"Sam Spade" wrote in message
...

In the days of the Berlin Airlift GCA was what we call PAR today. The
term PAR did not exist then. Today GCA means both PAR and ASR approach
procedures.


The term PAR predates the Berlin Airlift by almost a year.

After WWII there was quite a battle over which precision landing system
would become the standard.

The CAA and airlines favored ILS. The CAA had been developing the system
for nearly 20 years. From the CAA's perspective ILS was cheaper, GCA
required personnel to operate and personnel cost money. The airlines
favored ILS because it kept control in the cockpit.

The Navy and AOPA favored GCA. GCA didn't require any additional equipment
in the aircraft and ILS did, equipment which at that time wouldn't even fit
in most private or carrier aircraft.

The Air Force saw ILS and GCA as complementary systems, not competitive, and
felt both should be adopted.

GCA was composed of three radars. A search radar to locate aircraft in the
vicinity and direct them to the approach path and a set of two precision
radars, one that provided azimuth data and the other provided elevation
information.

In July 1947 the CAA administrator announced that it had been decided to
separate the GCA's radars into two types on the argument that ground
controlled approach was a method, not a system. The search radar was called
Airport Surveillance Radar (ASR), while the two precision radars were
together called Precision Approach Radar (PAR). This compromise solution
allowed the CAA to purchase the search radar without the approach radar,
protecting ILS while getting the benefits of traffic control radar.