With the exception of seaplanes, most airplanes feature landing gear. Consisting of nitrogen-filled tires, shock absorbers and other components, it allows them to safely land on runways. There are different types of landing gear, however, including retractable and semi-retractable.
What Is Retractable Landing Gear?
Retractable landing gear is characterized by its ability to fully retract into the belly of an airplane’s fuselage (or the airplane’s wings). While some small airplanes have fixed landing gear that remains fully extended at all times, most commercial airplanes have retractable landing gear. After taking off, the pilot will retract the airplane’s landing gear so that it no longer sticks out from the bottom of the airplane’s fuselage.
There are manual, electric and hydraulic retractable landing gear systems. Manual retractable landing gear systems require manual retraction. Electric retractable landing gear systems use electrically to retract into the belly of the airplane’s fuselage. Hydraulic retractable landing gear systems, on the other hand, use pressurized fluid for retraction. Regardless, all retractable landing gear systems can fully retract into the belly of the fuselage.
What Is Semi-Retractable Landing Gear?
Semi-retractable landing gear is characterized by its ability to partially retract into the belly of an airplane’s fuselage. It still consists of nitrogen-filled tires, shock absorbers and other components. There are also manual, electric and hydraulic semi-retractable landing gear systems. What defines semi-retractable landing gear, though, is that it only partially retracts.
Differences Between Retractable and Semi-Retractable Landing Gear
Neither retractable nor semi-retractable landing gear remains fully extended at all times. Rather, they are both designed to retract into the airplane. Retractable landing gear can fully retract into the belly of an airplane’s fuselage, whereas semi-retractable landing gear can partially retract.
Both types of landing gear minimize drag. Drag creates resistance that slows down airplanes during flight and increases their fuel consumption. By retracting the airplane’s landing gear, pilots can minimize drag and improve fuel efficiency. Semi-retractable landing gear, however, will always remain at least partially extended. The wheels will always be exposed to the airstream, resulting in increased drag.
While semi-retractable landing gear creates more drag than its fully retractable counterpart, it’s typically more reliable. Landing gear systems can fail, but failure is more common with fully retractable landing gear. According to a report by the American Aviation Safety Reporting System (ASRS), over one-third of all landing gear system failures are attributed to retraction failure.
