Landing Gear Retraction: Guidelines, Consequences, and Safety Considerations

The subject of landing gear retraction in aircraft operations is not only a matter of following procedural guidelines but also a critical aspect of safety and performance management. While there is no hard-and-fast rule for the maximum permitted time for retracting the landing gear, there are essential reasons for keeping it down, especially during taxiing and takeoff. A significant factor in the decision-making process is the issue of airspeed, and this article aims to explore this aspect in detail.

The Purpose of Keeping the Landing Gear Down

There are multiple valid reasons for not retracting the landing gear during taxiing and takeoff, the foremost of which is cooler brakes. When brakes are used extensively during taxiing, especially on long runways or when performing multiple stops, it is prudent to keep the landing gear down to allow the airflow to help cool the brakes. This is particularly important for aircraft like the ATR, where a distinct 'click' is heard indicating there's no weight on the landing gear struts.

Speed Limits and Safety Parameters

The speed limits for operating the landing gear are based on engineering calculations to ensure the components can handle the stress when the gear is down and locked. When being retracted or extended, these calculations are crucial to prevent failure. Aircraft engineers usually adopt a conservative approach, leading to stated limits that are often lower than the true operational capacity. However, pushing these limits is a dumb idea in aviation due to the potential for catastrophic failure. This is evidenced by the tragic Pinnacle Airlines Flight 3701 incident, where the pilots overextended the limits and lost their lives.

Normal Operations and Guidelines

In normal operations, the landing gear is typically retracted once the pilot has positive indications of a climb. This is effectively communicated using various instruments: the altimeter, vertical speed indicator, and radio altimeter. On ATR aircraft, there is an additional check via the 'idle gate' feature, which prevents power levers from being retarded beyond flight idle while the aircraft is airborne.

The process of retracting the landing gear on an aircraft like the ATR takes about 10 seconds. By this time, the aircraft is approximately 400 feet above the runway. It should be noted that while there are no official limits published for the maximum time to retract the landing gear, some sources suggest 15 to 20 seconds.

The Impact of Airspeed and Safety

Airspeed is the primary factor in determining whether the landing gear can be retracted. Each aircraft model has published speeds for operating the gear with the brakes and doors closed. For example, some aircraft may even have a maximum speed limit for the landing gear down and extended to prevent structural damage.

An incident with a Learjet years ago highlights the importance of adhering to these guidelines. When the Learjet encountered an over-speed condition, the pilot dropped the gear well beyond the published limits. This exorbitant action caused the landing gear doors to immediately depart from the airframe, creating significant drag that brought the aircraft’s speed down and allowed the pilot to regain control. This story underscores the critical nature of following the established guidelines.

Conclusion

In summary, despite the absence of any explicit maximum duration for landing gear retraction, the focus must be on airspeed and safety. Pilots must closely monitor the airspeed indicators and ensure they adhere to the guidelines and speed limits published for their aircraft model. This ensures the integrity of the landing gear and the safety of the flight. Proper adherence to these procedures not only minimizes the risk of mechanical failure but also enhances overall flight safety.

Keywords: landing gear retraction, aircraft safety, gear cooling, speed limits, flight operations