PTOL

PTOL (Point-Take-Off and Landing) is an evolving term describing special take-off and landing capabilities of Unmanned aerial vehicles (UAVs) and other aircraft.

PTOL indicates no requirement of runway for operations. Instead, ‘point’ suggests the length of runway required is actually, or near, zero, as well as implying a minimal-size location for touchdown and takeoff. Sometimes no prepared surface at all is needed.

PTOL is sometimes assisted by means VTOL and STOL do not need, e.g., a cable enforcing their converging on the intended landing location, this is worthwhile due to maintaining the air-vehicle's advantages, e.g. in case of using fixed-wing UAVs.

Advantages

PTOL capability enables UAVs and aircraft to land and takeoff on very confined locations like rooftops, ship decks and forest clearings. This is comparable to the VTOL, but it helps fixed-wing/simple UAVs do it, avoiding the complexity and cost of air-vehicle construction required for VTOL (jet-thrust-rotation engines, or engine pods/rotors tilting mechanisms).

This gains higher aerodynamic efficiency and allows smaller engines and lower cost, among others. Also, a true PTOL solution means exact touchdowns even in adverse conditions such as rolling/heaving ship deck, strong winds on land, or close to obstacles around (such as trees or rocks). Its ability to land a UAV direct onto a vehicle, with cushioning means, adds safety to deployed UAVs, suffices with no-runway/no pre-prepared area, and eases quick changing of the landing-site.

The enforced touchdown point characteristic seems to become advantageous over the manned helicopters and helicopter UAVs landing unassisted on rolling ships.

Implementation

PTOL takeoffs are a rather simple matter, as any rocket launched from a tube, or a UAV launched by a rail-launcher or similar means in effect make point-takeoff.

For the landings, several ideas have been proposed. An example for sea operations - catching a UAV into a parachute in the air behind a sailing ship, then lowering the UAV to the deck by pulling the parachute in.

Another idea is 'Cable-Assisted PTOL' for fixed-wing UAVs. The UAV makes a cable connection to a surface winch (on ship or ground) and the winch pulls the UAV down to the intended ‘point’. This is potentially useful for land and naval usage of fixed-wing UAVs.

Patents

Patent 4,753,400 "Shipboard air vehicle retrieval apparatus"

Patent 4,311,290 "Arrestment system"