QCAA Aerospace Systems flashcards
QCAA Aerospace Systems · Build recall with a focused review session.
33 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Load factor
- The ratio of lift to weight, n = L/W. In a level turn n = 1/cos(bank angle), so a 60-degree bank doubles the lift required and doubles the stall speed factor.
- Critical angle of attack
- The angle of attack at which airflow separates from the wing and lift reaches its maximum. Exceeding it causes a stall regardless of airspeed or attitude.
- Induced drag
- Drag created as a by-product of lift, caused by wingtip vortices and downwash. It decreases with higher airspeed and increases with higher lift coefficient and lower aspect ratio.
- Aspect ratio
- Wing span squared divided by wing area. Higher aspect ratio reduces induced drag, which is why gliders and long-range airliners use long, narrow wings.
- Bernoulli principle
- In steady streamline flow, an increase in fluid velocity is accompanied by a decrease in static pressure, provided no energy is added or removed from the flow.
- Newton's third law lift
- A wing deflects air downward, producing downwash. The equal and opposite reaction pushes the wing upward, contributing to total lift.
- Limit load
- The maximum load expected during service life. Structures must withstand limit load without permanent deformation, and ultimate load, usually 1.5 times limit, without failure.
- Young's modulus
- The ratio of tensile stress to tensile strain within the elastic region. A higher modulus means a stiffer material that deforms less under the same stress.
- Yield strength
- The stress at which a material begins to deform permanently. Below this value deformation is elastic and the material returns to its original shape when unloaded.
- Fatigue failure
- Failure from repeated cyclic stress below ultimate strength, initiating cracks that grow until the part fractures. Managed by safe-life replacement or fail-safe design.
- Static stability
- The tendency of an aircraft to return to equilibrium after a disturbance. Positive static stability means an initial restoring force; negative means the disturbance grows.
- Centre of pressure
- The point where the total aerodynamic force acts on a body. Its position relative to the centre of gravity determines the pitching moment on the aircraft.
- Brayton cycle
- The thermodynamic cycle of gas turbine engines: compression, constant-pressure heat addition, expansion and heat rejection. Higher pressure ratio raises thermal efficiency.
- Bypass ratio
- Bypass airflow divided by core airflow in a turbofan. High bypass ratios improve propulsive efficiency and reduce noise, suiting commercial transport aircraft.
- Specific fuel consumption
- Fuel flow per unit of thrust (TSFC) or per unit of power (PSFC). Lower values indicate a more fuel-efficient engine at a given operating condition.
- Rocket equation
- Delta-v equals specific impulse times gravitational acceleration times the natural log of the mass ratio. It gives the velocity change available from a rocket stage.
- Specific impulse
- Thrust divided by weight flow of propellant, measured in seconds. It indicates how efficiently a propulsion system uses propellant mass.
- Pascal's principle
- Pressure applied to a confined fluid is transmitted equally in all directions. Hydraulic systems use this to multiply force by using different piston areas.
- Pitot-static system
- A pressure system combining a forward-facing pitot tube and a static port. It supplies total and static pressure to airspeed, altitude and vertical speed instruments.
- Angle of attack
- The angle between the wing chord line and the relative airflow. Increasing it raises lift coefficient until the critical angle, beyond which the wing stalls.
- Turbofan engine
- A gas turbine in which a fan accelerates air both through the core and around it. The bypass air provides most of the thrust in modern airliners.
- Class G airspace
- Uncontrolled airspace where no ATC clearance is required. VFR flights must still meet visibility and cloud-clearance minima, and IFR separation is not provided.
- Hydraulic accumulator
- A pressure vessel storing fluid under gas pressure. It absorbs pressure surges, smooths pump demand and provides emergency pressure for limited operation.
- Redundancy in systems
- Duplication of critical components or channels so a single failure does not cause loss of function. Common in flight controls, hydraulics and electrical generation.
- Free-body diagram
- A diagram showing a single body isolated with all external forces drawn as labelled arrows from the body, used to apply Newton's laws.
- Gradient of a graph
- The slope of a line on a graph, equal to the rate of change of the vertical quantity with respect to the horizontal quantity, including its units.
- Area under a graph
- The region between a plotted line and the horizontal axis. It represents the product of the two quantities, such as distance from a speed-time graph.
- Explain command word
- An instruction requiring cause-and-effect reasoning that links a mechanism to an outcome, rather than a list of features or a simple description.
- Evaluate command word
- An instruction requiring a judgement supported by evidence, weighing strengths against limitations and reaching a justified conclusion against stated criteria.
- Significant figures
- The digits in a measurement that carry meaning about precision. Answers should be reported to the same precision as the least precise given value.
- Knot conversion
- One knot equals 0.514 metres per second, or one nautical mile per hour. Convert speeds to SI units before substituting into force or energy equations.
- Extended response structure
- A high-scoring answer states the relevant principle, applies it to the given system using supplied data, and identifies an assumption or limitation of the analysis.
- Multiple-choice elimination
- A technique of discarding options with incorrect units, impossible magnitudes or contradictions of the governing equation before comparing the remaining candidates.