Term
| Draw the Power required graph as a function of forward speed, include components of total power. |
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Definition
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Term
| What is the first step to put a helicopter in autorotation? |
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Definition
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Term
| What happens if a pilot doesn't adjust the input pitch fast enough to enter autorotation? |
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Definition
| Profile drag of the blade will slow the rotor beyond the point where autorotation can be achieved and rotor will stall experiencing excessive blade stall. |
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Term
| How much time does a pilot have to set the input pitch to put the helicopter in autorotation |
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Definition
| 1.5 to 4 seconds depending on helicopter |
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Term
| Why is blade taper important |
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Definition
| Without taper the lift coefficients at the root of the blade are relatively high and cannot operate at the best Cl/Cd ratio for the airfoil section. |
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Term
| What are two methods of rotor design that result in uniform inflow? |
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Definition
| Ideal twist and ideal taper. |
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Term
Find on the following Power vs Airspeed graph:
a.The Airspeed for max rate of climb and endurance
b.The airspeed for max range
c.Max level flight speed
[image] |
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Definition
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Term
| What is the effective distance for ground effect? |
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Definition
| Within one rotor diameter. |
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Term
| What is the primary factor in determining autorotative rate of descent? |
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Definition
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Term
| At approximately what forward speed does ground effect become negligible? |
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Definition
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Term
| In the equation of motion for a rotating body what does an instability in the C (damping) term represent? |
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Definition
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Term
In the equation of motion for a rotating body what does an instability in the K (stiffness) term represent?
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Definition
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Term
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Definition
| When the external forcing frequency is at or near the natural frequency of the structure. |
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Term
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Definition
| a self-excited oscillation with exponentially increasing amplitude caused by an interaction of elastic, aerodynamic and inertial forces and moments. |
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Term
| The fundamental frequency of the rotor noise is determined by? |
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Definition
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Term
| What are the three main sources of noise? |
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Definition
| Thickness, Normal Forces (Lift and Drag), and Turbulence (Shear Forces) |
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Term
| What type of acoustic source is caused by blade thickness |
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Definition
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Term
What type of acoustic source is caused by blade normal forces (lift and drag)
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Definition
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Term
What type of acoustic source is caused by blade turbulence?
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Definition
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Term
| Weathercock stability acts in which direction in relation to a helicopter in yaw? |
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Definition
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Term
| What causes weathercock stability? |
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Definition
| The tail rotor goes into a state of climb, without additional power this causes a loss of thrust which in turn decreases the anti-torque. |
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Term
| Why might the tail rotor be placed higher on the tail fin or canted? |
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Definition
| To resist the sideways movement produced by the tail rotor, thrust from the main rotor must be tilted to the opposite side, because the tail rotor and main rotor are usually separated by a distance this produces a rolling moment, canting or placing the rotor high on the tail minimize this couple. |
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Term
| Tail rotors are generally how large compared to the main rotor? |
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Definition
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