chapter  13
Microwave landing system
Pages 3

At the aircraft receiver, a pulse is detected each

time the respective beams sweep past the aircraft.

Consider an aircraft on the approach as illustrated

in Figure 13.3. The (azimuth) time referenced

scanning beam sweeps from left to right (‘TO’),

and then returns from right to left (‘FRO’). If the

aircraft is in position A, it is to the left of the

centreline and will receive a pulse at time interval

t1 as the beam sweeps ‘TO’, and then at time t2

when the beam sweeps ‘FRO’. The two pulses

are therefore close together with the aircraft to

the left of centreline. If the aircraft were in

position B, i.e. to the right of the centreline, it

would receive pulses at t3 and t4 due to the

relative position of the aircraft.