Nehru Institute of Technology Department of Aeronautical Engineering AE3301 Elements of Aeronautical Engineering Anna university Question Bank UNIT I PART A 1 Define Ornitopter Who invented it Ans An ornithopter is an aircraft that flies by flapping its wings Designers seek to imitate the flapping wing flight of birds bats and insects Though machines may differ in form they are usually built on the same scale as these flying creatures Manned ornithopters have also been built and some have been successful The machines are of two general types those with engines and those powered by the muscles of the pilot Perhaps because the prevailing technology is fixed wing aircraft people are mainly aware of the failed attempts at flapping wing flight This article describes only the more successful attempts The first ornithopters capable of flight were constructed in France in the 1870s Gustave Trouv s 1870 model flew a distance of 70 meters in a demonstration for the French Academy of Sciences 2 Write down the principle difference between lighter than air and heavier than airplanes Ans Heavier than air aircraft Heavier than air aerodynes including autogyros helicopters and variants and conventional fixed wing aircraft Fixed wing aircraft generally use an internal combustion engine in the form of a piston engine with a propeller or a turbine engine jet or turboprop to provide thrust that moves the craft forward through the air The movement of air over the airfoil produces lift that causes the aircraft to fly Exceptions are gliders which have no engines and gain their thrust initially from winches or tugs and then from gravity and thermal currents Lighter than air aircraft Lighter than air aerostats hot air balloons and airships Aerostats float in air in the same way that a ship floats in water by displacing the air around the craft with a lighter gas helium or hydrogen or hot air The distinction between a balloon and an airship is that an airship has some means of controlling forward motion and steering while balloons simply drift with the wind 3 What is the basic difference between a hot air balloon and an aircraft Ans Hot Air Balloons it is a lighter than air aircraft The balloon is filled with hot air or lighter gas and the controlling activity of drift with the wind Hot air balloons are limited by the amount of fuel they can carry Although they can drift for hours on the currents of air the heated air inside the balloon has to be re heated With out any real steering mechanism they are at the mercy of wind currents and weather Going up and coming down assent decent can be controlled with the use of ballast or the release of air Aircraft any machine or weight carrying device whether lighter or heavier than air designed to be supported by the air either by buoyancy or by dynamic action The movement of air over the airfoil produces lift that causes the aircraft to fly Exceptions are gliders which have no engines and gain their thrust initially from winches or tugs and then from gravity and thermal currents 4 State the two kinds of aircraft A Heavier than air aircraft including autogyros helicopters and variants and conventional fixed wing aircraft Fixed wing aircraft Helicopters VTOL and STOL Ans Ans B Lighter than air aircraft hot air balloons and airships 5 List out the difference classification of flight vehicles CLASSIFICATION AIRCRAFT 1 Classification by Configuration 2 Location and type of Landing Gear 3 Classification by Power Plants 4 Types of Fuselage 5 Classification by Purpose 6 Distinguish between biplane and monoplane aircraft Ans Monoplane has a single set of wings with a horizontal stabilizer and vertical stabilizer at the back of the aircraft which have become conventional configuration The aircraft have straight wing or swept wing BIPLANE has two set of wings or supporting surface mounted one above the other The Wright brothers called this a double Decker 7 Differentiate between biplane and monoplane Ans Same as above 8 What are biplane and monoplane Write down the advantages and disadvantages of biplane over monoplanes Ans Monoplane has a single set of wings with a horizontal stabilizer and vertical stabilizer at the back of the aircraft BIPLANE has two set of wings or supporting surface mounted one above the other BIPLANE Advantages 1 lift up to 20 percent more than can a similarly sized monoplane of similar wingspan 2 typically have a lower wingspan than a similar monoplane 3 greater manoeuvrability 4 very strong wing structure Disadvantage Configuration wing area produces more drag and less lift MONOPLANE 1 lift up reduced to 20 percent lesser than bi plane 2 typically have a more wingspan than a similar bi plane 3 lesser manoeuvrability 4 wing structure weaker than bi plane Configuration wing area produces less drag and more lift 9 Distinguish between a glider and a sail plane Ans Glider an engineless airplane flown by being manipulated into air currents that keep it aloft It gains their thrust initially from winches or tugs and then from gravity and thermal currents Gliders are planes that glide down to earth without power A good example might be a WW2 troop glider It s not designed to catch or ride thermals and climb just to be released from its tow plane and glide down to earth The space shuttle in its landing mode would be another example A sailplane is designed to ride the wind and climb in the thermals and other updrafts Glide ratio is more than glider ie 60 1 10 What are secondary control surfaces Ans Trimming Trim Tabs Trimming Tail Plane and Control Horn are the secondary control surfaces Trimming Trimming controls allow a pilot to balance the lift and drag being produced by the wings and control surfaces over a wide range of load and airspeed This reduces the effort required to adjust or maintain a desired flight attitude Trim Tabs Trim tabs are used to adjust the position of an associated main control surface They are often hinged to the back edge of the control surface with a control in the cockpit 11 What is the role of rudder Ans The rudder is mounted on the back edge of the fin in the tail When the pilot pushes the left pedal the rudder deflects left Pushing the right pedal causes the rudder to deflect right Deflecting the rudder right pushes the tail left and causes the nose to yaw right Centering the rudder pedals returns the rudder to neutral and stops the yaw 12 What is the purpose of elevator Ans The purpose of an elevator is to generate the