11.1 THEORY OF FLIGHT👌🏼 Flashcards
Aircraft rotates about 3 primary axes ?
- Lateral axis (pitch) (elevators etc)
- Longitudinal axis (roll) (Ailerons and spoilers)
- Vertical axis (yaw) (rudder)
Aircraft primary controls are ?
- ailerons
- elevators
- rudder
What are stabilators?
- dual purpose of horizontal stabiliser and elevators
- commonly found on high speed military combat aircraft
What are variable incidence stabilisers / THS ?
- limited ROM, used only for pitch trimming
- reduce drag
- long term adjustments
What are canards?
- where the horizontal stabiliser is positioned at the front of aircraft (ahead of main wings)
If a rudder is deflected left, where does the nose point?
- left
What are rudder limiters?
- restricts rudder deflection with increasing airspeed
What happens if you excessively use rudder during high speeds?
- lead to structural failure
What are elevons?
- combination of elevators and ailerons
- found on delta wing aircraft
- no horizontal stabiliser
- control surfaces for pitch and roll are located at trailing edge of the wing
What are Ruddervators?
- combination of a rudder and a elevator
- e.g. found on v tailed aircraft (do not have vertical or horizontal stabiliser)
Explain slots?
- located on leading edge
- allows high pressure air beneath wing to accelerate to the top of the wing and re-energises the boundary layer
- prevents separation, stagnation, and stall at higher AOA
- allows aircraft to fly at lower speeds at high AOA
- frequently situated in front of ailerons so inboard part of wing stalls first and aileron functions are maintained
- they produce a lot of drag
Explain slats?
- located on leading edge and same function as slot but adjustable
- increase camber, increase lift
- allows high pressure air to accelerate over wing to re-energise boundary layer
- can be selected as part of a configuration or manually
Explain flaps?
- Secondary flight controls are used to increase lift during slow speeds (take off and landing)
- produce significant drag (useful when landing)
- nose pitch down when flaps are out
What is a plain flap?
- 50% - 55% lift increase
- Cause a lot of drag
What is a split flap?
- 60% - 65% lift increase
- causes more drag than a plain flap
What is a slotted flap?
- slots near trailing edge when extended
- not as much drag as plain and split
- increases lift by 65% - 70%
- large aircraft often have double or even triple slotted flaps
What is a fowler flap?
- increases chord of wing then camber
- nose down pitch movement
- Increases lift the most (up to 95%)
Which flap has lift up to 95%
- Fowler flap
What is a slotted fowler flap?
- increase area of wing then camber
- increasing lift and giving lowest drag possible
What do heavy aircraft have in addition to trailing edge flaps?
- leading edge flaps
When leading edge flaps is retracted, where is it stored?
- leading edge of wing
Explain leading edge droop?
- device that improves airflow over the wings at high AOA
- entire leading edge rotates downstairs
- increases camber and lift
Explain Krueger flaps?
- lift enhancement devices on leading edge
- when deployed, produces nose up pitch
What are flaperons?
- dual purpose (ailerons that can function as a flap)
- during take off and landing they behave like flaps (it can still be used as a aileron)
What do drag inducing devices do?
- dump lift and increase drag
What are spoilers?
- hinged panel that interrupt airflow over the wing
- spoils lift
- e.g. of secondary flight controls
- increase drag
Spoilers can serve 3 distinct primary functions, what are they?
- flight spoilers (speed brakes)
- ground spoilers (lift dumpers)
- roll spoilers
Explain flight spoilers?
- referred to as speed brakes
- has a max deflection angle while airborne
Explain ground spoilers?
- all spoilers are equipped with ground spoilers function
- helps slow aircraft down by producing aerodynamic drag
Explain roll spoilers?
- used with ailerons to enhance roll control
- referred as ‘spoilerons’
- can be deployed on 1 wing to better the roll
- spoilers allow aircraft to roll without creating a twisting force
What are wing fences?
- reduce span wise flow and helps reduce the wing tip stalling on swept back aircraft
- usually installed on leading edge
- known as ‘boundary layer fences’
What are vortex generators?
- device used to re-energise boundary layer
- produces lift that acts sideways
- high pressure spills over the tip to enter low pressure side and causes a vortex
What are stall edges?
- known as ‘stall strip’
- encourages root to stall first
- bonded onto wings leading edge, usually at the wing root
What is aircraft trimming ?
- adjusts aerodynamic forces to maintain set attitude
Where are trim tabs located?
- trailing edge
How does a trim tab work?
- It is deflected in the direction that opposes flight control deflection
Explain balance tab?
- when control surface is deflected, the tab automatically moves in the opposite direction
Explain anti-balance tab?
- tab moves in the same direction as the control surface
- more effort required to deflect the control surface
What are Servo tabs?
- assists larger control surfaces to move
- servo tabs move opposite direction to the flight control
- pilot operated
What are spring tabs?
- like a servo tab, only works when the force on a flight control reaches a certain value
Subsonic compressible flow speeds?
Mach number < 0.8
Transonic compressible flow speeds?
- Mach number 0.8 - 1.2
Supersonic compressible flow speed?
- Mach number 1.2 - 5.0
Subsonic is greater or below the speed of sound?
What aircraft fly here?
- below
- commercial flights
Explain transonic flight?
- combination of subsonic and supersonic airflow
- ‘normal shock-wave’ is formed (90 degrees)
Explain supersonic flight?
- > speed of sound
- ## entire aircraft subject to supersonic airflow
Mach 1 = ?
- speed of sound
Air is compressible at what speeds?
- approx Mach 0.4
Explain a normal shock wave?
- air barrier perpendicular to airflow (90*)
- happens in transonic flight range
Explain Oblique shock waves?
- airflow formed at another angle
- faster than speed of sound (> Mach 1)
- as it passes through the wave, velocity of airflow is reduced but remains supersonic
- slight increase in temp and pressure
What is an expansion wave?
- supersonic airflow changes direction around curve/corner
- not a shockwave
- pressure, density and temp of air decrease
- velocity increases
Explain expansion wave?
- not shock waves
- supersonic airflow changes direction around curve or corner
- pressure, density and temp of air decreases
- velocity increases
What are the 2 ways to reduce wave drag
- vortex generators
- area rule
What is wave drag?
- total drag created from shock waves
Explain vortex generators?
- transfers energy from the free air stream to the boundary layer (produce vortex)
- reduce flow separation
- produces oblique shock wave inside the supersonic airflow
Explain the Area rule related to overcoming wave drag?
- reduce aircraft’s drag at transonic speeds
- Sears- Haack body is the shape with lowest theoretical wave drag in supersonic flow
Why is the fuselage waisted in aircraft?
- ensures the volume distribution is maintained as the ‘Sears-Haack profile’
What is aerodynamic heating also known as?
-friction heating
- friction of air heating airframe
How does sweepback increases the critical Mach number?
- longer chord
- reduced thickness
What flight control can be used as you are rolling to prevent side slip?
- rudder
