Principles Of Flight Flashcards
Define axis of rotation
The line through the rotor head at right angles to the plane of rotation.
The blades actually rotate around this axis
You are flying above freezing level in rain & notice ice on rotors. What effect does the ice on the middle of the rotors have on an auto rotation?
Higher rate of descent
Less range
List factors that may induce ground resonance.
Rotor Head
- Unbalanced blades
- Incorrect tracking
- Faulty lead/lag dampers
Fuselage Factors
- Ship operations
- Slope landings
- Uneven oleo/tire pressures
Disc loading on a helicopter is found by dividing the what?
Weight
By
Disc area
What is the point on an aerofoil through which lift acts called?
Centre of pressure
During forward cruising flight the individual rotor blades when compares to each other are operating how in regards to IAS, AoA & Lift
Act at unequal airspeed
Unequal angles of attack
Equal lift moment
Describe a recommended technique to avoid blade sailing in an anti-clockwise rotor system
Park with wind from the right of the helicopter & keep cyclic central
Why does an IGE hover require less power than an OGE hover?
Because induced flow & rotor drag are reduced
Spanwise lift of a rotor blade may be equalized how?
Decreasing the angle of attack towards the tip. Also known as washout.
Total rotor thrust always acts ______ the ______
In line with
Axis of rotation
When translational lift becomes effective on climb out, _______ increase & if collective is neither lowered or raised the rate of climb will initially ______?
Angles of attack
Increase
You need to land at some remote location. The reported conditions are hot & humid. You look at your performance graph & find it’s just within limits for landing.
What effect does humidity have?
You may not be able to land because humidity is not taken into account in most performance graphs.
What effect does Tailwind / Headwind on
- Rate of climb / descent
- Angle of climb / descent
RoC & RoD no change in either scenario.
AoC & AoD - Shallow with tailwind. Steepen with headwind.
Conditions that lead to tail rotor vortex ring state.
(Anti-clockwise main rotor)
- High rate hover turn to the right.
- Wind from the left.
- Sideways flight to the left.
Distinguish differences between symmetrical and non-symmetrical blades.
Symmetrical
- Chord line & mean camber line the same.
- Not as efficient at lift
- Fixed center of pressure
- Lower stall/critical angle
Non-Symmetrical
- Chord line different to main camber line
- Better production of lift
- Centre of pressure that moves
Define shaft axis
The line consistent with the rotor shaft (mast). Only when plane of rotation is exactly perpendicular to the shaft axis will the axis of rotation coincide with the shaft axis.
You make a climbing turn using max power, what will happen to rate & angle of climb if you increase Angle of Bank at the same ISA.
Climb rate decrease
Climb at shallower angle
You are hovering over a slope with just the front of the disc IGE.
What will helicopter tend to do?
Anticlockwise disc - Roll right
Clockwise disc - Roll left
How can vortex ring state develop?
- Some power in use
- Low airspeed (below translation)
- Moderate/High RoD (400-800fpm)
You are operating out of Denver at 5200” what effect does this have on the areas in the height velocity graph?
Both shaded areas increase in size due to high density altitude
You are hovering OGE with a 20kt headwind if the wind dissappears, will it affect power required & how?
Yes
Increased power required
You have tail rotor failure in cruise. On descent at 6-8ft above ground, aircraft begins to yaw to the right.
What should you do?
Roll off throttle to align aircraft with direction of travel & conduct running landing.
Spanwise imbalance is rectified by doing what?
Adjusting the weight at the tip of a blade
Describe differences between low inertia and high inertia blades
High Inertia
- RRPM fluctuates less
- Once rotating, requires less power
- Flares easier to execute
- Requires strong & heavy rotor head designs
Low Inertia
- More maneuverable
- Quicker to recover loss in RRPM
