Ground Effect: The Invisible Cushion That Makes Planes Float During Landing

Ever wondered why airplanes sometimes float just above the runway before finally touching down?
Why even experienced pilots occasionally overshoot the ideal touchdown point?

The answer lies in a powerful aerodynamic phenomenon that activates only when the aircraft gets very close to the runway:

➡️ Ground Effect

It’s invisible.
It’s unavoidable.
And it completely changes the way an aircraft behaves during the last few seconds of flight.

Let’s dive into this critical concept every pilot, aviation student, and enthusiast must understand.

What Is Ground Effect?

Ground Effect is the aerodynamic phenomenon that occurs when an aircraft flies very close to the ground — usually within a height equal to the aircraft’s wingspan or less.

In simple words:
👉 The ground blocks the wing’s downwash, reducing drag and increasing lift.

As a result:

• The aircraft stops descending rapidly
• It tends to float
• The pilot needs to adjust the flare timing and pitch

This is why landings sometimes look like the aircraft is “hovering” just above the runway momentarily.

Ground Effect: The Invisible Cushion That Makes Planes Float During Landing

Why Does Ground Effect Happen?

To understand ground effect, consider what wings normally do:

During normal flight (high above ground):

• Wings produce lift by pushing air downward (downwash).
• This downwash creates wingtip vortices — swirling air that increases drag (induced drag).

Near the ground (within 1 wingspan height):

The ground blocks the downwash and vortex formation.

Result:

• Wingtip vortices shrink
• Induced drag decreases
• Effective lift increases
• Aircraft becomes more efficient

This efficiency boost makes the aircraft want to stay in the air instead of landing.

What Does Ground Effect Do to an Aircraft?

When entering ground effect, an aircraft suddenly feels:

✔ More lift

✔ Less drag

✔ Reduced sink rate

✔ Increased floating tendency

✔ Delayed touchdown

This surprises beginner pilots because the aircraft doesn’t descend as expected.

How Close to the Ground Does Ground Effect Begin?

Ground effect is most noticeable when:

• Height < one wingspan
• Strongest at height < half wingspan
• Maximum at height < one-quarter wingspan

This means:

• A Boeing 737 (wingspan ~36 m) feels strong ground effect under ~18 m
• A Cessna 172 (wingspan ~11 m) feels it under ~5–6 m

The lower the aircraft → the stronger the effect.

Why Planes Float During Landing

During landing flare, the aircraft is already slowing down.
But as it enters ground effect:

• Lift suddenly increases
• Drag suddenly decreases
• Aircraft stops sinking
• Pilot feels like the plane wants to stay in the air

This “extra lift” makes the airplane float down the runway.

If flare is too strong or too early → the float lasts longer → the aircraft touches down too far ahead → risk of runway overrun.

How Pilots Manage Ground Effect

Pilots are trained to anticipate ground effect and compensate by:

✔ Maintaining correct approach speed

Approaching too fast = longer float
Too slow = hard landing or stall risk

✔ Flaring at the right height

Late flare → slam landing
Early flare → float & overrun

✔ Using proper pitch control

Avoiding over-flare which increases floating tendency

✔ Watching runway sight picture

Pilots rely on visual cues to judge height precisely

✔ Being ready for go-around

If float is excessive, executing a safe go-around is mandatory.

How Aircraft Design Affects Ground Effect

Some aircraft feel stronger ground effect due to:

✔ Larger wingspan

Wide wings → higher ground effect influence (e.g., gliders, Boeing 737, A350)

✔ Low-wing configuration

Low-wing aircraft enter ground effect earlier and more strongly.

✔ High-lift wing designs

More lift → more float.

✔ Heavy vs light aircraft

Light aircraft experience more noticeable floating.

Real-World Examples

1. Airbus A320 “runway float”

A320 pilots often comment that the aircraft floats easily if flare is excessive — thanks to strong ground effect interacting with Airbus fly-by-wire laws.

2. Boeing 777 long fuselage + big wings

Requires precise flare timing or it will float significantly.

3. Cessna 172 training

Student pilots consistently report unexpected floating during early landings.

Is Ground Effect Good or Bad?

It depends.

✔ Good for:

• Soft landings
• Reducing drag
• Improving efficiency
• Low-speed flight training

❌ Bad for:

• Long landings
• Overshooting touchdown zone
• Tailstrikes during over-flare
• Go-around misjudgments

Ground effect itself is neutral — but pilots must understand it thoroughly.

Final Takeaway

Ground Effect is the invisible aerodynamic cushion that makes aircraft float during landing.
It increases lift, reduces drag, and dramatically changes how aircraft behave near the runway.

Understanding ground effect is one of the most important skills in mastering landings.
It’s why pilots say:

“The runway doesn’t decide your landing.
Ground effect does.”