Independent landing monitoring system

A guidance system for airborne vehicles on a final approach landing path, comprising

• (a) ground-based means having transmitter means operative to deliver pulse sequences, each sequence comprising multiple guidance pulse signals having predetermined time spacings, and the sequences occurring at spaced time intervals;
• (b) said ground-based means having antenna means including plural directional radiating means directed to radiate signals upwardly along and adjacent to the final approach landing path, the radiating means being arranged in pairs operative to radiate paired guidance signals with respect to the landing path;
• (c) said ground-based means having pulse signal timing and switching means coupled to trigger the transmitter means and to connect it to the antenna means, the timing and switching means being operative to couple a different directional radiating means to the transmitter means to radiate each successive guidance pulse signal in a sequence of pulse signals, thereby to identify the directional radiating means in accordance with the time position in the sequence of the guidance pulse signal which it radiates;
• (d) airborne means having receiver means operative to receive and detect the radiated pulse signals in the sequence;
• (e) said airborne means having indicator means having means for indicating the degree of deviation of the vehicle from the landing path;
• and
• (f) said airborne means having pulse processor means responsive to the received pulse signals and to their time positions in the sequence and operative to pair the received pulse signals and to compare the intensities of the pulse signals from each pair of directional radiating means and to deliver to the indicator means output signals representing the relative intensities of the respective paired pulse signals to control said means for indicating deviation from the landing path.