Subsonic MCQs Aeronautical Engineering

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In subsonic flow, the velocity of the airflow is: A) Greater than the speed of sound B) Equal to the speed of sound C) Less than the speed of sound D) Unrelated to the speed of sound Answer: C) Less than the speed of sound The ‘Bernoulli’s principle’ is applicable to: A) Subsonic flows only B) Supersonic flows only C) Both subsonic and supersonic flows D) Transonic flows only Answer: A) Subsonic flows only At subsonic speeds, the relationship between pressure and velocity is described by: A) Bernoulli’s equation B) Navier-Stokes equations C) Rayleigh’s equation D) Prandtl’s boundary layer equations Answer: A) Bernoulli’s equation In a subsonic wind tunnel, the flow is typically: A) Isentropic and steady B) Compressible and turbulent C) Inviscid and compressible D) Irrotational and incompressible Answer: D) Irrotational and incompressible The ‘Mach number’ in subsonic flow is: A) Less than 1 B) Equal to 1 C) Greater than 1 D) Unrelated to subsonic flow Answer: A) Less than 1 The ‘lift coefficient’ for subsonic airfoils is primarily dependent on: A) Angle of attack B) Mach number C) Reynolds number D) Wing aspect ratio Answer: A) Angle of attack In subsonic flow over a streamlined body, the flowlines are: A) Parallel to the body B) Divergent around the body C) Convergent around the body D) Perpendicular to the body Answer: A) Parallel to the body The ‘drag coefficient’ in subsonic flow can be reduced by: A) Increasing the Reynolds number B) Increasing the Mach number C) Decreasing the airfoil camber D) Decreasing the angle of attack Answer: A) Increasing the Reynolds number In subsonic aerodynamics, ‘induced drag’ is primarily caused by: A) Wingtip vortices and lift generation B) Skin friction and surface roughness C) Pressure differences between the front and rear of the aircraft D) Airflow separation and turbulence Answer: A) Wingtip vortices and lift generation The ‘boundary layer’ in subsonic flow refers to: A) The region near the surface where viscous effects are significant B) The region far from the surface where the flow is inviscid C) The area where compressibility effects dominate D) The region of maximum airflow velocity Answer: A) The region near the surface where viscous effects are significant The ‘Prandtl-Glauert rule’ is used to: A) Predict subsonic aerodynamic characteristics from compressible flow data B) Calculate the drag coefficient at high Mach numbers C) Estimate the lift coefficient of transonic airfoils D) Analyze boundary layer behavior at different Reynolds numbers Answer: A) Predict subsonic aerodynamic characteristics from compressible flow data In subsonic flow, the airfoil’s ‘stall’ is characterized by: A) Flow separation and loss of lift B) Maximum lift coefficient and minimal drag C) Smooth and attached flow over the entire wing D) Increased airspeed and reduced drag Answer: A) Flow separation and loss of lift The ‘wing loading’ of an aircraft affects: A) The stall speed and maneuverability B) The drag coefficient and fuel efficiency C) The engine thrust and performance D) The wing shape and aerodynamic efficiency Answer: A) The stall speed and maneuverability The ‘drag polar’ of an airfoil describes: A) The relationship between drag and lift coefficients B) The variation of lift with angle of attack C) The relationship between speed and fuel consumption D) The variation of drag with airspeed Answer: A) The relationship between drag and lift coefficients The ‘Reynolds number’ in subsonic aerodynamics characterizes: A) The relative importance of inertial versus viscous forces B) The ratio of dynamic pressure to air density C) The ratio of lift to drag forces D) The change in pressure with altitude Answer: A) The relative importance of inertial versus viscous forces The ‘wing aspect ratio’ affects: A) The lift-to-drag ratio and stall characteristics B) The engine performance and fuel efficiency C) The size of the aircraft’s control surfaces D) The aircraft’s overall weight and balance Answer: A) The lift-to-drag ratio and stall characteristics In subsonic flow, the ‘lift-to-drag ratio’ of an airfoil is: A) Highest at moderate angles of attack B) Maximized at high speeds C) Unaffected by the Reynolds number D) Directly proportional to the airfoil’s camber Answer: A) Highest at moderate angles of attack The ‘boundary layer transition’ from laminar to turbulent flow: A) Increases skin friction and drag B) Reduces the total drag coefficient C) Improves the aerodynamic efficiency of the airfoil D) Minimizes flow separation and stall Answer: A) Increases skin friction and drag In subsonic flow, the ‘pressure drag’ is primarily caused by: A) Pressure differences and flow separation around the body B) Skin friction and surface roughness C) Airfoil camber and angle of attack D) Turbulent wake and vortex formation Answer: A) Pressure differences and flow separation around the body The ‘Clausius-Clapeyron relation’ in subsonic aerodynamics describes: A) The relationship between pressure and temperature in the atmosphere B) The variation of lift coefficient with airspeed C) The effect of wing shape on aerodynamic drag D) The effect of temperature on the aircraft’s engine performance Answer: A) The relationship between pressure and temperature in the atmosphere The ‘Mach number’ for a subsonic aircraft: A) Increases with altitude B) Decreases with altitude C) Remains constant with altitude D) Is not affected by altitude Answer: B) Decreases with altitude The ‘induced drag’ is reduced by: A) Increasing the aspect ratio of the wing B) Decreasing the Reynolds number C) Reducing the airfoil camber D) Increasing the airspeed Answer: A) Increasing the aspect ratio of the wing The ‘airfoil shape’ affects: A) The lift and drag characteristics of the airfoil B) The aircraft’s fuel consumption and performance C) The engine thrust and power output D) The aircraft’s stability and control Answer: A) The lift and drag characteristics of the airfoil In subsonic flow, the ‘pressure coefficient’ (Cp) is: A) The ratio of the local pressure to the free-stream pressure B) The ratio of the local velocity to the free-stream velocity C) The difference between the local pressure and free-stream pressure D) The ratio of the airfoil thickness to chord length Answer: A) The ratio of the local pressure to the free-stream pressure The ‘airfoil camber’ affects: A) The lift generation and stall characteristics B) The drag coefficient and fuel efficiency C) The engine thrust and power output D) The aircraft’s overall weight and balance Answer: A) The lift generation and stall characteristics The ‘streamline’ flow pattern in subsonic aerodynamics: A) Follows the contour of the body and minimizes drag B) Is characterized by turbulent eddies and vortices C) Involves high-speed compressible effects D) Is dominated by shock waves and wave drag Answer: A) Follows the contour of the body and minimizes drag The ‘total drag’ on a subsonic aircraft includes: A) Induced drag, parasitic drag, and form drag B) Engine drag, wing drag, and fuselage drag C) Frictional drag, pressure drag, and interference drag D) Vortex drag, wave drag, and skin friction drag Answer: A) Induced drag, parasitic drag, and form drag The ‘transonic regime’ is characterized by: A) Flow velocities near the speed of sound B) High-speed subsonic flow C) Low-speed supersonic flow D) Compressible flow effects at high Mach numbers Answer: A) Flow velocities near the speed of sound The ‘lift-to-drag ratio’ (L/D) is: A) A measure of the aerodynamic efficiency of the airfoil B) The ratio of lift to thrust in level flight C) The ratio of drag to weight during takeoff D) The ratio of induced drag to parasitic drag Answer: A) A measure of the aerodynamic efficiency of the airfoil The ‘maximum lift coefficient’ (Cl,max) is: A) The highest lift coefficient before flow separation occurs B) The lift coefficient achieved at high speeds C) The lift coefficient at zero angle of attack D) The lift coefficient corresponding to minimum drag Answer: A) The highest lift coefficient before flow separation occurs The ‘drag polar’ curve shows the relationship between: A) Drag coefficient and lift coefficient B) Drag coefficient and airspeed C) Lift coefficient and angle of attack D) Lift coefficient and drag-to-lift ratio Answer: A) Drag coefficient and lift coefficient In subsonic flow, ‘form drag’ is: A) Caused by the shape of the body and flow separation B) The drag due to friction along the surface of the body C) A result of the induced lift forces D) The drag associated with the airfoil’s camber Answer: A) Caused by the shape of the body and flow separation The ‘skin friction drag’ is: A) The drag due to friction between the air and the surface of the aircraft B) The drag resulting from pressure differences around the aircraft C) The drag caused by vortices at the wingtips D) The drag related to the airfoil’s thickness Answer: A) The drag due to friction between the air and the surface of the aircraft The ‘wing vortex’ in subsonic aerodynamics: A) Forms at the wingtips and contributes to induced drag B) Is a result of flow separation at the wing root C) Reduces the overall drag on the aircraft D) Increases the aircraft’s lift-to-drag ratio Answer: A) Forms at the wingtips and contributes to induced drag The ‘Prandtl’s boundary layer theory’ addresses: A) The behavior of the boundary layer in laminar and turbulent flow B) The effects of compressibility on high-speed flow C) The interaction between different layers of the atmosphere D) The formation of shock waves in supersonic flow Answer: A) The behavior of the boundary layer in laminar and turbulent flow The ‘lift equation’ for subsonic airfoils is given by: A) L = 0.5 * ρ * V^2 * S * Cl B) L = ρ * V * S * Cl C) L = 0.5 * ρ * V * S * Cl D) L = ρ * V^2 * S * Cl Answer: A) L = 0.5 * ρ * V^2 * S * Cl The ‘airfoil thickness-to-chord ratio’ affects: A) The lift and drag characteristics of the airfoil B) The weight and balance of the aircraft C) The engine thrust and performance D) The aircraft’s stability and control Answer: A) The lift and drag characteristics of the airfoil The ‘airfoil Reynolds number’ impacts: A) The transition point from laminar to turbulent flow B) The maximum lift coefficient of the airfoil C) The lift-to-drag ratio of the airfoil D) The aerodynamic efficiency of the entire aircraft Answer: A) The transition point from laminar to turbulent flow The ‘coefficient of lift’ (Cl) depends on: A) The airfoil shape and angle of attack B) The aircraft’s weight and balance C) The engine thrust and power output D) The fuel efficiency and consumption Answer: A) The airfoil shape and angle of attack The ‘stall angle of attack’ is: A) The angle at which the airfoil experiences flow separation B) The angle at which the aircraft achieves maximum lift C) The angle at which the drag coefficient is minimized D) The angle at which the wing reaches its maximum efficiency Answer: A) The angle at which the airfoil experiences flow separation In subsonic flow, ‘compressibility effects’ are: A) Negligible and do not significantly affect the flow B) Significant and cause changes in the flow characteristics C) Only relevant at supersonic speeds D) Primarily caused by changes in altitude Answer: A) Negligible and do not significantly affect the flow The ‘airfoil camber’ affects: A) The lift and drag characteristics of the airfoil B) The thrust-to-weight ratio of the aircraft C) The wing loading and aircraft performance D) The engine efficiency and fuel consumption Answer: A) The lift and drag characteristics of the airfoil The ‘drag coefficient’ (Cd) is influenced by: A) The airfoil shape and surface roughness B) The aircraft’s weight and balance C) The engine thrust and power output D) The aircraft’s altitude and temperature Answer: A) The airfoil shape and surface roughness The ‘airfoil chord length’ affects: A) The lift and drag characteristics of the airfoil B) The engine thrust and power output C) The aircraft’s weight and balance D) The aerodynamic stability of the aircraft Answer: A) The lift and drag characteristics of the airfoil The ‘lift-curve slope’ for subsonic airfoils is: A) The rate at which lift coefficient increases with angle of attack B) The rate at which drag coefficient increases with airspeed C) The change in lift with changes in Reynolds number D) The effect of camber on the airfoil’s lift coefficient Answer: A) The rate at which lift coefficient increases with angle of attack The ‘drag due to lift’ (induced drag) is minimized by: A) Increasing the aspect ratio of the wing B) Decreasing the Reynolds number C) Reducing the airfoil camber D) Increasing the airspeed Answer: A) Increasing the aspect ratio of the wing The ‘airspeed’ at which an aircraft stalls is affected by: A) The weight of the aircraft and the wing loading B) The engine power and thrust output C) The altitude and atmospheric pressure D) The wing shape and surface finish Answer: A) The weight of the aircraft and the wing loading The ‘wing aspect ratio’ affects: A) The lift-to-drag ratio and induced drag B) The aircraft’s stability and control C) The engine performance and efficiency D) The fuel consumption and range Answer: A) The lift-to-drag ratio and induced drag The ‘laminar boundary layer’ is characterized by: A) Smooth, orderly flow with minimal mixing B) Irregular, turbulent flow with significant mixing C) High velocity near the surface and large pressure gradients D) High levels of skin friction and drag Answer: A) Smooth, orderly flow with minimal mixing The ‘turbulent boundary layer’ is characterized by: A) Increased skin friction and drag B) Smooth, laminar flow with low drag C) Reduced skin friction and lower drag D) Minimal mixing and low levels of turbulence Answer: A) Increased skin friction and drag

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