Flight mechanics Flashcards

1
Q

Forces on an aircraft

A
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2
Q

Lift generation

A

Air passing over the upper surface moves faster than the air passing over the lower surface. The upper surface has lower pressure than the lower surface. Integrating the pressure difference over the length of the aerofoil produces a lift force. Pressure drag is also produced.

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3
Q

Resolving for straight and level flight

A

T=D L=W

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4
Q

Definition of lift force

A

The component of the total aerodynamic force acting perpendicular to the relative airflow

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5
Q

Definition of drag force

A

The aerodynamic force that acts parallel to the relative airflow direction

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6
Q

Define angle of attack

A

Angle that the chord line makes with the incoming airflow

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7
Q

Factors that influence lift or drag force on an object

A

relative airflow velocity

planform area of lifting surface

air density

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8
Q

Lift coefficient

A
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9
Q

Drag coefficient

A
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10
Q

Factors that affect lift or drag coefficient of an object

A

air viscosity

AOA

aerofoil shape

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11
Q

Induced drag

A

drag caused by the formation of trailing vortices dependent on aspect ratio

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12
Q

How and why does airspeed affect induced drag?

A

As airspeed increases, induced drag decreases

the down-wash component of the incoming air-stream becomes proportionally smaller as the incoming air velocity increases

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13
Q

Ways to reduce induced drag on a wing

A

increasing aspect ratio adding winglets decreasing wing chord increasing wing span

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14
Q

What does parasitic drag consist of?

A

Parasitic drag is also known as profile drag

Parasitic drag = pressure drag + skin friction

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15
Q

Pressure drag

A

pressure differences from front to back of aerofoil

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16
Q

Total pitching moment

A
17
Q

What happens when the moments about the centre of gravity equals zero?

A

there is no disturbing moment acting on the aircraft and flies along the desired flight path

18
Q

Pitching moment coefficient

A
19
Q

Define boundary layer

A

thin layer of air adjacent to the aerofoil’s surface

20
Q

Types of boundary layer

A

Laminar Turbulent

21
Q

Laminar boundary layer

A

low drag highly ordered

22
Q

Turbulent boundary layer

A

high drag completely disordered

23
Q

Define skin friction

A

equal and opposite force acting on the aerofoil, to the force retarding the air molecules

24
Q

Wing geometry

A
25
Q

Aspect ratio

A
26
Q

Aerodynamic centre

A

It is a fixed point for which the pitching moment is invariant with incidence

27
Q

Aerodynamic mean chord

A
28
Q

Simpler and less accurate definition of wing chord is geometric wing chord. Equation for geometric mean chord

A
29
Q

The power produced by an engine is converted into thrust by the propeller. Thrust produced is given by….

A