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Aerodynamics Final
| Question | Answer |
|---|---|
| Aerodynamics is the study of... | air in motion |
| Who was the first to achieve sustained, controlled and powered flight | wright bros |
| Did Bernoulli experiment in flight? | No |
| T/F: Man's first attempt at heavier than air flight was to create birdlike vehicles with wings that flapped | True |
| Glider and airplanes are... | heavier than air machiens |
| Sir George Cayley, Otto Lilenthal and Octave Chanute all had what in common? | They all experimented with gliders in the 1800's. |
| In which layer of the atmosphere do we live in? | Trophoshpere |
| The troposhpere extends from sea level to what what? | About 36,000 ft. |
| What layer of the atmosphere is directly above the tropopause? | stratosphere |
| Pressure Equation... | Force/Area |
| ISA is... | 1013 millibar or 29.92" mercury |
| Air pressure at 30,000 feet is (more or less) than air at sea level? | less |
| Density Equation... | Mass/Volume |
| The symbol for air density is... | p |
| The ISA value for sea level density is... | 1.2254 kg/m3 |
| Does the density of water change with depth? | No |
| T/F: The density of air changes with increasing altitude because air is compressable | True |
| Air density at 10,000 feet altitude is more or less dense than at sea level | Less |
| Which atmospheric property decreases fastest as you increase altitude from sea level | pressure |
| The ISA sea level temperature is... | 59F or 15.2C |
| The temperature of air decreasees on average by how much per 1000 ft.? | 2 degrees celcius |
| What conditions provide low density air (thin air) | hot, high altitude, humidity |
| helium filled balloon is able to float in air because... | there is slightly more pressure on it's lower surface than it's upper surface |
| static air pressure is caused by the weight of air above us. the formula is... | P=pgh |
| The chordline of an aerofoil is | a straight line joining the leading edge and the trailing edge |
| the mean camber line of an airfoil is | a line from the leading edge to the trailing edge equidistant from the upper and lower surfaces |
| a cambered airfoil set at 0 degrees AoA in an air stream will produce | lift and drag |
| the angle between the chord line and the relative wind/airflow is called what | angle of attack |
| 1/2 PV^2 is the formula for what? | Dynamic pressure |
| The thickness: chord ratio of an airfoil: | the ratio of the maximum thickness of an airfoil section to it's chord |
| if the angle of attack is increased slightly, the center of pressure will move where? | slightly forward. |
| a symmetrical airfoil set at zero degrees angle of incidence will produce how much lift in level flight | zero lift |
| the air on top of a cambered airfoil producing lift will: | increase velocity, and decrease static pressure |
| aspect ratio is what? | the ratio of the wingspan to the mean chord |
| the density of a gas can be expressed as... | mass/volume |
| T/F: The velocity of air increases and the static pressure decreases on the TOP of a cambered airfoil | True |
| The critical angle of a given aircraft is dependent on what | design of the wing, camber, etc. |
| T/F: Will exceeding the critical angle of attack produce a stall? | Yes |
| Describe what occurs in a stall | The airflow over the top surface of the wing seperates which results in a large increase in drag and a large loss in lift |
| if an aircraft's wings are slightly angled upward it is called what | dihedral |
| T/f: a high aspect ration wing will have a long span and a short chord | True |
| T/F: the wingspan is the distance from wing tip to wing tip | True |
| T/F: a wing is tapered the tip chord is less than the root chord | True |
| What is the approximate stall angle of a training aircraft | 18 degrees |
| What is the aspect ratio of a wing that has a mean chord of 6m and a wingspan of 30m | 5 |
| T/F: Span squared/Area is another way of calculating aspect ration | True |
| T/F: an airfoil will produce a downward force in a negative angle of attack | True |
| To maintain level flight at a steady airspeed what must thrust and drag be? | Equal |
| where is the stall warning vane located on a wing? | just below the leading edge |
| at psitive angles of attack, a wing produces the most lift when? | just before the stall |
| What part of the wing produces the most lift? | upper surface |
| What is the lift, drag, weight and thrust relationship in equal level flight? | Thrust=drag and lift=weight |
| T/F: weight acts perpendicular to relative air flow | True |
| A flap that moves back, increasing wing area and camber is called what | fowler flap |
| What is the center of pressure | where the lift acts on a wing |
| What does the S represent in the lift equation | wing area |
| T/F: Bernoulli's thory states that when dynamic pressure increases, static pressure decreases. | True |
| What is an approximate angle of attack for a training aircraft to produce the most lift for the least drag | about +3 degrees |
| Washout of a wing is what? | a decrease in angle of incidence from root to tip |
| What is the purpose of streamlining? | To reduce pressure or wake drag |
| Drag is the force that resists what? | Thrust |
| At high speed the drag on an aircraft is primarily what? (parasitic or induced) | parasitic |
| the speed of air at the surface of the wing in boundary layer is what? | zero |
| What is the best plan shape for a minimum drag wing? | Elliptical |
| What are the two types of flow associated with the boundary layer? | Turbulant and laminar |
| As speed increases, what happens to parasitic drag? | It increases as well |
| What is interference drag? | the additional drag resulting from the intersection of two parts of the airplane |
| What is installed to counteract interference drag? | Fillets |
| An antenna of .05 sq. ft. of a cross sectional area (S) produces 1 pound of drag in an airflow with a dynamic pressure (1/2pv^2) of 25 lbs/sq. ft. What is it's drag coefficient? | .8 |
| When gear is retracted, does total drag increase or deacrease? | Increase |
| When does the minimum total drag of an aircraft occur? | At the speed where parasite drag and lift induced drag are equal |
| T/F: lift induced drag would be associated with increased weight | true |
| what is the boundary layer of a body in a moving airstream | a thin later of air over the surface in which the air is slowed by the effects of friction |
| skin friction drag resulting from a laminar boundary layer will be more or less than from a turbulant layer? | less |
| A landing gear leg has a drag of 30 lbs at 100kts, it's drag at 200 kts would be what? | 120 lbs |
| if speed is decreased from 300 kts to 150 kts, the pressure or wake drag due to shape will be what? | a quarter |
| Will the drag of an aircraft increase or decrease with an incrase in air density? | Increase |
| When does floating on landing due to ground effect most likely occur? | when the distance above the surface is less than the wingspan of the aircraft |
| what is the cause of hazardous wake turbulance in large aircraft? | wingtip vortices |
| what will frost/ice do to the drag and lift of an aircraft? | increase drag and decrease lift |
| what phenomena causes lift induced drag? | wing tip vortices |
| what effect on lift induced drag does the ground effect have? | it decreases |
| T/F: When the undercarriage is lowered on an aircraft, the nose will pitch down and form drag will increase? | True |
| the point where the boundary layer changes from laminar flow to turbulant flow is called what? | transition point |
| laminar flow has more or less friction than turbulant flow? | less |
| Does a high aspect ratio wing increase or decrease lift induced drag? | decrease |
| In straight and level flight, how does parasite drag vary with airspeed? | V squared (directly square with the velocity) |
| Does the right wing vortice rotate clockwise or counterclockwise? | Right rotates counter clockwise and left rotates clockwise |
| At low speed, is the drag of an aircraft mostly parasitic or lift induced? | lift induced |
| What is the adverse pressure gradient? | the pressure gradient on the rear side of a shape where the air is flowing from low static pressure to high static pressure |
| what is the separation point? | the point where the air stops sticking to the shape of an object |
| What is downwash? | the downward deflection of the airflow behind a wing |
| if the weight of an aircraft is increased, for a constant speed, what will happen to profile and induced drag? | both will increase |
| What is the purpose of vortex generators? | to delay stall by reducing boundary layer seperation |
| T/F: Static pressure acts in all directions | TRUE |
| What effect on induced drag does entering the ground effect have? | lowers it |
| Does air flow from bottom to top or top to bottom in wing tip vortices? | bottom to top, around the wingtip |
| what is the approximate best angle of attack for a prop blade to the airflow passing? | 4 degrees |
| what can the pilot control in the cockpit to vary engine power? | use the throttle to control fuel flow and engine RPM |
| T/F: a prop blade slips through the air unlike a woodscre or corkscrew and so it can not be 100% efficient | TRUE |
| the pitch of a prop blade that produces the most efficient for a given speed is called what? | optimum angle of attack |
| the relative wind acting on a prop is the result of which two velocities | props rotational speed and aircraft's forward speed |
| does a prop spin faster at the base or the tip | the tip |
| in order to maintain a relatively constant angle of attack, props are manufactured with what? | blade twist |
| T/F: for the same amount of thrust produced, a prop accelerates a large mass of air with a relatively small acceleration where as a jet accelerates a small mass of air with a very large acceleration | true |
| Why is trying to increase the power an aircraft with a bigger engine difficult? | because parasite drag will increase and weight induced drag will increase as well |
| Newton's second law | Force=Mass X acceleration |
| in a variable speed prop, as airspeed increases, what must be done to the prop to maintain the most efficient AoA | the pitch must increase |
| In the event of an engine failure (in multi engine aircraft) what must be done to the prop blades in order to reduce drag | They must be feathered |
| Between which two strokes of a four stroke cycle does the spark occur? | Compression and power |
| What was the reason for early use of radial engines | more cylinders could be mounted and better cooling |
| what is the main factor that limits the diamter of a propeller blade? | the speed of the tip blade relative to the speed of sound |
| what is bypass air? | air that doesn't pass through the core of a jet engine and get burnt with fuel |
| How are a turbofan and a turbojet engine different? | in a turbojet, all of the air flows through the compressor of the engine where as some of the airflow with a turbofan engine flows around the outside of the core |
| what are the 4 stages of the ICE | intake, compression, power, exhaust |
| What is the most fuel efficient way of producing thrust, regardless of speed? | piston engine and prop |
| What is the greatest force on a prop? | centrifugal |
| what does a reaction engine do? | pushes a mass of air in the opposite direction to the aircraft |
| Newton's 3rd law states... | for every action there is an equal and opposite reaction |
| propellor twist is called... | wash out |
| Is a fixed pitch prop efficient at one speed or several? | One speed and RPM |
| the acronym PLANN or PLANK (same thing) is used for calculating what | power available from an internal combustino engine |
| What piston arrangement do most modern aircraft engine utilize? | horizontally opposed |
| what drives the compressor in a turbo jet or turbo fan | the turbine |
| Are the four forces in balance during ground roll on the runway? | No |
| the difference in power between power available and power required is called what? | excess power |
| which direction does an aircraft yaw if it loses an engine | in the direction of the dead engine |
| where on the power curve is the best glide ratio foudn | at the point of minimum drag |
| with respect to velocity, what is required in order to generate enough lift for takeoff | acceleration |
| during take off ground roll, what is the drag and thrust relationship | drag is less than thrust |
| during take off ground roll, what is the lift and weight relationship? | lift is less than weight |
| the drag curve, when applied to a piston engine aircraft is recalculated and called what? | power required curve |
| T/F: flying at a higher velocity than where the power required curve and the power available curve cross would produce a descent | True |
| What is Vx? | The best angle of climb speed, and the most altitude that can be obtained over a given amount of distance |
| Why is the power available curve not straight? | prop efficiency changes depending on air speed |
| Does airport elevation affect take off distance? | Yes |
| will best range airspeed with a tailwind be higher or lower than with a headwind | lower |
| when the power available and required curves are touching, straight and level flight is maintained but there is no climb capability. What is this spot called. | The absolute ceiling |
| Maxium range airspeed will produce what effects? | max distance for a given amount of fuel |
| at airspeeds slower than V (min power) (minimum power speed) results in... | max endurance, minimum sink rate, most time aloft |
| Is Vx less than Vy? | Yes it is |
| As aircraft weight increases, does power required increase or decrease? | increase |
| as altitude increases, does power available increase or decrease? | decrease |
| as drag increases, does power required increase or decrease? | increase |
Created by:
r5cross