8.3 Theory of Flight Flashcards
What are the four forces acting on an aircraft?
Lift
Weight
Thrust
Drag
Formula for moment?
Force times moment arm/length
For stable flight where must the centre of lift located?
Behind the centre of gravity
Where is the thrust line located?
Below the drag line
What is the glide ratio formula?
Forward speed divided by sink speed (triangle S divided by triangle H)
What is the vertical element of lift in a turn?
The vertical element of lift in a turn is the force that opposes the aircrafts weight
What is the horizontal element of lift in a turn?
The horizontal element of lift acts towards the centre of the turn, it is also the force that pulls the aircraft into the turn
What happens to lift in a turn?
Because of the two split components of lift, vertical and horizontal, the lift force is split, therefore it is reduced, so in order to maintain lift the angle of attack must be increased to maintain the same altitude
What is load factor?
Also known as G load, it is the resultant force(lift in a turn) divided by the weight
What effects the maximum bank angle? (G loading) ?
Passenger comfort and aircraft structural strength
During a turn what must be compensated for?
Extra weight brought about by the resultant of the centrifugal force and the weight
What is the flight envelope?
The range of combinations of speed, altitude, angle of attack, etc., within which a flying object is aerodynamically stable.
What factors effect the flight envelope?
The aircraft gross weight
The configuration of the aircraft (flaps and landing gear position etc.)
The applicable altitude.
What is the limit airspeed?
The limit airspeed is a design reference point for the aircraft, and an aircraft in flight above this speed may encounter a variety of adverse effects, including: destructive flutter, aileron reversal, wing divergence
What are structural limits?
These are the allowed positive and negative “g” limits of the aircraft
What are structural limits based on?
Structural limits are based on the strength of the aircraft structure
What is the effect of a large amount of airframe flexing?
A large amount of airframe flexing will lead to permanent deformation (a bent airframe) or component failure
What is the effect of a small amount of airframe flexing?
A lesser amount of flexing affects the lifetime of the airframe due to metal fatigue, etc
What are structural limits also known as?
Structural limits are also referred to as acceleration limits or limit load factors
What is the effect of overstressing the aircraft?
Exceeding the structural limits (overstress of aircraft) may or may not damage the aircraft. Numerous over stresses will shorten the service life of the aircraft
What are aeroelastic limits?
These define the maximum operating speeds in both Knots-Indicated Air Speed and Indicated Mach Number of the aircraft
What can occur if the aeroelastic limits are exceeded?
Above the Aeroelastic limits, structural damage or failure may occur as well as a loss of stability and/or control authority
What is the aeroelastic limit commonly referred to as ?
“Redline Airspeed”
What are the ultimate structural limits?
These define the ultimate operating strength limits of the aircraft. Flight operations beyond the ultimate structural limits will result in structural failure of some component of the aircraft
What is the percentage of additional strength with regards to the ultimate structural limit and structural limit?
150 %
What does lift augmentation acheive?
Lift augmentation increases the maximum lift coefficient in order to reduce the airspeed at take off and landing
What do flaps do to the wing?
Increase its camber
What does increased camber do to the airflow?
Accelerates the airflow over the top of the wing increasing lift production
What is the secondary effect of flaps for the wing?
It re-energises the boundary layer
What are the four main types of flap?
Plain
Split flap
Slotted flap
Fowler flap
Negative of the plain flap?
The abrupt change in camber can result in airflow
breaking away from the wing surface
A split flap is …
More efficient than the plain flap. The
airflow is less likely to break away
A slotted flap works by?
Forming a slot as the flap is lowered
also re-energises the airflow
A fowler flap works by?
Travels rearwards and downwards, increasing wing area as well as the camber
By what percentage does a fowler flap increase the coefficient of lift max by?
Up to 90%
How do slats work?
Slats create a slot in the leading edge and this allows airflow to re energise the boundary layer along with having a high cambered cross section
What do slats reduce?
The possibility of flow separation at high angles of attack
