Principles of Flight
What is the formula for Power (w)?
Force (N) x Distance (m) / Time (s)
What is the formula for kinetic energy?
KE = 1/2 m V ^2
What is the formula for Dynamic Pressure?
Q = 1/2 ρ V^2
What does total pressure equal?
Static pressure + Dynamic pressure
What is dynamic pressure equal to?
Total pressure - Static pressure
At what altitude is the tropopause?
What is the temperature above the tropopause?
What is the temperature lapse rate?
1.98 C per 1000ft
In the ISA, what is the density at sea level?
What is the pressure at sea level in the ISA?
what is the Kelvin to C formula?
K = C + 273
What is the unit of density?
kg/m3 (ρ - rho)
What is the unit of pressure?
N/m2 (Pa - Pascal)
What is the speed of sound on a 'normal' day at sea level
340 m/s (660 Kts TAS)
What is the formula for weight?
F = m x g (9.81)
What is the unit for work?
What is the formula for work?
Work (j) = Force x Distance (through which the force is applied)
What is Newton’s First Law of Motion?
’A body will remain at rest or in uniform motion in a straight line unless acted on by an external force’.
What is Newton’s Second Law of Motion?
’The acceleration of a body from a state of rest, or uniform motion in a straight line, is proportional to the applied force and inversely proportional to the mass’.
What is the definition of Velocity?
‘Rate of change of displacement’
What is Newton’s Third Law?
‘Every action has an equal and opposite reaction’
What is the definition of Acceleration?
‘Rate of change of velocity’.
What is the lift formula?
L = 1 / 2 ρ V^2 CL S
In the lift formula, if V is doubled, what must happen to CL?
Must be 1 / 4 of previous value
What is the lift formula when transposed for speed?
v = √ L / 1/2 ρ CL S
What is the taper ratio?
CT / CR
The ratio of the tip chord to the root chord
What does C r stand for?
Root chord (m)
The chord length at the wing centre line
What does C t stand for?
Tip chord (m)
The chord length at the wing tip
In wing terminology, what does b stand for?
The distance from tip to tip
In wing terminology, what does c stand for?
Average chord (m)
The mean geometric chord. The product of the span and the average chord is the wing area (b x c = S)
In wing terminology, what does S stand for?
Wing area (m^2) (b x c)
The plan surface area of the wing
In wing terminology, what does AR stand for?
Aspect ratio (b/c) (b^2/S)
The proportion of the span and the average chord
In wing terminology, what does MAC stand for?
Mean aerodynamic chord (m)
A rectangular wing of this chord and the same span would have broadly similar pitching moment characteristics
In wing terminology, what is the sweep angle?
The angle between the line of 25% chords and perpendicular to the root chord
When observing from behind, which way would wing tip vortices rotate?
Left - clockwise. Right anti clockwise
Effect on wing tip vortices: Airspeed
Reduced airspeed will increase strength of vortices
Effect on wing tip vortices: Gross weight
Increased weight will increase strength of vortices
Effect on wing tip vortices: Wingspan
WIll dictate the proximity of the two vortices
Effect on wing tip vortices: Configuration
Vortices are stongest in 'clean' config (for a given weight and speed)
Effect on wing tip vortices: Attitude
The higher the A o A, the stronger the vortices
How far can trailing vortices extent behind an aircraft?
Up to 9 nm
How far apart are two training vortices (generally)?
3/4 of the wingspan
How far do trailing votices drift?
Usually 500-1000ft downwards and then level off
If two vortices touch down, how will they behave (assuming no wind)?
The will move apart at 5kts at a height approx equal to half of the aircraft's wingspan
What happens to Cdi (Coefficient induced drag) in ground effect?
It is reduced
What happens to lift (L) in ground effect?
It is generally increased
What is lift on a wing most properly defined as?
Force acting perpendicular to the relative wind
The A o A of a wing directly controls the?
Distribution of pressures acting on the wing
What is parasite drag subdivided into? (3)
Skin friction drag
Form (pressure) drag
What is skin friction and form drag known as together?
Is parasite drag dependent or independent of lift generation?
Parasite drag and relationship with IAS
If IAS is doubled, parasite drag will be 4 times greater
If IAS is halved, parasite drag will be 1/4 it's previous value
What is the formula for parasite drag?
Dp = 1/2 ρ V^2 Cdp S
Do stronger wingtip vortices increase or decrease induced drag?
Will induced drag be higher or lower at heavier a/c weights?
Will induced drag decrease or increase with an increase in speed (for a constant lift force)?
Does a glider have a high or low wing aspect ratio?