LESSON 14 Chapter 13 Landing Performance ANA Chapter 2

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Flight Theory

Chapter 13

Landing Performance

Dole discusses 4 important landing factors

1. Approach paths and approach speeds

2. Hazards of hydroplaning

3. Deceleration during landing

4. The distance required to stop the aircraft

Pre-landing Performance

The glide is where an airplane will find equilibrium when the thrust force is reduced to 0.

Forces in the glide

Both lift and drag act as they normally do through the vertical and longitudinal axis.

Weight however acts directly toward the center of the earth.

Using vector analysis we can form a right 90 triangle below the aircraft.

Forces in the glide

The glide path is called gamma the component of the weight that acts in the direction of the vertical axis is = to weight x cos of gamma.

Remember it acts through the center of gravity and opposes lift.

The component that acts along the longitudinal axis is weight x sin of gamma. This component acts through the cg and opposes drag

Forces in the glide

Force equations for steady state glide are:

The flight path angle must be at a minimum to achieve best glide.

This only happens at L/Dmax. If the pilot tries to stretch the glide by pulling up the nose the glide range will decrease.

The Landing Approach

Remember that the approach speed is usually not the absolute minimum speed.

It may have factors such as weight, stall speed, minimum controllable speed, or P available vs P required.

On the approach the prop plane will have an advantage in that thrust is readily available almost immediately and induced airflow will provide some lift

The Landing Approach

On the jet plane, it may take some time for the engine to spool up and generate thrust

There is no induce airflow for most jets with the exception of a few like the C-17.

The Landing Approach

One thing you do have mainly in jets is the vertical component of thrust on the approach.

Because jets are flown at higher AOA the component of thrust is usually higher than that for prop powered aircraft.

Landing Distance

You can think of the landing distance in terms of kinetic energy that must be dissipated before the airplane is stopped.

KE = (M/2)V squared where m=mass (weight / 32.2) and V is touchdown velocity (fps) squared

Landing Distance

Landing distance is directly affected by weight

Double the weight and double the landing distance

While the effects of velocity are more pronounced

Double the landing speed and quadruple the energy to be dissipated

Forces on Aircraft during landing

Heavy aircraft do not use much aerodynamic braking.

The large mass of these airplanes need a more effective way to stop in a short amount of space.

Therefor thrust reversers and anti skid brakes are the choice of these behemoths. Ya that’s right I said behemoths.

Forces on Aircraft during landing

Smaller planes can take advantage of aerodynamic braking.

Because drag varies at the square, at half your landing speed the drag is about one quarter what it was at touchdown.

The general rule of thumb is to use aerodynamic braking for about one quarter of the landing roll out then use wheel brakes for the rest.

Forces on Aircraft during landing

Once the airplane is on the ground, hold the yoke full back to transfer as much weight as possible to the mains to give maximum normal force to increase brake effectiveness.

Braking action factors are:

1. Tire material

2. Tread design and wear

3. Runway surface material and condition

4. Amount of braking applied (wheel slippage)

5. Amount of normal force (squeezing force between tires and runway)

Braking action factors

Vary any one of the previously mentioned 5 things and landing rollout could be dramatically affected.

Landing surface

One should consider the surface before landing.

Application of brakes may not be possible such as ice or snow covered runways.

If you had a wheel inadvertently locked and a bare spot popped up you could blow a tire and cause a side swerve followed by runway exodus.

Braking action

In this case aerodynamic braking should be used to the fullest extent and plan on having a longer runway roll than usual.

The amount of normal force is critical to brake effectiveness. The more normal force, the better your stopping power.


The equations for landing are the same as for takeoff.

Weight, altitude, and wind all have the same effects.


This occurs when there is a build up of water between the tire and the surface.

There are 3 types of hydroplaning

1. dynamic

2. viscous

3. reverted rubber

Dynamic hydroplaning

this is when a wedge of water has separated the wheel from the runway.

When a rolling tire is analyzed, the ground friction causes a spin up moment resulting in tire rotation.

This moment causes the vertical ground reaction line to shift forward of the axle.

Dynamic hydroplaning

A wedge of water builds under the tire until the tire is lifted completely off the runway.

The equation for that speed is:

This type of hydroplaning usually only occurs in really heavy downpours.

Smooth tires and smooth runway surface will induce hydroplaning at lower water depths.

Viscous Hydroplaning

This variety is much more common than dynamic and occurs at lower speeds and lower water depths.

This is where a thin film of water lubricates the runway and contact with the pavement is partially lost.

This may occur on 32R where there is a lot of rubber deposits and no place for the water to go.

Reverted Rubber Hydroplaning

When the pilot locks up the brakes in such a manner as to cause the friction to heat the tire to the point of melting, the tire is said to have reverted to its natural state. 


The landing is not as greatly affected by altitude as the takeoff. Engine performance is not such a factor

A ground roll equation generic is .3V squared where V is landing velocity in true

Remember that you will have the same IAS but higher TAS and Ground speed


The biggest thing to remember is the density altitude

And that’s all I’m going to say about that

Airplane Weight

The higher weight will increase the stall speed and decrease the stall margin on approach but will also allow better braking effectiveness because you have more weight on the wheels on touch down.

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