# Questions - Aerodynamics, Assembly and Rigging

## Study Aid Questions

Fill in the Blanks

1. The study of objects in motion through the air and the ________ governing that motion come from the Greek combination of “aero” and “________”.

2. Atmospheric pressure is measured in ________ with a ________.

3. As an aircraft descends atmospheric pressure _______, the amount of oxygen in the air ________, and temperature ________.

4. Density varies ________ with temperature and ________ with pressure.

5. A body at rest does not move unless a force is applied to it is Newton’s law ________ and is known as the law of ________.

6. According to Bernoulli’s principle, fluid flowing through a constriction experiences a(n) ________ in speed.

7. Velocity increases and pressure decreases on the ________ of the wing.

8. A pilot can increase the lift of an aircraft by increasing the ________.

9. The acute angle the wing chord makes with the ________ axis is called angle of incidence.

10. The boundary layer is the layer of ________ closest to the surface and its behavior is controlled in order to minimize ________ drag and skin friction drag.

11. Fluids always move from ________ to ________ pressure. This principle explains the spanwise movement of air flow from the bottom of the wing ________ and upward around the wing creating spillage over the wingtip called ________.

12. An object that tends to returns to equilibrium is said to have positive ________ stability.

13. ________ control the lateral movements of the aircraft, the ________ controls the longitudinal movements, and the ________ controls the directional movements.

14. An autogryo is an aircraft with a horizontal rotor that is ________ and turns due to the passage of air ________ through the rotor.

15. The blade with the decreased angle of attack tends to flap ________.

16. The collective pitch control is operated with the ________ hand and is used to make pitch angle changes to ________ the main rotor blades.

17. There is a ________ of lift between the advancing and retreating blade.

18. Autorotation is possible through a freewheeling unit, a special ________ mechanism, which automatically disengages the engine in the event of its failure.

19. Helicopters with tandem rotors use the pedals to tilt the main rotors. When the ________ pedal is pushed forward the aft rotor moves to the ________.

20. Swaging tools generally have a ________ dimensions in an attempt to avoid defective or inferior swages.

21. Cables that travel completely through bulkheads require the use of a ________ and should not be deflected more than ________ from a straight line.

22. A groove or knurl around the end of the barrel of a ________ can be used to identify the ________ threads.

23. Structural alignment is the ________ of the main structural component related to the longitudinal datum line parallel to the aircraft centerline and the lateral datum line parallel to the line joining the ________.

24. Hard landings and abnormal flight experiences prompt a check of the wing ________ and angle of ________.

25. The most common method of safety wiring is the ________ however; a ________ method can be used for smaller screws and tight spaces.

## True or False

1. Air is considered a fluid. TRUE/FALSE

2. Atmospheric pressure changes with altitude. TRUE/FALSE

3. Aircraft can fly faster at lower altitudes because there is more pulling force from the engine cutting through the air. TRUE/FALSE

4. Density varies directly with humidity. TRUE/FALSE

5. Airflow over an airfoil can be explained using Bernoulli’s principle and this pressure differential is called lift. TRUE/FALSE

6. One wing can have numerous airfoil sections each with unique properties. TRUE/FALSE

7. The efficiency of a wing is measured in terms of wing camber and AOA. TRUE/FALSE

8. An aircraft has four forces acting upon it at all times: gravity, lift, thrust and weight. TRUE/FALSE

9. Induced drag increases as AOA increase. TRUE/FALSE

10. Center of pressure has the greatest affect on the stability of an aircraft. TRUE/FALSE

11. The vertical stabilizer is the primary surface that controls directional stability on the horizontal axis. TRUE/FALSE

12. Trim tabs enable the pilot to correct any unbalanced condition that may exist during flight without touching the flight controls. TRUE/FALSE

13. Canards are often used in swept wing aircraft to prevent spanwise air movements at high angles of attack. TRUE/FALSE

14. Stick shakers were installed in hydromechanical flight control systems which provide an artificial stall warning. TRUE/FALSE

15. At high forward speed a situation called retreating blade stall can occur because of the high AOA and slow relative wind speed. TRUE/FALSE

16. Control surfaces must be rebalanced whenever there is weight added to a control surface. TRUE/FALSE

17. The balance beam rebalancing method requires a specialized manufacturer made tool. TRUE/FALSE

18. Lead and steel are the most common materials used to balance control surfaces. TRUE/FALSE

19. The Type certification Data Sheet is issued by the manufacturer and includes information such as airspeed limitations, weight limits, and fuel type. TRUE/FALSE

20. A 7x19 cable is very rigid and used for engine controls and trim tab controls. TRUE/FALSE

21. Soldering cable ends is a common technique used to prevent fraying. TRUE/FALSE

22. Cables are checked for corrosion by bending them. TRUE/FALSE

23. A double‐wrap safety wire method is preferred when securing a turnbuckle. TRUE/FALSE

24. Rudder alignment is done by removing the controls surface from its hinges and passing a plumb bob though the hinge attachment holes. TRUE/FALSE

25. Cotter pins, unlike safety wire, can be re‐used. TRUE/FALSE

## Knowledge Application Questions

1. Why is air considered a fluid?
_____________________________________________________________________

2. What is atmospheric pressure and how is it measured?
_____________________________________________________________________

3. What is the relationship between density, pressure, and temperature?
_____________________________________________________________________

4. What is the difference between absolute humidity and relative humidity?
_____________________________________________________________________

5. What is Newton’s third law and what does it state?
_____________________________________________________________________

6. Describe how Bernoulli’s principle relates to a wing.
_____________________________________________________________________

7. Describe what happens to the resultant force as the AOA increases.
_____________________________________________________________________

8. Describe the other force produced besides lift as the relative motion of the air moves over the wing.
_____________________________________________________________________

9. What does control and controllability mean for a pilot and the aircraft?____________________________________________________________________

10. Explain the aerodynamic effect that occurs at and above the speed of sound.
_____________________________________________________________________

11. Explain what fully articulated means in relation to a helicopter rotor system.
_____________________________________________________________________

12. How does Newton’s third law relate to helicopters?
_____________________________________________________________________

13. Explain what a correlator is and what it does.
_____________________________________________________________________

14. What are the most common causes of high frequency vibrations?
_____________________________________________________________________

15. Why is no clutch necessary on a helicopter engine with a free turbine?
_____________________________________________________________________

16. Describe the use of pulleys and pulley guards.
_____________________________________________________________________

17. Control cable rigging generally consists of what three steps?
_____________________________________________________________________

18. What is the purpose of a turnbuckle?
_____________________________________________________________________

19. Where are cable drums typically found and what do they do?
_____________________________________________________________________

20. What are the types of inspection programs helicopter operates use in accordance with 14 CFR part 91?
_____________________________________________________________________

## Multiple Choice Questions

1. What happens to the pressure of a fluid in a container when it is heated?
a. Pressure increases
b. Pressure decreases
c. Pressure remains the same

2. At sea level, what is the average atmospheric pressure in psi, “Hg, and millibars respectively?
a. 1.47 psi, 29.92”Hg, 1013.25 mb
b. 14.7 psi, 29.92”Hg, 10.13 mb
c. 14.7 psi, 29.92”Hg, 1013.25 mb

3. A wing with a high fineness ratio has which of the following characteristics?
a. Thin wing, small amount of skin friction
b. Thick wing, small amount of skin friction
c. Thin wing, large amount of skin friction

4. When the AOA increases to maximum lift, what has been reached?
a. Critical angle
b. Burble point
c. Both A & B

5. ___________ is the quality of the response of an aircraft to the pilot's commands during maneuvers.
a. Stability
b. Controllability
c. Maneuverability

6. Which axis extends from nose to tail?
a. Vertical axis
b. Lateral axis
c. Longitudinal axis

7. What type of stability can be artificially increased with a yaw dampener?
a. Directional
b. Dynamic
c. Dutch roll

8. Which of the following type of aircraft structures reduce fuel consumption and increases range?
a. Wing fences
b. Winglets
c. Both A & B

9. Compressible aerodynamics deals with speeds at
a. Mach I and above
b. 250 mph and below
c. Mach 3‐Mach 5

10. Supersonic flight refers to flight between
a. 0‐Mach 1
b. Mach 1‐Mach 3
c. Mach 5 and above

11. The acute angle formed by the chord line of a wing and the relative wind is known as the
a. angle of attack
b. angle of incidence
c. longitudinal dihedral angle

12. Wing dihedral, a rigging consideration on most airplanes of conventional design, contributes most to stability of the airplane about its
a. longitudinal axis
b. lateral axis
c. vertical axis

13. Other than the manufacturer maintenance manual what other document could be used to determine the primary flight control surface deflection for an imported aircraft that is reassembled after shipment?
a. The certificate of airworthiness issued by the importing country
b. Import manual for the aircraft
c. Aircraft type certificate data sheet

14. If a pilot reports that an airplane flies left wing heavy, this condition may be corrected by
a. increasing the dihedral angle of the left wing, or decreasing the dihedral angle of the right wing, or both
b. increasing the angle of incidence of the left wing, or decreasing the angle of incidence of the right wing, or both
c. adjusting the dihedral angle of the left wing so that differential pressure between the upper and lower wing surfaces is increased

15. If the vertical fin of a single engine, propeller driven airplane is rigged properly, it will generally be parallel to
a. both the longitudinal and vertical axes
b. the vertical axis but not the longitudinal axis
c. the longitudinal axis but not the vertical axis

16. An airplane which has good longitudinal stability should have a minimum tendency to
a. pitch
b. roll
c. yaw

17. As the angle of attack of an airfoil increases, the center of pressure will
a. move toward the leading edge
b. remain stationary because both lift and drag components increase proportionally to increased angle of attack
c. move toward the trailing edge

18. The angle of incidence is that acute angle formed by
a. a line parallel to the wing from root to tip and a line parallel to the lateral axis of the aircraft
b. a line parallel to the wing chord and a line parallel to the longitudinal axis of the aircraft
c. the angular difference between the setting of the main airfoil and the auxiliary airfoil (horizontal stabilizer) in reference to the longitudinal axis of the aircraft

19. An airplane's center of lift is usually located aft of its center of gravity
a. to improve stability about the longitudinal axis
b. so that the airplane will have a tail heavy tendency
c. so that the airplane will have a nose heavy tendency

20. An airplane is controlled directionally about its vertical axis by the
a. ailerons
b. elevator(s)
c. rudder

21. The elevators of a conventional airplane are used to provide rotation about the
a. vertical axis
b. longitudinal axis
c. lateral axis

22. Washing in the left wing of a monoplane, for purposes of rigging corrections after flight test, will have what effect on the lift and drag of that wing?
a. Both drag and lift will decrease due to decreased angle of attack
b. Both drag and lift will increase due to increased angle of attack
c. The drag will decrease due to the effect of the lift increase

23. If the right wing of a monoplane is improperly rigged to a greater angle of incidence than designated in the manufacturer's specifications, it will cause the
a. airplane to be off balance both laterally and directionally
b. airplane to pitch and roll about the lateral axis
c. right wing to have both an increased lift and a decreased drag

24. The chord of a wing is measured from
a. leading edge to trailing edge
b. wingtip to wingtip
c. wing root to the wingtip

25. When the lift of an airfoil increases, the drag will
a. increase while the lift is changing but will return to its original value
b. also increase
c. decrease

26. What physical factors are involved in the aspect ratio of airplane wings?
a. Dihedral and angle of attack
b. Span and chord
c. Thickness and chord

27. Improper rigging of the elevator trim tab system will affect the balance of the airplane about its
a. vertical axis
b. lateral axis
c. longitudinal axis

28. An airplane that has a tendency to gradually increase a pitching moment that has been set into motion has
a. poor lateral stability
b. poor longitudinal stability
c. good lateral stability

29. The angle of incidence of an airplane
a. does not change in flight
b. affects the dihedral of the wings
c. is that angle between the relative wind and the chord of the wing

30. Buffeting is the intermittent application of forces to a part of an airplane. It is caused by
a. incorrect rigging of flaps
b. an unsteady flow from turbulence
c. incorrect rigging of ailerons

31. Movement of an airplane along its lateral axis (roll) is also movement
a. around or about the longitudinal axis controlled by the elevator
b. around or about the lateral axis controlled by the ailerons
c. around or about the longitudinal axis controlled by the ailerons

32. Rigging and alignment checks should not be undertaken in the open; however, if this cannot be avoided, the aircraft should be positioned
a. facing any direction since it makes no difference if the wind is steady (not gusting)
b. with the nose into the wind
c. obliquely into the wind

33. The correct dihedral angle can be determined by
a. measuring the angular setting of each wing at the rear spar with a bubble protractor
b. placing a straightedge and bubble protractor across the spars while the airplane is in flying position
c. using a dihedral board and bubble level along the front spar of each wing

34. The dihedral angle of a wing may be measured by placing a straightedge and level protractor on the
a. wing chord
b. front spar
c. wing root

35. Where would you find precise information to perform a symmetry alignment check for a particular aircraft?
a. Aircraft Specification or Type Certificate Data Sheet
b. Manufacturer's service bulletins
c. Aircraft service or maintenance manual

36. Proper wing twist in a sheet metal constructed wing can usually be checked by utilizing a
a. plum bob, string, and straightedge
b. straightedge, tape measure, and carpenter's square
c. bubble level and special fixtures described by the manufacturer

37. The vast majority of aircraft control cables are terminated with swaged terminals, that must be
a. corrosion treated to show compliance with the manufacturers requirements after the swaging operation
b. pull tested to show compliance with the manufactures requirements after the swaging operation
c. checked with a go-no-go gauge before and after, to show compliance with the manufacturers requirements after the swaging operation

38. What nondestructive checking method is normally used to ensure that the correct amount of swaging has taken place when installing swaged-type terminals on aircraft control cable?
a. Check the surface of the swaged portion of the terminal for small cracks which indicate incomplete swaging
b. Measure the finished length of the terminal barrel and compare with the beginning length
c. Use a terminal gauge to check the diameter of the swaged portion of the terminal

39. When inspecting a control cable turnbuckle for proper installation, determine that
a. the terminal end threads are visible through the safety hole in the barrel
b. the safety wire ends are wrapped a minimum of four turns around the terminal end shanks
c. no more than four threads are exposed on either side of the turnbuckle barrel

40. If all instructions issued by the swaging tool manufacturer are followed when swaging a cable terminal, the resultant swaged terminal strength should be
a. the full rated strength of the cable
b. 70 percent of the full rated strength of the cable
c. 80 percent of the full rated strength of the cable

41. Which is an acceptable safety device for a castle nut when installed on secondary structures?
a. Star washer
b. Cotter pin
c. Lockwasher

42. When used in close proximity to magnetic compasses, cotter pins are made of what material?
a. Anodized aluminum alloy
b. Corrosion resisting steel
c. Cadmium plated low carbon steel

43. When a fiber or nylon insert-type, self-locking nut can be threaded on a bolt or stud through the insert with only the fingers, it should be
a. reused only in a different location
b. rejected
c. re-torqued frequently

44. How are changes in direction of a control cable accomplished?
a. Pulleys
c. Bell cranks

45. What is the smallest size cable that may be used in aircraft primary control systems?
a. 1/8 inch
b. 1/4 inch
c. 5/16 inch

46. After repairing or recovering a rudder, the surface should be rebalanced
a. in its normal flight position
b. to its spanwise axis
c. to manufacturer's specifications

47. Placing a piece of cloth around a stainless steel control cable and running it back and forth over the length of the cable is generally a satisfactory method of
a. applying par-al-ketone
b. inspecting for wear or corrosion
c. inspecting for broken wires

48. The cable operated control system of an all metal aircraft, not incorporating a temperature compensating device, has been rigged to the correct tension in a heated hangar. If the aircraft is operated in very cold weather, the cable tension will
a. decrease when the aircraft structure and cables become cold
b. increase when the aircraft structure and cables become cold
c. be unaffected if stainless steel cable is installed

49. Very often, repairs to a control surface require static rebalancing of the control surface. Generally, flight control balance condition may be determined by
a. suspending the control surface from its leading edge in the streamline position and checking weight distribution
b. the behavior of the trailing edge when the surface is suspended from its hinge points
c. checking for equal distribution of weight throughout the control surface

50. Excessive wear on both of the sides of a control cable pulley groove is evidence of
a. excessive cable tension
b. pulley misalignment
c. cable misalignment

51. Fairleads should never deflect the alignment of a cable more than
a. 120
b. 30
c. 80

52. Where does the breakage of control cable wires occur most frequently?
a. Breakage usually occurs where cables are swaged to turnbuckle and ball terminals
b. Breakage sites are unpredictable and usually occur randomly anywhere along the length of a cable
c. Breakage usually occurs where cables pass over pulleys and through fairleads

53. With which system is differential control associated?
a. Aileron
b. Trim
c. Elevator

54. Which statement concerning the 100-hour inspection of an airplane equipped with a push pull tube type control system is true?
a. The terminal end threads of the turnbuckles should be visible through the safety hole in the barrel
b. The threaded rod ends should not be adjusted in length for rigging purposes because the rod ends have been properly positioned and staked during manufacture
c. The threaded rod ends should be checked for the amount of thread engagement by means of the inspection hole provided

55. If control cables are adjusted properly and the control surfaces tend to vibrate, the probable cause is
a. oil can effects on the control surfaces
b. excessive cable tension
c. worn attachment fittings

56. Stability about the axis which runs parallel to the line of flight is referred to as
a. longitudinal stability
b. lateral stability
c. directional stability

57. If the control stick of an aircraft with properly rigged flight controls is moved rearward and to the left, the right aileron will move
a. up and the elevator will move down
b. down and the elevator will move down
c. down and the elevator will move up

58. Movement of the cockpit control toward the nosedown position during a ground operational check of the elevator trim tab system will cause the trailing edge of the trim tab to move in which direction?
a. Downward regardless of elevator position
b. Upward regardless of elevator position
c. Downward if the elevator is in the UP position and upward if the elevator is in the DOWN position

59. If the control stick of an aircraft with properly rigged flight controls is moved forward and to the right, the left aileron will move
a. down and the elevator will move up
b. up and the elevator will move down
c. down and the elevator will move down

60. If the travel of an airplane's controls is correct but the cables are rigged exceptionally tight, what probable effect will this have when flying the airplane?
a. The pilot will be unable to fly the airplane hands off
b. The airplane will be heavy on the controls
c. The airplane will tend to fall off on one wing

61. During inspection of the flight control system of an airplane equipped with differential-type aileron control, side to side movement of the control stick will cause
a. each aileron to have greater down travel (from the streamlined position) than up travel
b. the left aileron to move through a greater number of degrees (from full up to full down) than the right aileron
c. each aileron to have a greater up travel (from the streamlined position) than down travel

62. A universal propeller protractor used to measure the degrees of aileron travel should be zeroed
a. with the aileron in the DOWN position
b. with the aileron in the NEUTRAL position
c. when the aircraft is in a level flight attitude

63. The universal propeller protractor can be used to measure
a. propeller track
b. aspect ratio of a wing
c. degrees of flap travel

64. A tension regulator in the flight control cable system of a large all metal aircraft is used primarily to
a. provide a means of changing cable tension in flight
b. retain a set tension
c. increase the cable tension in cold weather

65. (Refer to figure 1.) When the outside air temperature is 800F, select the acceptable 3/16 cable tension range.
a. 130 pounds minimum, 140 pounds maximum
b. 120 pounds minimum, 140 pounds maximum
c. 117 pounds minimum, 143 pounds maximum

66. Differential control on an aileron system means that
a. one aileron on one wing travels further up than the aileron on the opposite wing to adjust for wash in and wash out
b. the up travel is more than the down travel
c. the down travel is more than the up travel

67. Why is it generally necessary to jack an aircraft indoors for weighing?
a. So that air currents do not destabilize the scales
b. So weighing scales may be calibrated to 0 pounds
c. So aircraft may be placed in a level position

68. Which should be accomplished before jacking an aircraft?
a. Install critical stress panels or plates
b. Determine that the fuel tanks are empty
c. Make sure the aircraft is leveled laterally

69. Which rebalancing method can be performed without removing the control surface from the aircraft?
a. Calculation method
b. Scale method
c. Balance beam method

70. Where should rigging and alignment checks be performed?
a. On the ramp
b. In an enclosed hangar
c. At a specialized maintenance facility

71. ELT tests should be conducted
a. During the last 5 minutes of any hour
b. During the first 5 minutes of any hour
c. During the first 15 minutes of any hour

72. What type of rotor is found on aircraft with dual rotor blades?
a. Fully articulated
b. Semi rigid
c. Rigid

73. Drift in the direction of the tail rotor during hover is called
a. Ground effect
b. Translational tendency
c. Translational lift

74. Effective translational lift is experienced at what airspeed?
a. Between hover and 16 knots
b. Between 16‐24 knots
c. 24 knots and above

75. How does a pilot compensate for blowback?
a. Move the cyclic forward
b. Move the cyclic aft
c. Pull up on the collective

76. What component transmits the control inputs from the collective and cyclic to the main rotor blades?
a. Transmission
b. Control rod
c. Swash plate

77. Where is the throttle control located in a helicopter?
a. On the collective
b. On the cyclic
c. On a lever next to the collective

78. The auxiliary (tail) rotor of a helicopter permits the pilot to compensate for and/or accomplish which of the following?
a. Attitude and airspeed
b. Lateral and yaw position
c. Torque and directional control

79. The vertical flight of a helicopter is controlled by
a. collective pitch changes
b. cyclic pitch changes
c. increasing or decreasing the RPM of the main rotor

80. A decrease in pitch angle of the tail rotor blades on a helicopter
a. causes the tail to pivot in the opposite direction of torque rotation around the main rotor axis
b. causes the tail to pivot in the direction of torque rotation around the main rotor axis
c. is required to counteract main rotor torque produced by takeoff RPM

81. In rotorcraft external-loading, the ideal location of the cargo release is where the line of action passes
a. aft of the center of gravity at all times
b. forward of the center of gravity at all times
c. through the center of gravity at all times

82. A helicopter in forward flight, cruise configuration, changes direction by
a. varying the pitch of the main rotor blades
b. changing rotor RPM
c. tilting the main rotor disk in the desired direction

83. The purpose in checking main rotor blade tracking is to determine the
a. extent of an out of balance condition during rotation
b. flight path of the blades during rotation
c. relative position of the blades during rotation

84. In a hovering helicopter equipped with a tail rotor, directional control is maintained by
a. tilting the main rotor disk in the desired direction
b. changing the tail rotor RPM
c. varying the pitch of the tail rotor blades

85. If a single rotor helicopter is in forward horizontal flight, the angle of attack of the advancing blade is
a. equal to the retreating blade
b. more than the retreating blade
c. less than the retreating blade

86. Main rotor blades that do not cone by the same amount during rotation are said to be out of
a. balance
b. collective pitch
c. track

87. One purpose of the freewheeling unit required between the engine and the helicopter transmission is to
a. disconnect the rotor from the engine to relieve the starter load
b. automatically disengage the rotor from the engine in case of an engine failure
c. permit practice of autorotation landings

88. Which statement is correct concerning torque effect on helicopters?
a. As horsepower decreases, torque increases
b. Torque direction is the opposite of rotor blade rotation
c. Torque direction is the same as rotor blade rotation

89. What is the purpose of the free wheeling unit in a helicopter drive system?
a. It releases the rotor brake for starting
b. It relieves bending stress on the rotor blades during starting
c. It disconnects the rotor whenever the engine stops or slows below the equivalent of rotor RPM

90. Movement about the longitudinal axis (roll) in a helicopter is effected by movement of the
a. cyclic pitch control
b. collective pitch control
c. tail rotor pitch control

91. Movement about the lateral axis (pitch) in a helicopter is effected by movement of the
a. collective pitch control
b. cyclic pitch control
c. tail rotor pitch control

REFERENCES