H2-2a Airfoil, Airfow (2.8-2-17) Flashcards
2.8 Airfoil 2.9 Airflow, and reactions in the rotor disc, relative wind, rotational relative wind 2-11 Resultative relative wind, induced flow 2-12 Rotor blade angles 2-14 Powered flight, hovering flight 2-15 translating tendency, pendular action 2-16 coning, Coriolis effect, 2-17 gyroscopic precession
2-9 give one disadvantage of a non-symmetrical airfoil
The center of pressure travel up to 20% of the cord line creating undesired will work on the airfoil structure and greater production cost
2-9 define hub
On the mast, the attachment point for the root of the blade and the axis about which blade rotates
2-9 How is the angular position of the main rotor blade measured?
From the helicopters longitudinal axis and usually from the nose
2-9 What is the radial position of a segment of a blade?
The distance from the hub as a fraction of the total distance
2-9 what is tip-path plane
Rotational relative wind. The rotation of rotor blades as a turn about the mast produces rotational relative wind.
The term “rotational” in Rotational Relative Wind refers to the method of..
producing relative wind.
H.2-10 TAF
Total aerodynamic force aka Total Resultant force
2-10 what is induced flow
Downwash
2-10 is the blade angle of attack in the aft section of a helicopter greater or smaller than induced flow
Smaller
What happens to induced drag in ground effect.
the previous aft lifting force is now straight up, removing the induced drag
What is relative wind?
the airflow which moves parallel but against the airfoil
What is lifts relationship (angle) to resultant relative wind?
Lift acts perpendicular to resultant relative wind.
What is the angle of incidence on a helicopter
the angle between the chord line of a main or tail rotor blade and it’s rotor.
2-14 what is the primary means for compensating for dissymmetry of lift?
Flapping
H.2-15 The main transmission is mounted at a slight angle to the left. Why?
So that the rotor mast has a built-in tilt to oppose the tail rotor thrust
2-15 To which side is the tip path plane tilted in hover
Left
2-15 What is inherent slip slide?
In forward Flight, the tail rotor continues to push to the right and the helicopter makes a small angle with the wind when the rotors are level and the slip ball is in the middle. See 12-2
2-15 What is translating, tendency or translating drift?
Upon lift off, the helicopter will move to the right due to rear rotor anti-torque usage
What is rolling tendency?
When the entire helicopter moves to the right and angles upward due to tail rotor anti
What are the three types of rotor systems?
Rigid, Semi-Rigid, Fully Articulate
List characteristics of a fully articulated rotor system
Lead and lag, flap and feather independently
This characteristic of a semi rigid rotor system
Flap and feather, but do not lead and lag
What can a rigid rotor system do
Feather only
2-16 what are the three major causes of coning?
Lift, Weight, centrifugal force
conservation of angular momentum
Coriolis
What’s another name for Coriolis effect
Law of conservation of angular movement
What is angular movement
The movement of inertia (mass times distance from the center of rotation squared) multiplied by the speed of rotation
What are the four things that happen when coning
-G loading increases coning
-Blade diameter shrink
-center of gravity shifts inward
-Rotor RPM increases
What is CL max
Critical angle of attack.
Greatest coefficient of lift than can be produced.
What does CL stand for?
Coefficient of lift
What is Coefficient of lift
The coefficient of lift is a dimensionless number that describes the contribution to lift as a result of airfoil shape and angle of attack
What is the formula for Lift
L = Cl 1/2pV2 (squared) S
Lift = Coefficient of life
x 1/2 True airspeed (Air Density (or ROW) and Freestream Velocity (True airspeed)
x Wing surface area
Is it true that a higher AOA produces a lower IAS and vice versa
Yes
What is VRS
Vortex ring State. Dirty air
MEA
Minimum En Route Altitude (top # above “Low IFR map”) see OROCA
MEF
Maximum Elevation Figure (big3 small 1 on SAC)
MEL
Mimimum Equipment list - allowed to be broken and still fly
METAR
Meterological aerodrome report
MFD
Multi-Function Display
MH
Magnetic Heading
MIRL
Medium Intisity Runway Lighting (US Chart Sup)
MOA
Military Operations Area
MOCA
Minimum Obstical Clearance Altitude (Botton * # on “Low IFR” highway map”) see OROCA
MRA (reception)
R
Minimum Reception Altitude (R in a square at Victor intersections)
MSL
Mean Sea Level
MTOS (obscursion)
Mountain obscuration
MTR (military)
Military Training route (gray lines on SAC. VR (<1500ft AGL with 4 digits. above with 4 digit #) or IR (atc control and >1500ft AGL. 3 digit number). width from 4m to 16. Cross at 90* angle. Contact FSS.
MVFR
Marginal Visual Flight Rules
NAS (national)
National Airspace System
