flight Fuselage: Body of the aircraft. May be used to house the crew, payload, engine, and fuel tank. Flying wing aircraft do not have a fuselage. 11 Landing gear: It supports the aircraft while landing and on the ground. It weighs about 4-5% of the TOGW. Possible configurations are: Nosewheel, tailwheel and bicycle layout. 12 Anatomy of an aircraft : Propulsion Propulsion devices can be in the form of air breathing engines or rockets. Engines need air (oxygen) to operate, have high weight but low fuel consumption. It is the opposite for rockets. Thus rockets are more suitable for shot-time usage and thin atmosphere conditions. We will focus on air-breathing engines. There are several types: Piston engine: Used extensively in early aircraft, this kind of engine is now used only in small, low cost aircraft. It is heavy w.r.t. the power it provides. 13 Most reciprocating aircraft engines are based on the four-stroke Otto cycle. Four-stroke engines offers a good combination of power, weight, and efficiency. Two-cycle engines are less common, often used in model aircraft, ultralight aircraft, and unmanned aircraft. They offer high specific power (i.e., power per unit engine mass), are mechanically simple, but often have poor fuel consumption characteristics. 14 Anatomy of an aircraft : Propulsion Turbo-jet engine: Used mostly in fighters, turbo-jet engine is suitable for flying at high altitude/high speed (Mach 0.75-3.0). It works by compressing air and burning fuel in that air to create high speed air jet coming through a nozzle. It has high fuel consumption and high noise (higher than that of turboprops and turbofans), but penalty is not as large as altitude and airspeed increase. 15 Anatomy of an aircraft : Propulsion Turbojet engines are available in a wide range of sizes. Thrust from 220 N (50 lbf) to 270,000 N (60,000 lbf). Turbojet engines are lighter and have a smaller frontal area than a comparable reciprocating engine with propeller. Uninstalled thrust-to-weight ratio from 4 to 8. Turbofan or bypass engine: Based on turbojets, these engines use a large fan to provide much of the thrust. Some of the air through the fan bypasses the engine. 16 The ratio between the mass flow rate of air drawn in by the fan bypassing the engine core to the mass flow rate passing through the engine core is called bypass ratio (BPR). High BPR engines (shown bottom left) have lower fuel consumption, but they are heavier and limit top speed. Low BPR engines (bottom right) are lighter, enable higher speed, but have higher fuel consumption. 17 Anatomy of an aircraft : Propulsion Turbofan engines available in a wide range of sizes. Maximum thrust to approximately 510,000 N (115,000 lbf). Turbofans operate with high efficiency in the range of Mach numbers used by commercial transports (from Mach 0.65 to 0.80). Turbofans can also work well at supersonic speeds (up to Mach ~1.5), although for high Mach numbers a turbojet is a better choice. Thrust to weight ratio of 5 to 6. Turbofans are simpler than turboprops (no reduction gears and variable pitch mechanism necessary) and can operate at higher Mach numbers. 18 Mixing of hot and cold gasses in exhaust lowers engine noise (less than turbojet or turboprop for the same level of thrust). Turbo prop engine: They are also based on jet engines, but the main source of thrust is the propeller. They are powered by a shaft coming from the jet engine. Exhaust thrust is much less than propeller thrust. Suitable for aircraft flying at Mach 0.3 to 0.65, these engines have low fuel consumption and lower weight than piston engines. Turboprop engines are available in the power range from 375 to 7500 kW (500 to 10,000 hp). They operate with high efficiency in the range of Mach numbers used by regional transports (from Mach 0.4 to 0.7). 19 They have power to mass (weight) ratios of approximately 3.3 kW/kg (2 hp/lb). A turboprop engine has approximately 33% the mass of a reciprocating engine of the same power. Turboprop engines specific fuel consumption is higher than for a reciprocating engine/propeller combination, but much lower than that of a turbojet. Initial cost of a turboprop engine is higher than for a comparable reciprocating engine/propeller combination, but its maintenance costs are less and it is more reliable. A turboprop is heavier than a comparable turbojet or turbofan. 20 Anatomy of an aircraft : Avionics Avionic systems are the electronic systems used on an aircraft. As much as 40% of a new aircraft cost can be attributed to avionics. Those systems include but not limited to: • • • • • • • • Communications Navigation Radar Autopilot Instrument landing Targeting Forward-looking infra-red (FLIR) Radar counter-measures 21 Anatomy of an aircraft : Weapon systems They include guns, bombs, rockets and guided missiles Anatomy of an aircraft : Flight control systems The control system consists of the pilot, auto-pilot, linkages, actuators and the control device itself. Actuators convert control signals from the pilot/autopilot into a force to move the control device. Controls can be categorized onto three groups: Primary group includes ailerons, elevators and rudder. They create moments w.r.t. the C.G to change orientation of the aircraft. 22 Secondary group includes trim and spring tabs. Trim tabs help pilot balance the plane without using a primary control surface. Spring tabs reduce pilot effort in moving primary control surfaces. Auxiliary group contains wing flaps ,spoilers, speed brakes and slats. Flaps provide extra lift during takeoff, landing etc. to shorten landing strip required. They are hinged to the trailing edge and/or leading edge of the wing. 23 Flaps on leading edge are called slats. Spoilers or air brakes are for decreasing lift. They are retractable, and located on the upper surfaces of wings. Control linkages may be simple levers and wires for small and old aircraft, but in new and big planes, power controls and artificial feedback is more common. 24