Module Five Flashcards
What are the basic aerodynamic forces? (4)
Lift, drag, weight, and thrust.
How does flight happen?
Results when enough lift produced to overcome weight.
The aircraft’s lift must balance its weight, and its thrust must exceed its drag. Moving forward with enough speed to produce required lift.
The wings lift, and air flows faster above than below.
The engines thrust.
Drag is reduced by the smooth shape.
Weight is controlled by the aircraft’s materials.
When aircraft is flying straight and level at a constant speed, its lift = its weight, and its thrust = drag.
How does lift occur?
Created when air moves over a curved surface.
Air has further to travel on one side than the other, causing unequal pressure gradient, and resulting in lift.
Aircraft wings and propellors create most of the lift.
Lift only exists in moving fluid such as air.
The heavier, the more lift needed.
Define weight.
Function of gravity. Opposes lift.
Describe thrust in the aerodynamic setting.
Moves aircraft forward.
In fixed-wing - from propellor jet engine.
Describe drag.
Force generated by aircraft when moving through air.
The shape determines the amount of drag - “form drag”
Some drag produced by lift - “induced drag”
Total drag = form + induced drag
Describe flight control in fixed-wing aircraft.
Flight is controlled with moving surfaces around 3 axes.
Ailerons - attached to outer main wings, controls roll around plane’s longitudinal axis. Controls bank for coordinated turn.
Rudder - attached to tail fin, controls yaw around vertical axis for coordinated turn.
Elevator - attached to rear, controls pitch around aircraft’s vertical axis to control vertical altitude.
They are all needed for climbing and descending turns.
What are the basic aerodynamics of rotary wing aircraft?
Thrust derived from engine output to gearbox, which drives wing/series of wings in plane of rotation.
Describe flight control in rotary wing. (4)
Collective control - vector/disc size and direction causes displacement of heli, position of each rotor blade varies lift on each one
Cyclic control - vector/disc, adjusts position of individual blades causing discs to tilt and drags heli in desired direction
Tail rotor (pedals) - control direction, lifts through horizontal plane to prevent fuselage rotating. Adjust blade positions.
Throttle (engine) - controls thrust/rotational drive of blades to overcome drag.
Describe the design configurations of helicopters.
Aim to enhance performance and reduce risks.
Performance is enhanced by reducing weight and increasing effectiveness by increasing payload, speed, endurance. This is done by:
Efficient aerofoil designs
Modern materials
Increasing engine power: weight
Decreasing drag
What is helicopter performance determined by?
Internal factors - function of design - primary factor being power (single vs twin engine)
External factors - function of operational environment: reduced air density, high temps, altitude, and distance from ground cushion reduce power.
List the advantages of helicopters. (5)
Controlled hover
Winching/external loading
Fast transit times compared to road (100-160 knots)
Controlled operations at low speed
Can reach confined areas
List the disadvantages of helicopters. (13)
Limited forward airspeed
Longer transit times than fixed-wing
Decreased overall range capability (<250km)
Less endurance
Low operational ranges
Small space for providing care and bringing equipment
Carry one and sometimes two critical care pts, up to 6 non stretcher pts
2 x crew members
Weight and space restrictions
Limited/no ability to control temp
Usually can’t be pressurised
Incredibly difficult to intubate in.
Fly up to around 2500m elevation.
List the characteristics of transport modalities. (7)
Distance able to fly
Space available for pt care
Landing ability
Weather
Aircraft hazards
Costs
Role delineation
Is hot loading/unloading a good idea?
Time saved is usually not justifiable.
