Why Do Commercial Aircraft Have Retractable Landing Gear?

Introduction

While most general aviation aircraft and some small regional airliners like the DeHavilland Twin Otter may use fixed landing gear, the vast majority of commercial passenger jets leverage retractable landing gear. This design choice comes with various benefits and safety considerations that make it a standard feature in modern commercial aviation. This article will explore the reasons behind the prevalence of retractable landing gear in commercial aircraft.

The Benefits of Retractable Landing Gear

Retractable landing gear offers several advantages over fixed landing gear, making it a preferred choice for commercial aviation. One of the primary benefits is reduced aerodynamic drag during flight. When the gear is retracted, the aircraft experiences less air resistance, which can translate into improved fuel efficiency and overall performance. Additionally, reduced weight during flight is another significant advantage, as the gear is stored away when not in use, further contributing to better fuel economy.

Design Considerations for Retractable Landing Gear

The design of retractable landing gear is carefully crafted to ensure safety and reliability. There are several interlocks and mechanisms in place to prevent the gear from deploying unintentionally during flight. For example, if one interlock fails, the gear will not retract, serving as a safeguard. Furthermore, down lock pins can be inserted to ensure the gear remains down while the aircraft is on the ground, adding another layer of safety and preventing accidents on takeoff and landing.

Common Causes for Gear Not Retracting

Despite the robust design, there are scenarios where the gear may not retract. These can be due to various factors such as malfunctioning interlocks, the presence of down lock pins, or human error. In some cases, ground crew may leave down lock pins in the gear, and these pins may only be removed during a preflight inspection by the pilots. A maintenance technician may make this error if they are unqualified or unable to properly test the gear. In other instances, mechanical failures or incidents can also prevent the gear from retracting.

Historical and Practical Context

While there are a few aircraft that use fixed landing gear, they are typically smaller, less complex aircraft like the DeHavilland Twin Otter. These planes often operate in specific environments, such as short-haul routes or regional flights, where the benefits of fixed landing gear outweigh the need for retractable gear. However, for larger commercial airliners and freighters, retractable landing gear is a necessity due to the significant drag reduction it provides and its overall safety benefits.

Conclusion

In summary, the use of retractable landing gear in commercial aircraft is a well-designed solution that enhances both performance and safety. While there are occasional issues, such as the presence of down lock pins or mechanical failures, the advantages of retractable landing gear make it an industry standard. Whether we are discussing the DeHavilland Twin Otter or the latest commercial airliners, retractable landing gear has become an integral part of modern aviation design.