Aerodynamics
Describe Bernoulli’s principle and state which aerodynamic phenomenon it primarily explains.
Bernoulli: faster fluid velocity corresponds to lower static pressure; primarily explains pressure/velocity relations producing lift on an airfoil.
Name the four forces of flight.
Lift, Drag, Thrust, Weight.
Which control surface primarily rotates the aircraft about the longitudinal (roll) axis?
Ailerons.
What does F = ma (Newton’s 2nd Law) relate to in propulsion context (name the terms)?
F = ma: Force equals mass times acceleration (force, mass, acceleration).
Define payload in terms of aircraft weight components.
Payload: passengers, cargo, baggage (not fuel/oil unless specified by definition variant).
Define camber and explain its effect on lift production.
Camber: curvature of an airfoil’s mean line; increases camber generally increases lift coefficient at a given AoA.
Which parts belong to the airframe (select three) and explain why the engine is not considered an airframe component.
Airframe examples: Landing gear, fuselage, wings, stabilizers (engine not airframe because it’s the powerplant).
Define positive, neutral, and negative static stability and give a flight example where negative stability is beneficial.
Positive: returns to equilibrium; Neutral: remains displaced; Negative: diverges. Negative stability is useful for highly maneuverable stunt aircraft.
Name the four main sections of a turbine engine and put them in combustion process order.
1 Compressor, 2 Combustion chamber, 3 Turbine, 4 Exhaust.
List at least three performance effects of operating an aircraft overweight.
Increased tire wear; higher takeoff speed; longer runway; reduced range; lower max altitude.
Explain the Coanda effect and give one example of how it applies to an aircraft surface.
Coanda effect: tendency of a fluid jet to follow a nearby curved surface; example — airflow following the wing's upper surface, aiding lift.
List the main components of a basic hydraulic system and briefly describe the role of each component.
Pump (pressurizes/moves fluid), Reservoir (stores fluid), Actuator (converts fluid pressure to mechanical motion), Selector/Control valve (routes fluid), Flow divider (distributes flow).
Explain how center of gravity (CG) position relative to center of pressure affects stall characteristics and stability.
Forward CG increases longitudinal stability and improves stall recovery (nose-down tendency), aft CG reduces stability and can worsen stall characteristics.
Distinguish turbojet, turbofan, and turboshaft by their outputs and typical applications.
Turbojet: thrust from jet exhaust (high-speed jets); Turbofan: bypass fan + core (airliners); Turboshaft: extracts shaft power to drive rotors (helicopters).
Explain how increased load (keeping thrust constant) affects takeoff speed and runway distance required. Include basic reasoning using forces or energy.
More weight → higher required lift → higher AoA or speed → greater induced drag → higher takeoff speed → more energy needed → longer ground roll.
As angle of attack increases, describe the lift behavior up to and beyond the critical angle of attack; include cause for the sudden change.
Lift increases with AoA until the critical AoA; beyond that, boundary layer separation grows, and lift rapidly decreases (stall).
Explain cabin pressurization source in turbine aircraft and define “bleed air.”
Bleed air: high-pressure air tapped from compressor stages used to pressurize cabin.
For a stunt plane designed to maximize maneuverability, which stability type would you design toward and why? Include trade-offs.
Negative (or reduced positive) stability for maneuverability; trade-off: harder to trim and less forgiving, higher pilot workload.
Explain why the tip of a propeller blade travels faster than the root and one aerodynamic consequence of high tip speed.
Tip linear speed = rotational speed × radius — larger radius at tip gives higher linear speed; consequence: transonic tip effects, noise, compressibility losses.
In a steep banked turn that maintains level flight, explain how the effective weight (load factor) changes and the implications for structural limits. Provide the formula for load factor in a banked turn.
Load factor n = 1 / cos(bank angle); in a steep bank load factor increases, so effective weight increases = weight × n; structural and stall margin considerations.
Identify and contrast parasitic drag, induced drag, and interference drag; give one design or operational strategy to reduce each.
Parasitic drag: from form/skin friction/interference; reduce with smooth surfaces, fairings. Induced drag: rearward component of lift; reduce with higher aspect ratio or winglets. Interference drag: from intersecting components; reduce with fillets/fairings.
Describe the function of fuel pumps and explain why some aircraft may not require fuel pumps.
Fuel pump: moves fuel from tanks to engine under pressure; some small gravity-fed systems may not have pumps depending on tank placement and engine type.
Match these surfaces to their primary axes of rotation: aileron, elevator, rudder.
Aileron → roll/longitudinal; Elevator → pitch/lateral; Rudder → yaw/vertical.
Compare gyroplane and helicopter main-rotor power behavior during flight; explain how that affects autorotation capability.
Helicopter: engine drives rotor in flight; Gyroplane: engine spins rotor for startup only, rotor autorotates in flight driven by aerodynamic forces — gyroplanes rely on autorotation inherently.
Given a hypothetical simple scenario: an aircraft requires 1,200 m runway under standard weight. Describe qualitatively how required runway changes if weight increases by 10% and explain the aerodynamic/energy reasons.
Required runway increases (not linearly); heavier mass requires greater lift and kinetic energy for takeoff, so more speed and distance are needed — runway increases due to higher acceleration energy demands and higher induced drag.