

As the U.S. Navy’s battle and invasion fleets moved toward Japan in 1945, the Japanese responded with Kamikaze (Divine Wind) suicide bombers.

The Kamikazes were all types of aircraft, loaded with bombs and manned by pilots of various experience levels who made one-way flights to dive on American ships.

Though the Kamikazes were easy to shoot down with conventional fighters, they came in large numbers, at different altitudes and from many different directions and overwhelmed the American fleets’ command and control.

Radar coverage at this time was line of sight, so to obtain earlier warning, the Navy sent out radar equipped destroyers to act as picket ships between the Japanese bases and the U.S. forces, but well away from the fleet.

The Japanese countered by attacking these unsupported picket ships with the first wave of Kamikazes, and the small destroyers were quickly sunk or badly damaged. These losses soon became unsustainable and, with the invasion of Japan approaching and the expectation of a huge number of Kamikazes opposing the invasion, the Navy was desperate for a solution to the early warning problem.

The Navy decided to replace these vulnerable ships with aircraft carrying APS-20E airborne long range search radar, but the radar was very large, too big for a carrier aircraft. The Navy then launched “Project Cadillac II” to find an aircraft to combine long range scouting and patrol, airborne enemy threat detection, electronic countermeasures, and anti-submarine warfare.

Additionally, instead of sending the intelligence down to a ship’s combat intelligence center, the aircraft would have its own CIC to control the fighters and guide them to intercept the inbound Kamikazes, making it the first flying command center.

A number of different aircraft were considered for the role, but in the end, the Navy acquired 48 U.S. Army Air Force Boeing B-17Gs to carry the airborne early warning radar. The B-17 was chosen because the Navy was already using some B-17s as long range search and rescue aircraft, but more importantly because it could carry the radar and retain its guns, considered essential if the aircraft was to survive over the Sea of Japan.

The B-17s were given the U.S. Navy designation PB-1W. The Naval Air Material Center’s Naval Aircraft Modification Unit in Johnsville, Pa., modified the B-17s to PB-1W specification by sealing the bomb bay doors and installing 300 gallon drop tanks on each wing, in addition to the “Tokyo Tanks” mounted on the outer wings to give it longer range and loiter times on station. The 3,400 gallons of fuel gave the PB-1W the endurance of more than 22 hours.

The huge, one-megawatt AN/APS-20 Seasearch S-band radar set, manufactured by Hazeltine/General Electric, was mounted in a bulbous housing below what was formerly the bomb bay. The radar relay transmitter, an advanced version of Identification, Friend or Foe, a radio direction finder, instrument landing system, and a long range navigation system gave the PB-1s a state of the art electronics suite.

In the nose of the PB-1W, the chin turret and bomb sight were removed. The bombardier’s station itself was used for an observation station, while the navigator’s position was left unchanged.

The bomb bay was modified with two radar consoles mounted on either side of the walkway with the operators facing aft with their backs against the cockpit bulkhead. The CIC officer’s position was at the right rear of the bomb bay, and the left contained electronics and radio equipment. Floating smoke markers and flares were carried to be dropped during anti-submarine warfare or search and rescue missions.

Because of the length of the missions, a latrine and kitchen were included in the waist section. The AAF B-17 bomber crew was usually 10 men, but the Navy crew consisted of six officers (pilot, co-pilot, navigator, CIC officer and two radar operators/controllers) along with five enlisted men to maintain the equipment.

The first 20 B-17s were transferred to the U.S. Navy and flown directly to the Naval Aircraft Modification Unit during the summer of 1945.

The first unit, Patrol Bomber Squadron 101 (VPB-101), stood up at NAS Willow Grove to flight test the radar and received its first PB-1 (without radar) in September 1945, the month after Japan had surrendered, and its first radar equipped PB-1W in January 1946.

Post-war, the PB-1Ws had their armor and guns removed and were painted dark Navy blue.

As expected, the look-down radar could track the fleet and aircraft, but as a bonus, it could plot storms, giving the PB-1W hurricane hunter capabilities as well.

The Navy eventually had a total of 22 of their B-17s fully upgraded to PB-1Ws. Late in 1946, VPB-10 moved to Floyd Bennett Field in Brooklyn, N.Y., and then to NAS Quonset Point, R.I., where it was redesignated Airborne Early Warning Development Squadron Four (VX-4).

After the war, the PB-1W was used to mount patrols between Newfoundland and Iceland and around the Azores, guarding against a possible Soviet attack, and by 1947, PB-1Ws had been deployed to units operating with both the Atlantic and Pacific fleets.

The PPB-1Ws were replaced in 1954 with a dedicated early warning aircraft, the PO-1W, a modification of the civilian Lockheed Constellation, which also served in the Air Force as the EC-121.

(For questions or comments, contact Dr. Michel at marshall.michel@spangdahlem.af.mil.)