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What is the lift equation, and what does it tell you operationally? start learning
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L = ½ρV²SCL. Lift depends on air density, speed squared, wing area and lift coefficient; if one changes, another must compensate to maintain the required lift.
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What is angle of attack (AoA), and why is it more fundamental than airspeed for stall awareness? start learning
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AoA is the angle between the wing chord and relative airflow. A wing stalls when critical AoA is exceeded; the corresponding airspeed varies with weight, load factor and configuration.
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How does CL normally change with AoA? start learning
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It increases approximately linearly with AoA until near CLmax; beyond critical AoA, flow separation causes lift to decrease.
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Can an aircraft stall at any airspeed or pitch attitude? start learning
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Yes. A stall is caused by exceeding critical AoA, not by a particular airspeed or nose attitude.
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What is the correct aerodynamic priority in stall recovery? start learning
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Reduce AoA below the critical value first; then restore the desired flight path while managing thrust and configuration.
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Why is adding thrust alone not a stall recovery? start learning
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Because the wing remains stalled until AoA is reduced below critical.
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How does stall speed vary with load factor? start learning
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How does stall speed vary with weight? start learning
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It varies approximately with the square root of the weight ratio.
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What happens aerodynamically in a coordinated level turn as bank angle increases? start learning
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Required lift and load factor increase, which increases AoA for a given speed and raises stall speed.
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What is the load factor in a coordinated level turn? start learning
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n = 1 / cos(bank angle); approximately 1.4 g at 45° and 2 g at 60°.
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What is an accelerated stall? start learning
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A stall occurring at a load factor greater than 1 g, so it occurs at a higher airspeed than the 1 g stall.
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How do speed and bank angle affect turn radius and turn rate? start learning
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More bank decreases radius and increases turn rate; more speed increases radius and decreases turn rate for the same bank.
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Why is a skidding turn near the stall particularly dangerous? start learning
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Yaw and asymmetric AoA can cause one wing to stall more deeply, promoting spin entry.
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What two aerodynamic conditions are required for a spin? start learning
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A stalled wing and sustained yaw.
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How do parasite and induced drag vary with speed? start learning
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Parasite drag rises roughly with V²; induced drag rises strongly as speed decreases because higher CL is required.
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Under the simple drag-polar model, when is total drag minimum? start learning
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Approximately when parasite drag equals induced drag.
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What does maximum L/D represent operationally? start learning
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Maximum aerodynamic efficiency and, in still air, the shallowest glide angle / greatest still-air glide distance per unit altitude.
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Does aircraft weight change maximum L/D? start learning
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Approximately no for a given configuration, but a heavier aircraft reaches the same L/D at a higher speed and higher sink rate.
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How does aspect ratio affect induced drag? start learning
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Higher aspect ratio reduces induced drag for a given lift.
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Why do wingtip vortices form? start learning
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High pressure below the wing flows around the tip toward lower pressure above, producing trailing vortices and induced drag.
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When are wake vortices generally strongest? start learning
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When the generating aircraft is heavy, slow and clean.
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What is the main aerodynamic effect of ground effect? start learning
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It reduces downwash and induced drag, improving lift-to-drag performance close to the surface.
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What are the main aerodynamic effects of trailing-edge flaps? start learning
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They increase camber and CLmax, reducing stall speed, but also increase drag.
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What are the main aerodynamic effects of leading-edge slats? start learning
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They delay upper-surface flow separation, increasing CLmax and usually increasing critical AoA.
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What is the aerodynamic purpose of spoilers? start learning
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To reduce lift and increase drag; on landing they also transfer aircraft weight onto the wheels and improve braking effectiveness.
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What is the difference between static and dynamic stability? start learning
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Static stability describes the initial response to a disturbance; dynamic stability describes how the resulting motion develops with time.
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How does CG position affect longitudinal stability and efficiency? start learning
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A forward CG generally increases stability but requires more tail force and trim drag; an aft CG reduces stability and trim drag but reduces recovery/control margins.
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Why can an excessively aft CG make stall recovery more difficult? start learning
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Natural nose-down stability and available nose-down control margin are reduced.
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What is the dihedral effect? start learning
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A sideslip generates a restoring rolling moment; wing dihedral and sweep both contribute to it.
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Why are swept-wing aircraft prone to Dutch roll? start learning
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Strong coupling between directional and lateral stability produces a combined yaw-and-roll oscillation.
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What is the purpose of a yaw damper? start learning
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To automatically suppress unwanted yaw oscillations, particularly Dutch roll.
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Why are transport-aircraft wings swept? start learning
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Primarily to delay compressibility effects and increase the Mach number at which significant high-speed effects occur.
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How does wing sweep delay compressibility effects? start learning
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It reduces the airflow component normal to the leading edge, reducing the effective Mach seen by the aerofoil section.
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What is critical Mach number? start learning
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The lowest aircraft Mach number at which local airflow somewhere on the aircraft first reaches Mach 1.
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Can local airflow be supersonic while the aircraft is still subsonic? start learning
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Yes. Local airflow accelerates over the wing and can exceed Mach 1 before aircraft Mach reaches 1.
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What happens across a normal shock wave? start learning
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Flow decelerates abruptly from supersonic to subsonic while static pressure and temperature rise and total pressure decreases.
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start learning
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The additional drag associated with compressibility and shock-wave formation.
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start learning
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A nose-down pitching tendency at high Mach caused by aft changes in aerodynamic pressure distribution and shock-related effects.
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What is high-speed buffet? start learning
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Buffeting caused by shock-induced flow separation as compressibility effects increase.
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start learning
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A high-altitude condition where the margins between low-speed buffet/stall and high-speed buffet/MMO become small.
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Why does manoeuvring reduce buffet margin at high altitude? start learning
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Increased load factor requires higher CL and AoA, moving the aircraft closer to the low-speed buffet boundary.
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Why can a heavier aircraft have a smaller high-altitude buffet margin? start learning
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More lift is required at the same flight condition, requiring higher CL and AoA.
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What is the basic aerodynamic condition for a steady climb? start learning
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Thrust exceeds drag; the excess thrust balances the component of weight along the climb path.
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What determines climb gradient versus rate of climb? start learning
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Climb gradient is primarily related to excess thrust; rate of climb is primarily related to excess power.
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In a steady climb, is lift exactly equal to weight? start learning
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Usually not; lift approximately balances the component of weight perpendicular to the flight path, so it is slightly less than weight for a conventional climb.
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What determines the best still-air glide angle? start learning
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How does higher weight affect best-glide performance? start learning
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The best-glide angle is essentially unchanged, but the corresponding speed and sink rate are higher.
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What is the region of reversed command? start learning
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The low-speed region where flying slower requires more thrust/power because induced drag rises rapidly.
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What is the key limitation of manoeuvring speed VA? start learning
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It is not a universal “safe speed”; its protection applies only under defined certification assumptions and does not protect against every control combination, gust or structural load.
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How does VA change with aircraft weight? start learning
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It decreases as aircraft weight decreases.
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What is the difference between pitch attitude and AoA? start learning
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Pitch attitude is measured relative to the horizon; AoA is measured relative to the local airflow.
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Why can AoA change significantly without a large pitch-attitude change? start learning
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Because the flight-path angle and relative airflow can change rapidly.
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What is the key aerodynamic principle in an upset with excessive AoA? start learning
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Reduce AoA first; attempting to recover the flight path by pulling can deepen or maintain the stall.
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