Retractable Landing Gear - Landing Gear - Airframes & Aircraft Systems #15

Summary

This lesson delves into the design and construction of retractable main landing gear systems in aircraft, which are crucial for aerodynamic performance by reducing drag. It discusses various systems like hydraulic, pneumatic, and electrical that power the gear. The gear includes mechanical locks for secure positioning, indicators for crew awareness, and emergency lowering mechanisms. Wheel wells are typically sealed by doors for aerodynamic efficiency. The lesson also covers the geometric arrangement and physical location of landing gear, influenced by factors like aircraft size, role, and wing position. It highlights the importance of shock absorbers, steering mechanisms, and the various loads the gear must withstand during operation.

Takeaways

• 🔧 Retractable landing gear is designed to improve aerodynamic performance by reducing drag during flight.
• ⚙️ The operation of retractable landing gear is typically powered by hydraulic systems, but pneumatic or electrical systems are also used in some cases.
• 🔒 Mechanical locks are essential to ensure that each landing gear leg is securely in place when retracted or extended.
• 📡 Indicators are provided to the crew to confirm the position of each landing gear leg, ensuring safe operation.
• 🚫 Systems are in place to prevent gear retraction when the aircraft is on the ground, and warning devices prevent landing with the gear retracted.
• 🛫 Wheel wells are normally sealed by doors that close after the gear is retracted, contributing to the aerodynamic design.
• 📏 The placement and design of landing gear are determined by factors such as aircraft size, weight, intended role, and wing configuration.
• 🔄 Some aircraft feature steerable body gear to reduce turning circles and minimize tire scrubbing effects on the runway.
• 🔩 The main landing gear on larger aircraft is often attached to the wing, with some designs incorporating both wing and body gear.
• 📐 The design of the landing gear must accommodate various loads, including compressive, bending, and side loads experienced during different phases of flight and operation.

Q & A

What is the primary purpose of retractable landing gear on aircraft?

The primary purpose of retractable landing gear on aircraft is to improve aerodynamic performance by reducing drag during flight.

What are the common systems used to operate retractable landing gear?

Hydraulic systems are commonly used to operate retractable landing gear, but pneumatic or electrical systems are also sometimes used on smaller aircraft.

Why are mechanical locks important for retractable landing gear?

Mechanical locks are important to ensure that each leg of the landing gear is securely locked in either the up or down position for safety.

How does the landing gear system indicate its position to the flight crew?

The landing gear system includes indicators that inform the crew about the position of each leg, ensuring they know whether it is up or down.

What is the purpose of the wheel wells on an aircraft with retractable landing gear?

Wheel wells are where the wheels are housed when the landing gear is retracted. They are normally sealed by doors to reduce drag for aerodynamic reasons.

Why are some aircraft designed with high wing monoplane type landing gear?

Some aircraft are designed with high wing monoplane type landing gear to allow the floor of the aircraft to be as close to the ground as possible for ease of freight loading, despite the height of the wings.

How does the main landing gear attach to the wing on most modern aircraft?

On most modern aircraft, the main landing gear attaches to the wing with the leg being attached to the wing spars by a cylindrical beam or trunnion, allowing it to rotate laterally.

What is the function of the drag strut in the landing gear system?

The drag strut supports the leg of the landing gear in the fore-and-aft direction, helping to manage loads during takeoff and landing.

How does the jury strut contribute to the locking mechanism of the landing gear?

The jury strut geometrically locks the gear down by being pulled over center by the down lock actuator, ensuring the gear is securely in the down position.

What are the various loads that a landing gear unit must withstand during its life?

A landing gear unit must withstand compressive loads during landing, rearward bending loads during braking, side loads during crosswind landings and takeoffs, and longitudinal loads during pushback and towing.