Belly landing

A belly landing or gear-up landing occurs when an aircraft lands without its landing gear fully extended and uses its underside, or belly, as its primary landing device. Normally the term gear-up landing refers to incidents in which the pilot forgets to extend the landing gear, while belly landing refers to incidents where a mechanical malfunction prevents the pilot from extending the landing gear.

During a belly landing, there is normally extensive damage to the airplane. Belly landings carry the risk that the aircraft may flip over, disintegrate, or catch fire if it lands too fast or too hard. Extreme precision is needed to ensure that the plane lands as straight and level as possible while maintaining enough airspeed to maintain control. Strong crosswinds, low visibility, damage to the airplane, or unresponsive instruments or controls greatly increase the danger of performing a belly landing. Belly landings are one of the most common types of aircraft accidents nevertheless, and are normally not fatal if executed carefully.^{[clarification needed][citation needed]}

The most common cause of gear-up landings is the pilot simply forgetting to extend the landing gear before touchdown. On any retractable gear aircraft, lowering the landing gear is part of the pilot's landing checklist, which also includes items such as setting the flaps, propeller and mixture controls for landing. Pilots who ritually perform such checklists before landing are less likely to land gear-up. However, some pilots neglect these checklists and perform the tasks by memory, increasing the chances of forgetting to lower the landing gear. Even careful pilots are at risk, because they may be distracted and forget to perform the checklist or be interrupted in the middle of it by other duties such as collision avoidance or another emergency. In the picture shown above, the B-17 Dutchess' Daughter had landed normally, when the copilot inadvertently flipped the landing gear switch to retract. The gear collapsed near the end of the landing roll.

All aircraft with retractable landing gear are required to have a way to indicate the status of the landing gear, which is normally a set of lights that change colors from red to amber to green depending on whether the gear are up, in transit, or down. However, a distracted pilot may forget to look at these lights. This has led to aircraft designers building extra safety systems in the aircraft to reduce the possibility of human error. In small aircraft this most commonly takes the form of a warning light and horn which operate when any of the landing gear is not locked down and any of the engine throttles are retarded below a cruise power setting. However, the horn has been useless in situations when the pilot was unfamiliar with the aircraft and did not know what the horn sounding was meant to indicate. Pilots have sometimes confused the landing gear warning horn with the stall warning horn. In other cases, pilots cannot hear the horn on older aircraft due to wearing a modern noise-canceling headset.

In larger aircraft, the warning system usually excludes the engine power setting and instead warns the pilot when the flaps are set for landing but the landing gear is not. An alternative system uses the ground proximity warning system or radar altimeter to engage a warning when the airplane is close to the ground and descending with the gear not down. Most airliners incorporate a voice message system which eliminates the ambiguity of a horn or buzzer and instead gives the pilot a clear verbal indication: "GEAR NOT DOWN". In addition, large aircraft are designed to be operated by two pilots working as a team. One flies the aircraft and handles communications and collision avoidance, while the other operates the aircraft systems. This provides a sort of human redundancy which reduces the workload placed on any one crew member, and provides for one crew member to be able to check the work of the other. The combination of advanced warning systems and effective crew training has made gear-up landing accidents in large aircraft extremely rare.

In some cases, the pilot may be warned of an unsafe gear condition by the aircraft's flying characteristics. Often very sleek, high-performance airplanes will be very difficult to slow to a safe landing speed without the aerodynamic drag of the extended landing gear.^{[citation needed]}

Mechanical failure is another cause of belly landings. Most landing gear are operated by electric motors or hydraulic actuators. Multiple redundancies are usually provided to prevent a single failure from failing the entire landing gear extension process. Whether electrically or hydraulically operated, the landing gear can usually be powered from multiple sources. In case the power system fails, an emergency extension system is always available. This may take the form of a manually operated crank or pump, or a mechanical free-fall mechanism which disengages the uplocks and allows the landing gear to fall and lock due to gravity and/or airflow.

In cases where only one landing gear leg fails to extend, the pilot may choose to retract all the gear and perform a belly landing because he or she may believe it to be easier to control the aircraft during rollout with no gear at all than with one gear missing.