Kaman K-225
The Kaman K -225 is a fitted with a Flettner rotor helicopter double the Kaman Aerospace Corporation.
History
His first helicopter designed Charles Kaman mid-1940s. The on January 15, 1947 for the first time flown K -125 used on the rotor blades mounted so-called servo - flaps (servo flaps ) an invention of Kaman, which should reduce the control forces and stabilize the rotor blades. Was powered by a Lycoming piston engine with 125 hp. The K -125 was the basis for the K -190 multi-purpose helicopter that flew in December 1948 for the first time and in limited numbers with a 190 hp Lycoming O -435 payable piston engine was produced. The K -190 was the first helicopter from Kaman, who received a type - approval
The K -225 was developed from the K -190, which retained the structural design of its predecessor and a Lycoming O -435 -A2- piston engine started with a continuous output of 225 hp. The prototype and the first ten series machines were configured for the " spray insert " in agriculture. The State of Mississippi acquired a special version with an enclosed cabin for use in the field of oil exploration. The Turkish government bought some copies for training purposes and the agricultural use.
In July 1949, the U.S. Navy acquired two K -225 at a price of 25,000 dollars to gain experience with the unconventional rotor configuration and the new servo -flap system of the rotor. The Kaman as XHK -225 (Experimental Helicopter Kaman 225) designated machines were subjected to Naval Air Test Center ( NATC ) at Patuxent River, Maryland in-depth testing.
On December 10, 1951 flew for the first time a retrofitted XHK -225, in which the piston engine 502-2 (YT -50) turbine was replaced with 175 WPS by Boeing and thus was the world's first powered with a gas turbine helicopter. Despite the lower power the flight performance were significantly better, because the turbine had only half the weight of the piston engine. The XHK -225 was then further developed to Kaman HTK.