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NCAA PPL Principles of Flight study materials
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NCAA PPL Principles of Flight practice questions

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Question 1Principles of Flight

In unaccelerated level flight at a constant altitude, what is the relationship between lift and weight?

  1. Lift equals weight Correct answer.
  2. Lift is unrelated to weight
  3. Lift is greater than weight
  4. Lift is less than weight

Explanation

In steady, unaccelerated level flight the vertical forces must balance, so the total lift generated by the wing equals the aircraft's weight. Any excess of lift over weight would produce an upward acceleration and a climb or zoom rather than constant altitude.

Question 2Principles of Flight

Which statement best describes the four forces acting on an aircraft in steady, unaccelerated flight?

  1. Thrust acts vertically and lift acts horizontally
  2. Lift and drag both act rearward along the flight path
  3. Weight acts forward and thrust acts downward
  4. Lift opposes weight and thrust opposes drag Correct answer.

Explanation

In the conventional force diagram, lift acts perpendicular to the relative airflow and opposes weight, while thrust acts along the flight path and opposes drag. These pairings allow the aircraft to remain in equilibrium when the opposing forces are equal.

Question 3Principles of Flight

According to Bernoulli's principle as applied to a wing, what happens to static pressure in a region where airflow velocity increases?

  1. Static pressure stays exactly constant
  2. Static pressure decreases Correct answer.
  3. Static pressure increases
  4. Static pressure becomes equal to dynamic pressure

Explanation

Bernoulli's relationship states that in a streamline flow of constant total energy, an increase in velocity is accompanied by a decrease in static pressure. This pressure reduction over the upper surface contributes to the pressure distribution that produces lift.

Question 4Principles of Flight

What is the definition of the angle of attack?

  1. The angle between the wing chord line and the relative wind Correct answer.
  2. The angle between the wing chord line and the longitudinal axis
  3. The angle between the fuselage reference line and the horizon
  4. The angle between the flight path and the horizon

Explanation

Angle of attack is measured between the wing chord line and the direction of the relative wind, that is, the oncoming airflow. It is a key variable because lift varies with angle of attack up to the stalling angle.

Question 5Principles of Flight

What is the primary cause of an aerodynamic stall?

  1. The angle of attack exceeds the critical angle Correct answer.
  2. The engine loses power during a climb
  3. The aircraft exceeds its never-exceed speed
  4. The airspeed falls below the published stall speed for the weight

Explanation

A stall occurs when the angle of attack exceeds the critical angle at which airflow separates from the upper surface and lift drops sharply. A stall can happen at any airspeed or attitude if the critical angle of attack is exceeded.

Question 6Principles of Flight

How does increasing the bank angle in a level turn affect the load factor on the aircraft?

  1. The load factor decreases
  2. The load factor remains at one
  3. The load factor increases Correct answer.
  4. The load factor becomes negative

Explanation

In a level turn the vertical component of lift must still equal weight, so total lift, and therefore the load factor, must increase as bank angle steepens. At 60 degrees of bank the load factor reaches about 2.0.

Question 7Principles of Flight

What is the relationship between induced drag and airspeed in straight-and-level flight at a constant weight?

  1. Induced drag increases as airspeed increases
  2. Induced drag is greatest at the never-exceed speed
  3. Induced drag is unaffected by airspeed
  4. Induced drag decreases as airspeed increases Correct answer.

Explanation

Induced drag results from the lift production process and is inversely related to the square of airspeed. As airspeed increases, less angle of attack is needed for the same lift, so induced drag falls.

Question 8Principles of Flight

What is the function of wing dihedral in an aircraft design?

  1. To increase the stalling angle of attack
  2. To increase the rate of climb
  3. To reduce induced drag at high speed
  4. To provide lateral stability in a sideslip Correct answer.

Explanation

Dihedral, the upward angle of the wings from the root, produces a rolling moment that tends to level the wings when the aircraft sideslips. This contributes to positive lateral stability about the longitudinal axis.

Question 9Principles of Flight

An aircraft is flying at a constant true airspeed when it enters a region of denser air at the same indicated airspeed. What happens to the dynamic pressure and the required angle of attack?

  1. Dynamic pressure increases and the required angle of attack increases
  2. Dynamic pressure stays the same and the required angle of attack stays the same
  3. Dynamic pressure decreases and the required angle of attack increases
  4. Dynamic pressure increases and the required angle of attack decreases Correct answer.

Explanation

Dynamic pressure depends on air density as well as velocity, so at the same true airspeed denser air raises dynamic pressure. Because each unit of wing area produces more lift, a smaller angle of attack is needed to support the same weight.

Question 10Principles of Flight

An aircraft stalls at 50 knots in unaccelerated level flight. What is the approximate stalling speed in a level turn at 60 degrees of bank?

  1. 100 knots
  2. 58 knots
  3. 71 knots Correct answer.
  4. 65 knots

Explanation

At 60 degrees of bank the load factor is 2.0, and stalling speed increases with the square root of the load factor. Multiplying 50 knots by the square root of 2 gives about 71 knots.

Question 11Principles of Flight

Why does an aircraft's stalling speed increase as its weight increases?

  1. Heavier aircraft have a higher critical angle of attack
  2. Heavier aircraft must produce more lift, requiring a higher angle of attack at any given speed Correct answer.
  3. Heavier aircraft always fly at lower density altitudes
  4. Heavier aircraft have less wing area

Explanation

The critical angle of attack is essentially fixed, so a heavier aircraft must generate more lift before reaching that angle. Since lift depends on speed and angle of attack, the heavier aircraft needs a higher speed to reach the critical angle at a given altitude.

Question 12Principles of Flight

What is the effect of extending trailing-edge flaps for landing on the stalling speed and the stalling angle of attack?

  1. Stalling speed increases and the stalling angle of attack increases
  2. Stalling speed increases and the stalling angle of attack decreases
  3. Stalling speed decreases and the stalling angle of attack decreases Correct answer.
  4. Stalling speed decreases and the stalling angle of attack increases

Explanation

Flaps increase camber and lift coefficient, lowering the speed at which the wing can support the aircraft, so stalling speed falls. However, the increased camber also lowers the critical angle of attack, so the wing stalls at a lower angle.

Question 13Principles of Flight

What is the primary purpose of wing washout in an aircraft design?

  1. To reduce the dihedral effect in a sideslip
  2. To increase the maximum lift coefficient at the tip
  3. To ensure the wingtip stalls before the wing root
  4. To ensure the wing root stalls before the wingtip Correct answer.

Explanation

Washout twists the wing so that the tip has a lower angle of incidence than the root. As angle of attack increases, the root reaches its critical angle first, preserving aileron effectiveness and reducing the tendency to drop a wingtip at the stall.

Question 14Principles of Flight

Which condition produces the greatest induced drag for a given aircraft at a constant weight?

  1. High-speed cruise at low angle of attack
  2. Descent at idle power
  3. Slow flight at high angle of attack Correct answer.
  4. Flight at the never-exceed speed

Explanation

Induced drag is proportional to the square of the lift coefficient, which rises as angle of attack increases. Slow flight requires a high angle of attack to generate the needed lift, so induced drag is greatest there.

Question 15Principles of Flight

During a constant-altitude, constant-airspeed turn, the horizontal component of lift provides the centripetal force. What balances the vertical component of lift?

  1. Thrust
  2. Weight Correct answer.
  3. Drag
  4. The horizontal component of thrust

Explanation

In a level turn, lift is tilted inward, and its vertical component must equal weight to hold altitude. The horizontal component of lift supplies the centripetal force that curves the flight path.

Question 16Principles of Flight

What happens to the center of pressure on a cambered wing as the angle of attack increases from a low value toward the stall?

  1. It moves to the wingtip
  2. It moves rearward toward the trailing edge
  3. It remains exactly at the quarter-chord point
  4. It moves forward toward the leading edge Correct answer.

Explanation

At low angles of attack the center of pressure on a cambered wing lies well aft, and as angle of attack increases it moves forward toward the leading edge. This shift affects the pitching moment and is one reason trim changes with speed and angle of attack.

Question 17Principles of Flight

What is the significance of the aerodynamic center of a wing?

  1. It is the point where drag is minimized
  2. It is the point where lift is always zero
  3. It is the point where the pitching moment coefficient is essentially constant with angle of attack Correct answer.
  4. It is the point where the wing stalls first

Explanation

The aerodynamic center is the chordwise point about which the pitching moment coefficient remains nearly constant as angle of attack changes. Designers use it because it simplifies stability analysis compared with the moving center of pressure.

Question 18Principles of Flight

Why does an aircraft in a steady climb at a constant airspeed require more thrust than in level flight at the same airspeed?

  1. Because lift equals weight in a climb
  2. Because thrust must overcome a component of weight acting along the flight path Correct answer.
  3. Because drag increases in a climb at the same airspeed
  4. Because the wing produces no lift in a climb

Explanation

In a climb the flight path is inclined, so a component of weight acts rearward along the flight path and must be overcome by thrust in addition to drag. That is why excess thrust determines climb performance.

Question 19Principles of Flight

An aircraft is descending at a constant airspeed and constant rate of descent. How does the lift compare with the weight?

  1. Lift is less than weight Correct answer.
  2. Lift is zero
  3. Lift equals weight
  4. Lift is greater than weight

Explanation

In a steady descent the flight path is inclined downward, so lift must balance only the component of weight perpendicular to the flight path. Lift is therefore less than the total weight.

Question 20Principles of Flight

What is the effect of ground effect on an aircraft during the takeoff flare and initial climb?

  1. Induced drag increases and lift decreases
  2. Both lift and drag increase
  3. Induced drag decreases and lift increases for a given angle of attack Correct answer.
  4. Both lift and drag decrease equally

Explanation

Near the surface, the wingtip vortices are suppressed and downwash is reduced, which lowers induced drag and increases the effective lift for a given angle of attack. This is why an aircraft can lift off before reaching normal flying speed and may settle when leaving ground effect.

Question 21Principles of Flight

An aircraft with a high aspect ratio wing is compared with one of the same wing area and low aspect ratio. What is the expected effect on induced drag at the same lift coefficient?

  1. The high aspect ratio wing has higher parasite drag
  2. The high aspect ratio wing has higher induced drag
  3. Aspect ratio has no effect on induced drag
  4. The high aspect ratio wing has lower induced drag Correct answer.

Explanation

Induced drag is inversely proportional to aspect ratio for a given lift coefficient and wing area, because a long, narrow wing produces weaker tip vortices. Gliders exploit this with very high aspect ratio wings.

Question 22Principles of Flight

Why does a swept wing aircraft tend to have a lower maximum lift coefficient and different stall behavior than a straight wing?

  1. Sweep reduces the effective velocity component perpendicular to the leading edge, and the tip tends to stall first Correct answer.
  2. Sweep increases the wing's aspect ratio without changing stall behavior
  3. Sweep eliminates the critical angle of attack entirely
  4. Sweep increases the effective velocity component perpendicular to the leading edge, and the root stalls first

Explanation

Sweeping a wing reduces the chordwise velocity component that generates lift, lowering the maximum lift coefficient. Spanwise flow also tends to make the outer wing stall before the root, which is why sweep is often combined with fences or other boundary-layer controls.

Question 23Principles of Flight

What is the effect of deploying spoilers on a wing during flight?

  1. They decrease both lift and drag
  2. They increase lift and decrease drag
  3. They increase lift and increase drag
  4. They disrupt lift and increase drag Correct answer.

Explanation

Spoilers disrupt the smooth airflow over the upper surface, reducing lift and creating additional drag. Pilots use them to steepen a descent or to dump lift after touchdown.

Question 24Principles of Flight

Why is the load factor limited by maneuvering speed (VA) rather than by a single fixed airspeed for all weights?

  1. Because maneuvering speed increases as weight increases, since the wing reaches its limit load at a higher speed Correct answer.
  2. Because maneuvering speed applies only to turns, not to gust encounters
  3. Because maneuvering speed decreases as weight increases, since the wing reaches its limit load at a lower speed
  4. Because maneuvering speed is independent of weight and depends only on altitude

Explanation

Maneuvering speed is the speed at which the wing reaches its limit load factor at full deflection of the controls. A heavier aircraft reaches that load factor at a higher speed, so published maneuvering speed rises with weight up to the maximum certificated weight.

Question 25Principles of Flight

What is the effect of a rearward center of gravity on longitudinal static stability?

  1. It reduces the nose-down pitching moment and decreases stability Correct answer.
  2. It has no effect on the pitching moment
  3. It increases the nose-down pitching moment and increases stability
  4. It increases stability because the tail arm becomes longer

Explanation

Moving the center of gravity aft reduces the distance between the center of gravity and the aerodynamic center, reducing the nose-down moment that must be balanced by the tail. With less stabilizing moment and a shorter tail arm, static stability decreases and the aircraft may become unstable if the center of gravity moves behind the neutral point.

Question 26Principles of Flight

Which force opposes thrust along the flight path during a steady, unaccelerated cruise?

  1. Weight
  2. The horizontal component of lift
  3. Total drag Correct answer.
  4. Lift

Explanation

In unaccelerated flight the forces along the flight path must balance, so thrust equals total drag. Weight acts vertically downward and is balanced by lift, not by thrust. Any excess of thrust over drag would produce acceleration rather than a steady cruise.

Question 27Principles of Flight

According to Bernoulli's principle as applied to a venturi, what happens to static pressure where the airflow speed increases?

  1. Static pressure decreases Correct answer.
  2. Static pressure increases
  3. Static pressure becomes equal to total pressure
  4. Static pressure remains constant

Explanation

Bernoulli's principle states that in a streamline flow of constant total energy, an increase in dynamic pressure is accompanied by a decrease in static pressure. Total pressure stays constant, so faster-moving air has lower static pressure. This principle helps explain the pressure distribution over a wing.

Question 28Principles of Flight

What is the angle of attack of a wing?

  1. The angle between the wing chord line and the horizontal
  2. The angle between the leading and trailing edges of the wing
  3. The angle between the longitudinal axis and the flight path
  4. The angle between the wing chord line and the relative wind Correct answer.

Explanation

Angle of attack is defined as the angle between the chord line of the wing and the relative wind. It is a purely aerodynamic angle and does not depend on the aircraft's attitude relative to the horizon. Pitch attitude and angle of attack can differ significantly, for example during a climb or descent.

Question 29Principles of Flight

Which statement correctly describes the direction of the relative wind experienced by an aircraft in flight?

  1. It is parallel to and in the same direction as the flight path
  2. It is always horizontal regardless of the flight path
  3. It is parallel to and opposite the direction of the aircraft's flight path Correct answer.
  4. It is always perpendicular to the wing chord line

Explanation

Relative wind is the airflow produced by the aircraft's motion and is always parallel to and opposite the direction of the flight path. It is independent of the aircraft's attitude in space. Angle of attack is measured between this relative wind and the chord line.

Question 30Principles of Flight

What is the primary function of the horizontal stabilizer on a conventional airplane?

  1. To provide directional stability about the yaw axis
  2. To increase the lifting area of the main wing
  3. To provide lateral stability about the roll axis
  4. To provide longitudinal stability and control about the pitch axis Correct answer.

Explanation

The horizontal stabilizer provides longitudinal stability and serves as the mounting surface for the elevator, which controls pitch. Directional stability is the job of the vertical stabilizer, and lateral stability comes largely from wing dihedral. The horizontal tail typically produces a small downward force rather than contributing to wing lift.

Question 31Principles of Flight

What happens to the total drag of an aircraft as it accelerates from a speed below L/D max toward L/D max in level flight?

  1. Total drag remains constant
  2. Total drag decreases Correct answer.
  3. Total drag first increases, then decreases
  4. Total drag increases

Explanation

At speeds below L/D max, induced drag dominates and falls rapidly as airspeed increases, while parasite drag rises only gradually. The net effect is that total drag decreases until the minimum-drag speed is reached at L/D max. Beyond that speed, parasite drag dominates and total drag increases again.

Question 32Principles of Flight

What is the relationship between lift and dynamic pressure for a wing at a fixed angle of attack and constant density?

  1. Lift is independent of dynamic pressure
  2. Lift is proportional to the square root of dynamic pressure
  3. Lift is directly proportional to dynamic pressure Correct answer.
  4. Lift is inversely proportional to dynamic pressure

Explanation

The lift equation states that lift equals the lift coefficient times dynamic pressure times wing area. At a fixed angle of attack, the lift coefficient is constant, so lift varies directly with dynamic pressure. Because dynamic pressure rises with the square of airspeed, lift also rises with the square of airspeed.

Question 33Principles of Flight

What is the meaning of the term 'load factor' as used in airplane performance?

  1. The ratio of useful load to maximum gross weight
  2. The ratio of total lift to the aircraft's weight Correct answer.
  3. The ratio of wing loading to dynamic pressure
  4. The ratio of thrust to drag in level flight

Explanation

Load factor is the ratio of the total lift produced by the wings to the gross weight of the aircraft. In unaccelerated level flight it equals one, and it increases in turns or pull-ups. Load factor is usually expressed in units of g.

Question 34Principles of Flight

An aircraft in level flight at a constant true airspeed experiences a sudden increase in angle of attack while the airspeed is held constant. What happens to the lift coefficient and to the lift?

  1. The lift coefficient increases while the lift stays constant
  2. Both the lift coefficient and the lift increase Correct answer.
  3. The lift coefficient stays constant while the lift increases
  4. Both the lift coefficient and the lift decrease

Explanation

Below the stall angle, increasing the angle of attack raises the lift coefficient. With dynamic pressure and wing area unchanged, the higher lift coefficient produces more lift, so the aircraft would begin to accelerate upward unless trimmed. This is the basis of using angle of attack to control lift.

Question 35Principles of Flight

How does the lift coefficient of a wing behave as the angle of attack exceeds the critical angle?

  1. It decreases as the airflow separates from the upper surface Correct answer.
  2. It continues to increase until the wing reaches 30 degrees
  3. It increases sharply because dynamic pressure rises
  4. It remains constant at the maximum value

Explanation

Beyond the critical angle of attack the smooth airflow separates from the upper surface, destroying much of the low-pressure region that produced lift. The lift coefficient therefore drops, and the wing is stalled. This is why recovery from a stall requires reducing the angle of attack.

Question 36Principles of Flight

What is the effect of a forward center of gravity on the pitch control forces and on cruise performance of a conventional airplane?

  1. It increases the download on the tail and raises trim drag Correct answer.
  2. It reduces the download on the tail and lowers trim drag
  3. It has no effect on trim drag because weight is unchanged
  4. It eliminates the need for longitudinal static stability

Explanation

A forward center of gravity increases the nose-down pitching moment that the tail must counter, so the tail produces a larger download. This extra download adds to effective weight and requires more lift from the wing, raising trim drag. The result is higher fuel consumption and a slightly higher stall speed.

Question 37Principles of Flight

Why does a wing with a higher aspect ratio produce less induced drag than a lower aspect ratio wing of the same area and lift coefficient?

  1. It produces less parasite drag because its surface is smoother
  2. It operates at a lower angle of attack for the same lift
  3. It generates weaker wingtip vortices and a smaller downwash angle Correct answer.
  4. It has a higher critical Mach number in all flight regimes

Explanation

Induced drag arises from the rearward tilt of the lift vector caused by downwash from wingtip vortices. A high aspect ratio wing spreads the same lift over a longer span, weakening the vortices and reducing the downwash angle. The induced drag coefficient is inversely proportional to aspect ratio.

Question 38Principles of Flight

What is the primary purpose of a wing fence on a swept-wing airplane?

  1. To limit spanwise airflow and delay tip stall Correct answer.
  2. To increase the wing's aspect ratio without adding span
  3. To provide additional lift during the landing flare
  4. To reduce parasite drag at high cruise speeds

Explanation

A wing fence is a small chordwise surface that interrupts spanwise airflow along a swept wing. It helps keep the boundary layer from drifting outward and thinning at the tips, which delays tip stall and improves aileron effectiveness at high angles of attack. It is a stall-control device rather than a drag-reduction device.

Question 39Principles of Flight

An airplane is in a steady, unaccelerated descent at a constant airspeed. How does the required thrust compare with that needed for level flight at the same airspeed?

  1. Less thrust is required because weight contributes a forward component Correct answer.
  2. More thrust is required because lift must exceed weight
  3. The same thrust is required because airspeed is unchanged
  4. No thrust is required at all during any descent

Explanation

In a steady descent the flight path is inclined downward, so a component of weight acts along the flight path in the direction of motion. This component balances part of the drag, reducing the thrust required compared with level flight at the same airspeed. Lift is less than weight in a steady descent.

Question 40Principles of Flight

How does a headwind affect the maximum range of an airplane compared with still-air conditions?

  1. Range is unchanged because fuel flow depends only on airspeed
  2. Range decreases because the aircraft covers less ground per unit of fuel Correct answer.
  3. Range decreases only if the headwind exceeds the best-glide speed
  4. Range increases because the headwind increases true airspeed

Explanation

Range is a measure of distance over the ground for a given amount of fuel. A headwind reduces groundspeed for any given true airspeed, so the aircraft covers less ground per unit of fuel burned. The effect is most pronounced at low airspeeds, where the headwind is a larger fraction of groundspeed.

Question 41Principles of Flight

What is the significance of the best angle-of-climb speed, VX?

  1. It gives the greatest altitude gain per unit of horizontal distance Correct answer.
  2. It gives the lowest stalling speed in a climb
  3. It gives the lowest fuel flow in a climb
  4. It gives the greatest altitude gain per unit of time

Explanation

VX is the speed that yields the steepest climb path, maximizing altitude gained for each unit of horizontal distance covered. It is used to clear obstacles near the departure end of a runway. The best rate-of-climb speed, VY, maximizes altitude gain per unit of time instead.

Question 42Principles of Flight

How does an increase in aircraft weight affect the best glide speed?

  1. The best glide speed increases Correct answer.
  2. The best glide speed is unchanged
  3. The best glide speed decreases
  4. The best glide speed becomes equal to the stalling speed

Explanation

Best glide speed corresponds to the speed for maximum lift-to-drag ratio, which rises with the square root of the wing loading. A heavier aircraft must fly faster to achieve the same lift coefficient at the L/D max angle of attack. The glide angle remains the same, but the aircraft descends faster.

Question 43Principles of Flight

What is the effect of extending landing gear on the glide ratio of an airplane?

  1. The glide ratio is unchanged because weight is unchanged
  2. The glide ratio decreases because parasite drag increases Correct answer.
  3. The glide ratio increases because lift increases
  4. The glide ratio increases because the aircraft becomes more stable

Explanation

Extending the landing gear adds parasite drag, which shifts the total drag curve upward. The maximum lift-to-drag ratio therefore falls, so the aircraft covers less horizontal distance for each unit of altitude lost. This is why gear is retracted for a forced landing only when a landing area is assured.

Question 44Principles of Flight

An aircraft is flying at a constant indicated airspeed while climbing without changing configuration or power. What happens to the true airspeed?

  1. True airspeed remains constant because indicated airspeed is constant
  2. True airspeed increases as air density decreases Correct answer.
  3. True airspeed decreases as air density decreases
  4. True airspeed decreases because the angle of attack increases

Explanation

Indicated airspeed reflects dynamic pressure, which depends on density as well as true airspeed. As altitude increases and density falls, a given dynamic pressure corresponds to a higher true airspeed. This is why true airspeed is higher than indicated airspeed at altitude.

Question 45Principles of Flight

An aircraft stalls at 60 knots at a load factor of 1. What is the approximate stalling speed at a load factor of 4?

  1. 60 knots
  2. 120 knots Correct answer.
  3. 90 knots
  4. 150 knots

Explanation

Stalling speed increases with the square root of the load factor. The square root of 4 is 2, so the stalling speed doubles from 60 knots to about 120 knots. This is why maneuvering speed, which limits the load factor, is a critical structural and aerodynamic limit.

Question 46Principles of Flight

Why does a wing with significant dihedral tend to return to wings-level flight after a small disturbance in a slip?

  1. The lower wing meets the airflow at a higher effective angle of attack and produces more lift Correct answer.
  2. The vertical stabilizer forces the aircraft to roll level
  3. The center of gravity shifts laterally toward the lower wing
  4. The higher wing experiences greater dynamic pressure and produces more lift

Explanation

In a sideslip, the relative wind strikes the wing on the low side at a higher effective angle of attack because of the dihedral angle, generating more lift on that wing. The resulting rolling moment tends to raise the low wing and restore level flight. This is the mechanism of dihedral effect.

Question 47Principles of Flight

During a level turn at a constant airspeed, what happens to the induced drag compared with straight-and-level flight at the same airspeed?

  1. Induced drag decreases because the aircraft is banked
  2. Induced drag is unchanged because airspeed is constant
  3. Induced drag increases only if the turn is uncoordinated
  4. Induced drag increases because the wings must produce more lift Correct answer.

Explanation

In a level turn the lift vector is tilted, so its vertical component must still equal weight. The total lift must therefore exceed weight by the load factor, which raises the lift coefficient at a given airspeed. Higher lift coefficient means stronger wingtip vortices and greater induced drag, which is why turns require more power.

Question 48Principles of Flight

An aircraft is in a steady, coordinated turn at a constant altitude. How does the load factor vary with bank angle as the bank approaches 90 degrees?

  1. It increases linearly with the bank angle in degrees
  2. It decreases because the vertical component of lift falls
  3. It remains constant at 1 regardless of bank angle
  4. It increases without bound as the cosine of the bank angle approaches zero Correct answer.

Explanation

For a level turn the load factor equals one divided by the cosine of the bank angle. As the bank approaches 90 degrees, the cosine approaches zero and the required load factor grows without limit. In practice the aircraft stalls or reaches its structural limit long before such a bank can be sustained.

Question 49Principles of Flight

What is the effect of compressibility on a wing as the local airflow over the upper surface reaches the speed of sound?

  1. The wing stalls at a lower angle of attack with no change in drag
  2. Lift increases steadily because the air becomes denser
  3. The center of pressure moves forward without affecting handling
  4. Shock waves form and cause a rapid increase in drag and possible buffet Correct answer.

Explanation

When local airflow exceeds Mach 1, shock waves form on the wing, producing wave drag and often flow separation behind the shock. The result is a rapid drag rise, buffet, and possible loss of control effectiveness. This is why high-speed aircraft use swept or thin wings to raise the critical Mach number.

Question 50Principles of Flight

Why is the region of reversed command, or the back side of the power curve, important to a pilot during an approach?

  1. Above the minimum-drag speed, the aircraft cannot maintain altitude
  2. Below the minimum-drag speed, reducing airspeed requires more thrust and the aircraft responds sluggishly Correct answer.
  3. In this region, thrust has no effect on airspeed
  4. Below the minimum-drag speed, reducing airspeed requires less thrust and the aircraft accelerates

Explanation

On the back side of the power curve the aircraft is flying slower than the minimum-drag speed, where induced drag rises steeply as airspeed falls. To fly slower, the pilot must add power rather than reduce it, and airspeed control becomes sluggish. This is why approaches are flown with a margin above the minimum-drag speed.