Module 12 Helicopter Aerodynamics 100 Important Sentences for Revision

 1. Basic Helicopter Aerodynamics

1. A helicopter generates lift through rotating blades called a rotor.
2. Each rotor blade acts as an air foil.
3. Lift is created by blade rotation through the air.
4. The rotor provides both lift and thrust.
5. Airflow moves upward through the rotor in hover.
6. The rotor disc acts like a rotating wing.
7. Collective pitch controls total lift.
8. Cyclic pitch controls direction of flight.
9. Anti-torque pedals control yaw.
10. Autorotation allows safe landing without engine power.

2. Main Rotor System

11. The main rotor provides lift and directional control.
12. Rotor blades can flap, feather, and lead-lag.
13. Flapping allows blades to move up and down.
14. Feathering changes the pitch angle of blades.
15. Lead-lag movement prevents stress from rotation.
16. Fully articulated rotors have all three motions.
17. Semi-rigid rotors flap as a unit.
18. Rigid rotors have flexible blades for stress absorption.
19. The rotor hub connects the blades to the mast.
20. Blade tracking ensures equal lift from all blades.

3. Anti-Torque System

21. The tail rotor counteracts main rotor torque.
22. Torque reaction causes the fuselage to rotate opposite the rotor.
23. Tail rotor thrust is controlled by anti-torque pedals.
24. A fenestron is a ducted fan type tail rotor.
25. NOTAR stands for No Tail Rotor system.
26. NOTAR uses air jet thrust to counter torque.
27. Tail rotor drive is through shafts and gearboxes.
28. Tail rotor pitch links control thrust direction.
29. Tail rotor failure can cause uncontrolled yaw.
30. Proper inspection of tail rotor system is critical for safety.

4. Translational and Autorotational Flight

31. Translational lift occurs when helicopter gains forward speed.
32. Effective Translational Lift (ETL) occurs around 16–24 knots.
33. ETL increases lift and reduces power required.
34. Dissymmetry of lift occurs during forward flight.
35. Advancing blade generates more lift than retreating blade.
36. Blade flapping compensates for dissymmetry of lift.
37. Retreating blade stall occurs at high forward speeds.
38. In autorotation, rotor blades spin freely due to upward airflow.
39. Autorotation is used for engine-out landing.
40. Rotor RPM must be maintained within limits during autorotation.

5. Helicopter Controls

41. Collective lever changes pitch of all rotor blades equally.
42. Increasing collective increases lift and power demand.
43. Throttle controls engine power.
44. Cyclic stick changes the pitch angle cyclically around the disc.
45. Cyclic input tilts the rotor disc to move the helicopter.
46. Pedals control tail rotor thrust and yaw.
47. Power and control coordination is vital during flight.
48. Control rods and linkages transmit pilot inputs.
49. Hydraulic systems reduce pilot control effort.
50. Dual controls are often installed for training or redundancy.

6. Flight Characteristics

51. Hovering requires constant control input.
52. Ground effect increases lift when hovering near the ground.
53. Translational lift improves efficiency during forward motion.
54. Settling with power occurs when descending into own downwash.
55. Vortex ring state reduces lift and control.
56. Retreating blade stall limits top forward speed.
57. LTE (Loss of Tail Rotor Effectiveness) causes uncontrolled yaw.
58. Dynamic rollover occurs if one skid is stuck to the ground.
59. Mast bumping can occur in semi-rigid rotor systems.
60. Center of gravity affects stability and control.

7. Transmission and Gearboxes

61. Transmission transfers engine power to the main rotor.
62. The main gearbox reduces high engine RPM.
63. Drive shafts connect gearboxes to rotors.
64. Freewheeling unit allows autorotation when engine fails.
65. Intermediate gearbox changes drive angle to tail rotor.
66. Tail gearbox changes drive direction to vertical.
67. Lubrication is critical to prevent gearbox overheating.
68. Magnetic chip detectors monitor gearbox condition.
69. Torque meter measures engine torque load.
70. Vibration in transmission indicates possible imbalance.

8. Helicopter Structures

71. Fuselage supports all main helicopter components.
72. Semi-monocoque construction is common.
73. The tail boom supports tail rotor and stabilizers.
74. Skid or wheel landing gear supports weight on ground.
75. Vibration isolation mounts reduce transmitted vibration.
76. Composite materials are used for rotor blades and fuselage.
77. Structural inspection focuses on cracks, corrosion, and delamination.
78. Lightning protection is built into composite structures.
79. Access panels allow maintenance of internal components.
80. The structure must withstand both lift and torque loads.

9. Hydraulic and Fuel Systems

81. Hydraulic systems assist flight controls.
82. Pressure is maintained by hydraulic pumps.
83. Hydraulic failure increases control forces.
84. Backup systems ensure safety during hydraulic failure.
85. Fuel is stored in tanks within fuselage or sponsons.
86. Fuel pumps deliver fuel to the engine.
87. Crossfeed valves allow fuel balance between tanks.
88. Fuel filters prevent contamination.
89. Fuel quantity is indicated in cockpit gauges.
90. Always follow procedures for fuel draining and sampling.

10. Instruments and Safety Systems

91. Main rotor RPM is indicated on the tachometer.
92. Engine RPM and torque are monitored on the cockpit panel.
93. Vertical speed indicator shows rate of climb or descent.
94. Artificial horizon shows helicopter attitude.
95. Compass and gyro instruments indicate direction.
96. Warning lights alert pilot of system failures.
97. Vibration monitors detect rotor imbalance.
98. Fire detection systems use temperature sensors.
99. Flight data recorders store operational information.
100. Regular inspection ensures reliability and flight safety.