8.3 - Theory of Flight Flashcards
What are the 4 forces acting on an aircraft in flight?
Thrust
Drag
Weight
Lift
What is an aircraft’s centre of gravity?
The aircraft’s Centre of Gravity (CG) is the point on the aircraft at which all weight is considered to be concentrated. It is the point of balance.
(Note: it can change during flight - fuel burn/ cargo)
If the thrust line was above the drag line what effect would it have on the aircraft when thrust is increased?
This will give a nose down moment.
(This is non standard design)
What would happen to an aircraft if its Centre of Pressure was acting behind the Centre of Gravity?
This will give a nose down moment
(Normal design / counteracts nose up moment of lift vector being below Cg)
How are the forces of lift and weight, thrust and drag coupled together to prevent pitching moments?
Lift and Weight couple cause a nose down moment
(Centre of Pressure is behind Centre of Gravity)
Thrust and Drag couple cause a nose up moment
(Thrust vector is below Drag vector)
These opposite moments balance each other
What are the 3 axis of rotation of an aircraft?
Longitudinal Axis
Lateral Axis
Vertical (Normal) Axis
What axis does an aircraft roll and pitch about?
Roll - longitudinal axis
Pitch - lateral axis
What are the forces in a glide?
Weight
Lift
Drag
What does a glide ratio of 20:1 mean?
The glide ratio is the ratio of the horizontal distance an aircraft travels while gliding to every unit of vertical distance it descends.
Glide ratio = Horizontal distance : Vertical distance
(Large transport aircraft have a glide ratio of around 10:1)
What is the glide angle that will produce the greatest horizontal distance?
Approx 4 degrees AOA
What will happen to an aircraft that glides at an angle of attack greater than its optimum lift/drag ratio?
Anything up to and then after the optimum angle of attack will cause the L/D ratio to decrease causing the aircraft to hit the ground sooner.
State the action a pilot will take to return to a glide angle if his speed increases
only way speed increases in a glide is if the nose points downward.
To return to optimum glide angle, push nose up in order to decrease speed and return to original AOA
What causes airspeed to reduce in a climb?
A component of the aircraft’s weight acts in the same direction as, and parallel to, the total drag of the aircraft, thereby increasing the total effective drag.
What happens to the four forces acting on an aircaft while established in a climb?
The forces become balanced just like the level flight values.
What are the forces in a descent?
A descent, or glide, is a basic manoeuvre in which the aircraft is losing altitude in a controlled way with little or no engine power. Forward motion is maintained by gravity pulling the aircraft along an inclined path. The descent rate is controlled by the pilot balance the forces of gravity and lift
A component of the weight vector becomes the thrust.
Why will an aicraft slip in a turn?
An aircraft will slip in a turn when the centrifugal force is less than the horizontal lift force
Why is it necessary to increase the angle of attack in a medium bank turn?
Part of the lift force must become horizontal lift which means a decrease in vertical or standard lift.
This means that the wings must produce a higher amount of lift than was required for normal straight and level flight.
The extra lift means that, for a given speed the wing must be operated at a higher angle of attack in the turn and, in addition, the increase in the lift will be accompanied by an increase in drag
If an aircraft weighing 60,000Ibs has a stall speed of 140 kts, what will be the new stall speed if 20,000 Ibs is added?
The stall speed will increase.
What information can be ascertained from a V-n diagram?
The indicated airspeed and load factor that an aircraft can have when performing a manouvre (affects Gravity/ g’s) to operate safely in the flight envelope
What is the difference between a slot and a slat?
A slot is designed to improve the airflow conditions at high anges of attacka and slow speeds. Slots are generally fixed but become a huge problem at high speeds as they increase drag significantly.
Slats are the answer to slots. They are retractable and in a cruise, they don’t increase drag like slots. However when needed, they extend to increase the coefficient of lift and increase the stall angle.
Both slots and slats are located at the leading edge.
Describe briefly what happens to lift and drag as the trailing edge fowler flaps are extended.
The Fowler flap is of the area increasing type of flap and so, besides augmenting the coefficient of lift by increasing the camber, it increases the wing area and in so doing reduces the wing loading thus lowering the stalling speed further.
What are the advantages of a slotted flap over a plane flap?
The action of slotted flaps is to set up a favourable pressure gradient and so maintain a suitable boundary layer for a greater distance over the sharply deflected surface of the flap.
Where is a Krugar flap located?
(Freddie Krugar and Droop)
