CPL - General Knowledge SE

The Camber Line runs where on an airfoil?

Midway between the upper and lower surfaces

Lift acts in what direction relative to airflow?

Perpendicular to relative airflow

Drag acts in what direction relative to airflow?

Parallel to relative airflow

What defines stability in aircraft?

Centre of gravity in front of the centre of pressure

Where do lift and drag act through?

The centre of pressure

What is the formula for Aspect Ratio?

Span/Chord

What is Dihedral?

The angle between the wing (fuselage to wingtip) and the horizontal

What is the Lift Equation?

½ * air density * TAS² * wing area * coefficient of lift

What are the two types of drag?

Induced and Parasite

What are the components of parasite drag?

Skin friction, form drag, and interference drag

When is parasite drag the highest?

When air density, surface area, and velocity are highest

What causes induced drag?

Downwash from air flowing around the wing

What does downwash do to velocity?

Decreases velocity

What increases induced drag?

Low aspect ratio

When is induced drag highest?

Increased weight, low air density, high TAS

What is Total Drag equal to?

Parasite Drag + Induced Drag

Why is total drag highest at low speeds?

Because of induced drag

Why is total drag highest at high speeds?

Because of parasite drag

Where does weight act through?

The centre of gravity

Where does lift act through?

The centre of pressure

What is the formula for lift of the wing?

Weight + Lift of the tailplane

What is maximum range?

Greatest distance flown per unit of fuel used

How to achieve maximum range in a tailwind?

Decrease airspeed

How to achieve maximum range in a headwind?

Increase airspeed

What is endurance?

Time in the air on a given amount of fuel

Why does endurance decrease with altitude?

Lower air density requires more power to maintain thrust

What does the rate of climb depend on?

Excess power

What is Vy?

Speed where Power Available - Power Required is maximum

What does the angle of climb depend on?

Excess thrust

What is Vx?

Speed where Thrust - Drag is maximum

What is the service ceiling?

Maximum height where rate of climb is 100 FPM

What is the absolute ceiling?

Maximum height where rate of climb is 0 FPM or Vx = Vy

In a glide, what balances drag?

Forward component of weight

What does a tailwind do during descent?

Causes a shallow descent

What does a headwind do during descent?

Causes a steepened descent

At what angle of attack does a stall occur?

16°-18° (stalling angle of attack)

What helps stall recovery?

Rapid backward movement of the centre of pressure

Why is stall buffeting designed to begin at the root?

Keeps ailerons effective during stall

What is washout?

Angle of incidence is higher at root than tip

What does increasing camber at the root do?

Makes the root stall first

What do stall strips do?

Create early separation point to stall first

What are vortex generators?

Tabs that re-energize boundary layer to delay separation

What effect does frost on the wing have?

Reduces lift by 30% and increases drag by 40%

What causes turning in an aircraft?

Horizontal component of lift provides centripetal force

What is the formula for lift in a turn?

Lift = Straight and level lift * (1/cos(bank angle))

What is load factor?

Ratio of lift to weight

What is the rate of one turn?

3° per second

How to calculate bank angle for rate one turn?

TAS/10 + 7

What can an extreme forward CG cause?

Difficulty flaring during landing

What is the dihedral effect?

Lower aileron gets more airflow and corrects roll

What is lateral axis stability?

Centre of gravity is in front of centre of pressure

What causes vertical axis stability?

Sideslip causes correcting yaw moment

What is the effect of the slipstream from clockwise propellers?

Forces tail right and nose left

What rudder input is needed due to slipstream?

Right rudder

What is the primary effect of ailerons?

Roll control

What is the secondary effect of ailerons?

Causes the aircraft to roll

What are two solutions to adverse aileron yaw?

Frise ailerons and differential ailerons

How do differential ailerons reduce adverse yaw?

Down-going wing deflects more, creating more drag

How do frise ailerons reduce adverse yaw?

Upward aileron protrudes into slipstream, increasing drag

Why are masses placed in control surfaces?

To keep centre of gravity ahead of centre of lift and prevent flutter

What is the principle of balance tabs?

Small force far from hinge line equals large moment to balance control surface

What is a trim tab?

A balance tab used to balance control forces

What is a servo tab?

A tab that moves opposite to reduce control forces

What is an anti-servo tab?

A tab that moves in the same direction to increase control force

What do balance tabs do?

Reduce control forces by moving in the opposite direction

What do flaps do to the lift coefficient?

Increase it

What is the effect of flaps on climb gradient?

Lower climb gradient

What are the four strokes in a piston engine?

Intake, compression, combustion, exhaust

What is valve overlap in engines?

Inlet valve opens before exhaust stroke ends and exhaust valve stays open during intake

Why does valve overlap increase efficiency?

It helps push out exhaust gases with fresh mixture

What happens with a rich fuel mixture?

Excess fuel evaporates and cools combustion, reducing power

What happens with a lean mixture?

Less fuel results in cooler combustion and reduced power

What happens to the mixture as the aircraft climbs?

It becomes rich due to decreased air density

What's the difference between normal combustion and detonation?

Normal is smooth burning, detonation ignites at many points

What causes detonation?

Low octane fuel, hot engine, high manifold pressure

What color is AVGAS 80/87?

Red

What color is AVGAS 100/130?

Green

What color is 100LL?

Blue

What color is aviation turbine fuel?

Straw/yellow

What color is MOGAS 87-90?

Green

What color is MOGAS 84-87?

Undyed

What does a high oil rating indicate?

High viscosity

What oil is used in summer?

SAE 60

What oil is used in winter?

SAE 40

What is shock cooling?

Sudden cooling causing cracks and internal stresses

Why is power added during descents?

To prevent shock cooling

What causes carburetor icing?

Pressure drop and fuel evaporation in the venturi

What does carburetor heat do?

Warms unfiltered engine air from exhaust contact

What happens when carb heat is applied?

RPM decreases due to enriched mixture and reduced airflow

Why should carb heat not be used on the ground?

It draws unfiltered air

Do fuel-injected engines get carburetor icing?

No, but they can get inlet icing

What helps cool fuel-injected engine inlets?

Alternate doors drawing cooling air

What do turbochargers, turbonormalizers, and superchargers do?

Increase inlet air pressure at altitude

What is a normally aspirated engine?

One that uses atmospheric pressure without a compressor

What is a turbocharged engine?

One where exhaust-driven turbine increases inlet pressure above ASL

What is a turbonormalized engine?

Turbocharger increases pressure to sea level only

What is a supercharged engine?

Engine-driven compressor increases inlet pressure above ASL

What is manifold pressure?

Pressure in the inlet manifold; proportional to power

What is critical altitude?

Altitude where turbocharger can't maintain manifold pressure

What does the wastegate do?

Directs exhaust gases to turbine or bypasses them