"Vomit" bots, also called "power dumpers", were a hybrid between the shooter and the dumper. Muir-Hill moved on to producing dumpers also based on Fordson tractor skid units. Hand-cranked Lister diesel engines were used in many early dumpers. Virtually all modern jet aircraft are fitted with lift dumpers. Lift dumpers have only two positions, deployed and retracted. There were ball dumpers, floor shooters, ramp shooters and defensive robots. Spoilers are sometimes called "lift dumpers". Lift dumpers are almost always deployed automatically on touch down. Lift dumpers, a type of air brake, are mounted on the top of a fuselage. Barford manufacturers and sells a wide range of site dumpers. Dumpers are the most common cause of accidents involving construction plant. Out of these 132 collection points, as many as 42 are the dumpers. Some dumpers have FOPS (Falling Object Protection) as well.