Principles of Flight Flashcards
How does a wing generate lift?
Air over the wing gets accelerated and has a lower pressure. Air under the wing gets decelerated and has a higher pressure. This difference in pressure is what causes the lift.
What is ‘relative airflow’?
The movement of the glider through the air causes the air to flow past the glider in the opposite direction.
What is the angle of attack?
The angle at which the airflow arrives.
What is the chord of the wing?
A straight line from the leading edge to the trailing edge.
The direction of the lift force produced is at what angle to the relative airflow?
Right angle
When is total drag at a minimum?
When lift dependent drag is equal to zero lift drag.
What will be the reading on the ASI if the Dynamic source of the ASI is blocked?
It will not respond
What two quantities must be present for a glider to spin?
High AoA and yaw.
What is meant by the aspect ratio of a wing.
Ratio of wing length to chord length.
What is the purpose of the gliders fin?
To provide directional stability.
On a silver duration flight, soarable conditions stop after four and a half hours. You are at 5000 ft. What is the best speed to fly in order to complete the flight?
Minimum sink.
While maintaining the normal gliding attitude you notice that the air speed indicator is reading low and erratic. What is the most likely cause?
Water in the pitot system.
Wash out’ is a term used to describe a particular design feature of a glider. What does it describe?
A twist in the wing, such that the inboard part of the wing stalls before the outboard, hence preventing wing drop at the stall.
What is the approximate distribution of production of lift on a glider wing?
70 percent from above
30 percent from below
What happens to induced drag as airspeed is increased from the stall towards Vne?
Induced drag reduces inversely as the square of the IAS.
Three forces act on a glider in flight. Which force, or part of a force, causes a glider to turn?
Part of total lift acting in the direction of the turn.
If the 1 ‘g’ stalling speed is 34 knots, what will be the stalling speed in a steep turn with the accelerometer reading 4 ‘g’?
68kts
What is the importance of indicated airspeed (IAS) and true airspeed (TAS), when flying at altitude?
IAS is always less than TAS and the ASI under reads the true airspeed.
What is the aerodynamic purpose of the gliders tailplane?
Provide longitudinal stability
What is the definition of a Mean Camber line?
A line joining the centres of curvature between the Leading and
Trailing edges and equidistant from the upper and lower surfaces.
What happens to profile drag as airspeed is increased from the stall towards Vne?
Profile drag increases approximately as the square of the IAS.
In which direction does lift developed by the wing of an aircraft in flight act?
Perpendicular to chord line.
What does the Barometric Pressure Scale enable the pilot to achieve?
To reset the altimeter datum.
Why is the capacity flask insulated?
To prevent temperature changes affecting the variometer readings.
What causes adverse yaw or aileron drag?
An increase in lift dependent drag on the up going wing.
What is the purpose of a gliders dihedral?
To help increase lateral stability
What does stagnation point refer to?
The point on a wing leading edge where air is brought to rest.
What is the definition of Centre of Pressure?
The point on the chord line through which the force if lift acts
As angle of attack increases, what direction will the Centre of pressure move?
Forward until the stalling angle, then rapidly back.
The Pitot source is blocked on the Altimeter. What will the instrument read?
Fail to operate
