Chapter 18 - Forces Acting On An Aircraft

When we refer to Climb performance, we refer to…

1. Speed in the climb;

2. Rate of climb; and

3. Angle of climb.

The speed in the climb is determined by…

The speed in the climb is determined by the nose attitude selected.

The rate of the climb is determined by…

The rate of the climb (i.e: How fast am I gaining height?) is determined by the amount of power applied and the excess of power available over the power required to counteract the drag at the selected speed.

Put simply: The rate of climb depends on how much extra power the aircraft has. The more excess power available after overcoming drag, the faster the aircraft can climb.

The angle of climb is determined by…

The angle of climb (i.e: How steeply am I climbing?) is determined by the excess of thrust available over the drag at the climbing speed

Put simply: The angle of climb depends on how much extra thrust the aircraft has. The greater the excess thrust available over drag, the steeper the aircraft can climb.

The maximum rate of climb (V_y) is the speed at which…

The maximum rate of climb (V_y) is the speed at which there is the greatest excess power available over the power required.

The maximum angle of climb (V_x) is the speed at which…

The maximum angle of climb (V_x) is the speed at which there is the greatest excess thrust available over the drag at the climbing airspeed

What are the factors affecting climb performance?

• Power

• Airspeed

• Flap Extension

• Weight

• Altitude

• Temperature

• Manoeuvring

• Headwind and Tailwind Components

How does power affect climb performance?

Reduced power decreases climb performance. If the climb performance is inadequate, check that full power is set.

How does airspeed affect climb performance?

Flying faster or slower than the recommended airspeed can degrade the rate and/or angle of climb.

How does flap extension affect climb performance?

Extended flaps will decrease climb performance due to increased drag (power required curve moves upwards). Best climb is achieved with flaps up.

How does weight affect climb performance?

An increase in weight will degrade climb performance. The power required to maintain any given speed in level flight increases with increased weight. Therefore, there is a smaller excess available for climbing. Heavy weights can greatly degrade both the rate and angle of climb. Best climb is achieved at lighter aircraft weights.

How does altitude affect climb performance?

The decrease in air density as altitude is gained causes a decrease in both engine and airframe performance. The power required and power available curves move closer together and the climb performance gradually deteriorates.

If climb is continued, the power required/power available curves coincide and all power available will be needed at climbing speed to maintain level flight, i.e: The aircraft will have reached its absolute ceiling.

When an aircraft's climb rate steadily decreases to (100) feet per minute, this maximum usable altitude is called the service ceiling. Beyond this point, the air is too thin or the engine produces too little excess power to climb at any faster rate.

How does temperature affect climb performance?

Because air density is reduced, high ambient temperatures reduce climb performance.

How does manoeuvring affect climb performance?

Any manoeuvring in the climb will absorb some or all of the excess power available and climb will be reduced.

How does tailwind and headwind components affect climb performance?

Headwind and Tailwind components affect the climb angle over the ground, but not the rate of climb.