PRC Aeronautical Engineer Licensure Examination (Philippines)

Which of the following describes the relation between the lift coefficient (Cl) and the angle of attack (alpha) for a symmetric airfoil in the linear range?

• ACl is zero at zero angle of attack and increases linearly with a slope of approximately 2…
• BCl is positive at zero angle of attack and increases quadratically with alpha.
• CCl is negative at zero angle of attack and decreases linearly with a slope of -2*pi per r…
• DCl is zero at zero angle of attack and remains constant regardless of the angle of attack.

According to Bernoulli's equation for inviscid, incompressible flow, what happens to the static pressure of a fluid when its velocity increases along a streamline?

• AThe static pressure remains constant because total pressure changes.
• BThe static pressure decreases to balance the increase in dynamic pressure.
• CThe static pressure increases proportionally to the square of the velocity.
• DThe static pressure drops to zero immediately when any flow is initiated.

For a steady, incompressible, one-dimensional flow through a diverging duct, how do the velocity and volumetric flow rate change along the duct?

• AVelocity increases and the volumetric flow rate increases.
• BVelocity decreases and the volumetric flow rate remains constant.
• CVelocity remains constant and the volumetric flow rate decreases.
• DVelocity decreases and the volumetric flow rate decreases.

The pressure coefficient (Cp) at a point on an airfoil in incompressible flow is defined in terms of static pressure (p), free-stream static pressure (p_inf), and free-stream dynamic pressure (q_inf). What is the value of Cp at a stagnation point?

• ACp is equal to 0.
• BCp is equal to 1.
• CCp is equal to -1.
• DCp is equal to infinity.

If the ambient temperature at a specific flight altitude is -40 degrees Celsius, what is the speed of sound at this altitude? (Assume air behaves as a perfect gas with gamma = 1.4 and R = 287 J/kg*K)

• AApproximately 340.3 m/s
• BApproximately 306.0 m/s
• CApproximately 243.2 m/s
• DApproximately 150.0 m/s

An aircraft is flying at a true airspeed of 600 knots at an altitude where the local speed of sound is 580 knots. Which Mach regime describes this flight condition?

• ASubsonic flow
• BTransonic flow
• CSupersonic flow
• DHypersonic flow

What is the standard temperature lapse rate in the troposphere according to the U.S. Standard Atmosphere (which is also adopted by ICAO)?

• A-6.5 degrees Celsius per kilometer (-0.0065 K/m)
• B-1.0 degree Celsius per kilometer (-0.0010 K/m)
• C0 degrees Celsius per kilometer (isothermal)
• D3.2 degrees Celsius per kilometer (0.0032 K/m)

At what altitude does the tropopause begin in the ICAO Standard Atmosphere, separating the troposphere from the stratosphere?

• A11,000 meters (36,089 feet)
• B20,000 meters (65,617 feet)
• C32,000 meters (104,987 feet)
• D8,000 meters (26,247 feet)

The density ratio (sigma) is the ratio of local air density (rho) at altitude to the standard sea-level air density (rho_0). If the density ratio is 0.5328, what physical effect does this have on aerodynamic lift if velocity is held constant?

• ALift will increase because the air is thinner and flows faster.
• BLift will decrease to approximately 53.28% of its sea-level value.
• CLift will remain unchanged because lift only depends on velocity.
• DLift will drop to zero because air must have standard density to generate lift.

Which of the following equations represents the coefficient of induced drag (Cdi) for a finite wing with a 3D lift coefficient (CL), aspect ratio (AR), and Oswald efficiency factor (e)?

• ACdi = CL / (pi * e * AR)
• BCdi = CL^2 / (pi * e * AR)
• CCdi = CL^2 * pi * e * AR
• DCdi = Cd0 + CL^2 / (pi * e * AR)

A wing has a span of 12 meters and a planform area of 18 square meters. What is the aspect ratio of this wing, and what is its primary effect on induced drag?

• AAspect ratio is 8.0; a higher aspect ratio increases induced drag.
• BAspect ratio is 8.0; a higher aspect ratio reduces induced drag.
• CAspect ratio is 0.67; a lower aspect ratio reduces induced drag.
• DAspect ratio is 1.5; a lower aspect ratio increases induced drag.

How is the critical Mach number (Mcr) of an airfoil defined?

• AThe flight Mach number at which the entire flow over the airfoil becomes supersonic.
• BThe flight Mach number at which the local flow velocity at some point on the airfoil surf…
• CThe Mach number at which the aircraft experiences structural divergence due to aeroelasti…
• DThe flight Mach number at which drag coefficient increases abruptly by over 500%.

Which design feature is primarily utilized on modern commercial aircraft to delay the onset of wave drag and increase the critical Mach number?

• AForward-swept wings with thick airfoils.
• BSwept-back wings and supercritical airfoils.
• CUnswept rectangular wings with high camber.
• DVortex generators combined with deep stall control surfaces.

How do the thermodynamic properties of a fluid change when it passes through a normal shock wave in supersonic flow?

• APressure decreases, temperature decreases, density decreases, and Mach number increases.
• BPressure increases, temperature increases, density increases, and Mach number decreases.
• CPressure remains constant while temperature increases and total pressure increases.
• DPressure increases, temperature decreases, density decreases, and Mach number remains con…

For a given supersonic upstream Mach number, how does an oblique shock wave differ from a normal shock wave?

• AAn oblique shock wave is inclined to the flow and results in a subsonic downstream Mach n…
• BAn oblique shock wave is inclined to the flow and can result in either a subsonic or supe…
• CAn oblique shock wave does not cause any change in pressure or temperature.
• DAn oblique shock wave is parallel to the flow and does not turn the flow direction.

What changes occur in Mach number, pressure, and temperature when a supersonic flow passes through a Prandtl-Meyer expansion fan?

• AMach number decreases, pressure increases, and temperature increases.
• BMach number increases, pressure decreases, and temperature decreases.
• CMach number remains constant while pressure and temperature drop to zero.
• DMach number decreases, pressure decreases, and temperature increases.

Which non-dimensional parameter is primarily used to predict whether the boundary layer over a flat plate will transition from laminar to turbulent flow?

• AMach number
• BReynolds number
• CPrandtl number
• DFroude number

How do the skin friction drag and boundary layer thickness of a turbulent boundary layer compare to those of a laminar boundary layer at the same Reynolds number?

• ATurbulent boundary layers are thinner and have lower skin friction drag.
• BTurbulent boundary layers are thicker and have higher skin friction drag.
• CTurbulent boundary layers are thicker but have lower skin friction drag.
• DTurbulent boundary layers have identical thickness and drag characteristics.

An aircraft weighs 9,800 Newtons, has a wing area of 10 square meters, and a maximum lift coefficient (CLmax) of 1.2. If the density of air is 1.225 kg/m^3, what is the stall speed of the aircraft in steady level flight?

• AApproximately 36.5 m/s
• BApproximately 40.0 m/s
• CApproximately 81.6 m/s
• DApproximately 16.3 m/s

What is the physical cause of wingtip vortices, and what is their direction of rotation on left and right wings (viewed from behind the aircraft)?

• AVortices are caused by engine exhaust; they rotate clockwise on both wings.
• BVortices are caused by high-pressure air flowing from the lower surface to the upper surf…
• CVortices are caused by propeller slipstream; rotating counter-clockwise on both wings.
• DVortices are caused by high-pressure air flowing from the upper surface to the lower surf…

What is the mathematical criterion for an aircraft to possess static longitudinal stability?

• AThe slope of the pitching moment coefficient curve must be positive (dCm/dalpha > 0).
• BThe slope of the pitching moment coefficient curve must be negative (dCm/dalpha < 0).
• CThe pitching moment coefficient must be zero at all angles of attack.
• DThe lift curve slope must be negative (dCL/dalpha < 0).

How is the static margin of an aircraft defined, and what is its significance for longitudinal stability?

• AThe distance between the center of gravity and the aerodynamic center of the wing; it mus…
• BThe distance between the center of gravity (CG) and the aircraft neutral point (NP), expr…
• CThe distance between the leading edge of the wing and the CG; it must be minimized.
• DThe ratio of tail lift to wing lift; it must exceed 1.0 for stability.

Which of the following dynamic longitudinal stability modes is characterized by a long period, slow damping, and significant changes in altitude and airspeed?

• AShort period mode
• BPhugoid mode
• CDutch roll mode
• DSpiral mode

What coupled motion describes the lateral-directional instability known as 'Dutch Roll'?

• AA slow divergence where the bank angle increases without yaw.
• BA coupled rolling and yawing motion where the aircraft oscillates out of phase.
• CA longitudinal pitching oscillation that couples with throttle inputs.
• DA pure vertical pitching motion coupled with landing gear deployment.

In wind tunnel testing, what is the purpose of applying 'solid blockage' and 'wake blockage' corrections to the raw data?

• ATo account for the buoyancy force acting on the wind tunnel balance scale.
• BTo correct for the artificial acceleration of flow around the model caused by the physica…
• CTo prevent the tunnel wall boundary layers from turning laminar.
• DTo scale the model drag to match the full-scale Reynolds number.

Which thermodynamic cycle represents the ideal operating sequence for a four-stroke reciprocating aircraft engine?

• ABrayton cycle
• BOtto cycle
• CCarnot cycle
• DRankine cycle

What are the four consecutive thermodynamic processes that constitute the ideal Brayton cycle for gas turbines?

• AIsothermal compression, constant-pressure combustion, isothermal expansion, and constant-…
• BIsentropic compression, constant-pressure heat addition, isentropic expansion, and consta…
• CConstant-volume compression, isentropic combustion, constant-volume expansion, and isothe…
• DIsentropic compression, constant-volume heat addition, isentropic expansion, and constant…

How is the propulsive efficiency of an aircraft engine defined, and how does it relate to the exhaust velocity?

• AThe ratio of thermal energy input to thrust power; it increases as exhaust velocity incre…
• BThe ratio of useful thrust power to the rate of kinetic energy added to the fluid; it inc…
• CThe ratio of engine output shaft power to fuel energy; it is independent of exhaust veloc…
• DThe ratio of turbine power to compressor power; it decreases as exhaust velocity decrease…

What is the definition of the bypass ratio (BPR) in a turbofan engine, and what is its primary effect on engine efficiency?

• AThe ratio of fuel flow to air flow; a higher BPR increases thermal efficiency.
• BThe ratio of the mass flow rate of air bypassing the core to the mass flow rate of air en…
• CThe ratio of compressor air flow to turbine cooling air flow; a higher BPR reduces exhaus…
• DThe ratio of turbine stage count to compressor stage count; a higher BPR increases exhaus…

How does the Thrust Specific Fuel Consumption (TSFC) of a high-bypass turbofan compare to a pure turbojet, and why?

• ATSFC is higher for the turbofan because it bypasses useful air.
• BTSFC is lower for the turbofan because its higher propulsive efficiency reduces the fuel…
• CTSFC is identical because fuel burn depends only on combustor core size.
• DTSFC is higher for the turbofan because the fan adds significant mechanical friction.

In a reciprocating piston engine, how is Indicated Horsepower (IHP) related to Brake Horsepower (BHP) and Friction Horsepower (FHP)?

• AIHP = BHP / FHP
• BIHP = BHP + FHP
• CBHP = IHP + FHP
• DFHP = BHP + IHP

What is the effect of increasing altitude on the power output of a naturally aspirated reciprocating aircraft engine at constant RPM?

• APower increases because the exhaust backpressure is lower.
• BPower decreases because the lower air density reduces the mass of air drawn into the cyli…
• CPower remains constant because the fuel-to-air ratio is automatically adjusted.
• DPower increases because the temperature drop increases the density ratio.

Under what atmospheric and engine operating conditions is carburetor icing most likely to occur in a piston-engine aircraft?

• AVery dry air at temperatures below -20 degrees Celsius at full throttle.
• BHigh relative humidity at temperatures between -7 and 21 degrees Celsius at low throttle…
• CWarm, dry air at 35 degrees Celsius at cruise throttle.
• DExtreme freezing rain at any temperature with the carburetor heat turned on.

What is the primary difference in how superchargers and turbochargers are driven in aircraft reciprocating engines?

• ASuperchargers are driven by electric motors; turbochargers are driven directly by the cra…
• BSuperchargers are mechanically driven by the engine crankshaft; turbochargers are driven…
• CSuperchargers are driven by the hydraulic system; turbochargers are driven by ram air.
• DBoth systems are driven by the crankshaft, but turbochargers use a variable torque conver…

Which turbine blade cooling technique involves bleeding compressor air through small internal passages in the blade and venting it out through microscopic holes to create a thin, protective boundary layer of cooler air on the blade surface?

• AConvection cooling
• BFilm cooling
• CTranspiration cooling
• DImpingement cooling

What is the physical difference between a compressor stall and a compressor surge in a gas turbine engine?

• AA stall is a structural failure of the blades; a surge is an electrical failure of the en…
• BA stall is a local aerodynamic breakdown of flow over the compressor blades; a surge is a…
• CA stall involves fuel starvation; a surge involves excessive fuel flow.
• DA stall is a mechanical vibration of the shaft; a surge is an overspeed condition.

The advance ratio (J) of a propeller is defined in terms of true airspeed (V), rotational speed (n in rev/s), and propeller diameter (D). What is the formula for J, and how does it relate to propeller efficiency?

• AJ = n * D / V; efficiency increases linearly as J increases.
• BJ = V / (n * D); maximum propeller efficiency occurs at a specific optimum advance ratio…
• CJ = V * n * D; efficiency is inversely proportional to J.
• DJ = V^2 / (n * D); efficiency is constant for all values of J.

In a constant-speed propeller system, how does the governor adjust the blade pitch when the aircraft enters a descent and the engine begins to overspeed?

• AThe governor increases blade pitch to increase the load on the engine, slowing it back to…
• BThe governor decreases blade pitch to decrease the load on the engine, allowing it to spi…
• CThe governor shuts off fuel flow to the engine to slow it down.
• DThe governor disconnects the propeller from the engine crankshaft using a clutch.

What is the equivalent shaft horsepower (ESHP) of a turboprop engine defined as?

• AThe shaft horsepower delivered to the propeller plus the thrust horsepower produced by th…
• BThe shaft horsepower delivered to the propeller divided by the propeller efficiency.
• CThe total thrust produced by the engine exhaust alone, converted to horsepower.
• DThe shaft horsepower multiplied by the compressor pressure ratio.

Which type of gas turbine combustion chamber consists of a single continuous liner housed within an outer casing, surrounding the turbine shaft axis?

• ACan-type combustor
• BAnnular-type combustor
• CCan-annular combustor
• DRadial-flow combustor

Why does an afterburner increase the thrust of a turbojet or turbofan engine significantly, despite its very high fuel consumption?

• AIt increases the compressor pressure ratio by forcing air backwards.
• BIt injects fuel directly into the exhaust pipe where oxygen is still present, heating the…
• CIt cools the exhaust gas to increase its density and mass flow rate.
• DIt increases the mechanical efficiency of the turbine stages.

How is the specific impulse (Isp) of a rocket engine defined, and what does it measure?

• AThe ratio of thrust to the weight flow rate of propellant; it measures engine fuel effici…
• BThe ratio of chamber pressure to nozzle exit area; it measures engine structural strength.
• CThe total burn time of the rocket; it measures maximum payload capacity.
• DThe ratio of payload mass to structural mass; it measures structural efficiency.

What is the primary thermodynamic factor that limits the maximum allowable fuel-to-air ratio in a gas turbine combustion chamber?

• AThe structural temperature limit of the compressor blades.
• BThe maximum temperature that the turbine inlet guide vanes and rotor blades can withstand.
• CThe freezing point of aviation kerosene.
• DThe volumetric capacity of the exhaust tailpipe.

How do cascade-type thrust reversers in modern turbofan engines redirect airflow to decelerate the aircraft?

• AThey reverse the direction of rotation of the main fan spool.
• BThey deploy blocker doors to block the fan bypass duct and redirect the bypass air forwar…
• CThey inject water into the combustor to create drag-inducing steam.
• DThey rotate the entire engine 180 degrees on its mounts.

In gas turbine operations, what does the Engine Pressure Ratio (EPR) measure, and how is it used?

• AThe ratio of combustor pressure to compressor inlet pressure; it measures fuel flow rate.
• BThe ratio of total pressure at the turbine discharge to the total pressure at the compres…
• CThe ratio of oil pressure to fuel pressure; it measures bearing wear.
• DThe ratio of spool speed N1 to spool speed N2; it measures compressor stall margin.

On an aircraft structural V-n (Velocity-Load Factor) diagram, what is the physical meaning of the 'corner velocity' (also known as maneuvering speed)?

• AThe minimum speed at which the aircraft can land safely with full flaps.
• BThe intersection of the aerodynamic lift limit line and the structural limit load factor…
• CThe maximum speed at which the aircraft can fly in supersonic cruise.
• DThe speed at which the aircraft enters an uncontrollable spin.