Project Cadillac



The most technologically-advanced response to the increasing kamikaze threat was the US Navy’s Project Cadillac, which included the development of the world’s first AEW (Airborne Early Warning) system. The airborne element of this system was a modified TBM Avenger, mounting a rotating radar antenna 2.4m in diameter between the landing gear of the carrier aircraft, as well as the electronics needed to broadcast the radar image back to a ship’s CIC and a two-man crew to operate the equipment. The cutaway drawing shows how all the heavy and bulky electronics were packed into the TBM-3W. Besides the bulky radome for the APS-20, this Avenger was distinguished by the faired-over aft cockpit and the extra vertical fins added to the horizontal stabilizer.

There is no doubt that the findings of the SpecORG report would have been promulgated to the fleet had the invasion of Japan gone ahead. But apart from the tactical suggestions in that report, there was little in the way of new technology or tactics that could protect the ships of the fleets from the expected onslaught. There was talk of further extending the idea of the ‘Big Blue Blanket’ that was supposed to protect the ships of the fleets. The idea had originated with then-Cdr John ‘Jimmie’ Thach, serving as McCains Air Operations Officer. Known for inventing the ‘Thach Weave’ early in the war, a tactic that allowed the relatively unmaneuverable Wildcats to take on the far nimbler ‘Zeke’ in something like a fair fight, Thach proposed that US carriers double their fighter complement at the expense of dive-bombers and put a 24-hour CAP over Japanese airfields. Tried out at Mindoro with mixed results, the idea was tried again at Okinawa, adding radar picket destroyers to warn of Japanese attacks. The idea was revised and expanded again for the planned invasion of Japan. Besides more fighter aircraft flying from more aircraft carriers, the plan now included less reliance on picket destroyers and more on land-based and air-based radars. To achieve this, Marine units were being formed with radar mounted on specially-modified landing craft that could be beached on islands close to the enemy shore and put to immediate use. Even more innovative was the idea of airborne radar platforms, an early incarnation of today’s AEW (Airborne Early Warning) aircraft.

This was Project Cadillac. Based on experiments carried out by the MIT-RL (Massachusetts Institute of Technology – Radiation Laboratory) in 1942–3, the US Navy launched a project to mount a high-powered search radar on a carrier aircraft. As early as August 1942, MIT-RL had demonstrated the ability to broadcast the image on a radarscope to a remote location. By May 1943, a range of 50nm between an aircraft carrying the radar set and the remote base station had been achieved. Progress was remarkably rapid considering the long list of new technologies involved.

A new radar, designated AN/APS-20, was developed. It operated in the S-band (10cm wavelength) with a theoretical range of 130nm to detect a single low-altitude aircraft. (The practical detection range for a single Overwater target, taking sea-surface backscatter into account, was 45nm. Larger formations could be reliably detected at 100nm.) The radar included integral IFF and automatic orientation of the PPI image to true north, so that relayed radar image would not be affected by the aircraft’s heading. The base station could be any facility, such as a ship’s CIC, equipped with the necessary receiving equipment and PPI displays within a 100nm range of the airborne radar.

To deploy this system on an aircraft carrier required an aircraft capable of carrying a rotating radar antenna 2.4m in diameter and 1040kg of equipment, still capable of launching from and trapping on existing Essex-class aircraft carriers. The only aircraft that could meet these requirements was the TBM Avenger. A TBM-3 was taken off the Eastern Aircraft assembly line and delivered to the Navy’s Johnsville (PA) Air Development Center for modification. It emerged with the cockpit aft of the pilots seat faired over to make room for the radars electronics, stations for two operators in the aft fuselage, all armament and armor removed, small vertical fins added to the horizontal tail to aid directional stability and, most noticeably, a large faired radome hanging below the fuselage. The XTBM-3W, as this strange-looking aircraft was dubbed, first flew on 5 August 1944. Such was the urgency of this project that flight testing was hurriedly completed and an order for 27 addition conversions followed immediately. The first of these was delivered in March 1945 and successful carrier qualification trials were conducted on Ranger (CV 4) off San Diego between April and June. The plan was to have four-plane detachments deployed on Enterprise, Hornet (CV 12) and Bunker Hill in time to support the projected invasion of Kyushu, Operation Olympic, scheduled for 1 November. By extending the range at which kamikaze raids could be detected and the reliability with which they could be tracked, in particular low-altitude formations that could often elude sea-level radars until they were too close to intercept, these first AEW aircraft offered the best hope of blunting the anticipated kamikaze onslaught. An additional side-benefit, no doubt appreciated by every destroyerman in the US Navy, was the replacement of surface radar pickets with aircraft.

Ultimately, the defense of a ship came down to gunfire, as stated rather hopefully by the CO of Bache.

The only sure method of destroying suicide planes is by gunfire … Even a high volume of fire, whether hitting the plane or not, may sometimes distract the pilot causing him to splash harmlessly. It is believed that some of the suicide pilots freeze or flinch at the last second causing misses. After all, a KAMIKAZE gets no practice in his chosen profession and he must be perfect on his first and last attempt.

This certainly addresses a very basic element in this ‘dance of death’. The pilots diving their aircraft on Allied warships were, for the most part, young and inexperienced. The task they were being asked to perform was, at the same time, very simple and very difficult. The Japanese were aware that there was a tendency among these young men to close their eyes just before the crash, a very human reaction to the situation. They were repeatedly exhorted to keep their eyes open and to continue aiming their aircraft to the last moment. It is impossible to forget that these were very young men on both sides of this story.


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