# Shared Flashcard Set

## Details

V/STOL Final
Stuff to remember for NCState MAE452 Final
35
Aerospace Engineering
12/10/2010

## Additional Aerospace Engineering Flashcards

Term
 Basic Induced Velocity Equation
Definition
 [image]
Term
 Basic Power Equation
Definition
 P=TVi  or  [image]
Term
 Disk Loading is equal to   Typical Values?
Definition
 T/A   3 to 12 lb/ft2
Term
Definition
 Exponentially
Term
 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
Definition
 [image] P = 208561 ft lb/sec or 379 horsepower
Term
 Downwash is equal to
Definition
 Wi=2*Vi
Term
 Tip Speed is equal to
Definition
 Vtip=[image]*R
Term
 Conversion of frequency in Hz to angular velocity in radians per second
Definition
 ω = 2πf and  [image]
Term
 Average value for helicopter tip speed and frequency
Definition
 700 ft/sec 5 hz
Term
Definition
 T/P
Term
 What is the Advance Ratio?   What is an average value for advance ratio?
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.
Term
 Inflow Ratio is equal to
Definition
 [image]
Term
 Figure of Merit is equal to   Typical Values
Definition
 (Ideal Power)/(Actual Power)   .75 to .80
Term
 Kappa κ is used to symbolize?   What is its typical value?
Definition
 Induced Power Correction factor   ~1.25
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?
Definition
 Tip speed increases with blade radius therefore longer blades will stall more at higher thrusts.
Term
 Rotor performance is independent of the number of blades so long as performance is compared at the same
Definition
 Performance is compared at the same solidity
Term
 Effective area Ae is equal to
Definition
 B2A
Term
 Why would you not want to maximize the power loading for a helicopter in order to optimize the hover condition
Definition
 Because it makes forward flight worse than it makes hover better
Term
 β is used to signify
Definition
 flapping angle
Term
 β0 is used to signify
Definition
Term
 Blade flapping of 1/rev amounts to how many degrees at the root
Definition
 ~ +/- 15 degrees
Term
 γ is used to signify
Definition
 Lock Number
Term
 θ is used to signify
Definition
 Feathering Pitch or Blade Twist angle
Term
 The collective pitch is controlled by the collective stick and does what?
Definition
 Cones the rotor up; all blades twist at the same time giving more power to the rotor
Term
 The cyclic pitch is controlled by the cyclic stick and does what?
Definition
 Tilts the tip path plane; essentially to control direction
Term
 What are some advantages to a teetering rotor
Definition
 Simple and cheap, no lead lag dampers, and a teetering rotor has never gone unstable
Term
 Lead/Lag hinges are necessary because?
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
Term
 Decreasing the cyclic pitch moves the swash plate, what does this do to the blades
Definition
 Decreases the pitch of the advancing blades and increases the pitch of the retreating blades
Term
 Why does a helicopter, unlike an airplane propeller, have to have cyclic pitch?
Definition
 Because airplanes count on airflow over the wings, etc to aid in control.  Helicopters must hover!
Term
 What does it mean to assume that the blade is ideally twisted?
Definition
 That it is producing uniform inflow
Term
 What two forces must balance about the flap hinge
Definition
Term
 What does ζ signify?
Definition
 Lag angle
Term
 The flapping equation of motion includes the sum of three different moments, what are the sources of these moments?
Definition