How does the length of a rotor effect helicopter flight?
Helicopter performance depends on the length of the rotor blades. For heavy lifting, a large rotor works best, but short blades reduce drag and ultimately allow for higher maximum speeds. When the rotor spins fast, centrifugal force stretches the spring, and the blade tips expand, increasing overall length.
Can you stall a helicopter rotor blade?
Just as in an airplane, the wing or main rotor blade will stall if it gets slow enough and the angle of attack is exceeded. That’s the primary value in determining a helicopter’s VNE. Any faster and the retreating blade will stall. Lowering the nose won’t do anything in the helicopter, but lowering the collective will.
What happens if a helicopter stalls?
Once the engine fails or otherwise is shut off, the pilot must immediately lower the pitch, reducing lift and drag, and the helicopter will begin to descend. However, this isn’t typical because as soon as the freewheeling unit disengages the engine, the pilot is trained to respond appropriately immediately.
What can cause helicopter rotor blade tip stall?
High weight, low rotor r.p.m., high density altitude, turbulence and/or steep, abrupt turns are all conducive to retreating blade stall at high forward airspeeds as they increase the blade pitch to generate more thrust and hence increase the angle of attack.
How do you recover from a retreating blade stall?
Flight performance during a retreating blade stall Recovery involves lowering the collective pitch, relieving forward pressure on the cyclic or more commonly, both. Either of these control movements should restore the proper attached airflow over the retreating blade thus generating lift again.
What are the three warning signs of an impending retreating blade stall?
The major warnings of approaching retreating blade stall conditions are: Abnormal vibration….When operating at high forward airspeeds, the following conditions are most likely to produce blade stall:
- High blade loading (high gross weight)
- Low rotor RPM.
- High density altitude.
- Steep or abrupt turns.
- Turbulent air.
What is low RPM blade stall?
It means that if your blades are spinning fast enough, you should be able to fly. But if you lose RPM, there’s a chance that you might drop out of the sky (yes, like a brick) . This is called Blade Stall. Helicopters have low rotor RPM warning systems.
What causes low rotor RPM?
Low-rotor rpm can occur at almost any time, and it’s usually the result of improperly coordinating the collective and throttle. Often it happens at the end of an approach, where the pilot must raise the collective to arrest the helicopter’s descent and add power to enter a hover.
How low do helicopter blades go?
THE ROTOR SYSTEM OF THE HELICOPTER Many helicopter rotor systems can dip well below 6 feet from the ground level, which can potentially contact a person or object on the ground. Never carry anything above your head such as an umbrella while walking under the rotor system.