Landing Gear & Wheel Brake
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Sealing Solutions for Landing Gear and Wheel Brake Systems in Commercial Aviation
Safety during take-off, landing and taxiing
Landing gear and wheel brake systems are among the most safety-critical components in commercial aircraft. They bear the entire weight of the aircraft during take-off, landing and taxiing on the ground. Extreme mechanical forces, high temperature peaks and aggressive environmental influences such as moisture, de-icing agents and salt are all at play.
Reliable sealing solutions are crucial to prevent leaks, protect hydraulic systems and ensure long-term operational safety. Freudenberg Sealing Technologies develops products and materials that meet these challenges - for greater safety, efficiency and sustainability in commercial aviation.
Historical milestone
From grinding spur to high-tech landing gear
Early airplanes braked with simple wooden or metal grinding spurs. It was not until the 1930s that the retractable landing gear became established, which drastically reduced drag and is still the standard in aviation today. Modern landing gears are highly complex, hydraulic-electric systems.
Why are Seals so Critical for Landing Gear and Wheel Brakes?
Extreme loads occur during take-off and landing, which could not be controlled without reliable sealing systems. Seals prevent leaks in hydraulic systems, protect against corrosion, dirt and failures caused by thermal peaks. Seals must function reliably, especially in the nose wheel landing gear (tricycle landing gear), even under high lateral loads.
How Do the Landing Gear and Wheel Brake Systems Work in the Flight Phases?
Take-off
The landing gear absorbs the full weight of the aircraft, with kinetic energies of hundreds of tons. The wheel unit, shock absorbers and support structures act as central components. Seals in actuators and hydraulic systems ensure the transfer of energy and enable stable, safe acceleration.
Flight
After retraction, the chassis remains exposed to high pressure and temperature fluctuations. Seals protect sensitive components and ensure functionality until extension.
Landing
During landing, extreme impact forces act on the wheels and brakes. In addition to high pressure loads, strongly fluctuating lateral forces also act on the wheel and damping systems. Seals protect hydraulic cylinders and brake components against leaks - even during temperature peaks in the high-performance range. Emergency braking systems intervene redundantly in an emergency.
Rolling on the ground
Taxiing exposes chassis and brake systems to continuous loads. Strong vibrations and high frequencies at the piston rods generate briefly increased temperatures at the sealing edge. Shimmy dampers are also used here to suppress uncontrolled vibrations at the nose wheel. Without high-performance materials, this can lead to increased abrasion. Precise seals from Freudenberg Sealing Technologies prevent this wear and ensure stability, steering capability and minimal friction losses.
From Shock Load to Corrosion: Challenges in Detail
- Mechanical loads and wear: Shock and shear forces during touchdown/braking. High pressures and alternating lateral forces in shock absorbers and wheel suspensions.
- Temperature peaks during braking: within seconds several hundred °C and thus great thermal stress for sealing lips and materials.
- Vibrations and micromovements: Resonance and high- frequency vibrations increase friction and localized heating. This increases the risk of stick-slip and edge wear.
- Media and corrosion: Moisture, road salt and de-icing agents attack materials. This places high demands on chemical resistance and corrosion protection.
- Weight and efficiency: weighing up lightweight construction requirements versus stability. Friction optimization to reduce energy consumption and operating costs.
Did you know?
- Aircraft brakes can get hotter than 300 °C - comparable to volcanic rock.
- Although tires appear small in relation to the aircraft, main landing gear tires reach diameters of 1.1-1.4 m.
- When a long-haul jet touches down, it bears the load of over 20 fully loaded trucks.
Our Products for Chassis and Brake Systems
- High-performance seals: for hydraulic cylinders, actuators and transmissions
- O-rings, lubricant seals, wheel seals, PTFE seals, T- seals: also in large dimensions O-Ring T-Seal
- Brake pads and friction materials: for reliable deceleration even in extreme heat
- Protective coatings and surface treatments: Corrosion protection against moisture, salt and chemicals
O-Rings
Universal seals, ideal for static and dynamic applications, particularly flexible and reliable under high pressure loads.
T-Seal Extrusion
T‑shaped extrusions seat securely in channels to create a neat, stable edge seal with minimal flutter. Formulated for consistent performance under temperature swings and exposure to aviation fluids.
PTFE Seals
Outstanding thermal and mechanical resistance, particularly suitable for extreme temperature and pressure conditions.
Materials for Extreme Requirements
- High-strength composite materials: high load-bearing capacity and low weight
- Corrosion-resistant alloys: Protection against aggressive environmental influences
- Advanced elastomers: flexible, resistant to pressure and temperature fluctuations
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Why are seals in landing gears indispensable?
Landing gears and brakes are only as reliable as their sealing systems. They prevent leaks in hydraulic cylinders, protect against dirt and moisture and ensure function in the event of pressure and temperature peaks. Without these components, safe operation would hardly be possible.
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How hot do aircraft brakes get after landing?
During full braking, the brake disks can reach temperatures of over 300 °C - similar to molten volcanic rock. For this reason, only materials that retain their sealing effect even under extreme thermal stress are used.
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Which environmental factors pose the greatest risk to running gear?
In addition to mechanical stress, corrosion and chemical attacks are critical. Moisture, road salt or de-icing agents attack metal components and therefore also sealing points. Special elastomer materials protect the systems against these influences in the long term.
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How does brake-by-wire differ from a classic hydraulic brake?
While hydraulic brakes work with hydraulic fluid, with brake-by-wire the signal is transmitted electronically. This saves weight, simplifies maintenance and enables software adjustments - a milestone that was first introduced on the Concorde.
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How big are airplane tires?
The dimensions surprise many people: Main landing gear tires on airliners such as the Boeing 777 or Airbus A350 reach over one meter in diameter. In wide-body aircraft, several dozen tires can be in use at the same time.
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What materials are used in the landing gear and brake area?
Classic structural elements are made of steel, titanium or aluminum alloys, while brake discs are often made of carbon or ceramic. These are supplemented by high-performance polymers such as FKM, PTFE or FFKM, which can withstand corrosion and peak thermal loads.
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How are suspension and brake systems developed and tested?
Before a chassis takes off, it is tested in simulations in the laboratory. In hardware-in-the-loop tests, the hydraulics, electronics and brakes are already running under realistic conditions. Seals are integrated into the development process at an early stage to prevent subsequent failures.
FAQ – Landing Gear and Wheel Brake Systems in Commercial Aircraft – Overview of Seals, Materials and Technologies
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