Free EASA Module 8 Exam Flashcards

15°C (288.15 K) and 1013.25 hPa. Every atmospheric calculation in Module 8 starts from this datum before applying the lapse rate.

1.98°C per 1,000 ft (roughly 2°C/1,000 ft). Temperature falls steadily with altitude until the tropopause, where it stops changing.

36,090 ft. Above this height, temperature stays constant at -56.5°C - the lapse rate stops in the layer ISA models above the troposphere.

Pressure decreases exponentially (not in a straight line) with altitude - fastest near sea level and more slowly higher up - while temperature falls linearly to the tropopause.

Pressure altitude corrected for non-standard temperature. On a hot day the air is less dense than ISA predicts for that pressure altitude, so density altitude is higher than pressure altitude and aircraft/engine performance suffers.

Humid air is less dense than dry air at the same temperature and pressure, because water vapor molecules displace heavier nitrogen and oxygen molecules. Less dense air means less lift and less engine power for a given airspeed.

The temperature at which air becomes saturated with water vapor and condensation begins. Comparing dew point to actual air temperature gives relative humidity - the ratio of actual to maximum possible water vapor content.

A thin layer of air next to a surface where viscosity slows the airflow relative to the free stream - velocity ranges from zero at the surface (the no-slip condition) up to full free-stream speed at the layer's outer edge.

Laminar flow is smooth with lower skin friction but separates earlier. Turbulent flow has higher skin friction but mixes in energy from outside the layer, so it resists separation longer.

An adverse pressure gradient - air moving into a region of rising pressure loses momentum until it stops and reverses, separating from the surface. This is the root cause of an aerodynamic stall.

The chord line runs straight from the leading edge to the trailing edge. Camber is the curvature of the mean line (midway between the upper and lower surfaces) relative to the chord line - more camber generally raises lift at a given angle of attack.

Wingspan squared divided by wing area (span² / area). A high-aspect-ratio wing (long and narrow, like a glider's) is more aerodynamically efficient, with lower induced drag, than a low-aspect-ratio wing (short and wide, like a fighter's).

Washout twists the wing so the tip sits at a lower angle of incidence than the root. The root then stalls first, keeping the ailerons effective and giving the pilot a stall warning before the whole wing stops flying.

Free stream is the undisturbed air ahead of the aircraft, unaffected by it. Relative airflow is airflow direction relative to the aircraft or aerofoil - it runs parallel to, and opposite, the flight path.

Spanwise flow at the wingtip, caused by higher-pressure air beneath the wing spilling around the tip toward the lower pressure above, rolling into a vortex. They are strongest for a slow, heavy aircraft in a clean configuration.

The point on an aerofoil, usually near the leading edge, where local airflow velocity is zero and static pressure is at its maximum - the air has been brought fully to rest before splitting to flow over and under the surface.

As the velocity of a fluid increases, its static pressure decreases (and vice versa), provided total energy is conserved. This is the basic physical principle behind the pressure differences that develop over an aerofoil.

The pressure due to a moving airstream: q = 1/2 rho V squared. Added to static pressure it gives total pressure, and it is the term that appears directly in both the lift and drag equations.

As the duct narrows, velocity increases and static pressure decreases - the venturi effect, a direct application of Bernoulli's principle used to explain accelerated airflow over the cambered upper surface of an aerofoil.

L = CL x 1/2 rho V squared x S, where CL is the lift coefficient, rho is air density, V is true airspeed, and S is wing area. Lift is directly proportional to density, wing area, and CL, but proportional to the SQUARE of airspeed.

Lift increases by a factor of four, because lift varies with velocity squared in the lift equation - small speed changes have a large effect on the lift (and drag) produced.

Lift is directly proportional to air density - less dense air (hot day, high altitude, humid air) produces less lift for the same true airspeed and angle of attack, so a higher true airspeed is needed to generate the same lift.

The maximum value of the lift coefficient, reached just before the critical angle of attack is exceeded. Beyond CLmax, further increases in angle of attack cause lift to fall away sharply as the wing stalls.

The angle between an aerofoil's chord line and the relative airflow, not the aircraft's longitudinal axis. It changes continuously in flight as the pilot pitches and as airspeed changes.

Angle of incidence is the fixed rigging angle between the chord line and the aircraft's longitudinal axis, set during manufacture and unchanged in flight. Angle of attack is variable and measured against the relative airflow instead.

Approximately 25% of the chord back from the leading edge (the quarter-chord point). The pitching moment about this point stays essentially constant as angle of attack changes, unlike the centre of pressure, which moves.

Induced drag is a by-product of generating lift, caused by wingtip vortices and the resulting downwash. It is greatest at low speed and high angle of attack, such as climb or landing approach, and falls as speed increases.

It decreases - less angle of attack is needed to produce the required lift at higher speed, so vortex strength and induced drag both fall. This is the opposite trend to parasite drag.

Drag not directly related to producing lift: form (pressure) drag, skin-friction drag, and interference drag between components. It exists even at zero lift and rises with speed.

It rises, approximately with the square of airspeed - doubling speed roughly quadruples parasite drag. This is the opposite trend to induced drag, which falls as speed rises.

The parasite drag generated specifically by a wing section - its form drag plus skin-friction drag - as distinct from the parasite drag produced by the fuselage, tail, and other components.

Total drag is minimum where induced drag equals parasite drag. This condition gives the best (maximum) lift-to-drag ratio, and therefore the best glide range or most efficient cruise speed.

It plots lift coefficient (CL) against drag coefficient (CD). The point of maximum lift-to-drag ratio, the most efficient angle of attack, is found where a line from the origin is tangent to the curve.

The ratio of the aircraft's true airspeed to the local speed of sound. Mach 1.0 means the aircraft is traveling exactly at the speed of sound for the surrounding conditions.

The aircraft's flight Mach number at which airflow over part of the airframe, usually the accelerated flow over the wing's upper surface, first reaches Mach 1.0, even though the aircraft itself still flies below the speed of sound. Beyond Mcrit, shock waves and extra compressibility drag appear.

Lift, weight, thrust, and drag. In steady, straight-and-level, unaccelerated flight, lift equals weight and thrust equals drag.

A component of weight acting along the descending flight path balances drag, while the component of weight perpendicular to the flight path balances lift - this is how an unpowered aircraft flies steadily downhill.

The aircraft travels 10 feet forward for every 1 foot of altitude lost, with no wind. A higher glide ratio means better unpowered range for the same height loss.

The ratio of lift to weight (the 'g' loading on the aircraft and its structure). In level, unaccelerated flight, load factor is 1g; in a turn or pull-up it rises above 1g because lift must exceed weight to also supply centripetal force.

Stall speed rises with the square root of load factor, because more lift is needed to support the increased apparent weight. A 2g turn raises stall speed to about 1.41 times (the square root of 2) the normal 1g value.

The structural and aerodynamic limits of an aircraft, plotting load factor (n) against airspeed (V) - the maximum positive and negative g the structure can withstand, and the speed at which the wing stalls before those structural limits are reached.

Exceeding the critical angle of attack, which causes the boundary layer to separate from the upper surface and lift to collapse. Stall is an angle-of-attack event, not simply a low-airspeed event.

Flaps increase camber, raising CLmax so the wing produces the needed lift at a lower angle of attack and speed. Slats and slots re-energize the boundary layer over the upper surface with high-energy air, delaying separation to a higher angle of attack.

Autorotation following a stall in which one wing is more deeply stalled than the other, producing less lift and more drag on that side, so the aircraft yaws and rolls continuously about a vertical axis while descending.

The tailplane (horizontal stabilizer), acting about the lateral axis. If a gust pitches the nose up, an increased tailplane download restores the aircraft toward its trimmed attitude.

Dihedral - the upward angle of the wings from root to tip - generates a restoring rolling moment during a sideslip. Wing sweepback adds a similar dihedral-like effect, boosting lateral stability further.

The vertical fin, acting about the normal (vertical) axis - it 'weathercocks' the nose back into the relative airflow if the aircraft yaws off its flight path.

Static stability describes only the aircraft's initial tendency after a disturbance - whether it first moves back toward equilibrium. Dynamic stability describes how that motion develops over time, whether the resulting oscillation damps out, stays constant, or grows.

Oscillations that increase in amplitude over time instead of damping out. An aircraft can be statically stable, with an initial tendency to return, yet dynamically unstable if the resulting oscillation grows rather than decays.

An aft CG shortens the tailplane's effective moment arm and weakens longitudinal (pitch) stability, potentially reversing it beyond the aft limit. Dutch roll is a combined yaw-roll oscillation, seen especially on swept-wing aircraft that have strong lateral stability but weaker directional stability.