Autogyro.

This is coolbert:

Here from the Al Nofi StrategyPage CIC # 356:

"In addition to pressing for the adoption of the escort carrier on the eve of World War II, F.D.R. [President Roosevelt] also proposed that they be equipped with autogiros, an early type of rotary-wing aircraft, which he believed might be useful in anti-submarine operations, an idea that was rather ahead of its time."

The autogyro! And aircraft design in those years prior to World War Two [WW2] that seemed to be promising but for whatever reason or combination of reasons never seemed to come to fruition.

That autogyro sans wings the rotor providing lift but not directly powered by the conventional propeller driven engine. A STOL [short-takeoff-landing] airplane. That rotor freely rotating in contrast to a helicopter where the rotor is directly connected to the engine!

Surprisingly so, there were in those years prior to 1939 and during the war indeed some autogyro having a military applicability amongst the various combatants however limited in scope. This is all new to me!

British Avro Rota Mk1 Cierva Autogiro C30A

"Autogyros in 1940. No.529 RAF Squadron at RAF Halton were also equipped Avro Rota Mk1s to be used to assist the new Secret Radar Sites to calibrate their equipment. The were instructed to fly out to a known distance and height. The Radar operators could then use their position to tune their equipment to make it more accurate at spotting enemy bombers and fighter approaching the South Coast of England during the Battle of Britain."

Soviet Kamov A-7, autogyro-spotter.

"Kellett XR-3 modification of YG-1B (KD-1) of U.S. Army preserved at Yanks Air Museum, Chino airfield California, in January 2008". American military autogyro from those years prior to Pearl Harbor. In both "X" and "Y" versions. X for experimental and Y for prototype!
 

Japanese Kayaba Ka-1. The ka-1 actually used in the purpose of anti-submarine warfare airplane during WW2 in exactly the type of mission as envisioned by FDR. ONLY in a very limited manner but reputedly sinking at least one American submarine during the war.

That reputation of Roosevelt [FDR] as a dilettante a person involving himself in matters for which he had only a basic or very superficial knowledge, a dabbler especially interested in naval matters.

coolbert.