Flight Manoeuvres – Climb & Descent Performance

Flight Manoeuvres – Climb & Descent Performance

Revision

4 Forces in Straight & Level Flight

Power + Attitude = Performance

Reduce Thrust ➤ Nose will Drop

Increase Thrust ➤ Nose will Raise

Remember the Components of a Force…

A force acting on a point can be broken up into it’s horizontal (x) and vertical (y) components:

This is relevant to aviation when we manoeuvre the aircraft… 

Forces during Climb

Thrust needs to be greater to overcome the 2 rearward forces from drag & the rearward component of weight:

  • Lift < Weight
  • Thrust > Drag

Increasing Power improves Climb Performance

Best Climb Performance
Angle of Climb (AoC) vs Rate of Climb (RoC)

Definitions:

  • Angle of Climb (AoC): good for clearing obstacles
  • Rate of Climb (RoC): good for getting to altitude quickly

Another option is a Cruise Climb which prioritises least time to destination.

Best Angle of Climb

Maximum Angle of Climb (AoC) occurs at the airspeed and Angle of Attack combination which allows the maximum excess thrust.

Best Rate of Climb

Maximum Rate of Climb (RoC) for a typical propeller airplane occurs at an airspeed and Angle of Attack combination closer to L/DMAX.

Effects on Climb

Headwind / Tailwind

Weight

Increasing weight reduces climb performance!

The lower the curve, the lighter the weight, and the easer it is to achieve a set performance (less power and speed needed)

Climb of a piston aircraft usually occurs at full power, thus any reduction in power will reduce climb performance.

Any change in airspeed away from Best Rate / Angle of Climb point will result in reduced climb performance. That is, we need more power or more speed to achieve our best the same performance!

Altitude

Climb performance reduces as altitude increases due to the thinner air at higher altitudes

Flaps

The effect of Flap depends on how much of the flaps are extended into the airflow.

Reduced flaps allow a steeper gradient, as there is less drag to overcome
Effects on Descent

What happens to the Forces during Glide?

Lift and Drag are constant for the same speed! The remaining forces effect glide:

  • Thrust is zero
  • Weight acts straight down to the centre of the Earth
  • Weight has a component that acts:
  • Down opposite to Lift; and …
  • … Forward Opposite to Drag
  • Weight = Lift + Drag

What happens when we Add Power?

We enter a powered descent!

The descent angle is reduced and the forward component of weight is less:

  • Thrust is now included
  • Weight acts straight down to the centre of the Earth
  • Weight has a component that acts:
    • Down opposite to Lift and …
    • … Forward Opposite to Drag
  • Power Controls:
    • Rate of Descent
    • Descent Angle
    • Distance Travelled

Flaps

Lowering flaps increases drag!

To maintain speed the nose is lowered and a steeper Angle of Descent (AoD) is achieved.

Headwind / Tailwind

Windshear