Taking off from a body of water and overcoming the hump created by the bow wave requires about three times more power than is necessary for cruising above that water in surface effect. Several design aids have been attempted to overcome this hurdle: some lower the displacement drag at high speed; others increase the aerodynamic lift at low speed.
The HF introduces a completely new, third mode of locomotion, a large overhead lift fan. This type of fan takes the strain out of designing, on the one hand, a hull that can reach high water speeds efficiently. On the other hand, it enables the surface effect aerofoil that can lift efficiently even at low speeds. This allows each of the three modes, hull, lift fan and aerofoil, to operate within their gnaturalh speed envelope. In addition, the lift fan remains useful in hull borne and aerofoil borne modes to dampen attitude and roll fluctuations.