11.4 Landing Gear Systems
4 min read•august 12, 2024
Landing gear systems are crucial for aircraft safety and performance. They absorb landing impacts, enable ground movement, and affect aerodynamics. This section covers gear types, shock absorption, steering, and braking, highlighting how these components work together to support aircraft operations.
From tricycle setups to advanced , landing gear design balances weight, efficiency, and functionality. Understanding these systems is key to grasping how aircraft transition between air and ground, impacting everything from fuel economy to passenger comfort.
Landing Gear Configurations
Main Types of Landing Gear
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Top images from around the web for Main Types of Landing Gear
Landing gear - Wikipedia View original
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Main Landing Gear, Airbus A330/A340 | Built by Messier-Dowty… | Flickr View original
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- consists of two main wheels behind the center of gravity and a nose wheel
- Provides better visibility during ground operations
- Improves stability during takeoff and landing
- Reduces the risk of ground looping
- features two main wheels forward of the center of gravity and a small wheel under the tail
- Offers better performance on unpaved runways
- Allows for shorter takeoff distances
- Requires more skill to handle during ground operations
- can be withdrawn into the aircraft during flight
- Reduces aerodynamic drag, increasing aircraft speed and fuel efficiency
- Adds complexity and weight to the aircraft design
- Typically used in high-performance and commercial aircraft
- remains extended throughout the flight
- Simpler and lighter than retractable systems
- Requires less maintenance
- Commonly used in small general aviation aircraft and some military transports
Design Considerations and Performance Impact
- Weight distribution affects the choice between tricycle and tailwheel configurations
- Runway surface conditions influence the selection of fixed vs. retractable gear
- Aerodynamic efficiency plays a crucial role in determining gear type for different aircraft speeds
- Maintenance requirements vary significantly between fixed and retractable systems
- Operating costs increase with more complex landing gear configurations
- Aircraft mission profiles (short-field operations, long-range flights) impact landing gear design choices
Shock Absorption Systems
Types and Functions of Shock Absorbers
- Shock absorbers dissipate landing impact energy to protect the aircraft structure
- Reduce vertical loads transmitted to the airframe during touchdown
- Improve passenger comfort by minimizing abrupt movements
- Extend the lifespan of landing gear components and aircraft structure
- function as hydraulic shock absorbers in aircraft landing gear
- Consist of a cylinder filled with oil and compressed gas (typically nitrogen)
- Utilize a piston that compresses the fluid and gas mixture upon impact
- Provide progressive damping as the strut compresses
- Offer excellent energy absorption capabilities for their weight
Shock Absorption Mechanisms and Materials
- use stacked rubber discs to absorb impact
- Simple and lightweight design
- Suitable for smaller aircraft with lower landing speeds
- employ coiled springs for energy absorption
- Reliable and low-maintenance option
- Limited in their ability to handle high-energy impacts
- combine hydraulic fluid and gas for energy dissipation
- Offer adjustable damping characteristics
- Provide consistent performance across various temperatures
- increasingly used in modern shock absorption systems
- Offer high strength-to-weight ratios
- Allow for innovative designs that optimize energy absorption
Steering and Braking
Aircraft Steering Systems
- enables directional control during ground operations
- Hydraulic or electrical systems control nose wheel movement
- Steering angle typically limited to 30-60 degrees in each direction
- Some aircraft use differential braking for steering at low speeds
- often interconnected with nose wheel steering for improved control
- Allows pilots to steer using familiar flight controls
- Enhances coordination between air and ground maneuvering
- provides precise control in larger aircraft
- Located in the cockpit, usually on the side panel
- Allows for tighter turns and better maneuverability in confined spaces
Braking Systems and Technologies
- slow and stop aircraft on the ground
- most common in modern aircraft
- Multiple discs stacked together for increased braking power
- Hydraulic pressure applies force to brake pads, creating friction
- Anti-skid systems prevent wheel lock-up during heavy braking
- Sensors monitor wheel speed and detect impending skids
- Automatically modulate brake pressure to maintain optimal braking efficiency
- Improve stopping performance and reduce tire wear
- Carbon brakes offer advantages over traditional steel brakes
- Lighter weight, improving fuel efficiency
- Better heat dissipation, allowing for shorter cooling times between landings
- Longer service life, reducing maintenance costs
- automatically apply brakes upon landing or rejected takeoff
- Ensure consistent deceleration regardless of pilot input
- Reduce pilot workload during critical phases of flight
- Can be preset to different levels of braking intensity
Key Terms to Review (25)
Anti-skid system: An anti-skid system is a safety feature in aircraft landing gear that prevents wheel lockup during braking, which helps maintain control and stability while landing. By modulating brake pressure, it allows the wheels to continue rotating, reducing the risk of skidding on wet or slippery runways. This system is crucial for enhancing braking performance and improving overall safety during landings.
Autobrake systems: Autobrake systems are automated braking mechanisms designed to assist pilots in controlling an aircraft's deceleration upon landing. These systems enhance safety and efficiency by applying the brakes automatically based on predefined parameters, such as landing speed and weight. Autobrake systems help reduce pilot workload during landing, ensuring smoother deceleration while minimizing the risk of human error.
Braking systems: Braking systems are critical components of an aircraft's landing gear, designed to slow down or stop the aircraft upon landing and during taxiing. They are essential for ensuring safe landings and ground operations, using various mechanisms such as hydraulic, pneumatic, or electric systems to generate the required stopping force. A well-designed braking system contributes to the overall performance and safety of an aircraft, especially in adverse conditions.
Carbon brakes: Carbon brakes are a type of aircraft brake system that utilizes carbon composite materials for enhanced performance and heat resistance. These brakes are designed to manage the extreme temperatures generated during landing, providing efficient stopping power while being lighter and more durable compared to traditional metal brakes. This lightweight construction contributes significantly to overall aircraft performance and efficiency, particularly in high-speed, high-weight operations.
Carbon fiber composites: Carbon fiber composites are advanced materials made from a polymer matrix reinforced with carbon fibers, known for their high strength-to-weight ratio and durability. These composites are increasingly used in various applications, particularly in aerospace, due to their lightweight nature and ability to withstand high stresses and temperatures.
Disc brakes: Disc brakes are a type of braking system that uses a rotating disc or rotor and a caliper to slow down or stop a vehicle. This system provides better stopping power and heat dissipation compared to traditional drum brakes, making them more effective for landing gear systems in aircraft. The performance of disc brakes is crucial for ensuring safe landings and takeoffs, especially in high-speed or heavy aircraft.
Extension mechanism: An extension mechanism is a component of landing gear systems that allows for the deployment or retraction of the landing gear. This mechanism is critical in ensuring that the gear can be extended when preparing for landing and retracted during flight, enhancing aerodynamic efficiency and safety during operations.
Fixed landing gear: Fixed landing gear refers to a type of aircraft undercarriage that is permanently attached to the airframe and does not retract during flight. This design is often simpler and more robust than retractable systems, making it ideal for certain aircraft types, particularly those used for training or short-range operations. Fixed landing gear contributes to the overall weight, drag, and structural integrity of the aircraft.
Ground handling: Ground handling refers to the various services and operations that support an aircraft while it is on the ground, including loading and unloading passengers, baggage, cargo, and fueling. This process ensures that aircraft are prepared for departure and safe for flight operations. Ground handling is critical in maintaining the efficiency of airport operations and ensuring the safety and security of aircraft during their time on the ground.
Hydraulic system: A hydraulic system is a technology that uses pressurized fluid to transmit force and control movement in various mechanical applications. This system operates by using the principle of hydraulics, where incompressible fluid transmits power efficiently through pipes and cylinders. In aviation, hydraulic systems are critical for operating various components, including landing gear, brakes, and control surfaces.
Liquid spring shock absorbers: Liquid spring shock absorbers are a type of damping system used in landing gear that utilizes a liquid medium to absorb and dissipate energy during landing or takeoff. This technology provides better control over the shock absorption process compared to traditional mechanical springs, allowing for smoother landings and reduced stress on the aircraft structure. Liquid spring shock absorbers enhance the overall performance of landing gear systems by effectively managing the forces experienced during ground operations.
Load Factor: Load factor refers to the ratio of the actual load carried by an aircraft to the maximum load it can safely carry, expressed as a multiple of gravitational force (g). Understanding load factor is crucial for analyzing various aspects of flight performance, particularly during maneuvers, as it influences structural design, aerodynamic efficiency, and safety factors.
Nose wheel steering: Nose wheel steering refers to the system that allows the front wheel of an aircraft to pivot and steer during ground operations, such as taxiing, takeoff, and landing. This system enhances the pilot's ability to control the aircraft while on the ground, particularly in maintaining directional stability and navigating tight spaces. Nose wheel steering is crucial for effective maneuverability, helping prevent issues like skidding or veering off course during ground movements.
Oleo struts: Oleo struts are a type of shock absorber used in aircraft landing gear systems that utilize hydraulic fluid and compressed gas to absorb the impact during landing. These struts help to dampen the shocks and vibrations that occur when an aircraft touches down, providing a smoother landing experience and protecting both the aircraft structure and passengers. They play a critical role in maintaining the stability and performance of landing gear by ensuring proper load distribution during takeoff and landing.
Retractable landing gear: Retractable landing gear is a type of landing gear that can be raised or stowed within the aircraft's fuselage during flight to reduce drag and improve aerodynamic efficiency. This mechanism enhances performance by allowing aircraft to achieve higher speeds and better fuel economy compared to fixed landing gear systems, which remain exposed during flight.
Retraction Mechanism: The retraction mechanism refers to the system used in landing gear to retract the wheels and other components into the aircraft's fuselage during flight, reducing aerodynamic drag and improving performance. This mechanism is crucial for the smooth operation of landing gear systems, ensuring that the gear is stowed securely and can be deployed reliably when needed for landing.
Rubber disc shock absorbers: Rubber disc shock absorbers are components used in landing gear systems to absorb the shock and vibrations experienced during landing and taxiing. They consist of stacked rubber discs that compress and expand to dampen impact forces, providing smoother landings and protecting the airframe from stress. These shock absorbers are essential for maintaining structural integrity and enhancing passenger comfort during flight operations.
Rudder Pedals: Rudder pedals are foot-operated controls in an aircraft that allow the pilot to manipulate the rudder, which is a primary control surface used for yawing the aircraft. These pedals enable the pilot to adjust the direction of the airplane during flight, particularly when performing turns or coordinating with aileron input. By pressing on the left or right pedal, the pilot can tilt the nose of the aircraft in the desired direction, ensuring smoother and more controlled maneuvers.
Shock Absorber: A shock absorber is a mechanical device designed to dampen the oscillations of landing gear, enhancing stability and comfort during the landing and takeoff phases of flight. It plays a critical role in controlling the energy transfer from the landing gear to the aircraft structure, ensuring that the impact forces are absorbed rather than transmitted through the airframe. By doing so, shock absorbers help protect both passengers and the aircraft from excessive stresses.
Shock strut: A shock strut is a component of an aircraft's landing gear system that absorbs and dampens the impact forces experienced during landing and takeoff. It combines the functions of a shock absorber and a structural support, allowing for a smoother landing by reducing the loads transmitted to the airframe and enhancing the overall stability of the aircraft during ground operations.
Steel spring shock absorbers: Steel spring shock absorbers are mechanical devices used in landing gear systems to absorb and dampen the impact forces during landing and taxiing. These absorbers work by compressing and expanding steel springs to manage the energy generated from landing impacts, providing stability and comfort to the aircraft. They play a crucial role in ensuring the safety of both the aircraft structure and the passengers by minimizing sudden shocks and vibrations.
Tailwheel landing gear: Tailwheel landing gear, also known as conventional landing gear, is a type of aircraft landing gear configuration where the main wheels are positioned forward of the center of gravity, and a smaller wheel, or tailwheel, is located at the rear. This design is common in older aircraft and offers advantages such as better visibility during landing and takeoff, but it can also lead to more challenging handling characteristics on the ground.
Tiller steering wheel: A tiller steering wheel is a control device used in aircraft to manage the direction of the airplane while it is on the ground, especially during taxiing and low-speed maneuvers. It allows pilots to steer the aircraft by pivoting the front wheels through a mechanical linkage, providing precise control of directional movement. This type of steering mechanism is crucial for maintaining stability and maneuverability when taxiing, as well as for making tight turns on the ground.
Tire assembly: The tire assembly refers to the complete unit that consists of the tire, rim, and any associated components that enable a wheel to function properly. This assembly is critical for landing gear systems, as it provides the necessary support for the aircraft's weight during ground operations and helps absorb shocks during takeoff and landing. Additionally, the tire assembly plays a vital role in ensuring traction and stability during various phases of flight operations.
Tricycle Landing Gear: Tricycle landing gear is a configuration of aircraft landing gear that features a nose wheel at the front and two main wheels located at the rear, forming a triangular arrangement. This design enhances stability during takeoff and landing, providing better control on the ground compared to other configurations like tailwheel designs. Tricycle landing gear is commonly used in modern aircraft, making it an essential aspect of landing gear systems.