During the Second World War the U.S. Navy issued a specification for an “assault drone”. This was a secret project at the time, and remains largely unknown today. The aircraft were built with an option for manned flight, but for operational use they were intended to be piloted remotely by a controller in an Avenger torpedo bomber or a PB4Y patrol bomber.
By the early 1940s television technology had progressed to the point where it was feasible for use as a guidance system. The aircraft also featured a radar altimeter. Payload would consist of a 2,000 pound bomb load or a torpedo. The operator could drop the payload in a conventional manner or crash the drone into the target. Range of the guidance system was eight miles.
The TDN-1 was designed to be simple to produce and to use non-strategic materials wherever possible. The airframe was made of wood, and was powered by two 250 hp Lycoming 0-435-2 engines. Wingspan was 45 feet with a length of 37 feet. Brunswick, of bowling ball fame, produced the final 30 units of the 100 total production units built.
The USS Sable (IX-81) was selected for the first carrier trials of the TDN drone. The Sable was the former Greater Buffalo, a Great Lakes passenger steamer. She was purchased by the Navy and equipped with a flight deck for the purpose of training Naval Aviators in carrier landings and take offs. She and her sister ship, USS Wolverine (IX-64) were unique in having side-wheel propulsion. They operated exclusively in the safety of the Great Lakes, training carrier aviators throughout the war.
Three drones were hoisted aboard Sable from a barge at Traverse City, Michigan. This would be the first time drones would be launched from a U.S. aircraft carrier, although the British had launched their first drones in 1937 from HMS Pegasus.
Here are two drones secured to Sable’s flight deck. The landing gear could be jettisoned after launch. The weapons bay under the fuselage is clearly visible. The television camera is located in the nose.
This is one of the TDNs during her launch. Note the empty cockpit. For operational missions the windscreen and headrest would be removed and a fairing was installed over the cockpit opening.
Sable launched the TDNs while steaming astern – note the canvas LSO platform screen to the left, the arresting wires on the flight deck, and the smoke from her coal-fired boilers drifting over her bow. The day shape of two black balls hoisted above her island signal “not under command” which usually indicates a steering casualty. In this case it may be intended to encourage other mariners to give the ship a wide berth.
A rather steep launch! Note the Grumman Duck in the background. These tests were conducted on 10 August 1943. Video of TDN tests can be seen here: https://www.youtube.com/watch?v=-MzxIkr5JO0
The launch of the second aircraft was not successful. It stalled just after getting airborne and crashed into Lake Michigan. This picture captures it just before impact.
Testing included dropping inert bombs against a towed target sled. Here two bombs are seen just after release, with the Grumman Duck again in the background.
In this case the bombs fell just short of the target.
The TDN was also tested against a stationary target. In this case the aircraft carried the ordinance directly to the target, a precursor to the television-guided missiles of today.
A hit! Even though these tests validated the concept, the TDN was never used operationally. The USN did field a similar competing design, the TDR, which I will cover in a future post.
TDR assault drone here: