Part 107 Load part 2

Weight

The center of Gravity is the point at which, if a string was attached, the object would be in equilibrium.

Always pointed towards the center of the Earth, opposite to Lift.

If the weight of the aircraft exceed the Maximum Allowable Weight, the airfoil won’t be able to generate enough lift to counteract the weight.

Drag

Opposes Thrust.

During an un-accelerated flight, Thrust equals Drag.

Two types of drag.
✓ Parasite Drag,
✓ (Lift) Induced Drag.

Drag

Parasite Drag

Created as a byproduct of flying through the air.

Increases as speed increases.

Three different types:
✓ Form Drag: shape of an object (think Ferrari vs PT Cruiser),
✓ Interference Drag: 1 + 1 = 3,
✓ Skin Friction: imperfection on the surface of the lift-generating surface.

Drag

Induced Drag

With fixed-wing, generated as soon as lift is created.

With rotorcraft, created as soon as lateral motion starts.

Decreases as speed increases.

Greater angle of attack = greater induced drag

Drag

Stalls

Stalls

Occurs when the airfoil reaches the Critical Angle of Attack.

Most aircraft have a published stall speed at which the aircraft will stall.

However, a stall can happen at ANY airspeed but is usually associated with flying too slow.

The most efficient way to determine approach to a stall is by installing an angle of attack indicator.

Stalls

Stalls

The airflow is no longer laminar over the top of the wing, therefore lift is no longer produced.

In fixed-wing aircraft, this results in a nose drop.

Only way to recover from a stall is to lower the nose (reduce the angle of attack).

The weight of the plane is multiplied by the weight and the load factor.

40 pound plane at 30 degrees

Load factor at 30 degrees 1.154
40* 1.154
46 pounds the plane must beable to control

Load Factor and Stalling Speeds

Load factor increases with bank angle.

Stall speed also increases with load factor.

This is important when flying at slower airspeed since abrupt maneuvers can lead to stalling.

Remember that stall occurs when the critical angle of attack is reached, which can be at ANY airspeed.

Center of Gravity Location

Let’s define a few terms first

Center of Gravity (CG): the point at which, if a string was attached, the object would be in equilibrium. The point at which WEIGHT is applied.

Center of Pressure (CP): the point at which LIFT is applied.

Arm (A): the distance between the CG and where a force is applied.

Moment (M): the efficiency of a force. Calculated as:

Altitude

As altitude increases, outside pressure decreases.

As a result, engine performance decreases.

Lift is also reduced.

Think about flying at sea level versus flying in Denver.

Temperature and Humidity

As temperature increases, performance decreases.

As humidity increases, performance decreases.

A hot humid summer day = worst case scenario.

Weight

A heavier aircraft requires more lift to get off the ground.

More lift is achieved with a faster speed and/or higher angle of attack.

This leads to more drag which reduces overall performance:
✓ Longer take off/landing distance,
✓ Reduced climb performance.

Other Factors

Other factors to consider are:

✓ Runway/launch area length
✓ Surface
✓ Slope
✓ Surface Wind
✓ Obstacles