Monte-Copter, Inc. was incorporated in June, 1953, to develop a light helicopter featuring the "cold-jet" type of rotor tip-drive.

The company's first prototype was the Monte-Copter Model 10, which began its test programme in 1955. It has since undergone considerable development and in its current form is known as the Model 12.

A brief description of the Model 12 is given below, together with full details of the production development, designated the Model 15 Triphibian, which was scheduled for completion late in 1959.

MONTE-COPTER MODEL 12

This aircraft began life in 1955 as the two-seat Monte Copter Model 10, powered by a 135hp Lycoming O-290-D2 engine, driving a two-blade rotor with servo-control surfaces mounted at 90° to the blades. At that time it had small fixed wings to off-load the rotor in forward flight and a tail-boom carrying twin fins.

After initial tests had been completed, this airframe was modified into the Model 10A by removal of the wings and cabin skin and replacement of the Lycoming piston-engine by two Continental Model 140 (Turbomeca Palouste) air compressors. These engines were mounted on each side of the fuselage and were used to supply compressed air to rotor-tip nozzles, from which the air was ejected without any form of combustion, to turn the rotor.

Further modification of the airframe has led to the present Model 12, with the fuselage skin replaced and a single rudder, working in the jet efflux, instead of the former tail-boom. In this form, it has been flying successfully since May, 1958.

No specification details are available except that the Model 12 has an empty weight of 454kg and a normal loaded weight of 635kg. Its rotor has a diameter of 32 ft. (9.75 m.)

MONTE-COPTER MODEL 15 TRIPHIBIAN

Developed from the Monte-Copter Model 12, the Model 15 Triphibian is a three-seat light helicopter with a "cold-jet" type of rotor drive, in which the rotor is turned by ejecting compressed air from nozzles at the blade-tips, without any form of combustion. The prototype was scheduled for completion late in 1959. The Model 15 is of very simple design, with a fiberglass boat-type hull to permit operation from water as well as land. It has small delta wings to offload the rotor in forward flight. Fuel tanks on the wing-tips serve also as stabilising floats during water operations.

TYPE: Three-seat amphibious helicopter.

WINGS: Small delta wings to offload rotor. Conventional ailerons.

ROTOR SYSTEM: Two-blade main rotor with fully-articulated semi-rigid all-metal blades, attached to hub by specially-designed serrated fittings. Spherical bearings at pitch and flapping hinge. Area of each main blade 1.11m². Total disc area 94.76m². No anti-torque rotor.

ROTOR DRIVE: Cold-jet type, in which compressed air is ejected from blade-tip nozzles. Rotor/engine r.p.m. ratio 340/ 35,000.

FUSELAGE: Aluminium and magnesium bulkhead and keel structure, with fiberglass skin.

LANDING GEAR: Non-retractable tricycle type. Torsion bar shock-absorbers. Goodyear wheels, size 5.00x5. Goodyear hydraulic brakes. Wheel track 3.05m. Wheelbase 2.13m.

POWER PLANTS: One Continental Model 141 air-compressor, rated at 200 gas h.p, mounted in rear fuselage. Fuel in wings and in wing-tip tanks, with total capacity of 136 litres. Oil capacity 4.5 litres.

ACCOMMODATION: Pilot and two passengers in enclosed cabin, with forward-sliding canopy. Baggage compartment with capacity of 0.79m³. Provision for carrying one stretcher and attendant.

Jane's All the World's Aircraft, 1959-60

Monte-Copter Inc. was established in 1953 in Seattle to design and build light helicopters. The first design was the Model 10, which was a two-seat machine with a large bubble canopy and a tailboom mounting a tailplane with large twin rudders. The two-blade rotor had control paddles similar to the Hiller system. It was driven by a 135hp Lycoming O-290 engine which generated cold airflow to the rotor tips. This piston engine was then replaced by two externally-mounted Turbomeca Palouste turbojets. The prototype, N68P, flew in 1955 and was later modified to become the Model 12, with a single tail fin. Monte-Copter then built the three-seat Model 15 Triphibian (N69P) which flew in 1960. This was a very streamlined machine with a boat-shaped fibreglass fuselage, forward-sliding canopy, small stub wings with sponsons to house the main wheels and a small full depth rudder. It was powered by a 200hp Continental gas generator housed in the rear fuselage feeding compressed air to the rotor tip nozzles.

R.Simpson "Airlife's Helicopter and Rotorcraft", 1998

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Technical data for Model 15 Triphibian Main rotor diameter: 10.97m, overall length: 4.65m, overall width: 3.35m, height to top of rotor pylon: 2.52m, weight empty: 545kg, weight loaded: 907kg, max speed: 158km/h, cruising speed: 120km/h, rate of climb at sea level: 335m/min, ceiling: 4570m, normal range: 160km, range with auxiliary tanks: 290km