How Airliner Landing Gear Softens Touchdown—and How Hidden Damage Is Found

An airliner can touch down weighing well over a hundred tonnes, yet its landing gear usually turns that encounter with the runway into little more than a brief jolt. The secret is not simply strength: the gear lets the aircraft settle through a controlled distance, absorbing energy without springing straight back into the air.

But the gear does not work alone. Touchdown forces travel through its attachments into the surrounding aircraft structure. That is why, after a suspected hard landing, maintenance teams may need to look beyond the wheels and struts—even when everything appears normal from outside.

What Happens at Touchdown?

As the wheels meet the runway, the aircraft still has some downward motion. The landing gear must bring that motion under control while supporting the aircraft’s weight.

Trying to stop it almost instantly would produce very large forces. Instead, the tires and landing-gear struts deform in a controlled way, giving the aircraft a little distance over which to slow its descent.

Think of bending your knees when you jump down from a step. Your knees do not make your weight disappear; they spread the stopping action over more time and distance. Landing gear does something similar, with carefully engineered springs and fluid passages.

Tires provide the first cushion

The tires flex under load, contributing to the cushioning at touchdown. They are only part of the system, however. Most of the controlled movement comes from the landing gear’s shock struts.

Gas acts as a spring; oil controls the movement

A typical airliner uses an oleo-pneumatic shock strut: a telescoping shock absorber containing hydraulic fluid and compressed gas, usually nitrogen.

As the strut shortens:

1. The gas compresses. It acts like a spring, resisting further compression and helping support the aircraft.
2. Hydraulic fluid flows through restricted passages. The resistance to that flow controls how quickly the strut moves.
3. Energy is dissipated as heat. This reduces the tendency for the gear to rebound sharply.

The fluid’s role is called damping—controlling motion rather than merely storing energy.

The gas provides the spring action. The restricted oil flow keeps that spring action from becoming a bounce.

A spring alone would compress and then release much of its stored energy, pushing the aircraft upward again. Damping makes the response more controlled. The FAA’s airframe maintenance handbook describes how these shock-absorbing systems work.

Where Do the Forces Go?

Absorbing touchdown energy does not mean isolating the rest of the aircraft from all force. The landing gear still has to transmit loads into the structure that supports it.

The route those forces take is called a load path. It runs through the wheels and gear members, through joints and attachment fittings, and into the surrounding airframe.

This explains why the phrase “landing gear and its attachments, fuselage, wings, and engine pylons” matters in a structural inspection. The fuselage is the aircraft’s main body; engine pylons are the structures connecting the engines to the aircraft, usually beneath the wings. Depending on the design and severity of an event, an inspection may extend to these areas rather than stopping at the gear itself.

That does not mean every suspected hard landing requires every one of those structures to be inspected. The aircraft’s maintenance instructions determine the required scope.

Strong gear does not guarantee undamaged surroundings

The gear and its supporting structure are designed as a system. An unusually severe load may affect:

• Attachment fittings: the structural connections securing the gear.
• Pins and bolts: components that carry loads across joints.
• Bolt holes and surrounding material: areas where distortion or cracking may occur.
• Nearby airframe structure: members that distribute the loads farther into the aircraft.

The most obvious contact point is therefore not necessarily the only place damage can appear.

A Firm Landing Is Not Necessarily a Hard Landing

A touchdown that feels abrupt from your seat can still be entirely normal.

A firm landing is a controlled, deliberate touchdown within normal operating expectations. Trying to make every landing almost imperceptible can lead to floating farther down the runway rather than getting the aircraft securely on the ground. The FAA explicitly distinguishes firm landings from hard landings.

A hard landing, by contrast, is an event that may have imposed unusually high loads on the gear or airframe and needs assessment under the aircraft’s procedures.

Why the feeling in the cabin is not enough

The loads depend on more than how sharp the bump seems. Relevant factors include:

• The aircraft’s downward speed at touchdown.
• Its weight.
• How the wheels contact the runway.
• Sideways forces, known as side loads.
• The sequence and distribution of loading across the gear.

There is no single passenger-perceived “bump threshold” that separates a normal landing from a damaging one.

Likewise, overweight and hard are not synonyms. A gentle overweight landing may leave no damage, while a severe impact at a lower weight may require substantial inspection. Neither the label nor the cabin impression replaces the aircraft-specific assessment.

How Maintenance Teams Look for Hidden Damage

After a suspected hard or overweight landing, the question is not simply, “Does the gear look all right?” It is, “What checks does the approved maintenance procedure require for this event?”

1. Establish what happened

The starting point is the crew’s report, together with available recorded flight data and any automatic landing-load report.

These sources help maintenance personnel determine the required inspection scope. But an automatic report is not a complete substitute for reporting and assessment: the absence of an automatic warning does not necessarily rule out a damaging landing. Airbus highlights that point in its hard-landing case study for crews and maintenance personnel.

2. Check visible condition and dimensions

Initial examinations may look for:

• Hydraulic-fluid leaks.
• Abnormal shock-strut extension.
• Damaged tires or wheels.
• Bent, distorted, or misaligned components.
• Distortion around landing-gear attachments.

Dimensional checks go beyond appearance: measurements can reveal that a component or assembly is no longer in its specified position or shape.

3. Inspect joints and supporting structure

Where required, the examination becomes more detailed. Maintenance personnel inspect fittings, pins, bolts, bolt holes, and surrounding structure.

Some components may need removal to expose concealed surfaces. That extra access matters because a crack hidden behind a fitting cannot be ruled out by looking at the outside of the assembled gear.

4. Use nondestructive testing where specified

Nondestructive testing, or NDT, means examining a component for defects without destroying it. Different methods reveal different kinds of flaws:

These are not interchangeable “scan everything” tools. The material, component shape, suspected damage, and maintenance instructions determine which method is appropriate. The FAA’s inspection guidance describes their uses and limitations.

What Makes the Aircraft Ready to Fly Again?

A suspected hard landing does not automatically mean damage occurred. Nor does an intact-looking landing gear prove that none occurred.

The aircraft returns to service only after the applicable checks are complete and any findings have been resolved under its maintenance instructions. Sometimes those checks confirm that no damage is present; other events require further inspection, repair, or component replacement.

Landing gear manages the impact you can feel. Inspection checks for the consequences you cannot see.

That distinction is the heart of the system: controlled movement softens touchdown, strong attachments carry the remaining loads, and aircraft-specific inspections verify that the whole load path is still fit for flight.