Lycoming LVHX-1

The LVHX-1 (Landing Vehicle, Hydrofoil) was an experimental amphibian built by the Lycoming Division of AVCO for the US Marine Corps. Its mission matched that of the wheeled LVW: to carry a 5-ton payload from ships far offshore at high speed and then drive up the beach. To do this it rose onto fully submerged hydrofoils.

Background

The programme grew out of hydrofoil trials in the late 1950s with the test craft HALOBATES and a "Flying DUKW". The Flying DUKW was a DUKW fitted with foils, an autopilot and a Lycoming T53 gas turbine, which exceeded 30 knots in demonstrations off Miami. Encouraged by these results, the Marine Corps ordered two competing designs to one requirement: aluminium hulls 38 ft (11.6 m) long carrying 5 tons at 35 knots. Lycoming's LVHX-1 used submerged foils. Food Machinery Corporation's LVHX-2 had surface-piercing foils forward and a single submerged foil aft, and was powered by an 1,100 shp Solar turbine.

Design and trials

The wheels were carried on aircraft-style struts, shortened for retraction by pumping hydraulic fluid below the strut pistons. The submerged foils needed an automatic height-sensing control system, and the trials were troubled. Hydraulic leaks were constant, and the wheel struts sometimes failed to extend. Air could also be drawn down the front foil struts, "venting" a foil so that it lost lift and the vehicle crashed down and rolled to that side. A Lycoming engineer who watched some of the tests described the craft limping out of the Housatonic River, listing on a half-retracted strut and pumping sea water and red hydraulic fluid from its bilges.

In the end the cost and complexity of foil retraction and high-speed gas turbine propulsion were judged too great a price for the extra water speed, and hydrofoil landing craft were abandoned. Two LVHs were built. One was later seen at a Marine Corps museum at Camp Pendleton, California.