X-Files: Sub Plane

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In today’s Sydney Flyer article, author Anthony Coleiro shares his most recent instalment of his X-Files series. This is Anthony’s 142nd article under the ‘X-Files’ banner for the club magazine, and the first for 2022. 

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One of the TV shows I enjoyed as a youngster was the Jules Verne inspired Voyage to the Bottom of the Sea.  I looked forward to their underwater adventures and watching the flying sub in action entertained the imagination.  Well, believe it or not, the idea of a flying submarine was taken seriously.


In the early months of 1965, the US Navy in conjunction with Convair’s Electric Boat Division of General Dynamics Corporation undertook an interesting study into a submersible seaplane.  To give the designers maximum flexibility, no time limit was placed on the contract.  It was envisaged that the aircraft would fly at low level above the water to evade radar detection, land at the target area, submerge and pursue its objective under water, although its tactical role was obscure.  It was thought that this sort of craft could penetrate closed waters like the Baltic or Black Sea and then conduct underwater operations against the Russian fleet, the nemesis of the USA at that time.


The aircraft was to have a seaplane hull, a conventional wing and tail, with two jet engines mounted above the wings and a third on top of the mid-section of the hull.  Underwater propulsion power would be provided by batteries driving an electric motor giving an underwater speed in the vicinity of 6.5 to 10 knots.


On landing, the engine intakes would be sealed before the internal space of the aircraft apart from the pressure cockpit would be flooded to allow the aircraft to dive.  Precisely what jet engines were considered to power the aircraft, I have not been able to discover.


The aircraft would have a flight radius of 300 to 500 nm at 150-225 knots and an underwater range of 50 nm at 75 feet.  The planned payload would be from 227 – 680 kg.


As one can imagine, combining aircraft and submarine technology would not be a simple process especially if you expect a craft that gives reasonable performance in both modes.  They operate in a completely different medium that requires different engineering solutions.  Take for example the concept of the flying car, how long has that idea been kicked around and still we have not seen a practical example in common use.  The problems to overcome in both cases are complex and a lot of resources would need to be thrown at them.  In the case of the flying sub, one can imagine how valuable such a craft would be in any military’s inventory.


What became of this project is somewhat obscure.  Like UFOs spotted in the sky which most of these can be attributed to either natural phenomena or secret military aircraft it is the same in the sea. USOs or Unidentified Submersible Objects have been spotted from time to time and it has been speculated that indeed some of these sightings may be this craft.  Officially the US Navy does not have a flying submarine in its inventory, unofficially may be another matter.  It has been over 50 years since the concept was mooted and with no time limit imposed on the project, who knows if they really pulled off such an engineering feat.



May 1965

The Royal Aeronautical Society

Air Progress

July 1965

Conde Nast Publications Inc.

AirBP 36

Journal of the BP Group


The Alternative News Magazine

June-July 2020

NEXUS New Times

Anthony Coleiro

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