This historic film THE ARMY DOZEN AND THE H-13K SIOUX ON THE WARPATH was created by Bell Helicopter to showcase 12 “nap of the earth” maneuvers for pilots. Nap-of-the-earth (abbreviated NOE) is a type of very low-altitude flight course used by military aircraft to avoid enemy detection and attack in a high-threat environment.During NOE flight, geographical features are used as cover, exploiting valleys and folds in the terrain by flying in, rather than over, them. This keeps below enemy air defense radar coverage, avoiding being silhouetted against the sky. Other, mostly older terms include “ground-hugging”, “terrain masking”, “flying under the radar” and “hedgehopping”.

The so-called “Army Dozen,” a series of twisting, weaving and dodging flight configurations developed informally, in some cases borrowed or improved upon from tactics used by agricultural helicopter operators, aimed at using trees, hills, river beds as concealment and to confuse the enemy. Summarizing

some of the maneuvers performed by the H-13K are:

• Twists, which arc evasive skids at cruise speeds, spraying machine gun fire to develop enemy locations.

• Hit the deck, a rapid descent to avoid getting hit or sustaining additional damage.

• Low autorotation comprised of low- level autorotations from three to 15-ft. altitudes.

• Jump-fire-run, in which the helicopter executes a sharp vertical climb from a concealed position, stops abruptly at or slightly below tree-top level, fires a ma-chine gun burst at the enemy and then

peels off sharply for a getaway.

• Reversal, which involves making 180-deg. sharp turns in confined area, using maximum sideward stick displacement

• Cornering autorotation, which involves making autorotations from downwind or crosswind cruise, turning 90-deg. into the wind while at three to 15-ft. altitudes.

• Pinnacle stop, a low-level, high-speed approach to a pinnacle or hill and landing directly without gaining altitude above the pinnacle.

• Scramble, which involves a rapid lowlevel takeoff regardless of wind condition, for downwind takeoffs and emer- gencies.

• Quick squat, a low-level downwind landing with 180-deg. turn into the wind just prior to touchdown.

• Blivet, a low-level approach and landing in a confined area which may be smaller than the rotor diameter. This maneuver may involve flying through underbrush.

• Whoa-boy, a low-level quick stop usiing sideward flare to reduce exposure to the enemy.

• See-saw. a scries of snap vertical climbs and rapid descents for use in artillery fire spotting.

The helicopters shown, Bell H-13Ks, were apparently an experiment by the Army. These were actually converted H-13Hs with a larger diameter rotor and a 225 hp (168 kW) Franklin 6VS-335 engine (made for test evaluation).

The Bell H-13 Sioux was a two-bladed, single engine, light helicopter built by Bell Helicopter. Westland Aircraft manufactured the Sioux under license for the British military as the Sioux AH.1 and HT.2

The H-13 was used as an observation helicopter early in the Vietnam War, before being replaced by the OH-6 Cayuse in 1966.

The Bell 47 was ordered by the British Army as the Sioux to meet specification H.240, with licensed production by Westland Helicopters. In order to comply with the terms of its licence agreement with Sikorsky Aircraft, which prevented it building a U.S. competitor’s aircraft, Westland licensed the Model 47 from Agusta, who had purchased a license from Bell.[4] the first contract was for 200 helicopters. The first 50 helicopters of the contract were built by Agusta at Gallarate in Italy followed by 150 built by Westland at Yeovil. The first Westland Sioux made its maiden flight on 9 March 1965.

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This film is part of the Periscope Film LLC archive, one of the largest historic military, transportation, and aviation stock footage collections in the USA. Entirely film backed, this material is available for licensing in 24p HD, 2k and 4k. For more information visit http://www.PeriscopeFilm.com