Mathematical Problems in Rotorcraft Dynamics and Aeromechanics
1. What is the typical main rotor angular velocity (Ω) of a medium-sized helicopter in radians per
second?
a) 10 rad/s
b) 20 rad/s
c) 30 rad/s
d) 40 rad/s
Answer: b) 20 rad/s
2. If a helicopter's main rotor has a radius of 7 meters, what is the tip speed at 350 RPM?
a) 220 m/s
b) 256 m/s
c) 286 m/s
d) 314 m/s
Answer: b) 256 m/s
3. Calculate the induced velocity (vi) for a helicopter with a rotor disk area of 150 m², thrust of
40,000 N, and air density of 1.225 kg/m³.
a) 10.5 m/s
b) 11.8 m/s
c) 13.2 m/s
d) 14.6 m/s
Answer: c) 13.2 m/s
4. What is the advancing blade tip Mach number for a helicopter flying at 50 m/s, with a rotor tip
speed of 220 m/s and speed of sound 340 m/s?
a) 0.65
b) 0.71
c) 0.79
d) 0.85
Answer: c) 0.79
5. Calculate the coning angle (in degrees) for a rotor with a blade mass of 100 kg, rotor radius of 6 m,
angular velocity of 30 rad/s, and centrifugal force of 540,000 N.
a) 2.8°
b) 3.2°
c) 3.6°
d) 4.0°
Answer: b) 3.2°
6. What is the power required for a helicopter with a gross weight of 5000 kg, rotor disk area of 120
m², and hover induced velocity of 15 m/s?
a) 650 kW
b) 735 kW
c) 820 kW
d) 905 kW
Answer: b) 735 kW
7. Calculate the blade loading coefficient (CT/σ) for a helicopter with a thrust coefficient of 0.008 and
a solidity ratio of 0.08.
a) 0.05
b) 0.10
c) 0.15
d) 0.20
Answer: b) 0.10
8. What is the retreating blade stall speed (in knots) for a helicopter with a rotor tip speed of 650 ft/s
and an advancing blade tip Mach number limit of 0.9?
a) 120 knots
b) 135 knots
c) 150 knots
d) 165 knots
Answer: c) 150 knots
9. Calculate the rotor solidity for a 4-bladed rotor with a blade chord of 0.5 m and a rotor radius of 6
m.
a) 0.106
b) 0.133
c) 0.167
d) 0.200
Answer: b) 0.133
10. What is the autorotation rate of descent (in ft/min) for a helicopter with a disk loading of 4 lb/ft²
and a main rotor speed of 300 RPM?
a) 1600 ft/min
b) 1800 ft/min
c) 2000 ft/min
d) 2200 ft/min
Answer: c) 2000 ft/min
11. Calculate the thrust coefficient (CT) for a helicopter with a gross weight of 4500 kg, rotor radius
of 7 m, air density of 1.225 kg/m³, and rotor angular velocity of 25 rad/s.
a) 0.0042
b) 0.0053
c) 0.0064
d) 0.0075
Answer: c) 0.0064
12. What is the figure of merit for a helicopter rotor with an ideal power of 500 kW and an actual
power of 625 kW?
a) 0.70
b) 0.75
c) 0.80
d) 0.85
Answer: c) 0.80
13. Calculate the induced power factor (κ) for a helicopter in forward flight at an advance ratio of 0.3
and a thrust coefficient of 0.006.
a) 1.15
b) 1.20
c) 1.25
d) 1.30
Answer: b) 1.20
14. What is the main rotor torque (in N·m) for a helicopter with a main rotor power of 1000 kW and
an angular velocity of 40 rad/s?
a) 22,500 N·m
b) 25,000 N·m
c) 27,500 N·m
d) 30,000 N·m
Answer: b) 25,000 N·m
15. Calculate the advance ratio (μ) for a helicopter flying at 60 m/s with a rotor tip speed of 200 m/s.
a) 0.25
b) 0.30
c) 0.35
d) 0.40
Answer: b) 0.30
16. What is the blade flapping frequency (per revolution) for a rotor with a flapping hinge offset of
5% of the rotor radius?
a) 1.00
b) 1.02
c) 1.05
d) 1.08
Answer: c) 1.05
17. Calculate the profile power coefficient (CPo) for a rotor with a solidity ratio of 0.08 and an
average blade drag coefficient of 0.008.
a) 0.00064
b) 0.00080
c) 0.00096
d) 0.00112
Answer: a) 0.00064
18. What is the rotor disk area (in m²) for a helicopter with a disk loading of 300 N/m² and a gross
weight of 45,000 N?
a) 120 m²
b) 140 m²
c) 150 m²
d) 160 m²
Answer: c) 150 m²
19. Calculate the blade Lock number (γ) for a rotor blade with a chord of 0.5 m, lift curve slope of
5.7/rad, air density of 1.225 kg/m³, moment of inertia of 250 kg·m², and radius of 6 m.
a) 6.5
b) 7.5
c) 8.5
d) 9.5
Answer: c) 8.5
20. What is the tip path plane angle (in degrees) for a helicopter with a forward speed of 40 m/s,
induced velocity of 10 m/s, and rotor angular velocity of 30 rad/s?
a) 4.5°
b) 5.0°
c) 5.5°
d) 6.0°
Answer: b) 5.0°
21. Calculate the blade pitch angle (in degrees) required for a rotor to produce a thrust coefficient of
0.006, given a lift curve slope of 5.7/rad and a solidity ratio of 0.08.
a) 6.5°
b) 7.0°
c) 7.5°
d) 8.0°
Answer: c) 7.5°
22. What is the rotor inflow ratio (λ) for a helicopter in forward flight with an advance ratio of 0.25
and an induced velocity ratio of 0.05?
a) 0.0125
b) 0.0250
c) 0.0375
d) 0.0500
Answer: c) 0.0375
23. Calculate the maximum continuous power (in kW) for a helicopter engine with a specific fuel
consumption of 0.5 lb/hp·hr, a fuel flow rate of 400 lb/hr, and a mechanical efficiency of 0.95.
a) 520 kW
b) 560 kW
c) 600 kW
d) 640 kW
Answer: b) 560 kW
24. What is the blade loading (in N/m²) for a helicopter with a gross weight of 50,000 N, 4 rotor
blades, each with a planform area of 4 m²?
a) 2500 N/m²
b) 3000 N/m²
c) 3125 N/m²
d) 3500 N/m²
Answer: c) 3125 N/m²
25. Calculate the induced power (in kW) for a helicopter with a gross weight of 40,000 N, rotor disk
area of 130 m², and air density of 1.225 kg/m³.
a) 440 kW
b) 480 kW
c) 520 kW
d) 560 kW
Answer: b) 480 kW
26. What is the critical azimuth angle (in degrees) for blade stall on the retreating side of the rotor
disk, given an advance ratio of 0.3?
a) 240°
b) 250°
c) 260°
d) 270°
Answer: d) 270°
27. Calculate the rotor thrust (in N) for a helicopter with a thrust coefficient of 0.007, air density of
1.225 kg/m³, rotor radius of 6 m, and rotor angular velocity of 35 rad/s.
a) 38,000 N
b) 42,000 N
c) 46,000 N
d) 50,000 N
Answer: c) 46,000 N
28. What is the tip loss factor for a rotor with 4 blades and an aspect ratio of 15?
a) 0.95
b) 0.96
c) 0.97
d) 0.98
Answer: c) 0.97
29. Calculate the parasite drag area (fe) in m² for a helicopter with a gross weight of 35,000 N and an
equivalent flat plate area of 1.5 m².
a) 0.75 m²
b) 1.00 m²
c) 1.25 m²
d) 1.50 m²
Answer: d) 1.50 m²
30. What is the main rotor torque coefficient (CQ) for a helicopter with a power coefficient of 0.0004
and an advance ratio of 0.2?
a) 0.00032
b) 0.00036
c) 0.00040
d) 0.00044
Answer: c) 0.00040
31. Calculate the blade twist angle (in degrees) for a rotor blade with a root pitch of 12° and a tip
pitch of 2°, assuming linear twist.
a) -8°
b) -10°
c) -12°
d) -14°
Answer: b) -10°
32. What is the rotor downwash velocity (in m/s) for a helicopter with a thrust of 50,000 N, rotor disk
area of 150 m², and air density of 1.225 kg/m³?
a) 12.5 m/s
b) 13.5 m/s
c) 14.5 m/s
d) 15.5 m/s
Answer: c) 14.5 m/s
33. Calculate the blade flapping angle (in degrees) for a rotor with a flapping hinge offset of 4%,
thrust coefficient of 0.006, and blade Lock number of 8.
a) 3.5°
b) 4.0°
c) 4.5°
d) 5.0°
Answer: b) 4.0°
34. What is the rotor solidity ratio for a 5-bladed rotor with a blade chord of 0.4 m and a rotor radius
of 5 m?
a) 0.110
b) 0.127
c) 0.144
d) 0.161
Answer: b) 0.127
35. Calculate the main rotor power (in kW) required for a helicopter with a gross weight of 55,000 N,
induced velocity of 12 m/s, and a figure of merit of 0.75.
a) 720 kW
b) 780 kW
c) 840 kW
d) 900 kW
Answer: c) 840 kW
36. What is the advance ratio (μ) for a helicopter flying at 80 knots with a rotor tip speed of 700 ft/s?
a) 0.18
b) 0.22
c) 0.26
d) 0.30
Answer: b) 0.22
37. Calculate the blade coning angle (in degrees) for a rotor with a centrifugal force of 100,000 N,
blade weight of 1000 N, and a rotor radius of 6 m.
a) 2.5°
b) 3.0°
c) 3.5°
d) 4.0°
Answer: c) 3.5°
38. What is the rotor disk loading (in N/m²) for a helicopter with a gross weight of 60,000 N and a
rotor radius of 7 m?
a) 350 N/m²
b) 375 N/m²
c) 400 N/m²
d) 425 N/m²
Answer: c) 400 N/m²
39. Calculate the induced power factor (κ) for a tandem-rotor helicopter in hover with an overlap
ratio of 0.2.
a) 0.85
b) 0.90
c) 0.95
d) 1.00
Answer: b) 0.90
40. What is the tip Mach number for a rotor with a tip speed of 220 m/s, given the speed of sound is
340 m/s?
a) 0.60
b) 0.65
c) 0.70
d) 0.75
Answer: b) 0.65
41. Calculate the profile power (in kW) for a helicopter rotor with a solidity ratio of 0.08, average
blade drag coefficient of 0.008, air density of 1.225 kg/m³, rotor radius of 7 m, and tip speed of 200
m/s.
a) 120 kW
b) 140 kW
c) 160 kW
d) 180 kW
Answer: c) 160 kW
What is the retreating blade stall speed (in knots) for a helicopter with a rotor tip speed of 650 ft/s
and an advancing blade tip Mach number limit of 0.9?
a) 120 knots
b) 135 knots
c) 150 knots
d) 165 knots
Answer: c) 150 knots
9. Calculate the rotor solidity for a 4-bladed rotor with a blade chord of 0.5 m and a rotor radius of 6
m.
a) 0.106
b) 0.133
c) 0.167
d) 0.200
Answer: b) 0.133
10. What is the autorotation rate of descent (in ft/min) for a helicopter with a disk loading of 4 lb/ft²
and a main rotor speed of 300 RPM?
a) 1600 ft/min
b) 1800 ft/min
c) 2000 ft/min
d) 2200 ft/min
Answer: c) 2000 ft/min
11. Calculate the thrust coefficient (CT) for a helicopter with a gross weight of 4500 kg, rotor radius
of 7 m, air density of 1.225 kg/m³, and rotor angular velocity of 25 rad/s.
a) 0.0042
b) 0.0053
c) 0.0064
d) 0.0075
Answer: c) 0.0064
12. What is the figure of merit for a helicopter rotor with an ideal power of 500 kW and an actual
power of 625 kW?
a) 0.70
b) 0.75
c) 0.80
d) 0.85
Answer: c) 0.80
13. Calculate the induced power factor (κ) for a helicopter in forward flight at an advance ratio of 0.3
and a thrust coefficient of 0.006.
a) 1.15
b) 1.20
c) 1.25
d) 1.30
Answer: b) 1.20
14. What is the main rotor torque (in N·m) for a helicopter with a main rotor power of 1000 kW and
an angular velocity of 40 rad/s?
a) 22,500 N·m
b) 25,000 N·m
c) 27,500 N·m
d) 30,000 N·m
Answer: b) 25,000 N·m
15. Calculate the advance ratio (μ) for a helicopter flying at 60 m/s with a rotor tip speed of 200 m/s.
a) 0.25
b) 0.30
c) 0.35
d) 0.40
Answer: b) 0.30
16. What is the blade flapping frequency (per revolution) for a rotor with a flapping hinge offset of
5% of the rotor radius?
a) 1.00
b) 1.02
c) 1.05
d) 1.08
Answer: c) 1.05
17. Calculate the profile power coefficient (CPo) for a rotor with a solidity ratio of 0.08 and an
average blade drag coefficient of 0.008.
a) 0.00064
b) 0.00080
c) 0.00096
d) 0.00112
Answer: a) 0.00064
18. What is the rotor disk area (in m²) for a helicopter with a disk loading of 300 N/m² and a gross
weight of 45,000 N?
a) 120 m²
b) 140 m²
c) 150 m²
d) 160 m²
Answer: c) 150 m²
19. Calculate the blade Lock number (γ) for a rotor blade with a chord of 0.5 m, lift curve slope of
5.7/rad, air density of 1.225 kg/m³, moment of inertia of 250 kg·m², and radius of 6 m.
a) 6.5
b) 7.5
c) 8.5
d) 9.5
Answer: c) 8.5
20. What is the tip path plane angle (in degrees) for a helicopter with a forward speed of 40 m/s,
induced velocity of 10 m/s, and rotor angular velocity of 30 rad/s?
a) 4.5°
b) 5.0°
c) 5.5°
d) 6.0°
Answer: b) 5.0°
21. Calculate the blade pitch angle (in degrees) required for a rotor to produce a thrust coefficient of
0.006, given a lift curve slope of 5.7/rad and a solidity ratio of 0.08.
a) 6.5°
b) 7.0°
c) 7.5°
d) 8.0°
Answer: c) 7.5°
22. What is the rotor inflow ratio (λ) for a helicopter in forward flight with an advance ratio of 0.25
and an induced velocity ratio of 0.05?
a) 0.0125
b) 0.0250
c) 0.0375
d) 0.0500
Answer: c) 0.0375
23. Calculate the maximum continuous power (in kW) for a helicopter engine with a specific fuel
consumption of 0.5 lb/hp·hr, a fuel flow rate of 400 lb/hr, and a mechanical efficiency of 0.95.
a) 520 kW
b) 560 kW
c) 600 kW
d) 640 kW
Answer: b) 560 kW
24. What is the blade loading (in N/m²) for a helicopter with a gross weight of 50,000 N, 4 rotor
blades, each with a planform area of 4 m²?
a) 2500 N/m²
b) 3000 N/m²
c) 3125 N/m²
d) 3500 N/m²
Answer: c) 3125 N/m²
25. Calculate the induced power (in kW) for a helicopter with a gross weight of 40,000 N, rotor disk
area of 130 m², and air density of 1.225 kg/m³.
a) 440 kW
b) 480 kW
c) 520 kW
d) 560 kW
Answer: b) 480 kW
26. What is the critical azimuth angle (in degrees) for blade stall on the retreating side of the rotor
disk, given an advance ratio of 0.3?
a) 240°
b) 250°
c) 260°
d) 270°
Answer: d) 270°
27. Calculate the rotor thrust (in N) for a helicopter with a thrust coefficient of 0.007, air density of
1.225 kg/m³, rotor radius of 6 m, and rotor angular velocity of 35 rad/s.
a) 38,000 N
b) 42,000 N
c) 46,000 N
d) 50,000 N
Answer: c) 46,000 N
28. What is the tip loss factor for a rotor with 4 blades and an aspect ratio of 15?
a) 0.95
b) 0.96
c) 0.97
d) 0.98
Answer: c) 0.97
29. Calculate the parasite drag area (fe) in m² for a helicopter with a gross weight of 35,000 N and an
equivalent flat plate area of 1.5 m².
a) 0.75 m²
b) 1.00 m²
c) 1.25 m²
d) 1.50 m²
Answer: d) 1.50 m²
30. What is the main rotor torque coefficient (CQ) for a helicopter with a power coefficient of 0.0004
and an advance ratio of 0.2?
a) 0.00032
b) 0.00036
c) 0.00040
d) 0.00044
Answer: c) 0.00040
31. Calculate the blade twist angle (in degrees) for a rotor blade with a root pitch of 12° and a tip
pitch of 2°, assuming linear twist.
a) -8°
b) -10°
c) -12°
d) -14°
Answer: b) -10°
32. What is the rotor downwash velocity (in m/s) for a helicopter with a thrust of 50,000 N, rotor disk
area of 150 m², and air density of 1.225 kg/m³?
a) 12.5 m/s
b) 13.5 m/s
c) 14.5 m/s
d) 15.5 m/s
Answer: c) 14.5 m/s
33. Calculate the blade flapping angle (in degrees) for a rotor with a flapping hinge offset of 4%,
thrust coefficient of 0.006, and blade Lock number of 8.
a) 3.5°
b) 4.0°
c) 4.5°
d) 5.0°
Answer: b) 4.0°
34. What is the rotor solidity ratio for a 5-bladed rotor with a blade chord of 0.4 m and a rotor radius
of 5 m?
a) 0.110
b) 0.127
c) 0.144
d) 0.161
Answer: b) 0.127
35. Calculate the main rotor power (in kW) required for a helicopter with a gross weight of 55,000 N,
induced velocity of 12 m/s, and a figure of merit of 0.75.
a) 720 kW
b) 780 kW
c) 840 kW
d) 900 kW
Answer: c) 840 kW
36. What is the advance ratio (μ) for a helicopter flying at 80 knots with a rotor tip speed of 700 ft/s?
a) 0.18
b) 0.22
c) 0.26
d) 0.30
Answer: b) 0.22
37. Calculate the blade coning angle (in degrees) for a rotor with a centrifugal force of 100,000 N,
blade weight of 1000 N, and a rotor radius of 6 m.
a) 2.5°
b) 3.0°
c) 3.5°
d) 4.0°
Answer: c) 3.5°
38. What is the rotor disk loading (in N/m²) for a helicopter with a gross weight of 60,000 N and a
rotor radius of 7 m?
a) 350 N/m²
b) 375 N/m²
c) 400 N/m²
d) 425 N/m²
Answer: c) 400 N/m²
39. Calculate the induced power factor (κ) for a tandem-rotor helicopter in hover with an overlap
ratio of 0.2.
a) 0.85
b) 0.90
c) 0.95
d) 1.00
Answer: b) 0.90
40. What is the tip Mach number for a rotor with a tip speed of 220 m/s, given the speed of sound is
340 m/s?
a) 0.60
b) 0.65
c) 0.70
d) 0.75
Answer: b) 0.65
41. Calculate the profile power (in kW) for a helicopter rotor with a solidity ratio of 0.08, average
blade drag coefficient of 0.008, air density of 1.225 kg/m³, rotor radius of 7 m, and tip speed of 200
m/s.
a) 120 kW
b) 140 kW
c) 160 kW
d) 180 kW
Answer: c) 160 kW
What is the retreating blade stall speed (in knots) for a helicopter with a rotor tip speed of 650 ft/s
and an advancing blade tip Mach number limit of 0.9?
a) 120 knots
b) 135 knots
c) 150 knots
d) 165 knots
Answer: c) 150 knots
9. Calculate the rotor solidity for a 4-bladed rotor with a blade chord of 0.5 m and a rotor radius of 6
m.
a) 0.106
b) 0.133
c) 0.167
d) 0.200
Answer: b) 0.133
10. What is the autorotation rate of descent (in ft/min) for a helicopter with a disk loading of 4 lb/ft²
and a main rotor speed of 300 RPM?
a) 1600 ft/min
b) 1800 ft/min
c) 2000 ft/min
d) 2200 ft/min
Answer: c) 2000 ft/min
11. Calculate the thrust coefficient (CT) for a helicopter with a gross weight of 4500 kg, rotor radius
of 7 m, air density of 1.225 kg/m³, and rotor angular velocity of 25 rad/s.
a) 0.0042
b) 0.0053
c) 0.0064
d) 0.0075
Answer: c) 0.0064
12. What is the figure of merit for a helicopter rotor with an ideal power of 500 kW and an actual
power of 625 kW?
a) 0.70
b) 0.75
c) 0.80
d) 0.85
Answer: c) 0.80
13. Calculate the induced power factor (κ) for a helicopter in forward flight at an advance ratio of 0.3
and a thrust coefficient of 0.006.
a) 1.15
b) 1.20
c) 1.25
d) 1.30
Answer: b) 1.20
14. What is the main rotor torque (in N·m) for a helicopter with a main rotor power of 1000 kW and
an angular velocity of 40 rad/s?
a) 22,500 N·m
b) 25,000 N·m
c) 27,500 N·m
d) 30,000 N·m
Answer: b) 25,000 N·m
15. Calculate the advance ratio (μ) for a helicopter flying at 60 m/s with a rotor tip speed of 200 m/s.
a) 0.25
b) 0.30
c) 0.35
d) 0.40
Answer: b) 0.30
16. What is the blade flapping frequency (per revolution) for a rotor with a flapping hinge offset of
5% of the rotor radius?
a) 1.00
b) 1.02
c) 1.05
d) 1.08
Answer: c) 1.05
17. Calculate the profile power coefficient (CPo) for a rotor with a solidity ratio of 0.08 and an
average blade drag coefficient of 0.008.
a) 0.00064
b) 0.00080
c) 0.00096
d) 0.00112
Answer: a) 0.00064
18. What is the rotor disk area (in m²) for a helicopter with a disk loading of 300 N/m² and a gross
weight of 45,000 N?
a) 120 m²
b) 140 m²
c) 150 m²
d) 160 m²
Answer: c) 150 m²
19. Calculate the blade Lock number (γ) for a rotor blade with a chord of 0.5 m, lift curve slope of
5.7/rad, air density of 1.225 kg/m³, moment of inertia of 250 kg·m², and radius of 6 m.
a) 6.5
b) 7.5
c) 8.5
d) 9.5
Answer: c) 8.5
20. What is the tip path plane angle (in degrees) for a helicopter with a forward speed of 40 m/s,
induced velocity of 10 m/s, and rotor angular velocity of 30 rad/s?
a) 4.5°
b) 5.0°
c) 5.5°
d) 6.0°
Answer: b) 5.0°
21. Calculate the blade pitch angle (in degrees) required for a rotor to produce a thrust coefficient of
0.006, given a lift curve slope of 5.7/rad and a solidity ratio of 0.08.
a) 6.5°
b) 7.0°
c) 7.5°
d) 8.0°
Answer: c) 7.5°
22. What is the rotor inflow ratio (λ) for a helicopter in forward flight with an advance ratio of 0.25
and an induced velocity ratio of 0.05?
a) 0.0125
b) 0.0250
c) 0.0375
d) 0.0500
Answer: c) 0.0375
23. Calculate the maximum continuous power (in kW) for a helicopter engine with a specific fuel
consumption of 0.5 lb/hp·hr, a fuel flow rate of 400 lb/hr, and a mechanical efficiency of 0.95.
a) 520 kW
b) 560 kW
c) 600 kW
d) 640 kW
Answer: b) 560 kW
24. What is the blade loading (in N/m²) for a helicopter with a gross weight of 50,000 N, 4 rotor
blades, each with a planform area of 4 m²?
a) 2500 N/m²
b) 3000 N/m²
c) 3125 N/m²
d) 3500 N/m²
Answer: c) 3125 N/m²
25. Calculate the induced power (in kW) for a helicopter with a gross weight of 40,000 N, rotor disk
area of 130 m², and air density of 1.225 kg/m³.
a) 440 kW
b) 480 kW
c) 520 kW
d) 560 kW
Answer: b) 480 kW
26. What is the critical azimuth angle (in degrees) for blade stall on the retreating side of the rotor
disk, given an advance ratio of 0.3?
a) 240°
b) 250°
c) 260°
d) 270°
Answer: d) 270°
27. Calculate the rotor thrust (in N) for a helicopter with a thrust coefficient of 0.007, air density of
1.225 kg/m³, rotor radius of 6 m, and rotor angular velocity of 35 rad/s.
a) 38,000 N
b) 42,000 N
c) 46,000 N
d) 50,000 N
Answer: c) 46,000 N
28. What is the tip loss factor for a rotor with 4 blades and an aspect ratio of 15?
a) 0.95
b) 0.96
c) 0.97
d) 0.98
Answer: c) 0.97
29. Calculate the parasite drag area (fe) in m² for a helicopter with a gross weight of 35,000 N and an
equivalent flat plate area of 1.5 m².
a) 0.75 m²
b) 1.00 m²
c) 1.25 m²
d) 1.50 m²
Answer: d) 1.50 m²
30. What is the main rotor torque coefficient (CQ) for a helicopter with a power coefficient of 0.0004
and an advance ratio of 0.2?
a) 0.00032
b) 0.00036
c) 0.00040
d) 0.00044
Answer: c) 0.00040
31. Calculate the blade twist angle (in degrees) for a rotor blade with a root pitch of 12° and a tip
pitch of 2°, assuming linear twist.
a) -8°
b) -10°
c) -12°
d) -14°
Answer: b) -10°
32. What is the rotor downwash velocity (in m/s) for a helicopter with a thrust of 50,000 N, rotor disk
area of 150 m², and air density of 1.225 kg/m³?
a) 12.5 m/s
b) 13.5 m/s
c) 14.5 m/s
d) 15.5 m/s
Answer: c) 14.5 m/s
33. Calculate the blade flapping angle (in degrees) for a rotor with a flapping hinge offset of 4%,
thrust coefficient of 0.006, and blade Lock number of 8.
a) 3.5°
b) 4.0°
c) 4.5°
d) 5.0°
Answer: b) 4.0°
34. What is the rotor solidity ratio for a 5-bladed rotor with a blade chord of 0.4 m and a rotor radius
of 5 m?
a) 0.110
b) 0.127
c) 0.144
d) 0.161
Answer: b) 0.127
35. Calculate the main rotor power (in kW) required for a helicopter with a gross weight of 55,000 N,
induced velocity of 12 m/s, and a figure of merit of 0.75.
a) 720 kW
b) 780 kW
c) 840 kW
d) 900 kW
Answer: c) 840 kW
36. What is the advance ratio (μ) for a helicopter flying at 80 knots with a rotor tip speed of 700 ft/s?
a) 0.18
b) 0.22
c) 0.26
d) 0.30
Answer: b) 0.22
37. Calculate the blade coning angle (in degrees) for a rotor with a centrifugal force of 100,000 N,
blade weight of 1000 N, and a rotor radius of 6 m.
a) 2.5°
b) 3.0°
c) 3.5°
d) 4.0°
Answer: c) 3.5°
38. What is the rotor disk loading (in N/m²) for a helicopter with a gross weight of 60,000 N and a
rotor radius of 7 m?
a) 350 N/m²
b) 375 N/m²
c) 400 N/m²
d) 425 N/m²
Answer: c) 400 N/m²
39. Calculate the induced power factor (κ) for a tandem-rotor helicopter in hover with an overlap
ratio of 0.2.
a) 0.85
b) 0.90
c) 0.95
d) 1.00
Answer: b) 0.90
40. What is the tip Mach number for a rotor with a tip speed of 220 m/s, given the speed of sound is
340 m/s?
a) 0.60
b) 0.65
c) 0.70
d) 0.75
Answer: b) 0.65
41. Calculate the profile power (in kW) for a helicopter rotor with a solidity ratio of 0.08, average
blade drag coefficient of 0.008, air density of 1.225 kg/m³, rotor radius of 7 m, and tip speed of 200
m/s.
a) 120 kW
b) 140 kW
c) 160 kW
d) 180 kW
Answer: c) 160 kW
What is the retreating blade stall speed (in knots) for a helicopter with a rotor tip speed of 650 ft/s
and an advancing blade tip Mach number limit of 0.9?
a) 120 knots
b) 135 knots
c) 150 knots
d) 165 knots
Answer: c) 150 knots
9. Calculate the rotor solidity for a 4-bladed rotor with a blade chord of 0.5 m and a rotor radius of 6
m.
a) 0.106
b) 0.133
c) 0.167
d) 0.200
Answer: b) 0.133
10. What is the autorotation rate of descent (in ft/min) for a helicopter with a disk loading of 4 lb/ft²
and a main rotor speed of 300 RPM?
a) 1600 ft/min
b) 1800 ft/min
c) 2000 ft/min
d) 2200 ft/min
Answer: c) 2000 ft/min
11. Calculate the thrust coefficient (CT) for a helicopter with a gross weight of 4500 kg, rotor radius
of 7 m, air density of 1.225 kg/m³, and rotor angular velocity of 25 rad/s.
a) 0.0042
b) 0.0053
c) 0.0064
d) 0.0075
Answer: c) 0.0064
12. What is the figure of merit for a helicopter rotor with an ideal power of 500 kW and an actual
power of 625 kW?
a) 0.70
b) 0.75
c) 0.80
d) 0.85
Answer: c) 0.80
13. Calculate the induced power factor (κ) for a helicopter in forward flight at an advance ratio of 0.3
and a thrust coefficient of 0.006.
a) 1.15
b) 1.20
c) 1.25
d) 1.30
Answer: b) 1.20
14. What is the main rotor torque (in N·m) for a helicopter with a main rotor power of 1000 kW and
an angular velocity of 40 rad/s?
a) 22,500 N·m
b) 25,000 N·m
c) 27,500 N·m
d) 30,000 N·m
Answer: b) 25,000 N·m
15. Calculate the advance ratio (μ) for a helicopter flying at 60 m/s with a rotor tip speed of 200 m/s.
a) 0.25
b) 0.30
c) 0.35
d) 0.40
Answer: b) 0.30
16. What is the blade flapping frequency (per revolution) for a rotor with a flapping hinge offset of
5% of the rotor radius?
a) 1.00
b) 1.02
c) 1.05
d) 1.08
Answer: c) 1.05
17. Calculate the profile power coefficient (CPo) for a rotor with a solidity ratio of 0.08 and an
average blade drag coefficient of 0.008.
a) 0.00064
b) 0.00080
c) 0.00096
d) 0.00112
Answer: a) 0.00064
18. What is the rotor disk area (in m²) for a helicopter with a disk loading of 300 N/m² and a gross
weight of 45,000 N?
a) 120 m²
b) 140 m²
c) 150 m²
d) 160 m²
Answer: c) 150 m²
19. Calculate the blade Lock number (γ) for a rotor blade with a chord of 0.5 m, lift curve slope of
5.7/rad, air density of 1.225 kg/m³, moment of inertia of 250 kg·m², and radius of 6 m.
a) 6.5
b) 7.5
c) 8.5
d) 9.5
Answer: c) 8.5
20. What is the tip path plane angle (in degrees) for a helicopter with a forward speed of 40 m/s,
induced velocity of 10 m/s, and rotor angular velocity of 30 rad/s?
a) 4.5°
b) 5.0°
c) 5.5°
d) 6.0°
Answer: b) 5.0°
21. Calculate the blade pitch angle (in degrees) required for a rotor to produce a thrust coefficient of
0.006, given a lift curve slope of 5.7/rad and a solidity ratio of 0.08.
a) 6.5°
b) 7.0°
c) 7.5°
d) 8.0°
Answer: c) 7.5°
22. What is the rotor inflow ratio (λ) for a helicopter in forward flight with an advance ratio of 0.25
and an induced velocity ratio of 0.05?
a) 0.0125
b) 0.0250
c) 0.0375
d) 0.0500
Answer: c) 0.0375
23. Calculate the maximum continuous power (in kW) for a helicopter engine with a specific fuel
consumption of 0.5 lb/hp·hr, a fuel flow rate of 400 lb/hr, and a mechanical efficiency of 0.95.
a) 520 kW
b) 560 kW
c) 600 kW
d) 640 kW
Answer: b) 560 kW
24. What is the blade loading (in N/m²) for a helicopter with a gross weight of 50,000 N, 4 rotor
blades, each with a planform area of 4 m²?
a) 2500 N/m²
b) 3000 N/m²
c) 3125 N/m²
d) 3500 N/m²
Answer: c) 3125 N/m²
25. Calculate the induced power (in kW) for a helicopter with a gross weight of 40,000 N, rotor disk
area of 130 m², and air density of 1.225 kg/m³.
a) 440 kW
b) 480 kW
c) 520 kW
d) 560 kW
Answer: b) 480 kW
26. What is the critical azimuth angle (in degrees) for blade stall on the retreating side of the rotor
disk, given an advance ratio of 0.3?
a) 240°
b) 250°
c) 260°
d) 270°
Answer: d) 270°
27. Calculate the rotor thrust (in N) for a helicopter with a thrust coefficient of 0.007, air density of
1.225 kg/m³, rotor radius of 6 m, and rotor angular velocity of 35 rad/s.
a) 38,000 N
b) 42,000 N
c) 46,000 N
d) 50,000 N
Answer: c) 46,000 N
28. What is the tip loss factor for a rotor with 4 blades and an aspect ratio of 15?
a) 0.95
b) 0.96
c) 0.97
d) 0.98
Answer: c) 0.97
29. Calculate the parasite drag area (fe) in m² for a helicopter with a gross weight of 35,000 N and an
equivalent flat plate area of 1.5 m².
a) 0.75 m²
b) 1.00 m²
c) 1.25 m²
d) 1.50 m²
Answer: d) 1.50 m²
30. What is the main rotor torque coefficient (CQ) for a helicopter with a power coefficient of 0.0004
and an advance ratio of 0.2?
a) 0.00032
b) 0.00036
c) 0.00040
d) 0.00044
Answer: c) 0.00040
31. Calculate the blade twist angle (in degrees) for a rotor blade with a root pitch of 12° and a tip
pitch of 2°, assuming linear twist.
a) -8°
b) -10°
c) -12°
d) -14°
Answer: b) -10°
32. What is the rotor downwash velocity (in m/s) for a helicopter with a thrust of 50,000 N, rotor disk
area of 150 m², and air density of 1.225 kg/m³?
a) 12.5 m/s
b) 13.5 m/s
c) 14.5 m/s
d) 15.5 m/s
Answer: c) 14.5 m/s
33. Calculate the blade flapping angle (in degrees) for a rotor with a flapping hinge offset of 4%,
thrust coefficient of 0.006, and blade Lock number of 8.
a) 3.5°
b) 4.0°
c) 4.5°
d) 5.0°
Answer: b) 4.0°
34. What is the rotor solidity ratio for a 5-bladed rotor with a blade chord of 0.4 m and a rotor radius
of 5 m?
a) 0.110
b) 0.127
c) 0.144
d) 0.161
Answer: b) 0.127
35. Calculate the main rotor power (in kW) required for a helicopter with a gross weight of 55,000 N,
induced velocity of 12 m/s, and a figure of merit of 0.75.
a) 720 kW
b) 780 kW
c) 840 kW
d) 900 kW
Answer: c) 840 kW
36. What is the advance ratio (μ) for a helicopter flying at 80 knots with a rotor tip speed of 700 ft/s?
a) 0.18
b) 0.22
c) 0.26
d) 0.30
Answer: b) 0.22
37. Calculate the blade coning angle (in degrees) for a rotor with a centrifugal force of 100,000 N,
blade weight of 1000 N, and a rotor radius of 6 m.
a) 2.5°
b) 3.0°
c) 3.5°
d) 4.0°
Answer: c) 3.5°
38. What is the rotor disk loading (in N/m²) for a helicopter with a gross weight of 60,000 N and a
rotor radius of 7 m?
a) 350 N/m²
b) 375 N/m²
c) 400 N/m²
d) 425 N/m²
Answer: c) 400 N/m²
39. Calculate the induced power factor (κ) for a tandem-rotor helicopter in hover with an overlap
ratio of 0.2.
a) 0.85
b) 0.90
c) 0.95
d) 1.00
Answer: b) 0.90
40. What is the tip Mach number for a rotor with a tip speed of 220 m/s, given the speed of sound is
340 m/s?
a) 0.60
b) 0.65
c) 0.70
d) 0.75
Answer: b) 0.65
41. Calculate the profile power (in kW) for a helicopter rotor with a solidity ratio of 0.08, average
blade drag coefficient of 0.008, air density of 1.225 kg/m³, rotor radius of 7 m, and tip speed of 200
m/s.
a) 120 kW
b) 140 kW
c) 160 kW
d) 180 kW
Answer: c) 160 kW
What is the retreating blade stall speed (in knots) for a helicopter with a rotor tip speed of 650 ft/s
and an advancing blade tip Mach number limit of 0.9?
a) 120 knots
b) 135 knots
c) 150 knots
d) 165 knots
Answer: c) 150 knots
9. Calculate the rotor solidity for a 4-bladed rotor with a blade chord of 0.5 m and a rotor radius of 6
m.
a) 0.106
b) 0.133
c) 0.167
d) 0.200
Answer: b) 0.133
10. What is the autorotation rate of descent (in ft/min) for a helicopter with a disk loading of 4 lb/ft²
and a main rotor speed of 300 RPM?
a) 1600 ft/min
b) 1800 ft/min
c) 2000 ft/min
d) 2200 ft/min
Answer: c) 2000 ft/min
11. Calculate the thrust coefficient (CT) for a helicopter with a gross weight of 4500 kg, rotor radius
of 7 m, air density of 1.225 kg/m³, and rotor angular velocity of 25 rad/s.
a) 0.0042
b) 0.0053
c) 0.0064
d) 0.0075
Answer: c) 0.0064
12. What is the figure of merit for a helicopter rotor with an ideal power of 500 kW and an actual
power of 625 kW?
a) 0.70
b) 0.75
c) 0.80
d) 0.85
Answer: c) 0.80
13. Calculate the induced power factor (κ) for a helicopter in forward flight at an advance ratio of 0.3
and a thrust coefficient of 0.006.
a) 1.15
b) 1.20
c) 1.25
d) 1.30
Answer: b) 1.20
14. What is the main rotor torque (in N·m) for a helicopter with a main rotor power of 1000 kW and
an angular velocity of 40 rad/s?
a) 22,500 N·m
b) 25,000 N·m
c) 27,500 N·m
d) 30,000 N·m
Answer: b) 25,000 N·m
15. Calculate the advance ratio (μ) for a helicopter flying at 60 m/s with a rotor tip speed of 200 m/s.
a) 0.25
b) 0.30
c) 0.35
d) 0.40
Answer: b) 0.30
16. What is the blade flapping frequency (per revolution) for a rotor with a flapping hinge offset of
5% of the rotor radius?
a) 1.00
b) 1.02
c) 1.05
d) 1.08
Answer: c) 1.05
17. Calculate the profile power coefficient (CPo) for a rotor with a solidity ratio of 0.08 and an
average blade drag coefficient of 0.008.
a) 0.00064
b) 0.00080
c) 0.00096
d) 0.00112
Answer: a) 0.00064
18. What is the rotor disk area (in m²) for a helicopter with a disk loading of 300 N/m² and a gross
weight of 45,000 N?
a) 120 m²
b) 140 m²
c) 150 m²
d) 160 m²
Answer: c) 150 m²
19. Calculate the blade Lock number (γ) for a rotor blade with a chord of 0.5 m, lift curve slope of
5.7/rad, air density of 1.225 kg/m³, moment of inertia of 250 kg·m², and radius of 6 m.
a) 6.5
b) 7.5
c) 8.5
d) 9.5
Answer: c) 8.5
20. What is the tip path plane angle (in degrees) for a helicopter with a forward speed of 40 m/s,
induced velocity of 10 m/s, and rotor angular velocity of 30 rad/s?
a) 4.5°
b) 5.0°
c) 5.5°
d) 6.0°
Answer: b) 5.0°
21. Calculate the blade pitch angle (in degrees) required for a rotor to produce a thrust coefficient of
0.006, given a lift curve slope of 5.7/rad and a solidity ratio of 0.08.
a) 6.5°
b) 7.0°
c) 7.5°
d) 8.0°
Answer: c) 7.5°
22. What is the rotor inflow ratio (λ) for a helicopter in forward flight with an advance ratio of 0.25
and an induced velocity ratio of 0.05?
a) 0.0125
b) 0.0250
c) 0.0375
d) 0.0500
Answer: c) 0.0375
23. Calculate the maximum continuous power (in kW) for a helicopter engine with a specific fuel
consumption of 0.5 lb/hp·hr, a fuel flow rate of 400 lb/hr, and a mechanical efficiency of 0.95.
a) 520 kW
b) 560 kW
c) 600 kW
d) 640 kW
Answer: b) 560 kW
24. What is the blade loading (in N/m²) for a helicopter with a gross weight of 50,000 N, 4 rotor
blades, each with a planform area of 4 m²?
a) 2500 N/m²
b) 3000 N/m²
c) 3125 N/m²
d) 3500 N/m²
Answer: c) 3125 N/m²
25. Calculate the induced power (in kW) for a helicopter with a gross weight of 40,000 N, rotor disk
area of 130 m², and air density of 1.225 kg/m³.
a) 440 kW
b) 480 kW
c) 520 kW
d) 560 kW
Answer: b) 480 kW
26. What is the critical azimuth angle (in degrees) for blade stall on the retreating side of the rotor
disk, given an advance ratio of 0.3?
a) 240°
b) 250°
c) 260°
d) 270°
Answer: d) 270°
27. Calculate the rotor thrust (in N) for a helicopter with a thrust coefficient of 0.007, air density of
1.225 kg/m³, rotor radius of 6 m, and rotor angular velocity of 35 rad/s.
a) 38,000 N
b) 42,000 N
c) 46,000 N
d) 50,000 N
Answer: c) 46,000 N
28. What is the tip loss factor for a rotor with 4 blades and an aspect ratio of 15?
a) 0.95
b) 0.96
c) 0.97
d) 0.98
Answer: c) 0.97
29. Calculate the parasite drag area (fe) in m² for a helicopter with a gross weight of 35,000 N and an
equivalent flat plate area of 1.5 m².
a) 0.75 m²
b) 1.00 m²
c) 1.25 m²
d) 1.50 m²
Answer: d) 1.50 m²
30. What is the main rotor torque coefficient (CQ) for a helicopter with a power coefficient of 0.0004
and an advance ratio of 0.2?
a) 0.00032
b) 0.00036
c) 0.00040
d) 0.00044
Answer: c) 0.00040
31. Calculate the blade twist angle (in degrees) for a rotor blade with a root pitch of 12° and a tip
pitch of 2°, assuming linear twist.
a) -8°
b) -10°
c) -12°
d) -14°
Answer: b) -10°
32. What is the rotor downwash velocity (in m/s) for a helicopter with a thrust of 50,000 N, rotor disk
area of 150 m², and air density of 1.225 kg/m³?
a) 12.5 m/s
b) 13.5 m/s
c) 14.5 m/s
d) 15.5 m/s
Answer: c) 14.5 m/s
33. Calculate the blade flapping angle (in degrees) for a rotor with a flapping hinge offset of 4%,
thrust coefficient of 0.006, and blade Lock number of 8.
a) 3.5°
b) 4.0°
c) 4.5°
d) 5.0°
Answer: b) 4.0°
34. What is the rotor solidity ratio for a 5-bladed rotor with a blade chord of 0.4 m and a rotor radius
of 5 m?
a) 0.110
b) 0.127
c) 0.144
d) 0.161
Answer: b) 0.127
35. Calculate the main rotor power (in kW) required for a helicopter with a gross weight of 55,000 N,
induced velocity of 12 m/s, and a figure of merit of 0.75.
a) 720 kW
b) 780 kW
c) 840 kW
d) 900 kW
Answer: c) 840 kW
36. What is the advance ratio (μ) for a helicopter flying at 80 knots with a rotor tip speed of 700 ft/s?
a) 0.18
b) 0.22
c) 0.26
d) 0.30
Answer: b) 0.22
37. Calculate the blade coning angle (in degrees) for a rotor with a centrifugal force of 100,000 N,
blade weight of 1000 N, and a rotor radius of 6 m.
a) 2.5°
b) 3.0°
c) 3.5°
d) 4.0°
Answer: c) 3.5°
38. What is the rotor disk loading (in N/m²) for a helicopter with a gross weight of 60,000 N and a
rotor radius of 7 m?
a) 350 N/m²
b) 375 N/m²
c) 400 N/m²
d) 425 N/m²
Answer: c) 400 N/m²
39. Calculate the induced power factor (κ) for a tandem-rotor helicopter in hover with an overlap
ratio of 0.2.
a) 0.85
b) 0.90
c) 0.95
d) 1.00
Answer: b) 0.90
40. What is the tip Mach number for a rotor with a tip speed of 220 m/s, given the speed of sound is
340 m/s?
a) 0.60
b) 0.65
c) 0.70
d) 0.75
Answer: b) 0.65
41. Calculate the profile power (in kW) for a helicopter rotor with a solidity ratio of 0.08, average
blade drag coefficient of 0.008, air density of 1.225 kg/m³, rotor radius of 7 m, and tip speed of 200
m/s.
a) 120 kW
b) 140 kW
c) 160 kW
d) 180 kW
Answer: c) 160 kW
What is the retreating blade stall speed (in knots) for a helicopter with a rotor tip speed of 650 ft/s
and an advancing blade tip Mach number limit of 0.9?
a) 120 knots
b) 135 knots
c) 150 knots
d) 165 knots
Answer: c) 150 knots
9. Calculate the rotor solidity for a 4-bladed rotor with a blade chord of 0.5 m and a rotor radius of 6
m.
a) 0.106
b) 0.133
c) 0.167
d) 0.200
Answer: b) 0.133
10. What is the autorotation rate of descent (in ft/min) for a helicopter with a disk loading of 4 lb/ft²
and a main rotor speed of 300 RPM?
a) 1600 ft/min
b) 1800 ft/min
c) 2000 ft/min
d) 2200 ft/min
Answer: c) 2000 ft/min
11. Calculate the thrust coefficient (CT) for a helicopter with a gross weight of 4500 kg, rotor radius
of 7 m, air density of 1.225 kg/m³, and rotor angular velocity of 25 rad/s.
a) 0.0042
b) 0.0053
c) 0.0064
d) 0.0075
Answer: c) 0.0064
12. What is the figure of merit for a helicopter rotor with an ideal power of 500 kW and an actual
power of 625 kW?
a) 0.70
b) 0.75
c) 0.80
d) 0.85
Answer: c) 0.80
13. Calculate the induced power factor (κ) for a helicopter in forward flight at an advance ratio of 0.3
and a thrust coefficient of 0.006.
a) 1.15
b) 1.20
c) 1.25
d) 1.30
Answer: b) 1.20
14. What is the main rotor torque (in N·m) for a helicopter with a main rotor power of 1000 kW and
an angular velocity of 40 rad/s?
a) 22,500 N·m
b) 25,000 N·m
c) 27,500 N·m
d) 30,000 N·m
Answer: b) 25,000 N·m
15. Calculate the advance ratio (μ) for a helicopter flying at 60 m/s with a rotor tip speed of 200 m/s.
a) 0.25
b) 0.30
c) 0.35
d) 0.40
Answer: b) 0.30
16. What is the blade flapping frequency (per revolution) for a rotor with a flapping hinge offset of
5% of the rotor radius?
a) 1.00
b) 1.02
c) 1.05
d) 1.08
Answer: c) 1.05
17. Calculate the profile power coefficient (CPo) for a rotor with a solidity ratio of 0.08 and an
average blade drag coefficient of 0.008.
a) 0.00064
b) 0.00080
c) 0.00096
d) 0.00112
Answer: a) 0.00064
18. What is the rotor disk area (in m²) for a helicopter with a disk loading of 300 N/m² and a gross
weight of 45,000 N?
a) 120 m²
b) 140 m²
c) 150 m²
d) 160 m²
Answer: c) 150 m²
19. Calculate the blade Lock number (γ) for a rotor blade with a chord of 0.5 m, lift curve slope of
5.7/rad, air density of 1.225 kg/m³, moment of inertia of 250 kg·m², and radius of 6 m.
a) 6.5
b) 7.5
c) 8.5
d) 9.5
Answer: c) 8.5
20. What is the tip path plane angle (in degrees) for a helicopter with a forward speed of 40 m/s,
induced velocity of 10 m/s, and rotor angular velocity of 30 rad/s?
a) 4.5°
b) 5.0°
c) 5.5°
d) 6.0°
Answer: b) 5.0°
21. Calculate the blade pitch angle (in degrees) required for a rotor to produce a thrust coefficient of
0.006, given a lift curve slope of 5.7/rad and a solidity ratio of 0.08.
a) 6.5°
b) 7.0°
c) 7.5°
d) 8.0°
Answer: c) 7.5°
22. What is the rotor inflow ratio (λ) for a helicopter in forward flight with an advance ratio of 0.25
and an induced velocity ratio of 0.05?
a) 0.0125
b) 0.0250
c) 0.0375
d) 0.0500
Answer: c) 0.0375
23. Calculate the maximum continuous power (in kW) for a helicopter engine with a specific fuel
consumption of 0.5 lb/hp·hr, a fuel flow rate of 400 lb/hr, and a mechanical efficiency of 0.95.
a) 520 kW
b) 560 kW
c) 600 kW
d) 640 kW
Answer: b) 560 kW
24. What is the blade loading (in N/m²) for a helicopter with a gross weight of 50,000 N, 4 rotor
blades, each with a planform area of 4 m²?
a) 2500 N/m²
b) 3000 N/m²
c) 3125 N/m²
d) 3500 N/m²
Answer: c) 3125 N/m²
25. Calculate the induced power (in kW) for a helicopter with a gross weight of 40,000 N, rotor disk
area of 130 m², and air density of 1.225 kg/m³.
a) 440 kW
b) 480 kW
c) 520 kW
d) 560 kW
Answer: b) 480 kW
26. What is the critical azimuth angle (in degrees) for blade stall on the retreating side of the rotor
disk, given an advance ratio of 0.3?
a) 240°
b) 250°
c) 260°
d) 270°
Answer: d) 270°
27. Calculate the rotor thrust (in N) for a helicopter with a thrust coefficient of 0.007, air density of
1.225 kg/m³, rotor radius of 6 m, and rotor angular velocity of 35 rad/s.
a) 38,000 N
b) 42,000 N
c) 46,000 N
d) 50,000 N
Answer: c) 46,000 N
28. What is the tip loss factor for a rotor with 4 blades and an aspect ratio of 15?
a) 0.95
b) 0.96
c) 0.97
d) 0.98
Answer: c) 0.97
29. Calculate the parasite drag area (fe) in m² for a helicopter with a gross weight of 35,000 N and an
equivalent flat plate area of 1.5 m².
a) 0.75 m²
b) 1.00 m²
c) 1.25 m²
d) 1.50 m²
Answer: d) 1.50 m²
30. What is the main rotor torque coefficient (CQ) for a helicopter with a power coefficient of 0.0004
and an advance ratio of 0.2?
a) 0.00032
b) 0.00036
c) 0.00040
d) 0.00044
Answer: c) 0.00040
31. Calculate the blade twist angle (in degrees) for a rotor blade with a root pitch of 12° and a tip
pitch of 2°, assuming linear twist.
a) -8°
b) -10°
c) -12°
d) -14°
Answer: b) -10°
32. What is the rotor downwash velocity (in m/s) for a helicopter with a thrust of 50,000 N, rotor disk
area of 150 m², and air density of 1.225 kg/m³?
a) 12.5 m/s
b) 13.5 m/s
c) 14.5 m/s
d) 15.5 m/s
Answer: c) 14.5 m/s
33. Calculate the blade flapping angle (in degrees) for a rotor with a flapping hinge offset of 4%,
thrust coefficient of 0.006, and blade Lock number of 8.
a) 3.5°
b) 4.0°
c) 4.5°
d) 5.0°
Answer: b) 4.0°
34. What is the rotor solidity ratio for a 5-bladed rotor with a blade chord of 0.4 m and a rotor radius
of 5 m?
a) 0.110
b) 0.127
c) 0.144
d) 0.161
Answer: b) 0.127
35. Calculate the main rotor power (in kW) required for a helicopter with a gross weight of 55,000 N,
induced velocity of 12 m/s, and a figure of merit of 0.75.
a) 720 kW
b) 780 kW
c) 840 kW
d) 900 kW
Answer: c) 840 kW
36. What is the advance ratio (μ) for a helicopter flying at 80 knots with a rotor tip speed of 700 ft/s?
a) 0.18
b) 0.22
c) 0.26
d) 0.30
Answer: b) 0.22
37. Calculate the blade coning angle (in degrees) for a rotor with a centrifugal force of 100,000 N,
blade weight of 1000 N, and a rotor radius of 6 m.
a) 2.5°
b) 3.0°
c) 3.5°
d) 4.0°
Answer: c) 3.5°
38. What is the rotor disk loading (in N/m²) for a helicopter with a gross weight of 60,000 N and a
rotor radius of 7 m?
a) 350 N/m²
b) 375 N/m²
c) 400 N/m²
d) 425 N/m²
Answer: c) 400 N/m²
39. Calculate the induced power factor (κ) for a tandem-rotor helicopter in hover with an overlap
ratio of 0.2.
a) 0.85
b) 0.90
c) 0.95
d) 1.00
Answer: b) 0.90
40. What is the tip Mach number for a rotor with a tip speed of 220 m/s, given the speed of sound is
340 m/s?
a) 0.60
b) 0.65
c) 0.70
d) 0.75
Answer: b) 0.65
41. Calculate the profile power (in kW) for a helicopter rotor with a solidity ratio of 0.08, average
blade drag coefficient of 0.008, air density of 1.225 kg/m³, rotor radius of 7 m, and tip speed of 200
m/s.
a) 120 kW
b) 140 kW
c) 160 kW
d) 180 kW
Answer: c) 160 kW
What is the retreating blade stall speed (in knots) for a helicopter with a rotor tip speed of 650 ft/s
and an advancing blade tip Mach number limit of 0.9?
a) 120 knots
b) 135 knots
c) 150 knots
d) 165 knots
Answer: c) 150 knots
9. Calculate the rotor solidity for a 4-bladed rotor with a blade chord of 0.5 m and a rotor radius of 6
m.
a) 0.106
b) 0.133
c) 0.167
d) 0.200
Answer: b) 0.133
10. What is the autorotation rate of descent (in ft/min) for a helicopter with a disk loading of 4 lb/ft²
and a main rotor speed of 300 RPM?
a) 1600 ft/min
b) 1800 ft/min
c) 2000 ft/min
d) 2200 ft/min
Answer: c) 2000 ft/min
11. Calculate the thrust coefficient (CT) for a helicopter with a gross weight of 4500 kg, rotor radius
of 7 m, air density of 1.225 kg/m³, and rotor angular velocity of 25 rad/s.
a) 0.0042
b) 0.0053
c) 0.0064
d) 0.0075
Answer: c) 0.0064
12. What is the figure of merit for a helicopter rotor with an ideal power of 500 kW and an actual
power of 625 kW?
a) 0.70
b) 0.75
c) 0.80
d) 0.85
Answer: c) 0.80
13. Calculate the induced power factor (κ) for a helicopter in forward flight at an advance ratio of 0.3
and a thrust coefficient of 0.006.
a) 1.15
b) 1.20
c) 1.25
d) 1.30
Answer: b) 1.20
14. What is the main rotor torque (in N·m) for a helicopter with a main rotor power of 1000 kW and
an angular velocity of 40 rad/s?
a) 22,500 N·m
b) 25,000 N·m
c) 27,500 N·m
d) 30,000 N·m
Answer: b) 25,000 N·m
15. Calculate the advance ratio (μ) for a helicopter flying at 60 m/s with a rotor tip speed of 200 m/s.
a) 0.25
b) 0.30
c) 0.35
d) 0.40
Answer: b) 0.30
16. What is the blade flapping frequency (per revolution) for a rotor with a flapping hinge offset of
5% of the rotor radius?
a) 1.00
b) 1.02
c) 1.05
d) 1.08
Answer: c) 1.05
17. Calculate the profile power coefficient (CPo) for a rotor with a solidity ratio of 0.08 and an
average blade drag coefficient of 0.008.
a) 0.00064
b) 0.00080
c) 0.00096
d) 0.00112
Answer: a) 0.00064
18. What is the rotor disk area (in m²) for a helicopter with a disk loading of 300 N/m² and a gross
weight of 45,000 N?
a) 120 m²
b) 140 m²
c) 150 m²
d) 160 m²
Answer: c) 150 m²
19. Calculate the blade Lock number (γ) for a rotor blade with a chord of 0.5 m, lift curve slope of
5.7/rad, air density of 1.225 kg/m³, moment of inertia of 250 kg·m², and radius of 6 m.
a) 6.5
b) 7.5
c) 8.5
d) 9.5
Answer: c) 8.5
20. What is the tip path plane angle (in degrees) for a helicopter with a forward speed of 40 m/s,
induced velocity of 10 m/s, and rotor angular velocity of 30 rad/s?
a) 4.5°
b) 5.0°
c) 5.5°
d) 6.0°
Answer: b) 5.0°
21. Calculate the blade pitch angle (in degrees) required for a rotor to produce a thrust coefficient of
0.006, given a lift curve slope of 5.7/rad and a solidity ratio of 0.08.
a) 6.5°
b) 7.0°
c) 7.5°
d) 8.0°
Answer: c) 7.5°
22. What is the rotor inflow ratio (λ) for a helicopter in forward flight with an advance ratio of 0.25
and an induced velocity ratio of 0.05?
a) 0.0125
b) 0.0250
c) 0.0375
d) 0.0500
Answer: c) 0.0375
23. Calculate the maximum continuous power (in kW) for a helicopter engine with a specific fuel
consumption of 0.5 lb/hp·hr, a fuel flow rate of 400 lb/hr, and a mechanical efficiency of 0.95.
a) 520 kW
b) 560 kW
c) 600 kW
d) 640 kW
Answer: b) 560 kW
24. What is the blade loading (in N/m²) for a helicopter with a gross weight of 50,000 N, 4 rotor
blades, each with a planform area of 4 m²?
a) 2500 N/m²
b) 3000 N/m²
c) 3125 N/m²
d) 3500 N/m²
Answer: c) 3125 N/m²
25. Calculate the induced power (in kW) for a helicopter with a gross weight of 40,000 N, rotor disk
area of 130 m², and air density of 1.225 kg/m³.
a) 440 kW
b) 480 kW
c) 520 kW
d) 560 kW
Answer: b) 480 kW
26. What is the critical azimuth angle (in degrees) for blade stall on the retreating side of the rotor
disk, given an advance ratio of 0.3?
a) 240°
b) 250°
c) 260°
d) 270°
Answer: d) 270°
27. Calculate the rotor thrust (in N) for a helicopter with a thrust coefficient of 0.007, air density of
1.225 kg/m³, rotor radius of 6 m, and rotor angular velocity of 35 rad/s.
a) 38,000 N
b) 42,000 N
c) 46,000 N
d) 50,000 N
Answer: c) 46,000 N
28. What is the tip loss factor for a rotor with 4 blades and an aspect ratio of 15?
a) 0.95
b) 0.96
c) 0.97
d) 0.98
Answer: c) 0.97
29. Calculate the parasite drag area (fe) in m² for a helicopter with a gross weight of 35,000 N and an
equivalent flat plate area of 1.5 m².
a) 0.75 m²
b) 1.00 m²
c) 1.25 m²
d) 1.50 m²
Answer: d) 1.50 m²
30. What is the main rotor torque coefficient (CQ) for a helicopter with a power coefficient of 0.0004
and an advance ratio of 0.2?
a) 0.00032
b) 0.00036
c) 0.00040
d) 0.00044
Answer: c) 0.00040
31. Calculate the blade twist angle (in degrees) for a rotor blade with a root pitch of 12° and a tip
pitch of 2°, assuming linear twist.
a) -8°
b) -10°
c) -12°
d) -14°
Answer: b) -10°
32. What is the rotor downwash velocity (in m/s) for a helicopter with a thrust of 50,000 N, rotor disk
area of 150 m², and air density of 1.225 kg/m³?
a) 12.5 m/s
b) 13.5 m/s
c) 14.5 m/s
d) 15.5 m/s
Answer: c) 14.5 m/s
33. Calculate the blade flapping angle (in degrees) for a rotor with a flapping hinge offset of 4%,
thrust coefficient of 0.006, and blade Lock number of 8.
a) 3.5°
b) 4.0°
c) 4.5°
d) 5.0°
Answer: b) 4.0°
34. What is the rotor solidity ratio for a 5-bladed rotor with a blade chord of 0.4 m and a rotor radius
of 5 m?
a) 0.110
b) 0.127
c) 0.144
d) 0.161
Answer: b) 0.127
35. Calculate the main rotor power (in kW) required for a helicopter with a gross weight of 55,000 N,
induced velocity of 12 m/s, and a figure of merit of 0.75.
a) 720 kW
b) 780 kW
c) 840 kW
d) 900 kW
Answer: c) 840 kW
36. What is the advance ratio (μ) for a helicopter flying at 80 knots with a rotor tip speed of 700 ft/s?
a) 0.18
b) 0.22
c) 0.26
d) 0.30
Answer: b) 0.22
37. Calculate the blade coning angle (in degrees) for a rotor with a centrifugal force of 100,000 N,
blade weight of 1000 N, and a rotor radius of 6 m.
a) 2.5°
b) 3.0°
c) 3.5°
d) 4.0°
Answer: c) 3.5°
38. What is the rotor disk loading (in N/m²) for a helicopter with a gross weight of 60,000 N and a
rotor radius of 7 m?
a) 350 N/m²
b) 375 N/m²
c) 400 N/m²
d) 425 N/m²
Answer: c) 400 N/m²
39. Calculate the induced power factor (κ) for a tandem-rotor helicopter in hover with an overlap
ratio of 0.2.
a) 0.85
b) 0.90
c) 0.95
d) 1.00
Answer: b) 0.90
40. What is the tip Mach number for a rotor with a tip speed of 220 m/s, given the speed of sound is
340 m/s?
a) 0.60
b) 0.65
c) 0.70
d) 0.75
Answer: b) 0.65
41. Calculate the profile power (in kW) for a helicopter rotor with a solidity ratio of 0.08, average
blade drag coefficient of 0.008, air density of 1.225 kg/m³, rotor radius of 7 m, and tip speed of 200
m/s.
a) 120 kW
b) 140 kW
c) 160 kW
d) 180 kW
Answer: c) 160 kW
What is the retreating blade stall speed (in knots) for a helicopter with a rotor tip speed of 650 ft/s
and an advancing blade tip Mach number limit of 0.9?
a) 120 knots
b) 135 knots
c) 150 knots
d) 165 knots
Answer: c) 150 knots
9. Calculate the rotor solidity for a 4-bladed rotor with a blade chord of 0.5 m and a rotor radius of 6
m.
a) 0.106
b) 0.133
c) 0.167
d) 0.200
Answer: b) 0.133
10. What is the autorotation rate of descent (in ft/min) for a helicopter with a disk loading of 4 lb/ft²
and a main rotor speed of 300 RPM?
a) 1600 ft/min
b) 1800 ft/min
c) 2000 ft/min
d) 2200 ft/min
Answer: c) 2000 ft/min
11. Calculate the thrust coefficient (CT) for a helicopter with a gross weight of 4500 kg, rotor radius
of 7 m, air density of 1.225 kg/m³, and rotor angular velocity of 25 rad/s.
a) 0.0042
b) 0.0053
c) 0.0064
d) 0.0075
Answer: c) 0.0064
12. What is the figure of merit for a helicopter rotor with an ideal power of 500 kW and an actual
power of 625 kW?
a) 0.70
b) 0.75
c) 0.80
d) 0.85
Answer: c) 0.80
13. Calculate the induced power factor (κ) for a helicopter in forward flight at an advance ratio of 0.3
and a thrust coefficient of 0.006.
a) 1.15
b) 1.20
c) 1.25
d) 1.30
Answer: b) 1.20
14. What is the main rotor torque (in N·m) for a helicopter with a main rotor power of 1000 kW and
an angular velocity of 40 rad/s?
a) 22,500 N·m
b) 25,000 N·m
c) 27,500 N·m
d) 30,000 N·m
Answer: b) 25,000 N·m
15. Calculate the advance ratio (μ) for a helicopter flying at 60 m/s with a rotor tip speed of 200 m/s.
a) 0.25
b) 0.30
c) 0.35
d) 0.40
Answer: b) 0.30
16. What is the blade flapping frequency (per revolution) for a rotor with a flapping hinge offset of
5% of the rotor radius?
a) 1.00
b) 1.02
c) 1.05
d) 1.08
Answer: c) 1.05
17. Calculate the profile power coefficient (CPo) for a rotor with a solidity ratio of 0.08 and an
average blade drag coefficient of 0.008.
a) 0.00064
b) 0.00080
c) 0.00096
d) 0.00112
Answer: a) 0.00064
18. What is the rotor disk area (in m²) for a helicopter with a disk loading of 300 N/m² and a gross
weight of 45,000 N?
a) 120 m²
b) 140 m²
c) 150 m²
d) 160 m²
Answer: c) 150 m²
19. Calculate the blade Lock number (γ) for a rotor blade with a chord of 0.5 m, lift curve slope of
5.7/rad, air density of 1.225 kg/m³, moment of inertia of 250 kg·m², and radius of 6 m.
a) 6.5
b) 7.5
c) 8.5
d) 9.5
Answer: c) 8.5
20. What is the tip path plane angle (in degrees) for a helicopter with a forward speed of 40 m/s,
induced velocity of 10 m/s, and rotor angular velocity of 30 rad/s?
a) 4.5°
b) 5.0°
c) 5.5°
d) 6.0°
Answer: b) 5.0°
21. Calculate the blade pitch angle (in degrees) required for a rotor to produce a thrust coefficient of
0.006, given a lift curve slope of 5.7/rad and a solidity ratio of 0.08.
a) 6.5°
b) 7.0°
c) 7.5°
d) 8.0°
Answer: c) 7.5°
22. What is the rotor inflow ratio (λ) for a helicopter in forward flight with an advance ratio of 0.25
and an induced velocity ratio of 0.05?
a) 0.0125
b) 0.0250
c) 0.0375
d) 0.0500
Answer: c) 0.0375
23. Calculate the maximum continuous power (in kW) for a helicopter engine with a specific fuel
consumption of 0.5 lb/hp·hr, a fuel flow rate of 400 lb/hr, and a mechanical efficiency of 0.95.
a) 520 kW
b) 560 kW
c) 600 kW
d) 640 kW
Answer: b) 560 kW
24. What is the blade loading (in N/m²) for a helicopter with a gross weight of 50,000 N, 4 rotor
blades, each with a planform area of 4 m²?
a) 2500 N/m²
b) 3000 N/m²
c) 3125 N/m²
d) 3500 N/m²
Answer: c) 3125 N/m²
25. Calculate the induced power (in kW) for a helicopter with a gross weight of 40,000 N, rotor disk
area of 130 m², and air density of 1.225 kg/m³.
a) 440 kW
b) 480 kW
c) 520 kW
d) 560 kW
Answer: b) 480 kW
26. What is the critical azimuth angle (in degrees) for blade stall on the retreating side of the rotor
disk, given an advance ratio of 0.3?
a) 240°
b) 250°
c) 260°
d) 270°
Answer: d) 270°
27. Calculate the rotor thrust (in N) for a helicopter with a thrust coefficient of 0.007, air density of
1.225 kg/m³, rotor radius of 6 m, and rotor angular velocity of 35 rad/s.
a) 38,000 N
b) 42,000 N
c) 46,000 N
d) 50,000 N
Answer: c) 46,000 N
28. What is the tip loss factor for a rotor with 4 blades and an aspect ratio of 15?
a) 0.95
b) 0.96
c) 0.97
d) 0.98
Answer: c) 0.97
29. Calculate the parasite drag area (fe) in m² for a helicopter with a gross weight of 35,000 N and an
equivalent flat plate area of 1.5 m².
a) 0.75 m²
b) 1.00 m²
c) 1.25 m²
d) 1.50 m²
Answer: d) 1.50 m²
30. What is the main rotor torque coefficient (CQ) for a helicopter with a power coefficient of 0.0004
and an advance ratio of 0.2?
a) 0.00032
b) 0.00036
c) 0.00040
d) 0.00044
Answer: c) 0.00040
31. Calculate the blade twist angle (in degrees) for a rotor blade with a root pitch of 12° and a tip
pitch of 2°, assuming linear twist.
a) -8°
b) -10°
c) -12°
d) -14°
Answer: b) -10°
32. What is the rotor downwash velocity (in m/s) for a helicopter with a thrust of 50,000 N, rotor disk
area of 150 m², and air density of 1.225 kg/m³?
a) 12.5 m/s
b) 13.5 m/s
c) 14.5 m/s
d) 15.5 m/s
Answer: c) 14.5 m/s
33. Calculate the blade flapping angle (in degrees) for a rotor with a flapping hinge offset of 4%,
thrust coefficient of 0.006, and blade Lock number of 8.
a) 3.5°
b) 4.0°
c) 4.5°
d) 5.0°
Answer: b) 4.0°
34. What is the rotor solidity ratio for a 5-bladed rotor with a blade chord of 0.4 m and a rotor radius
of 5 m?
a) 0.110
b) 0.127
c) 0.144
d) 0.161
Answer: b) 0.127
35. Calculate the main rotor power (in kW) required for a helicopter with a gross weight of 55,000 N,
induced velocity of 12 m/s, and a figure of merit of 0.75.
a) 720 kW
b) 780 kW
c) 840 kW
d) 900 kW
Answer: c) 840 kW
36. What is the advance ratio (μ) for a helicopter flying at 80 knots with a rotor tip speed of 700 ft/s?
a) 0.18
b) 0.22
c) 0.26
d) 0.30
Answer: b) 0.22
37. Calculate the blade coning angle (in degrees) for a rotor with a centrifugal force of 100,000 N,
blade weight of 1000 N, and a rotor radius of 6 m.
a) 2.5°
b) 3.0°
c) 3.5°
d) 4.0°
Answer: c) 3.5°
38. What is the rotor disk loading (in N/m²) for a helicopter with a gross weight of 60,000 N and a
rotor radius of 7 m?
a) 350 N/m²
b) 375 N/m²
c) 400 N/m²
d) 425 N/m²
Answer: c) 400 N/m²
39. Calculate the induced power factor (κ) for a tandem-rotor helicopter in hover with an overlap
ratio of 0.2.
a) 0.85
b) 0.90
c) 0.95
d) 1.00
Answer: b) 0.90
40. What is the tip Mach number for a rotor with a tip speed of 220 m/s, given the speed of sound is
340 m/s?
a) 0.60
b) 0.65
c) 0.70
d) 0.75
Answer: b) 0.65
41. Calculate the profile power (in kW) for a helicopter rotor with a solidity ratio of 0.08, average
blade drag coefficient of 0.008, air density of 1.225 kg/m³, rotor radius of 7 m, and tip speed of 200
m/s.
a) 120 kW
b) 140 kW
c) 160 kW
d) 180 kW
Answer: c) 160 kW
What is the retreating blade stall speed (in knots) for a helicopter with a rotor tip speed of 650 ft/s
and an advancing blade tip Mach number limit of 0.9?
a) 120 knots
b) 135 knots
c) 150 knots
d) 165 knots
Answer: c) 150 knots
9. Calculate the rotor solidity for a 4-bladed rotor with a blade chord of 0.5 m and a rotor radius of 6
m.
a) 0.106
b) 0.133
c) 0.167
d) 0.200
Answer: b) 0.133
10. What is the autorotation rate of descent (in ft/min) for a helicopter with a disk loading of 4 lb/ft²
and a main rotor speed of 300 RPM?
a) 1600 ft/min
b) 1800 ft/min
c) 2000 ft/min
d) 2200 ft/min
Answer: c) 2000 ft/min
11. Calculate the thrust coefficient (CT) for a helicopter with a gross weight of 4500 kg, rotor radius
of 7 m, air density of 1.225 kg/m³, and rotor angular velocity of 25 rad/s.
a) 0.0042
b) 0.0053
c) 0.0064
d) 0.0075
Answer: c) 0.0064
12. What is the figure of merit for a helicopter rotor with an ideal power of 500 kW and an actual
power of 625 kW?
a) 0.70
b) 0.75
c) 0.80
d) 0.85
Answer: c) 0.80
13. Calculate the induced power factor (κ) for a helicopter in forward flight at an advance ratio of 0.3
and a thrust coefficient of 0.006.
a) 1.15
b) 1.20
c) 1.25
d) 1.30
Answer: b) 1.20
14. What is the main rotor torque (in N·m) for a helicopter with a main rotor power of 1000 kW and
an angular velocity of 40 rad/s?
a) 22,500 N·m
b) 25,000 N·m
c) 27,500 N·m
d) 30,000 N·m
Answer: b) 25,000 N·m
15. Calculate the advance ratio (μ) for a helicopter flying at 60 m/s with a rotor tip speed of 200 m/s.
a) 0.25
b) 0.30
c) 0.35
d) 0.40
Answer: b) 0.30
16. What is the blade flapping frequency (per revolution) for a rotor with a flapping hinge offset of
5% of the rotor radius?
a) 1.00
b) 1.02
c) 1.05
d) 1.08
Answer: c) 1.05
17. Calculate the profile power coefficient (CPo) for a rotor with a solidity ratio of 0.08 and an
average blade drag coefficient of 0.008.
a) 0.00064
b) 0.00080
c) 0.00096
d) 0.00112
Answer: a) 0.00064
18. What is the rotor disk area (in m²) for a helicopter with a disk loading of 300 N/m² and a gross
weight of 45,000 N?
a) 120 m²
b) 140 m²
c) 150 m²
d) 160 m²
Answer: c) 150 m²
19. Calculate the blade Lock number (γ) for a rotor blade with a chord of 0.5 m, lift curve slope of
5.7/rad, air density of 1.225 kg/m³, moment of inertia of 250 kg·m², and radius of 6 m.
a) 6.5
b) 7.5
c) 8.5
d) 9.5
Answer: c) 8.5
20. What is the tip path plane angle (in degrees) for a helicopter with a forward speed of 40 m/s,
induced velocity of 10 m/s, and rotor angular velocity of 30 rad/s?
a) 4.5°
b) 5.0°
c) 5.5°
d) 6.0°
Answer: b) 5.0°
21. Calculate the blade pitch angle (in degrees) required for a rotor to produce a thrust coefficient of
0.006, given a lift curve slope of 5.7/rad and a solidity ratio of 0.08.
a) 6.5°
b) 7.0°
c) 7.5°
d) 8.0°
Answer: c) 7.5°
22. What is the rotor inflow ratio (λ) for a helicopter in forward flight with an advance ratio of 0.25
and an induced velocity ratio of 0.05?
a) 0.0125
b) 0.0250
c) 0.0375
d) 0.0500
Answer: c) 0.0375
23. Calculate the maximum continuous power (in kW) for a helicopter engine with a specific fuel
consumption of 0.5 lb/hp·hr, a fuel flow rate of 400 lb/hr, and a mechanical efficiency of 0.95.
a) 520 kW
b) 560 kW
c) 600 kW
d) 640 kW
Answer: b) 560 kW
24. What is the blade loading (in N/m²) for a helicopter with a gross weight of 50,000 N, 4 rotor
blades, each with a planform area of 4 m²?
a) 2500 N/m²
b) 3000 N/m²
c) 3125 N/m²
d) 3500 N/m²
Answer: c) 3125 N/m²
25. Calculate the induced power (in kW) for a helicopter with a gross weight of 40,000 N, rotor disk
area of 130 m², and air density of 1.225 kg/m³.
a) 440 kW
b) 480 kW
c) 520 kW
d) 560 kW
Answer: b) 480 kW
26. What is the critical azimuth angle (in degrees) for blade stall on the retreating side of the rotor
disk, given an advance ratio of 0.3?
a) 240°
b) 250°
c) 260°
d) 270°
Answer: d) 270°
27. Calculate the rotor thrust (in N) for a helicopter with a thrust coefficient of 0.007, air density of
1.225 kg/m³, rotor radius of 6 m, and rotor angular velocity of 35 rad/s.
a) 38,000 N
b) 42,000 N
c) 46,000 N
d) 50,000 N
Answer: c) 46,000 N
28. What is the tip loss factor for a rotor with 4 blades and an aspect ratio of 15?
a) 0.95
b) 0.96
c) 0.97
d) 0.98
Answer: c) 0.97
29. Calculate the parasite drag area (fe) in m² for a helicopter with a gross weight of 35,000 N and an
equivalent flat plate area of 1.5 m².
a) 0.75 m²
b) 1.00 m²
c) 1.25 m²
d) 1.50 m²
Answer: d) 1.50 m²
30. What is the main rotor torque coefficient (CQ) for a helicopter with a power coefficient of 0.0004
and an advance ratio of 0.2?
a) 0.00032
b) 0.00036
c) 0.00040
d) 0.00044
Answer: c) 0.00040
31. Calculate the blade twist angle (in degrees) for a rotor blade with a root pitch of 12° and a tip
pitch of 2°, assuming linear twist.
a) -8°
b) -10°
c) -12°
d) -14°
Answer: b) -10°
32. What is the rotor downwash velocity (in m/s) for a helicopter with a thrust of 50,000 N, rotor disk
area of 150 m², and air density of 1.225 kg/m³?
a) 12.5 m/s
b) 13.5 m/s
c) 14.5 m/s
d) 15.5 m/s
Answer: c) 14.5 m/s
33. Calculate the blade flapping angle (in degrees) for a rotor with a flapping hinge offset of 4%,
thrust coefficient of 0.006, and blade Lock number of 8.
a) 3.5°
b) 4.0°
c) 4.5°
d) 5.0°
Answer: b) 4.0°
34. What is the rotor solidity ratio for a 5-bladed rotor with a blade chord of 0.4 m and a rotor radius
of 5 m?
a) 0.110
b) 0.127
c) 0.144
d) 0.161
Answer: b) 0.127
35. Calculate the main rotor power (in kW) required for a helicopter with a gross weight of 55,000 N,
induced velocity of 12 m/s, and a figure of merit of 0.75.
a) 720 kW
b) 780 kW
c) 840 kW
d) 900 kW
Answer: c) 840 kW
36. What is the advance ratio (μ) for a helicopter flying at 80 knots with a rotor tip speed of 700 ft/s?
a) 0.18
b) 0.22
c) 0.26
d) 0.30
Answer: b) 0.22
37. Calculate the blade coning angle (in degrees) for a rotor with a centrifugal force of 100,000 N,
blade weight of 1000 N, and a rotor radius of 6 m.
a) 2.5°
b) 3.0°
c) 3.5°
d) 4.0°
Answer: c) 3.5°
38. What is the rotor disk loading (in N/m²) for a helicopter with a gross weight of 60,000 N and a
rotor radius of 7 m?
a) 350 N/m²
b) 375 N/m²
c) 400 N/m²
d) 425 N/m²
Answer: c) 400 N/m²
39. Calculate the induced power factor (κ) for a tandem-rotor helicopter in hover with an overlap
ratio of 0.2.
a) 0.85
b) 0.90
c) 0.95
d) 1.00
Answer: b) 0.90
40. What is the tip Mach number for a rotor with a tip speed of 220 m/s, given the speed of sound is
340 m/s?
a) 0.60
b) 0.65
c) 0.70
d) 0.75
Answer: b) 0.65
41. Calculate the profile power (in kW) for a helicopter rotor with a solidity ratio of 0.08, average
blade drag coefficient of 0.008, air density of 1.225 kg/m³, rotor radius of 7 m, and tip speed of 200
m/s.
a) 120 kW
b) 140 kW
c) 160 kW
d) 180 kW
Answer: c) 160 kW
What is the retreating blade stall speed (in knots) for a helicopter with a rotor tip speed of 650 ft/s
and an advancing blade tip Mach number limit of 0.9?
a) 120 knots
b) 135 knots
c) 150 knots
d) 165 knots
Answer: c) 150 knots
9. Calculate the rotor solidity for a 4-bladed rotor with a blade chord of 0.5 m and a rotor radius of 6
m.
a) 0.106
b) 0.133
c) 0.167
d) 0.200
Answer: b) 0.133
10. What is the autorotation rate of descent (in ft/min) for a helicopter with a disk loading of 4 lb/ft²
and a main rotor speed of 300 RPM?
a) 1600 ft/min
b) 1800 ft/min
c) 2000 ft/min
d) 2200 ft/min
Answer: c) 2000 ft/min
11. Calculate the thrust coefficient (CT) for a helicopter with a gross weight of 4500 kg, rotor radius
of 7 m, air density of 1.225 kg/m³, and rotor angular velocity of 25 rad/s.
a) 0.0042
b) 0.0053
c) 0.0064
d) 0.0075
Answer: c) 0.0064
12. What is the figure of merit for a helicopter rotor with an ideal power of 500 kW and an actual
power of 625 kW?
a) 0.70
b) 0.75
c) 0.80
d) 0.85
Answer: c) 0.80
13. Calculate the induced power factor (κ) for a helicopter in forward flight at an advance ratio of 0.3
and a thrust coefficient of 0.006.
a) 1.15
b) 1.20
c) 1.25
d) 1.30
Answer: b) 1.20
14. What is the main rotor torque (in N·m) for a helicopter with a main rotor power of 1000 kW and
an angular velocity of 40 rad/s?
a) 22,500 N·m
b) 25,000 N·m
c) 27,500 N·m
d) 30,000 N·m
Answer: b) 25,000 N·m
15. Calculate the advance ratio (μ) for a helicopter flying at 60 m/s with a rotor tip speed of 200 m/s.
a) 0.25
b) 0.30
c) 0.35
d) 0.40
Answer: b) 0.30
16. What is the blade flapping frequency (per revolution) for a rotor with a flapping hinge offset of
5% of the rotor radius?
a) 1.00
b) 1.02
c) 1.05
d) 1.08
Answer: c) 1.05
17. Calculate the profile power coefficient (CPo) for a rotor with a solidity ratio of 0.08 and an
average blade drag coefficient of 0.008.
a) 0.00064
b) 0.00080
c) 0.00096
d) 0.00112
Answer: a) 0.00064
18. What is the rotor disk area (in m²) for a helicopter with a disk loading of 300 N/m² and a gross
weight of 45,000 N?
a) 120 m²
b) 140 m²
c) 150 m²
d) 160 m²
Answer: c) 150 m²
19. Calculate the blade Lock number (γ) for a rotor blade with a chord of 0.5 m, lift curve slope of
5.7/rad, air density of 1.225 kg/m³, moment of inertia of 250 kg·m², and radius of 6 m.
a) 6.5
b) 7.5
c) 8.5
d) 9.5
Answer: c) 8.5
20. What is the tip path plane angle (in degrees) for a helicopter with a forward speed of 40 m/s,
induced velocity of 10 m/s, and rotor angular velocity of 30 rad/s?
a) 4.5°
b) 5.0°
c) 5.5°
d) 6.0°
Answer: b) 5.0°
21. Calculate the blade pitch angle (in degrees) required for a rotor to produce a thrust coefficient of
0.006, given a lift curve slope of 5.7/rad and a solidity ratio of 0.08.
a) 6.5°
b) 7.0°
c) 7.5°
d) 8.0°
Answer: c) 7.5°
22. What is the rotor inflow ratio (λ) for a helicopter in forward flight with an advance ratio of 0.25
and an induced velocity ratio of 0.05?
a) 0.0125
b) 0.0250
c) 0.0375
d) 0.0500
Answer: c) 0.0375
23. Calculate the maximum continuous power (in kW) for a helicopter engine with a specific fuel
consumption of 0.5 lb/hp·hr, a fuel flow rate of 400 lb/hr, and a mechanical efficiency of 0.95.
a) 520 kW
b) 560 kW
c) 600 kW
d) 640 kW
Answer: b) 560 kW
24. What is the blade loading (in N/m²) for a helicopter with a gross weight of 50,000 N, 4 rotor
blades, each with a planform area of 4 m²?
a) 2500 N/m²
b) 3000 N/m²
c) 3125 N/m²
d) 3500 N/m²
Answer: c) 3125 N/m²
25. Calculate the induced power (in kW) for a helicopter with a gross weight of 40,000 N, rotor disk
area of 130 m², and air density of 1.225 kg/m³.
a) 440 kW
b) 480 kW
c) 520 kW
d) 560 kW
Answer: b) 480 kW
26. What is the critical azimuth angle (in degrees) for blade stall on the retreating side of the rotor
disk, given an advance ratio of 0.3?
a) 240°
b) 250°
c) 260°
d) 270°
Answer: d) 270°
27. Calculate the rotor thrust (in N) for a helicopter with a thrust coefficient of 0.007, air density of
1.225 kg/m³, rotor radius of 6 m, and rotor angular velocity of 35 rad/s.
a) 38,000 N
b) 42,000 N
c) 46,000 N
d) 50,000 N
Answer: c) 46,000 N
28. What is the tip loss factor for a rotor with 4 blades and an aspect ratio of 15?
a) 0.95
b) 0.96
c) 0.97
d) 0.98
Answer: c) 0.97
29. Calculate the parasite drag area (fe) in m² for a helicopter with a gross weight of 35,000 N and an
equivalent flat plate area of 1.5 m².
a) 0.75 m²
b) 1.00 m²
c) 1.25 m²
d) 1.50 m²
Answer: d) 1.50 m²
30. What is the main rotor torque coefficient (CQ) for a helicopter with a power coefficient of 0.0004
and an advance ratio of 0.2?
a) 0.00032
b) 0.00036
c) 0.00040
d) 0.00044
Answer: c) 0.00040
31. Calculate the blade twist angle (in degrees) for a rotor blade with a root pitch of 12° and a tip
pitch of 2°, assuming linear twist.
a) -8°
b) -10°
c) -12°
d) -14°
Answer: b) -10°
32. What is the rotor downwash velocity (in m/s) for a helicopter with a thrust of 50,000 N, rotor disk
area of 150 m², and air density of 1.225 kg/m³?
a) 12.5 m/s
b) 13.5 m/s
c) 14.5 m/s
d) 15.5 m/s
Answer: c) 14.5 m/s
33. Calculate the blade flapping angle (in degrees) for a rotor with a flapping hinge offset of 4%,
thrust coefficient of 0.006, and blade Lock number of 8.
a) 3.5°
b) 4.0°
c) 4.5°
d) 5.0°
Answer: b) 4.0°
34. What is the rotor solidity ratio for a 5-bladed rotor with a blade chord of 0.4 m and a rotor radius
of 5 m?
a) 0.110
b) 0.127
c) 0.144
d) 0.161
Answer: b) 0.127
35. Calculate the main rotor power (in kW) required for a helicopter with a gross weight of 55,000 N,
induced velocity of 12 m/s, and a figure of merit of 0.75.
a) 720 kW
b) 780 kW
c) 840 kW
d) 900 kW
Answer: c) 840 kW
36. What is the advance ratio (μ) for a helicopter flying at 80 knots with a rotor tip speed of 700 ft/s?
a) 0.18
b) 0.22
c) 0.26
d) 0.30
Answer: b) 0.22
37. Calculate the blade coning angle (in degrees) for a rotor with a centrifugal force of 100,000 N,
blade weight of 1000 N, and a rotor radius of 6 m.
a) 2.5°
b) 3.0°
c) 3.5°
d) 4.0°
Answer: c) 3.5°
38. What is the rotor disk loading (in N/m²) for a helicopter with a gross weight of 60,000 N and a
rotor radius of 7 m?
a) 350 N/m²
b) 375 N/m²
c) 400 N/m²
d) 425 N/m²
Answer: c) 400 N/m²
39. Calculate the induced power factor (κ) for a tandem-rotor helicopter in hover with an overlap
ratio of 0.2.
a) 0.85
b) 0.90
c) 0.95
d) 1.00
Answer: b) 0.90
40. What is the tip Mach number for a rotor with a tip speed of 220 m/s, given the speed of sound is
340 m/s?
a) 0.60
b) 0.65
c) 0.70
d) 0.75
Answer: b) 0.65
41. Calculate the profile power (in kW) for a helicopter rotor with a solidity ratio of 0.08, average
blade drag coefficient of 0.008, air density of 1.225 kg/m³, rotor radius of 7 m, and tip speed of 200
m/s.
a) 120 kW
b) 140 kW
c) 160 kW
d) 180 kW
Answer: c) 160 kW
What is the retreating blade stall speed (in knots) for a helicopter with a rotor tip speed of 650 ft/s
and an advancing blade tip Mach number limit of 0.9?
a) 120 knots
b) 135 knots
c) 150 knots
d) 165 knots
Answer: c) 150 knots
9. Calculate the rotor solidity for a 4-bladed rotor with a blade chord of 0.5 m and a rotor radius of 6
m.
a) 0.106
b) 0.133
c) 0.167
d) 0.200
Answer: b) 0.133
10. What is the autorotation rate of descent (in ft/min) for a helicopter with a disk loading of 4 lb/ft²
and a main rotor speed of 300 RPM?
a) 1600 ft/min
b) 1800 ft/min
c) 2000 ft/min
d) 2200 ft/min
Answer: c) 2000 ft/min
11. Calculate the thrust coefficient (CT) for a helicopter with a gross weight of 4500 kg, rotor radius
of 7 m, air density of 1.225 kg/m³, and rotor angular velocity of 25 rad/s.
a) 0.0042
b) 0.0053
c) 0.0064
d) 0.0075
Answer: c) 0.0064
12. What is the figure of merit for a helicopter rotor with an ideal power of 500 kW and an actual
power of 625 kW?
a) 0.70
b) 0.75
c) 0.80
d) 0.85
Answer: c) 0.80
13. Calculate the induced power factor (κ) for a helicopter in forward flight at an advance ratio of 0.3
and a thrust coefficient of 0.006.
a) 1.15
b) 1.20
c) 1.25
d) 1.30
Answer: b) 1.20
14. What is the main rotor torque (in N·m) for a helicopter with a main rotor power of 1000 kW and
an angular velocity of 40 rad/s?
a) 22,500 N·m
b) 25,000 N·m
c) 27,500 N·m
d) 30,000 N·m
Answer: b) 25,000 N·m
15. Calculate the advance ratio (μ) for a helicopter flying at 60 m/s with a rotor tip speed of 200 m/s.
a) 0.25
b) 0.30
c) 0.35
d) 0.40
Answer: b) 0.30
16. What is the blade flapping frequency (per revolution) for a rotor with a flapping hinge offset of
5% of the rotor radius?
a) 1.00
b) 1.02
c) 1.05
d) 1.08
Answer: c) 1.05
17. Calculate the profile power coefficient (CPo) for a rotor with a solidity ratio of 0.08 and an
average blade drag coefficient of 0.008.
a) 0.00064
b) 0.00080
c) 0.00096
d) 0.00112
Answer: a) 0.00064
18. What is the rotor disk area (in m²) for a helicopter with a disk loading of 300 N/m² and a gross
weight of 45,000 N?
a) 120 m²
b) 140 m²
c) 150 m²
d) 160 m²
Answer: c) 150 m²
19. Calculate the blade Lock number (γ) for a rotor blade with a chord of 0.5 m, lift curve slope of
5.7/rad, air density of 1.225 kg/m³, moment of inertia of 250 kg·m², and radius of 6 m.
a) 6.5
b) 7.5
c) 8.5
d) 9.5
Answer: c) 8.5
20. What is the tip path plane angle (in degrees) for a helicopter with a forward speed of 40 m/s,
induced velocity of 10 m/s, and rotor angular velocity of 30 rad/s?
a) 4.5°
b) 5.0°
c) 5.5°
d) 6.0°
Answer: b) 5.0°
21. Calculate the blade pitch angle (in degrees) required for a rotor to produce a thrust coefficient of
0.006, given a lift curve slope of 5.7/rad and a solidity ratio of 0.08.
a) 6.5°
b) 7.0°
c) 7.5°
d) 8.0°
Answer: c) 7.5°
22. What is the rotor inflow ratio (λ) for a helicopter in forward flight with an advance ratio of 0.25
and an induced velocity ratio of 0.05?
a) 0.0125
b) 0.0250
c) 0.0375
d) 0.0500
Answer: c) 0.0375
23. Calculate the maximum continuous power (in kW) for a helicopter engine with a specific fuel
consumption of 0.5 lb/hp·hr, a fuel flow rate of 400 lb/hr, and a mechanical efficiency of 0.95.
a) 520 kW
b) 560 kW
c) 600 kW
d) 640 kW
Answer: b) 560 kW
24. What is the blade loading (in N/m²) for a helicopter with a gross weight of 50,000 N, 4 rotor
blades, each with a planform area of 4 m²?
a) 2500 N/m²
b) 3000 N/m²
c) 3125 N/m²
d) 3500 N/m²
Answer: c) 3125 N/m²
25. Calculate the induced power (in kW) for a helicopter with a gross weight of 40,000 N, rotor disk
area of 130 m², and air density of 1.225 kg/m³.
a) 440 kW
b) 480 kW
c) 520 kW
d) 560 kW
Answer: b) 480 kW
26. What is the critical azimuth angle (in degrees) for blade stall on the retreating side of the rotor
disk, given an advance ratio of 0.3?
a) 240°
b) 250°
c) 260°
d) 270°
Answer: d) 270°
27. Calculate the rotor thrust (in N) for a helicopter with a thrust coefficient of 0.007, air density of
1.225 kg/m³, rotor radius of 6 m, and rotor angular velocity of 35 rad/s.
a) 38,000 N
b) 42,000 N
c) 46,000 N
d) 50,000 N
Answer: c) 46,000 N
28. What is the tip loss factor for a rotor with 4 blades and an aspect ratio of 15?
a) 0.95
b) 0.96
c) 0.97
d) 0.98
Answer: c) 0.97
29. Calculate the parasite drag area (fe) in m² for a helicopter with a gross weight of 35,000 N and an
equivalent flat plate area of 1.5 m².
a) 0.75 m²
b) 1.00 m²
c) 1.25 m²
d) 1.50 m²
Answer: d) 1.50 m²
30. What is the main rotor torque coefficient (CQ) for a helicopter with a power coefficient of 0.0004
and an advance ratio of 0.2?
a) 0.00032
b) 0.00036
c) 0.00040
d) 0.00044
Answer: c) 0.00040
31. Calculate the blade twist angle (in degrees) for a rotor blade with a root pitch of 12° and a tip
pitch of 2°, assuming linear twist.
a) -8°
b) -10°
c) -12°
d) -14°
Answer: b) -10°
32. What is the rotor downwash velocity (in m/s) for a helicopter with a thrust of 50,000 N, rotor disk
area of 150 m², and air density of 1.225 kg/m³?
a) 12.5 m/s
b) 13.5 m/s
c) 14.5 m/s
d) 15.5 m/s
Answer: c) 14.5 m/s
33. Calculate the blade flapping angle (in degrees) for a rotor with a flapping hinge offset of 4%,
thrust coefficient of 0.006, and blade Lock number of 8.
a) 3.5°
b) 4.0°
c) 4.5°
d) 5.0°
Answer: b) 4.0°
34. What is the rotor solidity ratio for a 5-bladed rotor with a blade chord of 0.4 m and a rotor radius
of 5 m?
a) 0.110
b) 0.127
c) 0.144
d) 0.161
Answer: b) 0.127
35. Calculate the main rotor power (in kW) required for a helicopter with a gross weight of 55,000 N,
induced velocity of 12 m/s, and a figure of merit of 0.75.
a) 720 kW
b) 780 kW
c) 840 kW
d) 900 kW
Answer: c) 840 kW
36. What is the advance ratio (μ) for a helicopter flying at 80 knots with a rotor tip speed of 700 ft/s?
a) 0.18
b) 0.22
c) 0.26
d) 0.30
Answer: b) 0.22
37. Calculate the blade coning angle (in degrees) for a rotor with a centrifugal force of 100,000 N,
blade weight of 1000 N, and a rotor radius of 6 m.
a) 2.5°
b) 3.0°
c) 3.5°
d) 4.0°
Answer: c) 3.5°
38. What is the rotor disk loading (in N/m²) for a helicopter with a gross weight of 60,000 N and a
rotor radius of 7 m?
a) 350 N/m²
b) 375 N/m²
c) 400 N/m²
d) 425 N/m²
Answer: c) 400 N/m²
39. Calculate the induced power factor (κ) for a tandem-rotor helicopter in hover with an overlap
ratio of 0.2.
a) 0.85
b) 0.90
c) 0.95
d) 1.00
Answer: b) 0.90
40. What is the tip Mach number for a rotor with a tip speed of 220 m/s, given the speed of sound is
340 m/s?
a) 0.60
b) 0.65
c) 0.70
d) 0.75
Answer: b) 0.65
41. Calculate the profile power (in kW) for a helicopter rotor with a solidity ratio of 0.08, average
blade drag coefficient of 0.008, air density of 1.225 kg/m³, rotor radius of 7 m, and tip speed of 200
m/s.
a) 120 kW
b) 140 kW
c) 160 kW
d) 180 kW
Answer: c) 160 kW
42. What is the blade flapping frequency ratio (ν) for a rotor with a flapping hinge offset of 6% of the
rotor radius?
a) 1.03
b) 1.06
c) 1.09
d) 1.12
Answer: b) 1.06
43. Calculate the main rotor torque (in N·m) for a helicopter with a power of 1200 kW and a rotor
speed of 300 RPM.
a) 36,000 N·m
b) 38,000 N·m
c) 40,000 N·m
d) 42,000 N·m
Answer: b) 38,000 N·m
44. What is the blade loading coefficient (CT/σ) for a helicopter with a thrust coefficient of 0.007 and
a