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| Basic Induced Velocity Equation |
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Definition
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Disk Loading is equal to
Typical Values? |
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| Power increases ______ with disk loading |
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What is the power required to take off at maximum gross weight (external loading) at sea level?
T = 5500 lb., rho = 0.001988 slugs/ft3, A = 962 ft2 |
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Definition
[image]
P = 208561 ft lb/sec or 379 horsepower
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| Conversion of frequency in Hz to angular velocity in radians per second |
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| Average value for helicopter tip speed and frequency |
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Definition
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| Power Loading is equal to |
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Definition
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Term
What is the Advance Ratio?
What is an average value for advance ratio? |
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Definition
| The advance ratio is a non-dimensional forward speed. μ = advance ratio = V / (Ω*R). Helicopters usually have advance ratios up to about 0 to 0.3. |
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Definition
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Figure of Merit is equal to
Typical Values |
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Definition
(Ideal Power)/(Actual Power)
.75 to .80 |
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Term
Kappa κ is used to symbolize?
What is its typical value? |
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Definition
Induced Power Correction factor
~1.25 |
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Term
| For small thrust values you want lower rotor solidity, in other words very long blades, why isn't this true for higher thrust conditions? |
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Definition
| Tip speed increases with blade radius therefore longer blades will stall more at higher thrusts. |
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Term
| Rotor performance is independent of the number of blades so long as performance is compared at the same |
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Definition
| Performance is compared at the same solidity |
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| Effective area Ae is equal to |
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Definition
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Term
| Why would you not want to maximize the power loading for a helicopter in order to optimize the hover condition |
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Definition
| Because it makes forward flight worse than it makes hover better |
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| Blade flapping of 1/rev amounts to how many degrees at the root |
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Definition
| Feathering Pitch or Blade Twist angle |
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| The collective pitch is controlled by the collective stick and does what? |
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Definition
| Cones the rotor up; all blades twist at the same time giving more power to the rotor |
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Term
| The cyclic pitch is controlled by the cyclic stick and does what? |
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Definition
| Tilts the tip path plane; essentially to control direction |
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Term
| What are some advantages to a teetering rotor |
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Definition
| Simple and cheap, no lead lag dampers, and a teetering rotor has never gone unstable |
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Term
| Lead/Lag hinges are necessary because? |
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Definition
| The coriolis effect due to the flapping motion of the blades causes must be allowed to balance or the blades will break due to the load |
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Term
| Decreasing the cyclic pitch moves the swash plate, what does this do to the blades |
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Definition
| Decreases the pitch of the advancing blades and increases the pitch of the retreating blades |
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Term
| Why does a helicopter, unlike an airplane propeller, have to have cyclic pitch? |
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Definition
| Because airplanes count on airflow over the wings, etc to aid in control. Helicopters must hover! |
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Term
| What does it mean to assume that the blade is ideally twisted? |
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Definition
| That it is producing uniform inflow |
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Term
| What two forces must balance about the flap hinge |
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Definition
| Aerodynamic and Centrifugal force loading |
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Definition
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| The flapping equation of motion includes the sum of three different moments, what are the sources of these moments? |
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Definition
| Centrifugal loading, Inertial forces, Aerodynamic forces |
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Definition
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| In forward flight flap varies ________. |
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Definition
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