11.1.1 Aerodynamics and Flight Controls Flashcards
What are the three primary axis?
Lateral
Longitudinal
Vertical
What movement is through the lateral axis?
Pitch
What control surface is responsible for pitch?
Elevators
What movement is through the longitudinal axis?
Roll
What flying controls are responsible for roll?
Ailerons
What movement is through the vertical axis?
Yaw
Where is the vertical axis located?
In the centre of gravity.
What flying control is responsible for yaw?
Rudder
Besides the three primary flight controls on large aircraft what can be added to increase efficiency of the flying control surface?
Roll spoilers and/or speed brakes
Where are ailerons located?
Outboard trailing edge of the wing.
What happens when the pilot moves the control stick to the right?
Right aileron up
Left aileron down
When moving the control stick right why does the right aileron come up?
It reduces the camber of the wing reducing the lift.
How is dynamic energy calculated?
1/2 PV^2
What is energy in the air proportional too?
The square of airspeed
If airspeed is doubled what pressure is felt on the flying control?
Quadruple.
What is aileron lockout?
At higher speed the outboard aileron is locked.
Why is aileron lockout used?
To prevent the structure taking on too much force.
Spoilers are used to reduce lift, what else do they counteract?
Lift induced drag that causes adverse yaw.
What system are the spoilers linked too?
Ailerons
What is the purpose of roll spoilers?
To execute an accurate turn and reduce the requirement for a large aileron deflection at high speeds.
Where are elevators located?
The trailing edge of the horizontal stabiliser.
What are stabilators?
Dual purpose that combine the elevators and horizontal stab.
On light aircraft with stabilators what are they normally equipped with?
Anti-balance tab.
What is a THS?
Trimmable horizontal stab, used for pitch trimming.
What advantage does a THS offer?
Reduced drag due to reduced elevator deflection?
What is a THS also known as?
Variable Incidence Stabiliser.
What happens when a THS angle of attack is increased?
Nose down
How is the angle of incidence controlled of a THS?
Screw jack controlled by the pilots pitch trim wheel.
What is a canard?
Essentially the THS but moved forward of the wing.
What is the primary role of a canard?
Pitch control
The stability that canards offer also enhances what?
Stall resistance and manoeuvrability.
How do the canards assist in stall prevention?
They can stall first causing a nose down pitch that helps the aircraft recover.
What does the rudder limiter do?
Restricts the rudders amount of deflection with increasing air speed.
How do roll and yaw have secondary effect on one another?
As the aircraft yaws one wing advances and increases its lift effect.
When is the only time rudder is used independently?
Crosswind or engine failure.
How is adverse yaw overcome in aircraft?
Designs such as frise ailerons.
What is a frise aileron?
Control surface with a specially contoured leading edge.
How are differential ailerons rigged to oppose adverse yaw?
The up going aileron is deflected more than the down going one, creating a drag imbalance.
What does an aileron interconnect system help with?
Adverse roll
What aircraft experience adverse roll?
Ones with a high vertical stab.
Swept wing are prone to dutch roll, how is it combatted?
Yaw dampening.
What is the yaw dampener?
Servo unit that moves the rudder in response to inputs from a gyroscope or accelerometer that detects yaw rate.
What two common combined flying controls are there?
Elevons
Ruddervators.
Where are elevons found?
Delta wing aircraft.
What two forces are combined in a elevon?
Pitch and roll
What does a ruddervator combine?
Rudder and elevator.
What aircraft use ruddervators?
V-tailed aircraft
Ruddervator- to produce a left yaw movement what do the flying controls do?
Deflects the left hand down and left, right hand goes up and left.
How are the inputs to a ruddervator applied?
Through a mixer unit.
What do V tailed aircraft have to prevent yawing?
Longer fuselage.
What are some of the common high lift devices?
Slots
Slats
Flaps
LE Flaps
Flaperons
What are slots?
Fixed convergent ducts or gaps.
What do slots allow?
High pressure air from beneath to accelerate to the top and reenergise the boundary layer.
What is the disadvantage of slots?
They produce a lot of drag.
What are slats?
Like slots but moveable.
What is a plain flap?
Hinged flap that adds 50-55% lift
What is a split flap?
Hinged panel that splits from the upper surface, adds 60-65% lift.
What is a slotted flap?
Modular flaps that extend and add 65-70% lift.
What is a fowler flap?
Split flap that forms part of the underside of the TE and increases lift 95%.
Where can LE flaps be found?
Heavy aircraft.
What is LE droop?
LE section rotates down increasing camber.
What is a krueger flap?
Lift device fitted to the LE, lower surface of the LE that hinges out.
What is a flaperon?
Aileron that is also a flap.
What is the difference between air brakes and spoilers?
Air brakes are designed to raise drag whilst not effecting lift.
What is the function of a spoiler?
To increase drag to augment a controlled descent
Depending on the aircraft, spoilers can serve up to three distinct primary functions, what are they?
Flight spoilers
Ground spoilers
Roll spoilers
What is a flight spoiler?
Speed brake
Is the deflection of airborne spoilers more or less than ground spoilers?
Less
What do the spoilers do in armed mode?
Remain retracted and locked only deploying automatically.
What is ground spoiler mode?
Max extension of the speed brakes.
How do ground spoilers help the aircraft with braking?
They dump the lift forcing the weight of the aircraft onto the landing gear.
What are roll spoilers?
Spoilerons, used in conjunction with the ailerons for roll control.
Which spoilers are the roll spoilers?
Outboard or mid
What spoilers are the decent control?
Inboard
What is the benefit of using the spoilers to roll the aircraft?
Avoids twisting and therefore adverse yaw.
What two directions are particles split in the airflow over the LE?
Along it and at right angles, producing spanwise flow.
What does spanwise flow do?
Thicken the boundary layer towards the wingtip making it prone to seperation.
What are the design solutions to spanwise flow?
Wing fences, saw tooth LE.
What is a wing fence?
Flat plates that limit boundary layer outflow before it begins to stagnate.
What else are wing fences known as?
Boundary layer fences and stall fences.
What is a saw tooth?
LE zig zag cut out, creates a small vortex that limits outflow.
What are saw tooths best for?
Swept back wings
What is a vortex generator?
Device used to re-energise the slow moving boundary layer.
What do vortex generators produce in terms of lift?
Sideways lift, high pressure spills over the tip and causes a vortex.
What is a stall wedge?
LE device near the wing root encouraging the root to stall first.
On what type of wing are stall wedges used?
Tapered
What are stall wedges also known as?
Stall strips
What is boundary layer suction?
Powered system that sucks the boundary layer flow from closely sucked vertical slots.
What does trimming an aircraft mean?
Adjusting the aerodynamic forces on the control surfaces to maintain straight and level flight.
What is a trim tab?
Used to compensate for the imbalance, they are small control surfaces located on the TE.
Can trim tabs be fixed or moveable?
Both
What are trim tabs used on?
Light aircraft
What way do trim tabs act to help the flying control?
In the opposite deflection.
What is a balance tab?
Assists in moving the flying control via a rod that pulls it in the opposite direction reducing the force required.
What is an anti-balance tab?
Moves in the same direction as the flying control, adding resistance.
What is the point of an anti balance tab?
To make a flying control less sensitive.
What is a servo tab?
Used where it would take too much force to move a flying control.
Where are servo tabs used?
Large aircraft.
In which direction does a servo tab work?
Opposite to the flying control.
What is a spring tab?
Like a servo tab, it has a spring mechanism that must be overcome when the force on the flying control becomes too high.
What is mass balance of a flying control?
The position of the CG and CP and the hinge point.
What happens if the cg of a control surface is aft of the hinge line?
Inertia is felt and an oscillation will follow.
What is the difference between torsional flutter and flexural?
Flexural, caused by the movement of the aileron lagging behind the rise and fall of the outer portion of the wings as it flexes.
How is flexural flutter prevented?
Mass balancing the flying control.
What is key about the mass balance of a flying control?
The closer to the wingtip it is the smaller it should be.
What is flying control bias?
Specific config or setting applied to control surfaces to achieve desired characteristics.
After adjustment of bias what must all trim position gauges show in the flight deck?
0
Where is the CP normally for balanced controls?
1/3 of the chord length from the leading edge.
What is horn balance?
Aids deflection, the horn is located forward of the hinge line.
What is a balance panel?
Plate connected to the leading edge.
What does a balance panel do?
Divides the space in front of the control surface in too two chambers.
