# 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?

36089ft (11,000m)

## What is the temperature above the tropopause?

-56.5 C

## What is the temperature lapse rate?

1.98 C per 1000ft

## In the ISA, what is the density at sea level?

1.225 kg/m^3

## What is the pressure at sea level in the ISA?

1013.25 hPa

## 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?

Joule

## 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?

Span (m)

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

Interference drag

## What is skin friction and form drag known as together?

Profile drag

## Is parasite drag dependent or independent of lift generation?

Independent

## 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?

Increase

## Will induced drag be higher or lower at heavier a/c weights?

Higher

## Will induced drag decrease or increase with an increase in speed (for a constant lift force)?

Decrease

## Does a glider have a high or low wing aspect ratio?

High