first aerosanis may have been built by young Igor Sikorsky in 1909–10, before he built multi-engine airplanes and helicopters. They were very light plywood vehicles on skis, propelled by old airplane engines and propellers. Scout car A scout car is a military armoured reconnaissance vehicle, capable of off-road mobility and often carrying mounted weapons such as machine guns for offensive capabilities and crew protection. They often only carry an operational crew aboard, which differentiates them from wheeled armoured personnel carriers (APCs) and infantry mobility vehicles (IMVs), but early scout cars, such as the open-topped US M3 scout car could carry a crew of seven. The term is often used synonymously with the more general term armoured car, which also includes armoured civilian vehicles. They are also differentiated by being designed and built for purpose, as opposed to improvised "technicals" which might serve in the same role. Reconnaissance vehicle A reconnaissance vehicle, also known as a scout vehicle, is a military vehicle used for forward reconnaissance. Both tracked and wheeled reconnaissance vehicles are in service. In some nations, light tanks such as the M551 Sheridan and AMX-13 are also used by scout platoons. Reconnaissance vehicles are usually designed with a low profile or small size and are lightly armoured, relying on speed and cover to escape detection. Their armament ranges from a medium machine gun to an autocannon. Modern examples are often fitted with ATGMs and a wide range of sensors. Some armoured personnel carriers and infantry mobility vehicle, such as the M113, TPz Fuchs, and Cadillac Gage Commando double in the reconnaissance role. Internal security vehicle An internal security vehicle (ISV), also known as an armoured security vehicle (ASV), is a combat vehicle used for suppressing civilian unrest. Security vehicles are typically armed with a turreted heavy machine gun and auxiliary medium machine gun. The vehicle is designed to minimize firepower dead space and the vehicles weapons can be depressed to a maximum of 12°. Non-lethal water cannons and tear gas cannons can provide suppressive fire in lieu of unnecessary deadly fire. The vehicle must be protected against weapons typical of riots. Protection from improvised incendiary devices is achieved though coverage of the air intake and exhaust ports as well as a strong locking mechanism on the fuel opening. Turret and door locks prevent access to the interior of the vehicle by rioters. Vision blocks, ballistic glass and window shutters