Reg.No: SNS College of Technology, Coimbatore-35. (Autonomous) B.E/B.Tech- Internal Assessment -II Academic Year 2019-2020 (ODD) B Eighth Semester Aeronautical Engineering 16AEOE1 - Basic Aeronautical Engineering Time: 11/2 Hours Maximum Marks: 50 Answer All Questions PART - A (5x 1 = 5Marks) 1. In NACA Four digit airfoil the last two digits indicates a) Maximum camber b) Maximum thickness c) Maximum lift co-efficient d) Position of Maximum Camber 2. If Mach number = 1, then the flow is called a) Sonic b) Subsonic c) Transonic d) Supersonic 3. In a Monocoque structure, the load is resisted by a) Stringer b) Skin c) Longerons d) Cowling 4. Young’s Modulus of Aluminum a) 50 GPa b) 70 GPa c) 100 GPa d) 200 GPa 5. Which one of the following material has strength to weight ratio very high a) Aluminum b) Steel c) Magnesium d) Composite 6. Define Drag and their types. A force acting on aero plan, which is parallel to the direction of relative wind a opposite to thrust direction under level flight. TYPES: Profile Drag, Skin Friction Drag, Interference drag, Form Drag 7. Explain Symmetric and unsymmetrical airfoils. • Symmetric : Upper and lower surfaces are mirror image, A mean 1 camber line is coincident with chord line. A symmetric airfoil will also have a just camber of Zero. • Unsymmetrical: An asymmetric airfoil for which the mean camber line will be above the chord line. 8. Define camber in an airfoil. Camber line: curved line from the leading edge to the trailing edge, which is equivalent between the upper surface and the lower surfaces of the airfoil. 9. Differentiate between Monocoque and Semi Monocoque construction. Monocoque:- A structure in which the outer skin carries the primary stresses and is free of internal bracing. Semi-monocoque:- An aircraft structure in which the outer skin in inadequate to carry the primary stresses, and is reinforced by frames, formers and longerons. 10. List the main advantages and disadvantages of composite materials for aircraft structure. Advantage High strength to weight ratio Less weight Design Flexibility Corrosive Resistances Disadvantage High Cost Complicated in damage inspection 2 11. (a) Discuss in details about the classification of aircraft with suitable sketches. Classification according to purpose A) Civil airplanes:- Cargo transport (regional 100-200 seats passengers‘ travel. Turbofan, long range, mail distribution, 250-450 seats turbo fan) Agriculture Ambulance Executive travel Training and sports Air taxi and charter Forestry Fish and wild life survey Construction Arial photography Off – shore drilling B) Military airplanes: Trainers Fighters Transport 14 Bombers Reconnaissance Surveillance Electronic warfare Flight refilling tanks Vertical / short take off and landing aircraft Anti – submarine warfare aircraft Stealth aircraft Classifications by power plant 1. Type of engine used: Piston engine Turboprop Turbo Prop Turbofan Ramjet 2. Number of engines used and engine location Single engine Twin engine 3 Multi engine Location of power plant Engine in fuselage Pusher engine located in the rear fuselage Jet engine submerged in the wing Jet engine located on the rear fuselage Jet engines in nacelles suspended under the wing Jet engines located within the rear fuselage Classifications by configuration: Type of fuselage : Conventional single fuselage design Twin fuselage design Pod and boom construction Types of landing gear: Retractable landing gear Non – retractable landing gear Tail wheel landing gear Nose wheel landing gear Bicycle landing gear TYPES OF FUSELAGE ROUND SQUARE OVAL (or) (b) Explain 4-digit and 5- digit series of NACA airfoil with examples. The NACA airfoils are airfoil shapes for aircraft wings developed by the National Advisory Committee for Aeronautics (NACA). The shape of the NACA airfoils is described using a series of digits following the word "NACA". The parameters in the numerical code can be entered into equations to precisely generate the cross-section of the airfoil and calculate its properties. Four-digit series 14 First digit describing maximum camber as percentage of the chord. Second digit describing the distance of maximum camber from the airfoil leading edge in tens of percents of the chord. Last two digits describing maximum thickness of the airfoil as percent of the chord. The NACA 0012 airfoil is symmetrical, the 00 indicating that it has no 4 camber. The 15 indicates that the airfoil has a 12% thickness to chord length ratio: it is 12% as thick as it is long. For example, the NACA 4415 airfoil has a maximum camber of 4% located 40% (0.4 chords) from the leading edge with a maximum thickness of 15% of the chord. NACA 5 Digit series NACA 23012 5 NACA 6 Digit series NACA 63A010 AIRFOIL NACA 63-010A airfoil Max thickness 10% at 35% chord Max camber 0% at 0% chord Source 12. (a) Discuss in detail, with a help of neat sketches, the construction of a typical wing. primary structure: A critical load-bearing structure on an aircraft. If this structure is severely damaged, the aircraft cannot fly. Secondary structure: Structural elements mainly to provide enhanced aerodynamics. Fairings, for instance, are found where the wing meets the body or at various locations on the leading or trailing edge of the wing. Wing structure Many high-wing airplanes have external braces, or wing struts, which transmit the flight and landing loads through the struts to the main 14 fuselage structure. Since the wing struts are usually attached approximately halfway out on the wing, this type of wing structure is called semi- cantilever. A few high-wing and most low-wing airplanes have a full cantilever wing designed to carry the loads without external struts. The principal structural parts of the wing are spars, ribs, and stringers. These are reinforced by trusses, I-beams, tubing, or other devices, including the skin. The wing ribs determine the shape and thickness of the wing (airfoil). In most modern airplanes, the fuel tanks either are an integral part of the wing structure, or consist of flexible containers mounted 6 inside of the wing. Attached to the rear, or trailing, edges of the wings are two types of control surfaces referred to as ailerons and flaps. Ailerons extend from about the midpoint of each wing outward toward the tip and move in opposite directions to create aerodynamic forces that cause the airplane to roll. Flaps extend outward from the fuselage to near the midpoint of each wing. The flaps are normally flush with the wing´s surface during cruising flight. When extended, the flaps move simultaneously downward to increase the lifting force of the wing for takeoffs and landings. Empennage Structure 7 The correct name for the tail section of an airplane is empennage. The empennage includes the entire tail group, consisting of fixed surfaces such as the vertical stabilizer and the horizontal stabilizer. The movable surfaces include the rudder, the elevator, and one or more trim tabs. A second type of empennage design does not require an elevator. Instead, it incorporates a one-piece horizontal stabilizer that pivots from a central hinge point. This type of design is called a stabilator, and is moved using the control stick, just as you would the elevator. The rudder is attached to the back of the vertical stabilizer. During flight, it is used to move the airplane´s nose left and right. The rudder is used in combination with the ailerons for turns during flight. The elevator, which is attached to the back of the horizontal stabilizer, is used to move the nose of the airplane up and down during flight. Trim tabs are small, movable portions of the trailing edge of the control surface. These movable trim tabs, which are controlled from the cockpit, reduce control pressures. Trim tabs may be installed on the ailerons, the rudder, and/or the elevator. (or) (b) Explain with suitable diagram Monocoque and Semi - Monocoque fuselage construction. 14 • The fuselage is the main structure, or body, of the aircraft. 8 • It provides space for personnel, cargo, controls, and most of the accessories. • The power plant, wings, stabilizers, and landing gear are attached to it. • There are four general types of fuselage construction: 1. Truss 2.Monocoque 3.Geodesic 4.Stressed skin. Truss Type • A truss is a rigid framework made up of members, such as beams, struts, and bars to resist deformation by applied loads. • The truss-framed fuselage is generally covered with fabric. • The truss-type fuselage frame is usually constructed of steel tubing welded together in such a manner that all members of the truss can carry both tension and compression loads It has diagonally web members and longitudinally longerons. They are sub classified in to • Pratt truss type • Warren truss type PRATT TRUSS • Early days • Wooden or metal structure • Great weight • Difficult to streamline • Box with tubular longerons + vertical members • The primary strength members are the four longerons the 9 longerons were connected with rigid vertical and lateral members called struts but the diagonal members were made of strong steel wire and were designed to carry tension only. WARREN TRUSS • Longerons + only Diagonal Members • Force transfer to every others structure • Capable to carry tension + compression • Reduce amount of webs work • More space , strength , rigidity • Better streamline Monocoque Type • The monocoque (single shell) fuselage relies largely on the strength of the skin or covering to carry the primary loads. • The design may be divided into: – Monocoque – Semimonocoque – Reinforced shell • Different portions of the same fuselage may belong to either of the two classes, but most modern aircraft are considered to be of semimonocoque type construction. • The true monocoque construction uses formers, frame assemblies, and bulkheads to give shape to the fuselage. However, the skin carries the primary stresses. • The biggest problem in monocoque construction is maintaining enough strength while keeping the weight within limits.