The BTR-50 (BTR stands for Bronetransporter (), literally "armored transporter") is a Soviet amphibious armored personnel carrier (APC) based on the PT-76 light tank. The BTR-50 is tracked, unlike most in the BTR series, which are wheeled. The BTR-50 shares many similarities with two other APCs, the OT-62 TOPAS and the Type 77. While the OT-62 is an improved copy of the BTR-50 developed jointly by Czechoslovakia and Poland, the Type 77, based on the Type 63 amphibious light tank developed by the People's Republic of China (PRC), is not a copy of the BTR-50. Description Like the PT-76, the BTR-50 has a flat, boat-shaped hull. Unlike the PT-76, it has a new superstructure added to the front of the vehicle. The hull of the BTR-50 is made of all-welded steel with the crew compartment in the front, the troop compartment in the center and the engine compartment at the rear. It has the ability to transport up to 20 fully equipped infantrymen, who sit on benches that run across the full width of the troop compartment. They embark and disembark the APC by climbing over the sides of the hull. The driver sits in the center of the front of the hull and has three vision blocks and periscopes located at the top of the sloping glacis plate. During night operations, the center periscope can be swapped for the TVN-28 night vision device, which gives the driver clear vision up to 60 meters. The driver also has a small hatch that opens upwards—while it cannot be used to leave the vehicle, it can be opened in relatively safe areas for extra vision. In combat, the hatch is closed and the driver can use a vision block. There is an emergency hatch under the driver's seat. The commander, who sits on the left side of the vehicle at the front, has three vision blocks and periscopes in a projecting bay. On top of this bay is a cupola that opens forward and can be locked vertically; it has a vision block facing forward. The vehicle can operate in temperatures from −40 °C to +40 °C. The torsion bar suspension consists of six evenly spaced large rubber-tired road wheels with a drive sprocket at the rear and an idler at the front. The road wheels are hollow to assist its amphibious capabilities. These wheels increase the APC's buoyancy by 30%. There