Lesson 3 Aerodynamics of Flight Part 2 Flashcards
What are the three regions of the rotor?
Stalled (Large force against rotation, rotor drag 25%), Driving (Good, produced force in the direction of the rotation 45-75%), Driven (Slight force against rotation 30%)
Blade forces move to which side of the rotor in forward flight? Why?
The retreating side because of dissymmetry of lift.
What happens to the driving region when you raise or lower the collective in an autorotation?
When you raise the collective, less driving, more drag.
Lower collective, more driving, less drag
Explain what happens to the RPM in an autorotation when you:
1) raise collective
2) lower collective
3) forward cyclic
4) rear cyclic
1) RPM decreases
2) RPM increases
3) RPM decreases
4) RPM increases
What is the shaded area of the high/velocity diagram?
This is the area that may not allow for a safe autorotation, given an engine failure.
When in an autorotation and turning, you must do what to the collective? Why?
Raise the collective slightly, in order to prevent a rotor overspeed.
Describe an autorotative flair (2 items)
- Aft cyclic to tilt the disc back against the wind
- This speeds the rotor system RPM up (storing energy in the rotor system to cushion landing
In the autorotation, how do updrafts and downdrafts affect the rotor RPM?
Updrafts, increase rotor RPM
Downdrafts, decrease rotor RPM
What is effective translational lift (4 items)
- Occurs between 16-24 knots
- Helicopter moves out of wing tip vortices
- Tail rotor becomes more efficient
- Helicopter climbs and yaws left
What is transverse flow (5 items)
- Front of rotor is in undisturbed horizontal air
- Rear of rotor is in disturbed vertical air
- 10-20 knots
- Helicopter shudders due to unequal induced drag
- Nose climbs, rolls right (gyroscopic precession), yaws left (tail rotor)
What is translational lift
- Additional lift occurs
- Induced flow is more horizontal
- Angle of attack increases
- Induced drag decreases
