Abstract: The speeds of two wheels are detected by means of wheel speed transducers associated with each wheel, each producing a DC voltage signal proportional to the respective wheel speed. The circuit includes two electric comparators, each having two inputs and one output, each output controlling a fault indicator in the form of an incandescent light. The two inputs for each comparator are the two produced DC voltage signals; and each comparator is identified with one transducer which provides a triggering wheel speed signal, with the other transducer providing a reference wheel speed signal. Sensitivity resistors provide a positive bias on the reference signal input to each comparator. Normally the two wheel speed signals are the same; however, when a triggering wheel speed signal increases a selected amount relative to the reference wheel speed signal, responsive to an underinflated tire, the associated comparator switches to activate the fault light to indicate an underinflated tire.

Abstract: A wheel speed transducer, for each braked wheel of an aircraft, produces a DC voltage signal which is proportional to the wheel rpm. In one aspect, the system compares the wheel speed voltage signal with a fixed threshold voltage signal proportional to a selected wheel rpm which is indicative of a selected threshold ground speed such as 15 knots. When the threshold ground speed is reached, the system indicator advises that each wheel is or is not rolling at that speed. Another aspect of this system functions immediately after lift-off. The wheel speed voltage signal is compared with a modified wheel speed reference signal, which is maintained at a slightly lower voltage level for normal deceleration and which has a limited maximum rate of decrease determined electronically.