Aerodynamics Flashcards
(174 cards)
1
Q
Define chord line…
A
The straight line connecting the leading and trailing edge of an airfoil.
2
Q
Vmu
A
Minimum Unstick Speed, slower speed to get airborne, etc.
3
Q
What causes the phenomena referred to as “much tuck”?
A
The movement of the shock wave aft forces the wing’s center of pressure aft, causing the aircraft a tendency to pitch nose down without enough tail down force.
4
Q
What is the effect of winglets?
A
Winglets are method of creating an artificial aspect ratio. Wingtip vortices increase drag by downwash induction. Winglets are small wings places at an AOA with respect to the resultant flow of the free airstream and the vortex flow. The lift vector of the winglet points in the forward direction. The forward component of this vector therefore gives a force in the direction of flight that is actually negative drag or thrust.
5
Q
What is the Subsonic regime?
A
Aircraft mach speed where all the local air flow is less than the speed of sound. The mach range is below .75 Mach.
6
Q
What does the term “power” imply?
A
Power implies work rate.
7
Q
What is P-factor?
A
P-factor is the yaw effect that is experienced on propellor driven airplanes. At low airspeeds and high angles of attack, the descending blade produces more thrust than the ascending blade
8
Q
How does the wake turbulence vortex circulate around each wingtip?
A
Outward, upward and around each tip. Since the pressure differential is caused by a lower pressure above the wing and a higher pressure below the wing, the air from the bottom moves out, up and around.
9
Q
How does frost affect stall speed?
A
It increases stall speed and lowers the angle of attack at which the aircraft will stall. Ice, frost and snow.
10
Q
What three conditions are required to cause dynamic hydroplaning?
A
The conditions required to cause dynamic hydroplaning are high speed, standing water and poor surface macro texture.
11
Q
What is viscous hydroplaning?
A
Viscous hydroplaning occurs when there is a thin film of water covering a smooth surface such as a painted or rubber coated portion of the runway. Viscous hydroplaning can occur at much lower speeds than dynamic hydroplaning.
12
Q
You are on a heading of 180 @ 20NM. You want to be at a heading of 270@ 10NM. The winds are 240@30 kts. What is your heading to the fix and what is your timing outbound?
A
2 formulas to accurately determine this. The first is the pythagorean theorem, or a^2 + b^2 = c^2. Using this you determine the heading to fly is 333°, to get 333°. With the angle now known, using an E6B to convert for Wind Correction Angle.
13
Q
How can turbulent air cause an increase in the stall speed of an airplane?
A
When the aircraft is flying at a high speed with the wings at a low angle of attack, a sudden current of air moving upward changes the relative wind direction as it meets the airfoil. This increases the angle of attack.
14
Q
Why is humid air worse for performance than dry air?
A
Water vapor is lighter than air; consequently, moist air is lighter than dry air. Therefore, as the water content of the air increases, the air becomes less dense, increasing density altitude and decreasing performance.
15
Q
How does a yaw damper work?
A
By deflecting the rudder slightly in flight as needed to control yawing in turbulence and to eliminate the coupled roll/yaw dynamic condition known as Dutch roll. It also works automatically to keep all turns properly coordinated between the roll and yaw modes.
16
Q
What are the pros and cons of a swept wing?
A
Pro : Only a component of the forward velocity will hit the wing chordwise. This allows the airplane to fly at a higher Mach number. Con: The wing tips have a tendency to stall first. To counteract this, the outer portion of the wing is designed with a smaller angle of attach than the thicker inner portion near the root. There is also a predisposition towards dutch roll, which is when an aircraft tends to roll whenever it yaws.
17
Q
Which laws relate to the development of thrust in any power-plant?
A
Newton’s laws of motion. More specifically, the second law; a body of mass “m” subject to a net force “F” undergoes an acceleration “a” that has the same direction as the force and a magnitude that is directly proportional to the force and inversely proportional to the mass, i.e., F=ma. The third law; for every action there is an equal and opposite action.
18
Q
Why does an aircraft lose speed in a turn?
A
An increase in AOA is required to hold an aircraft at a steady altitude (due to a loss in the vertical component of lift). Since the AOA is increased, there is a corresponding increase in induced drag. This causes a loss of airspeed in proportion to the angle of bank.
19
Q
Vr
A
Rotation Speed
20
Q
V1
A
Decision Speed
21
Q
How does Vmc change with altitude?
A
At sea level Vmc increases. At high altitudes Vmc decreases. Remember, parameters which are good for Vmc are not necessarily good for engine performance.
22
Q
If the left engine is inoperative and the runway choices are 18/36 and 12/30 and the winds are 210 at 30 knots, what runway should you use?
A
A crosswind coming on the side of the operating engine is most favorable; in the air, it requires less rudder to keep the aircraft aligned with the runway (‘into’ the wind counteracts weathervane). Therefore, with the winds out of 210, runway 18 would be the best choice for the above scenario as it keeps the wind off the right side of the aircraft and thus, into the good engine.
23
Q
What factors affect V1?
A
V1 is calculated for gross weight, flap setting, pressure altitude and temperature. Runway contaminates, inoperative anti-skid or anything that reduces stopping performance will also lower V1 as an abort would have to occur at a lower speed.
24
Q
As a parcel of air rises, what is the affect on its Pressure? Density? Temperature?
A
When a parcel of air is forced to rise it expands because its pressure decreases. As pressure decreases so, too, does density. The temperature decreases with altitude for this parcel of air.
25
Define chord…
This is the precise distance of the width of the wing from the leading to the trailing edge along the chord line.
26
What is negative static stability?
When an aircraft continues to diverge from an equilibrium after it has been disturbed about one of its axis.
27
They decide to move the cargo more aft of the original position. What does this do?
Yoke pressure during rotation decreases and takeoff distance decreases.
28
With regard to the jet airplane, what two values are plotted on a thrust curve chart?
Thrust available (T) versus thrust required, or drag (D). for a given speed, altitude and configuration. Generally, the jet airplane will require consideration of the thrust required and the propeller airplane will require consideration of the power required.
29
What is the difference between thrust and power?
Thrust is ‘force’. Force is what accelerates an object to either change its speed or its direction (or both). The amount of work you do (energy you use) in a given period of time, is Power. Thrust is what pulls or pushes the airplane through the air, power is what produces the thrust.
30
What affect does altitude have on mach number?
Mach number is the ration of TAS to the speed of sound. The speed of sound in the atmosphere varies only with temperature. As the temperature increases, so too does the speed of sound, and vice versa. Assuming a climb to altitude is achieved at a constant TAS, mach will increase with altitude
31
V2
Best Climb Gradient
32
What is the mean chamber line?
It is the location, or the set of points forming a curve, halfway between the upper and lower surfaces as measured perpendicular to the mean camber line itself.
33
Can you name 3 components of parasitic drag?
Form drag, skin friction and interference
34
Is the stall speed for an aircraft the same at different altitudes?
The stalling speed of a particular aircraft is not a fixed value for all flight situations, but a given aircraft always stalls at the same AOA regardless of airspeed, weight, load factor, or density altitude.
35
What is Air Density?
The air’s thickness determined by pressure, temperature and humidity.
36
What sequence of events would stop a turbine aircraft the quickest?
A firm touchdown at the target touchdown point, followed by the deployment of ground spoilers, the timely selection of thrust reverse (if installed), and the smooth application of maximum braking will result in the shortest landing distance ground roll, particularly on wet or contaminated runway surfaces.
37
How does an aircraft stall?
An aircraft stall results from a rapid decrease in lift caused by the separation of airflow from the wings surface brought on by exceeding the critical AOA
38
What is the definition of V2?
Takeoff Safety Speed. V2 ensures that the airplane can maintain an acceptable climb gradient with the critical engine inoperative.
39
Why does a tailwind increase takeoff roll?
The effect of a tailwind is to require the airplane to achieve a greater ground speed to attain the lift-off speed. A tailwind which is 10 percent of the takeoff airspeed will increase the takeoff distance approximately 21 percent.
40
You are flying at 250 KIAS in 1G flight. You nose the aircraft over to 0G flight, which of the following is true? A.) Induced drag is decreased B.) Parasite drag is decreased C.) Both are decreased D.) Total drag is zero
Drag caused by the development of lift is induced drag, if the aircraft is in a zero G condition lift must be equal to zero (Load = Lift/Weight). If load = 0 and weight is unchanged, lift must equal 0, therefore induced drag is decreased. A wing surface, even at zero lift, will have “profile” drag due to skin friction and form.
41
What effect does CG have on range and stability?
With an aft CG, an airplane will be less stable but have an increased range (due to slightly higher cruise speed).
42
With an inoperative engine, what technique should a pilot use to choose the most suitable runway?
A crosswind coming on the operating engine side is most favorable; on the ground it lowers the minimum control speed; in the air. it requires less rudder to keep the aircraft aligned with the runway (‘into’ the wind counteracts weathervane). Counteracting the yaw of the dead engine requires some amount of rudder, a crosswind on top of the asymmetrical thrust lowers the remaining available rudder authority for excess crosswind.
43
You are descending through moderate icing conditions, and your pitot-static system ices up. What does your airspeed indicator show?
A decrease in airspeed.
44
How does center of gravity affect range and stability?
An aft CG will be less stable and will cruise faster for a given power setting, thus increasing the range. A forward CG will be more stable in pitch and roll but will have a slower cruise speed and thus, a decreased range.
45
Define Accelerate-go distance…
Accelerate-go distance is the horizontal distance required to continue the takeoff and climb to 35 feet, assuming an engine failure at V1
46
Can you cruise further on one engine or two engines in a twin turbojet aircraft?
If an engine fails during optimum cruise of a turbojet airplane, the airplane must descend and will experience a loss in range. However, the turbojet airplane is generally overpowered at LDmax, and a loss of a power-plant will not cause a significant change in maximum endurance.
47
When is wake turbulence generated?
Wake turbulence is generated from the moment an aircraft leaves the ground until it touches down, since trailing vortices are a byproduct of wing lift. Prior to takeoff or touchdown pilots should note the rotation or touchdown point of the preceding aircraft.
48
Does a forward CG require an aircraft to fly at a higher or lower angle of attack for a given weight/configuration?
Moving an airplane CG more forward necessitates an increase in the wing-body lift force which can only be accomplished by increasing the airplane angle of attack. Alternatively, you could say that for any given angle of attack, the lift coefficient is greater at the more aft CG position.
49
What factors should be considered when landing in conditions conducive to hydroplaning?
The approach should be flown: on speed, on centerline and on glide path.
50
What does the term ‘faired’ mean with regard to aileron, rudder and elevator position?
Faired, i.e. not deflected from its neutral position, the aileron is aligned with the wing, the rudder is aligned with the vertical tail, the elevator is aligned with the stabilizer.
51
What are the characteristics of an aircraft loaded at the aft limit?
There’s a benefit to loading a plane toward, but within aft CG limits: faster cruise. This is a result of tail-down force, while only an aerodynamic load, must be carried by the airplane. When the aircraft is loaded aft, less tail-down force is required to achieve aircraft balance. Therefore, an aft-loaded airplane requires less lift than one that is loaded forward. This translates to faster cruise and better climb rate.
52
What are 4 effects of an aircraft climbing out of ground effect?
The aircraft will require a higher AoA to maintain the same coefficient of lift.
An increase in induced drag will require an increase in thrust.
Decreased stability and a nose-up change in moment.
A reduction in static pressure and an increase in indicated speed.
53
What is the difference between stalls at high altitude and low altitude?
Not as much thrust at higher altitude for recovery is available.
54
What influences the turn-radius the most? Altitude, Weight, Load Factor, Airspeed?
Airspeed. The radius of turn (R) can be computed using a simple formula. The radius of turn is equal to the velocity squared (V^2) divided by 11.26 times the tangent of the bank angle. Since velocity is squared, a higher airspeed will affect the radius of the turn greater than any other factor.
55
What is the definition of drag?
Drag is a force produced by the flow of a viscous fluid over a body, acting in a direction parallel to the free stream direction of the flow.
56
A swept-wing airplane with weak static directional stability and increased dihedral causes an increase in ____?
Dutch roll tendency. A swept wing airplane has an increase in dihedral effect. When an airplane’s dihedral effect is large in comparison with its static directional stability its Dutch roll tendencies will increase.
57
What is the Transonic regime?
Aircraft mach speed where some but not all local air flow velocities are Mach 1.0 or above. The mach range is Mach numbers from .75 to 1.20.
58
What is aerodynamic pressure ?
It is force per unit area exerted on a surface. If you hold your hand out of a moving car with the palm into the wind, it is the force exerted on your palm. It exist because air molecules are striking the surface of your hand and transferring some of their momentum to the surface.
59
Define region of reverse command?
It is the region of flight speeds below maximum endurance airspeed (L/Dmax) where a decrease in speed requires an increase in power.
60
The rudder controls yaw around the _____ axis and exhibits which type of stability?
(Vertical, Directional) The rudder controls yaw around the vertical axis and exhibits directional stability.
61
As an aircraft’s CG moves rearward, what are some of the affects?
An increased aft CG will cause an aircraft to be less stable in both pitch and roll. However, reduced aerodynamic loading of the horizontal tail will slightly lower stall speed and increase cruise speed for a given power setting.
62
Which of the following factors affect Vmc more; gross weight at its maximum or a CG in the most critical position?
The location of the weight with respect to CG is more critical than the weight of the aircraft.
63
Negative camber
mean camber line is below chord line.
64
Why does drag increase in a climb?
When the flightpath is inclined upward, a component of the airplane’s weight acts in the same direction as, and parallel to, the total drag of the airplane, thereby increasing the total effective drag.
65
What is induced drag?
Induced drag results from the production of lift. The pressure differential between upper and lower surfaces of the wing induces a vortex at each tip, causing a down push on the air leaving the trailing edge, This downwash causes the stream to depart down from incoming air. The lift vector, perpendicular to the actual airflow tilts back, resulting in lift in the streamwise direction. Induced drag is greatest at low airspeeds.
66
In a straight wind aircraft which portion of the wing stalls first?
In most straight-wing aircraft, the wing is designed to stall the wing root first. The wing root reaches its critical AoA first making the stall progress outward toward the wingtip. By having the wing root stall first, aileron effectiveness is maintained at the wingtips, maintaining controllability of the aircraft.
67
What is a servo tab?
An auxiliary control mounted on a primary control surface, which automatically moves in the direction opposite of the primary control
68
What is service ceiling?
Service Ceiling is the altitude where the rate of climb is only 100 feet per minute.
69
Define Accelerate-stop distance….
Accelerate-stop distance is the runway length required to accelerate to a specified speed (either VR or VLOF, as specified by the manufacturer), experience an engine failure, and bring the airplane to a complete stop.
70
What affects landing distance the most, gross weight or speed?
Speed
71
Positive camber
mean camber line is above chord line.
72
What is the advantage of a swept wing over a straight wing?
Swept wings generally have higher cruising speeds due to a higher critical mach number.
73
What is force divergence?
The mach number which produces a sharp change in the drag coefficient. Also referred to as “drag divergence” or “drag rise’. This number exceeds Critical Mach by 5-10%. Associated with drag rise is buffet, trim and stability charges and a decrease in control surface effectiveness. Control surfaces may “buzz”.
74
Define angle of incidence…
Using a thrust curve chart how can one determine the maximum angle of climb?
75
Using a thrust curve chart how can one determine the maximum angle of climb?
The maximum angle of climb would occur at a speed of L/Dmax.
76
What actions should be taken if deceleration is not detected and hydroplaning is suspected?
The nose should be raised and aerodynamic drag utilized to decelerate to a point where the brakes become effective.
77
You are in a landing roll-out with full reverse thrust, when you lose the left engine and the airplane is veering right. What do you do?
Retard both reverse thrusters to IDLE and counteract the yaw with rudder and differential breaking.
78
If you decrease AOA how does that affect induced drag?
Induced drag is inversely proportional to the square of the airspeed. Higher speeds are typically achieved at a lower angle of attack, and thus, a reduction of Induced drag.
79
The minimum speed at which dynamic hydroplaning can start is directly related to?
tire pressure.
80
When an aircraft is at a height equal to its wing span, what approximate reduction is there is induced drag? At 1/2 its span? At 1/10 its span?
Within a height equal to its wing span, an aircraft will experience only a 1-2% reduction of induced drag. At 1/2 its span the reduction is approximately 23%. At 1/10 its span the reduction in induced drag is approximately 48%.
81
What is a “shock wave”?
A dramatic change in pressure and density over a few inches of the wing surface. A shock wave forms at the point where supersonic airflow slows back to subsonic.
82
Enroute at FL310 the altimeter is correctly set to 29.92. On descent into the destination, the pilots fail to set the altimeters to the current local setting of 30.23. If the field elevation 310′, and the altimeter is functioning properly, what will it indicate on landing?
Sea lever. One inch of Hg pressure is equal to 1,000 feet. If the altimeter is not set properly when descending in to the local area with local area with a local altimeter setting of 30.23, an error of 310 feet will result. If the altimeter is set lower than the actual setting (i.e. at 29.92 instead of 30.23), if will read lower than the actual altitude.
83
What are the effects of a blocked pitot tube?
The ASI is affected by a blocked pitot tube. At the alt that the pitot tube becomes blocked, the ASI remains constant and doesn’t reflect changes in speed. At an alt higher than where the pitot tube becomes blocked, the ASI displays a higher than actual airspeed. The pressure in the pitot system remains constant when the atmospheric pressure (and static pressure) are decreasing. At lower alt, it will indicate a lower airspeed.
84
Where are anti-servo tabs used primarily?
Attached to stabilators. Because stabilators pivot around a central hinge point, they are extremely sensitive to control inputs and aerodynamic loads. Anti-servo tabs are incorporated on the trailing edge to decrease sensitivity. They deflect in the same direction as the stabilator. This results in an increase in the force required to move the stabilator, thus making it less prone to pilot-induced over-controlling.
85
Define pitch attitude.
The angular relationship between the longitudinal axis of the aircraft and the actual horizon.
86
One of the aerodynamic benefits of a rearward CG is an increased cruise speed, what causes this affect?
A rearward CG is beneficial with regard to cruise speed because of the reduced loading of the horizontal tail surface. Remember, the center of lift is behind the center of gravity, therefore the tail keeps the nose up. With a rear CG less nose up is required and therefore the amount of drag is slightly reduced on the horizontal surface, less drag equals more speed for a given power setting.
87
What is Static Pressure?
Pressure of the air that is still, or not moving, measured perpendicular to the surface of the aircraft. At sea level, the static pressure of air is 14.7 psi or 29.92 in Hg.
88
What is the definition of lift?
Lift is the force produced by the flow of a viscous fluid over a body, acting in a direction perpendicular to the free stream direction of the flow.
89
What is a neutral static stability?
When an aircraft is disturbed about one of its axis, and it remains in its new, disturbed, state.
90
Define the term Density as it relates to airflow
Density is the mess of a substance per unit volume.
91
Would an altimeter read high or low in lower than standard pressure?
It would incorrectly read higher than the actual altitude Flying into clod weather has the same affect. Remember, High to Low, look out below.
92
Is the center of lift (for an aircraft of conventional design) forward or aft of the airplane’s center of gravity? Why?
The center of lift is always behind the center of gravity. This imparts static pitch stability; if the airplane pitches nose up about the center of gravity the lift force of the wing will increase, creating a nose-down pitch moment about the CG. If the CG moves more forward the upward wing/body lift force must increase and the tail downward force must increase by an equal amount; the converse is true if the CG moves more aft.
93
What would cause the airplane to hydroplane the most?
Under inflated tires.
94
What is reverted rubber hydroplaning?
Reverted rubber hydroplaning occurs during a locked wheel skid. Water trapped between the tire and the runway is heated by friction, and the tire rides along a pocket of steam.
95
Does an aft CG require a slower of faster takeoff speed? Why?
At a given attitude such as a takeoff attitude, the lift coefficient is greater at a more aft CG then it follows that, for the specified conditions, at a more aft CG the takeoff speeds will be somewhat slower. For a 727 at 130,000 pounds, the difference between an aft and forward CG is as much as 3 knots (Vr) and 250 feet shorter takeoff distance.
96
You are taking off on runway 15L in ATL, V1-123, VR-135, V2-147. You have an engine failure at 130kts IAS, What do you do?
Continue the takeoff and climb at 147 KIAS. V1 is the earliest point from which an engine out takeoff can be continued and the airplane attain a height of 35 feet at the end of the runway. In this scenario, the aircraft is 7 knots faster than V1 so the aircraft must takeoff.
97
What defines and determines a critical engine in a twin-engine aircraft?
Because of P-Factor on most propeller driven airplanes, the loss of one particular engine at high angles of attack would be more detrimental to performance than the loss of the other. One of the engines has its thrust line closer to the aircraft centerline. The loss of this engine would more adversely affect the performance and handling of the aircraft; therefore this is the critical engine.
98
Define relative wind…
It is the direction of the airflow with respect to the airfoil.
99
What does L/D Max give you for jet aircraft?
At this point, the least amount of power is required for both the maximum lift and minimum drag. This will provide maximum endurance.
100
What are the effects of landing on a narrow runway?
The tendency is to fly a lower than normal approach.
101
Under which condition is a forward CG most critical?
Short runways or obstacle limited takeoffs. With CG forward, the aircraft’s tail must generate a greater amount of downward lift, the wings must then create more lift to offset the greater download. The increased lift creates more drag and thus requires a longer takeoff roll to achieve the higher speed required for takeoff. For short runways, a rearward CG offers better performance, more weight and better climb weight limit.
102
You have been advised that cargo has been shifted from a forward cargo hold to an aft one. How does that affect the aircraft’s stability and cruise speed?
Less Stable, higher Cruise Speed.
103
What affects indicated stall speed?
ReferenceNaval Aviators page 39: “The airspeed at which stall occurs will be determined by weight, load factor and altitude but the angle of attack is unaffected.”
104
What happens to the viscosity of air as the air’s temperature increases ?
Unlike liquids where an increase in temperature results in a lower viscosity ( think engine oil), for gases, viscosity increases as temperature increases.
105
What are the effects of an aft CG on Vmc?
As the center of gravity moves forward, the moment arm between the rudder and the CG is lengthened, increasing the leverage of the rudder (which lowers Vmc speed). With an aft CG, the moment arm is reduced thus lowering the effectiveness of the rudder and increasing Vmc speed.
106
What speed is affected if you have a contaminated runway?
V1 is reduced with a contaminated runway (to maintain a balanced field length). The stopping performance of the aircraft is degraded. This requires that an aborted takeoff start at a lower speed and with more runway and stopway remaining. This means that both the runway limited takeoff weight and the V1 used for takeoff will be lower than normal.
107
Which form of drag is most affected by ground effect?
The reduction in induced flow due to ground effect causes a significant reduction in induced drag but does not have a direct effect on parasite drag.
108
What does wing dihedral provide?
It provides positive static lateral stability. Basically, when one wing is lower than the other, wing dihedral causes the lower wing to produce more lift, thereby causing a rolling moment around the longitudinal axis returning the aircraft to straight and level flight.
109
What is Temperature?
Temperature is the measure of the average kinetic energy of the particles in a gas.
110
What is the definition of V1?
V1 is the maximum speed in the takeoff at which the pilot must take the first action ( apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. Also, V1 is the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance.
111
Why does specific range increase with an increase in altitude?
Greater True Airspeed (greater TAS for same thrust), Lower Intel Air Temps (reduces specific fuel consumption), Increased Engine RPM’s (specific fuel consumption reduces as normal RPM is approached), Lower Fuel Consumption. Increased TAS accounts for two-thirds of the benefit while increased engine performance accounts for the other third.
112
In a skidding turn, is the centrifugal force greater than or less than the horizontal component of lift?
The centrifugal force is greater than the horizontal component of lift. A skidding turn results from an excess of centrifugal force over the horizontal lift component. The rate of turn is too great for the angle of bank. Correction of a skidding turn involves a reduction in the RoT, an increase in bank, or a combination of the two changes.
113
What is dynamic hydroplaning?
Dynamic hydroplaning occurs when a tire rolls through standing water, forms a bow wave, and then rolls up on top of the wave, losing all contact with the runway. The minimum speed at which dynamic hydroplaning can start is related to tire pressure. As a rule of thumb, dynamic hydroplaning will start at a speed greater than nine times the square root of the tire pressure in pounds per sq. in.
114
As a parcel of air rises, what is the affect on its Pressure? Density? Temperature?
When a parcel of air is forced to rise it expands because its pressure decreases. As pressure decreases so, too, does density. The temperature decreases with altitude for this parcel of air.
115
The true airspeed at which an airplane stalls varies with…
Load factor, weight and density altitude.
116
How do CG shifts affect stall and cruise speeds?
CG influences wing lift and AOA, amount of force on the tail, and amount of force the stabilizer needs for equilibrium. Airplanes stall at higher speeds with fwd CGs because stall AOA is reached at higher speeds due to increased wing loading. Increased loading results in slower speeds. Airplanes cruise faster with aft CG because of reduced drag caused by a smaller angle of attack and less downward deflection of the stabilizer.
117
The elevator/stab controls pitch around the _axis.
Lateral
118
Why will an engine produce more power on a dry day versus a humid day?
Water vapor has less mass than dry air, therefore, humid or moist air is less dense than dry air.
119
Define angle of attack.
Angle between the relative wind and the chord line of the wing.
120
What is the difference between static and dynamic stability?
Static stability describes the initial reaction of the airplane after it has been disturbed. Dynamic stability describes the long-term tendency of an aircraft that has positive static stability.
121
What is excess thrust?
Excess thrust is the difference between thrust and drag. During a steady climb, for example, the rate of climb will depend on excess power while the angle of climb is a function of excess thrust.
122
What is “coffin corner”?
At high altitudes a climb or cruise Mach can be maintained that results in an AOA that is both near the stalling AOA (stall buffet), and can cause much buffet if turbulence is encountered. The airspeed margin is quite narrow in this condition, either speeding up or slowing results in buffet.
123
At a higher altitude why does it take longer to recover from a stall?
Less power available at higher altitudes.
124
What causes the effect known as ground effect?
When an aircraft comes within several feet of the surface, a change occurs in the flow pattern around the aircraft because the vertical component of the airflow around the wing is restricted by the surface. An aircraft flying in ground effect will require less thrust and a lower than normal AoA. A hazardous situation is possible because the recommended takeoff speed may not be achieved.
125
What is critical mach?
The free stream mach number at which sonic flow is first obtained somewhere on the surface of the airfoil.
126
What is the definition of Vmc?
Vmc is the minimum airspeed at which directional control can be maintained with the critical engine inoperative
127
The ailerons control roll around the _axis and exhibit which type of stability?
The ailerons control roll around the longitudinal axis and exhibit lateral stability.
128
You are flying into a very strong jet stream. You are trying to conserve fuel. What should you do?
Climb as high (for fuel efficiency) and fly as fast as you can.
129
What is Standard Atmosphere?
Sea lever pressure is 29.92″ Hg and 15A° C (59A°F). The standard lapse rate is approximately 1″ Hg decrease per 1,000 feet of altitude.
130
What is an anti-servo tab?
An adjustable tab attached to the trailing edge of a stabilator that moves in the same direction as the primary control. It is used to make the stabilator less sensitive.
131
What has the greatest effect on hydroplaning?
Under inflated tires.
132
With TAS constant, what happens to Mach speed with a gain in altitude?
Mach speed will increase, Mach is the ratio of TAS to the Speed of Sound. As altitude increases, the Speed of Sound decreases. TAS remains the same so as a ratio to the Speed of Sound, the Mach number will increase.
133
What should be considered in reference to hydroplaning?
Tire pressure, Weight, Hard or Soft Touchdown, Depth of Standing Water.
134
An airplane traveling at 200 knots generates what amount of lift as the same airplane traveling at 100 knots (AOA and other factors remain constant)? The same? Twice as much? Four times as much?
The airplane will generate four times the lift as the same airplane traveling at 100 knots.
135
Define critical angle of attack…
The angle of attack at which a wing stalls regardless of airspeed, flight attitude, or weight.
136
What happens to the airspeed indicator when both the ram air and drain holes in the pitot system are blocked?
The airspeed indicator acts like an altimeter.
137
What do you do if a heavy aircraft departs in front of you while on an approach to land on the same runway?
Land before the rotation point or go around.
138
Define the term Velocity as it relates to airflow
Velocity is a flowing gas is the velocity of an infinitesimally small fluid element (parcel of air) as it sweeps through a fixed point.
139
After going missed on an approach, what airspeed would you climb out at if diverting?
L/D Max or Max Range
140
What do vortex generators do?
High speed shock waves can cause separation to occur on the airfoil and form small wakes behind them. Vortex generators are small wing-like surfaces that project into the airstream. A vortex is formed at the tip of the generators, and adds energy to the air in the boundary layer, which prevents separation. The generators tend to break up the shock waves. Both actions delay separation and give greater control effectiveness.
141
What happens to landing speed with varying… /headwinds/altitude/temperature/TAS/ground speed?
Ground speed for landing will be slower with a headwind. Ground speed will be faster with altitude and temperature due to a higher true airspeed.
142
What is load factor?
Load factor: ration of lift developed by an airplane to its weight. In level flight, the wings support the weight of the aircraft needed to maintain equilibrium. Gusts and maneuvers attempt to change the path or the airplane, but because of its inertia, the airplane remains on its original path. The force of inertia, produced by acceleration, is added to the force of gravity, and a new apparent weight results.
143
When are wing-tip vortices most severe?
The intensity or strength of wing-tip vortices is directly proportional to the weight of the airplane and inversely proportional to the wingspan and speed of the airplane. The heavier and slower the airplane, the greater the angle of attack and the stronger the wing-tip vortices with maximum strength occurring during the takeoff, climb, and landing phases of flight.
144
When setting the altimeter, it is accepted that pilots should ignore the effects of nonstandard temperature and pressure, except for ….
Low temperatures and pressures which should be considered for terrain clearance.
145
Which maximum range factors decrease as fuel is burned and weight decreases?
The optimum airspeed and power setting may decrease. The optimum altitude may increase. Since it is seldom practical to change speed and altitude constantly, it is common to maintain a constant Mach cruise at a flight level close to optimum. As fuel is burned, thrust is reduced to maintain the constant mach number.
146
What makes an airplane stall?
When the angle of attack of the wing exceeds the critical angle of attack.
147
Does altitude affect stall speed?
An increase in altitude will produce a decrease in density and increase the true airspeed at stall. Also, an increase in altitude will alter compressibility and viscosity effects and generally speaking, cause the indicated stall speed to increase. This particular consideration is usually significant only above altitudes of 20,000 ft.
148
As the angle of attack increases on a wing below its stall speed, lift increases/decreases?
As the angle of attack increases, the lift produced by the wing increases proportionately. This is true until the angle of attack exceeds a critical value and then the wing stalls.
149
What is the definition of Vmu?
Minimum unstick speed. The minimum speed at which an airplane can be rotated off the ground without experience a tail-strike.
150
What is static stability?
It is the initial reaction of an aircraft after is has been disturbed from equilibrium in one or more axes of rotation.
151
Define maximum range….
Maximum range for a jet airplane occurs when the airplane is flying at a velocity such that the aerodynamic condition produces a maximum proportion between the square root of the lift coefficient C(L) and the drag coefficient C(D). Turbojets always has a best range speed higher than (L/D) Max.
152
What determines the optimum cruise altitude for a jet airplane?
Aircraft weight. At the beginning of cruise flight, the relatively high initial weight of the airplane will require specific values of airspeed, altitude and power setting to produce the recommended cruise condition.
153
What is a disadvantage of a swept-wing design?
Dutch-roll tendencies, wing tips stall first, reduced max coefficient of lift.
154
Flying at 200 knots, what bank angle would you use for a standard rate turn (3 degrees/sec)?
30° True airspeed determines the angle of bank necessary to maintain a standard rate turn. A simple way to determine this amount is to divide the airspeed by 10 and add one-half the result. A rule of thumb to determine the approximate angle of bank required for a standard rate turn is to use 15 percent of the airspeed. 1.5*(TAS/10) or 200/10 X 1.5 = 30 degrees.
155
Symmetrical airfoil
mean camber line coincides with chord line.
156
Does a headwind result in a greater or lesser climb angle over the ground?
Greater. By reducing the airplane’s horizontal speed without affecting its vertical speed, a headwind results in a greater climb angle over the ground, a tailwind produces a smaller climb angle over the ground.
157
After an Engine Failure always climb at?
V2 or best climb gradient speed which yields the most altitude per mile.
158
What is adverse yaw?
A condition of flight in which the nose of an airplane tends to yaw toward the outside of the turn. This is caused by the higher induced drag on the outside wing, which is also producing more lift. Induced drag is a byproduct of the lift associated with the outside wing.
159
What is the Supersonic regime?
Aircraft mach speed where all of the air flow around the aircraft exceeds Mach 1.0 The mach range is Mach numbers from 1.20 to 5.00.
160
How is lift produced?
Air flowing over curved wing surfaces. Air flowing over the top of the wing is deflected further than air flowing under the wing and is therefore accelerated. Bernoulli’s Principle states that as gas is accelerated, its pressure decreases. Thus the pressure on the upper wing surface is lower than on that of the lower surface and lift is produced.
161
How does altitude affect mach number?
Mach number is equal to TAS divided by the speed of sound. As altitude increases so does TAS, however, speed of sound decreases. Therefore, looking at the ration relationship of TAS to speed of sound, mach number will increase as altitude increases.
162
What is Viscosity?
Viscosity is the property of a fluid or semi fluid that causes it to resist flowing. Air is an example of a fluid whose viscosity can not be observed.
163
If landing in full reverse, you start drifting left, what should you do?
Take left engine out of reverse.
164
What two factors affect lift in a turn?
Angle of attack and airspeed. The same factors that affect lift in straight and level flight affect lift in a turn.
165
What are properties of airflow as they relate to an airplane?
The viscosity, density, compressibility, and temperature of the air determine how the air will flow around a plane. The viscosity of a fluid is its resistance of flow. Air sticks to a surface which slows down the flow. At flow speeds less than 220 MPH, air is practically incompressible. However, at speeds closer to sound (660 MPH), air density varies. The effects of temperature change also become important at these speeds.
166
What is the purpose of vortex generators?
Vortex generators are used to delay or prevent shock wave induced boundary layer separation encountered in transonic flight.
167
What is Mach tuck?
Mach tuck is when wing’s center of pressure moves aft as its speed approaches the sound barrier. The father aft the center of pressure moves, the greater the down moment generated by the wing. As the aircraft pitches down, its airspeed climbs, worsening the tuck effect. Recovering from Mach tuck requires slowing airspeed. However, airload on the tail can reach the point where there is not enough pitch authority for recovery.
168
What is Humidity?
Humidity, also called relative humidity, refers to the amount of water vapor contained in the atmosphere, and expressed as a percentage of the maximum amount of water vapor the air can hold.
169
Define maximum endurance
Maximum endurance for a jet airplane occurs when the airplane is flying at a minimum thrust required ie, at a velocity such that (L/D) is maximum (Minimum Drag).
170
What has an effect on specific range?
Specific Range = TAS / Fuel Flow (pounds per hour). It is normally expressed in Nautical Air Miles per 1,000 pounds of fuel. Factors that affect this include; Gross weight, Altitude, Aircraft configuration.
171
Why would a swept wing aircraft roll if you were to push on the rudder?
Because the advancing wing has a higher angle of attack (dihedral effect) and presents a greater span to the airstream. The lift differential is greater and produces a greater rolling moment. These characterization cause a roll-yawing oscillation known as “Dutch Roll”.
172
What is parasite drag?
The friction and pressure drag of the tail surfaces, fuselage, engine nacelles, landing gear and any other component of the airplane which is exposed to the airflow (plus the profile drag of the wing) make up the ‘form drag’ caused by moving an object through a gaseous medium.
173
Using a power curve chart how can one determine the maximum rate of climb?
The maximum angle of climb (Vx) would occur where there exists the greatest difference between power available (Pa) and power required (D), i.e. the maximum Pa (power) – D (drag).
174
What is balanced field length?
A balanced field takeoff is a condition where the accelerate-stop distance required (ASDR) is equal to the takeoff distance required (TODR) for the aircraft weight, engine thrust, aircraft configuration and runway condition.
