When Radar Came to Town 

On January 7, 1952, after five years of testing and modifications to a radar system used 

by the Army and Navy in World War II, the Civil Aeronautics Administration 

inaugurated radar departure control procedures at its Washington National Airport. Six 

months later it began radar approach control procedures at the airport. 

Originally developed by the British during World War II, radar provided an important 

tool for U.S. armed forces in World War II. RAdio Detection And Ranging equipment, 

coined RADAR by the U.S. Navy in 1940, allowed the military to adapt and use a new 

landing aid called ground control approach (GCA). The military selected Gilfillan 

Brothers, Inc. (today part of ITT), in Los Angles, CA, to develop the system in 1942. The 

following year, U.S Air Force air traffic controllers began routinely using GCA 

equipment to help military pilots land safely in poor visibility. The system was not 

designed for en route air traffic control. 

The GCA system included two oscillating radar antennas with narrow “pencil beams.” 

One scanned side to side (azimuth), the other up and down (elevation). A controller 

observed the precise angle returns from these azimuth and elevation radars and radioed 

landing guidance to the pilot. GCA also had a 360-degree rotating radar to monitor entire 

terminal area. It used a “fan” beam (narrow in azimuth and tall in elevation) to detect 

planes out to about 30 miles from the airport and up to altitudes of about 10,000 feet. 

GCA consisted of two six-inch radar displays using cathode ray tubes. One screen 

displayed the approaching aircraft, which allowed the radar operator to direct pilots into a 

waiting position using voice radio. The other display helped the controller determine how 

the pilot should steer to find the proper heading and approach angle to land. The 

controller literally talked the pilot down using radio. The system required a five-man 

crew housed in a mobile trailers that could roll to a new runway or even a new airport 

when needed. 

The CAA had no radar during the war years. After the war, CAA acquired four Gilfillan 

MPN-1 GCA trailers from the Army Air Force. CAA installed the trailers, identical to 

those used by the military during the war, at four airports: Washington National; Chicago 

Midway; Newark; LaGuardia. CAA and the Air Transport Association (ATA) paid for 

installation costs, and the CAA paid for all operation and maintenance costs. During the 

tests, conducted on a cooperative basis by the CAA, Army, Navy, ATA, and Gilfillan 

Brothers, CAA controllers operationally used the equipment to evaluate it and ascertain 

how they could use radar and how it could be adapted to civil aviation. 

On April 3, 1947, CAA controllers began in-service evaluations of the GCA radar system 

at Washington National and Chicago Municipal airports. New York's La Guardia and 

Newark airport received similar equipment later in the year. The CAA reduced the five 

man crew with a two-man crew. As Stan Seltzer, then the chief controller at Washington 

National, recalled, the trailer truck “was installed at the north end of the airport, adjacent 

to runway 18-36. The front of the GCA faced south toward the threshold of runway 36, 
Washington National’s primary instrument runway. Tower controllers used their personal 

cars to drive to and from the trailer. There was no paved road – just nice, gooey mud.” 

Each trailer had two radar scopes for use by the controllers. The area surveillance scope, 

provided controllers with a “birds-eye view of traffic within approximately thirty miles 

radius of the airport. The second radar scope presented two different views for about 

seven to ten miles out along the approach path to the airport. The upper half of the scope 

presented a vertical view of the approach path showing the ideal glide path to the runway 

together with mileage range marks from the runway. The bottom half of the same scope 

presented an “overhead” view of the same area and showed the centerline of the approach 

path to the runway, with similar mileage range marks. 

The controller on the area surveillance scope provided pilots of the arriving aircraft with 

headings and altitude information, guiding him toward the final approach path. As the 

aircraft neared the approach path, control was transferred to the second controller (known 

as the “final controller”) who would then provide headings to establish the aircraft on the 

final approach path and inform the pilot when to begin his gradual descent along the glide 

path. The controller provided the pilot distance from runway information during his 

progress as well as necessary corrections in heading and/or descent rate to ensure the 

aircraft would remain on the runway centerline and glide path to the runway. 

CAA controllers quickly determined that the surveillance feature of the radar system 

afforded them instant vital information that they often received late, or not at all, from 

voice communications with the pilot. The 30-mile search scan portion of the GCA 

(airport surveillance radar or ASR), allowed controllers to “see” the position of aircraft 

under their control or in their area of control. The planes showed up as “pips” or dots of 

light on the scope to show the direction and distance the planes were from the airport. 

GCA ensured controllers maintained adequate separation between aircraft since they 

Gilfillan MPN-1 GCA Trailer at Washington National Airport 
could now “see” how far the planes were from each other. Being able to see the 

heretofore “invisible” planes allowed them to expedite departures and arrivals. In fact, 

controllers at LaGuardia Airport reported GCA helped triple the landing rate to 15 planes 

per hour. 

 

Despite the benefits of GCA, the instrument landing system (ILS) remained the CAA’s 

primary landing system. GCA was only available at the four airport field test sites, and 

then only if offered by controllers or requested by pilots. As Seltzer explained, “CAA 

controllers learned to make GCA approaches by ‘offering’ civilian pilots approaches 

during good weather conditions. Eventually they made approaches during instrument 

weather condition if a pilot requested or accepted their offer.” In fact, on December 29, 

1948, controllers at National offered a GCA approach to the pilot of President Harry 

Truman’s airplane, The Independence, when the President returned to Washington, DC, 

from a trip. The pilot accepted the offer, thus, Truman became the first U. S. President to 

be on an aircraft during a GCA approach. “Many controllers,” said Seltzer, “became 

geniuses at suggesting things to pilots based on the controllers’ radar observations. It was 

clearly a great tool... if only we would be permitted to use it.” 

Many airline pilots, on the other hand, seemed reluctant to use GCA. The Air Line Pilots 

Association (ALPA), for example, initially opposed the use of radar for approach and 

departure control. Fearing a loss of control, some pilots objected to controllers giving 

them instructions – advisories or information could be given, but not instructions. From 

his experience, Seltzer related that some pilots asserted that “...no controller is gonna put 

his hands on my throttles or any other controls in my cockpit!” While others, claimed 

radar would be used by CAA as a tool for “spying” on pilots. 

 

The controllers’ evaluation of GCA convinced CAA 

officials of the utility of radar for air traffic control – 

not just for approach and departures. This early 

experiment with radar also convinced the airlines of 

the need to adapt radar to air traffic control. ATA 

hired Stan Seltzer in December 1951 to work on 

gaining acceptance of the use of radar for air traffic 

control. As part of that effort, American Airlines 

loaned Captain Sam Saint (also an ALPA member) 

to head ATA’s Navigation/Traffic Control Division 

in Washington, DC. Along with Seltzer and Saint, 

another American Airlines pilot and ALPA member, 

Walt Jensen, and the CAA’s Ed Barrow worked 

tirelessly on ATC and radar issues. Their efforts 

succeeded and in January 1952, the CAA officially 

commissioned radar departure control at Washington 

National Airport using an ASR-1 developed for 

especially for the CAA. 

 1950s ASR-1