12/31/2009. In 1977 Dott. Ing. Stelio Frati developed the all-metal two-seat F.15F Delfino (Delphin) version of his F.15 Picchio (Woodpecker) series that had been produced by Procaer (Progetti e Costruzioni Aeronautiche) of Milan. The sole example (c/n 39A) was produced at his company Costruzioni Aeronautiche General Avia at Milan, Italy.

Fitted with a 200 hp Lycoming IO-360-A1B engine, and registered as I-PROL, it was first flown on October 20, 1977. Planned production by Procaer did not materialize and the project was abandoned. Reportedly the aircraft crashed into Lago di Annone on October 14, 1984.

In the 1990s the program was revived involving Eurospace Costruzioni Aeronautiche (Rome, Italy) for marketing, HOAC (Wiener Neustadt, Austria) as an agent and Sokol (Nizhniy Novgorod, Russia) for series production. First flight by one of the two prototypes took place in November 1994, they were designated Eurospace F.15F Excalibur and registered I-EXCA (c/n unknown) and OE-VPY (c/n 15-002) .

However, this project fell through as well, reportedly leaving Sokol with a number of unfinished aircraft frames, parts and components for up to thirty aircraft. In 2000 at least two airframes were shipped to the USA to be finished by private owners.

Douglas R. Karlsen of Deland, Florida fitted one with a (derated) 400 hp Allison 250-B17C turbine engine and registered N24VK (as a Karlsen K7) it first flew on May 10, 2002. Subsequently it was fitted with a 285 hp Continental IO-520 piston engine, as seen in the picture above.