From Graeme Buckley
In his interesting article on flying submarines, Paul Marks discussed the design history of such machines (3 July, p 32). One early design he didn’t mention, however, was the Piaggio P.7, an Italian racing seaplane built for the Schnieder Trophy race in 1929.
While not fully submersible, the Piaggio P.7 was designed to float on its wings with the lower fuselage submerged. The propulsion system was unusual. While in the water, the engine powered a marine propeller in the tail. When the pilot wished to take off, the seaplane would rise on waterskis until the front propeller was clear of the water. Then the engine’s power was sent to the front propeller, theoretically allowing a normal seaplane take-off. The craft was built, but never became airborne.
From Stephen Winkworth
I wonder how many people reading your article “A sub takes to the skies” were reminded, as I was, of that boys’ adventure classic The Flying Submarine by Percy F. Westerman. Written nearly a century ago, many of the problems you outline are mentioned, although the solutions – based on a techno-magical, gravity-neutralising gas called “helia” – are appropriate to airships rather than aircraft.
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Westerman admitted one limitation to his flying submarine, “The Amphibian” – it could not imitate diving birds because, in order to submerge, the vessel had to undergo the lengthy process of taking on water to expel the helia.
Little has changed. The more modern technology of the jet engine also has problems with the transition from air to water, as Graham Hawkes, your quoted engineer, warns. Perhaps developers will have to look to string theory for ways to create a gravity neutraliser.
Opio, France
Thorndon, Wellington, New Zealand
