|Nagler VG-1 "Vertigyro"|
A little known Compound-type system was developed by the now-gone Nagler Helicopter Company in the early 1960s. The craft was a one-of-a-kind system, which certainly could be discerned at first look at the machine.
The prototype was constructed in only six months from a collection of existing aircraft parts and pieces. It used a Piper "Colt" fuselage and powerplant (a Lycoming four-cylinder 108hp engine), while the over-fuselage rotor system and controls came from a French Sud-Aviation "Djinn" helicopter.
Another power source existed with a Garrett gas turbine compessor, which provided the compressed gas pressure necessary to power the rotor-tip-mounted propulsion units. A number of new components were incorporated in the design, including the fins, certain control components, and new skinning at portions on the rotor mounting area.
The design of the strange little VTOL then had helicopter controls inserted in place of the standard Colt controls, although the elevator trim control system of the Colt was retained. Yaw control of the "Vertigyro" during the hovering condition was a complicated technique by movement of the rudder within the turbine exhaust slipstream. The movement was controlled by the pilot using movement of the rudder pedals.
A twist-grip pitch control lever in the cockpit enabled control of the turbine air-bleed valve. Interestingly, the turbine always operated at the same speed.
The company claimed a number of advantages to its unique design, including outstanding operating economics and better performance in either operation as an autogyro or pure helicopter.
The plane's operating technique involved flying the plane in the pure helicopter mode with all the power directed to the rotor with the front propeller feathered, or the pure autogyro condition with all the power being provided by the conventional front propeller.
Initial flight testing of the "Vertigyro" occurred in January 1964. Both the different flight characteristics of the plane were successfully demonstrated.
The success saw the company start development of a VG-2 version with a more powerful engine. Neither the VG-1, or any of its follow-ons, though, would ever make it to production.
S.Markman & B.Holder "Straight Up: A History of Vertical Flight", 2000