Stelio Frati

by James Gilbert

James Gilbert is editor and publisher of Pilot Magazine in England.

Stelio Frati was born in Milan, Italy, in 1919; he'll thus be eighty in 1999. He was mad about aviation even as a child and was an aeromodeller of talent, being Italian national champion in powered free-flight models in 1940. One of his model sailplanes of that time unofficially beat the world endurance record, flying for two and a half hours-and that was before radio control, remember.

Frati studied at the Milan Polytechnic from 1938 to 1943 and graduated as a mechanical engineer-the school didn't have an aeronautical section till later. In the Milan Polytechnic was the "Centro Studi ed Esperienze per il Volo a Vela" (CVV), where Frati helped design various sailplanes.

The Assalto Radioguidato

During 1941-43, he contributed to the design of the Assalto Radioguidato, a kind of flying bomb powered by a big radial engine. A pilot was supposed to get this monster airborne, then jettison its landing gear and later bail out, leaving the crew of another plane to direct the "bomb" to its target by radio control. It was an unsophisticated device, the brainchild of the chief of staff of the Italian Air Force, and intended to be used against Allied shipping in the Mediterranean. Five were built and two flown, but they were never used in action.

By 1944 the war was happily over for Italy, and Frati's old school did now have an aeronautical section. He was invited back as a deputy to the professor and stayed ten years, teaching and expanding his knowledge of aircraft design.

Thereafter he became a freelance airplane designer, selling his projects once they were developed to whichever Italian manufacturer wished to build them. The first was a (frankly ugly) 20 hp motorglider, the Ditta Movo F.M.1 Passero (Sparrow), which despite its low power yet managed a 94 mph maximum speed.

The first of Frati's sleek low-wing monoplanes was the 1951 F.4 Rondone (Swift), two seats, all wood, with an 85 hp Continental-although one Rondone was powered with a 65 hp Walter Mikron engine from Czechoslovakia. The prototype Rondone was actually built by the gliding section of the CVV in Milan. The ten or twenty production Rondones had a C90 engine and were built by Aeronaut. Lombarda and Ambrosini.
Ambrosini F.4 Rondone: 65 hp Walter Mikron engin

These Rondones further established Frati's enduring reputation for designing light planes with phenomenal speed for the power. Their maximum (on just 90 hp, remember) was 160 mph; and one, flown by Inginio Guagnellini, actually held several world speed records in the early 1950's, achieving 169 mph over 100km.

F.5 Trento

His next design was an all-wood tandem two-seater powered by a tiny high-revving French jet engine, a Turbomeca Palas. This F.5 Trento had a structure that was an adaptation of glider techniques. The choice of wood was perhaps not so bizarre as you might think: early Marks of the very successful British de Havilland Vampire jet fighter were also made of wood. Only a prototype Trento was ever built, in 1952 by Caproni-who twelve years earlier, in 1940, had built Italy's first "jet" aircraft, the N.1, which employed a piston engine to drive a three-stage ducted fan. The Trento had no mean performance: a maximum of 242 mph on just 330 pounds of thrust.

Pasotti built the sole prototype of the F.6 Airone (Heron), a four-seat twin not unlike a mini-Apache in appearance, but built entirely of wood and powered by two C90's-though it was offered with 105 hp Walter Minors or 135 hp Lycoming 0290D's.

The F.7 designation was given to a three-seat adaptation of the earlier F.4-still with the C90. The F.7 first flew on February 10, 1954; ten were built by Pasotti.

F.8L Falco

The F.8 was the famous Falco (Hawk); and it was also the first design to have quite unmistakably the famous "Frati" look to it: beautifully streamlined, marvelously slender and graceful, with not an unnecessary extra square inch of wetted area of cross-section. The prototype Falco, with a C90, first flew on June 15, 1955, which is nearly forty-five years ago. To better appreciate how advanced it was, reflect that it was exactly contemporary with the Piper Tripacer!

The first production Falco was the F.8L Series I, with a 135 hp Lycoming 0-290-D2B and an enlarged wing by comparison with the prototype; ten of these were built by Aviamilano, and twenty of the Series II with a 150 hp Lycoming 0-320-A2A. Another company, Aeromere, built sixty of the Series III Falco America, which still had the 0-320 and the fixed-pitch prop, but was in other ways improved. The final production version was the Super Falco Series IV, with the 0-320-B3B engine of 160 hp, a constant-speed prop, and improved soundproofing. Twenty of these were built by Laverda, motor scooter manufacturers and successors to the old Aeromere company.

The 1956 F.9 Sparviero (Sparrow Hawk) was a single-engine version of the little Airone twin; one example only was built, also by Pasotti. It was powered by a big old 240 hp Hirth inverted V-8, which gave it a maximum speed of 200 mph; the Hirth was later replaced by a 250 hp Lycoming GO-435-C2.

F.14 Nibbio

The prototype F.14 Nibbio (Kite Hawk) first flew on January 16, 1958. The Nibbio was clearly derived from the Falco and was essentially a scaled-up four-seat version of it with a 180 hp Lycoming and a 204 mph maximum speed. Ten were built, with deliveries beginning in 1959. Cruise speed was 185 mph.



The first F.15 Picchio (Woodpecker) flew on May 7, 1959. It was a three-seater with the same 160 hp engine as the two-seat Falco, and with hinge-up cabin doors instead of the Falco's sliding canopy. It was the first Frati-designed lightplane to have some metal in its structure: a thin sheet of aluminum alloy was bonded to the plywood skin as a tough exterior shell. Procaer built the Picchio: fifteen of the F.15 three-seater version with the 160 hp Lycomings, 54 F.15A's with four seats and a 180 hp Lycoming and a 195 mph top speed; and 35 F.15B's with increased wing area, enlarged wing tanks and, in consequence, a 6 mph slower speed but 110 pounds more useful load, at 1,100 pounds. This B model also had all-metal control surfaces, and it was the first Frati design to gain an FAA type certificate. There was also a F.15C model with a 260hp Continental IO-470-E.

It was a Picchio, you may remember, that the great Max Conrad was ferrying across the Atlantic when he had engine problems in mid-ocean. He was able to nurse it as far as the Greenland coast, where he put it down gear-up on a glacier and was happily rescued unhurt.

F.400 Cobra
Procaer also built the 1960 F.400 Cobra, an exciting two-seat jet powered by an 880 pound thrust Turbomeca Marboré engine. Maximum speed was 360 mph, economy cruise 236 mph, useful load 1,323 pounds, initial climb 2,350 fpm. The Cobra had the same kind of structure as the Picchio, metal-clad wood; but there seems to have been no more of a market for wooden two-seat jets in 1960 than there had been eight years earlier. The Cobra came to naught: the prototype was destroyed in a crash, and the second prototype, with four seats and a 1,058 pound thrust engine, was never completed.

SF-260

Thereafter Stelio Frati designed in metal. He had done marvelous work in wood: that thin, graceful airframe of the Falco was actually stressed to an ultimate 8.7g at gross weight, 9.4g at aerobatic weight; yet equipped and ready to fly, it weighs no more than 1,200 pounds empty. You and I may know that wood is as fine a material for airplanes as metal-in some important ways, better-but the mass of the buying public has doubts about the durability of wood and prefers metal airframes. Actually, the 1959 Mooney had a wood spar and several have broken in flight giving the early Moony's a bad name.

In the end you must give the market what it wants. And certainly Stelio Frati's first all-metal airplane has been a considerable success, built and sold in larger numbers than any of his previous designs. Its prototype was named the F.250 (because it was powered by a 250 hp Lycoming) and first flew on July 15, 1964. Production airplanes, all built by SIAI Marchetti, had a 260 hp Lycoming and became the SF.260. Those first off the line were designated the SF.260A and were for the civil market; but the bulk of the production run has been the SF.260M version, a two/three seat military trainer version bought by a dozen different air forces for teaching students basic flying skills, IFR, aerobatics, night and formation flying. There is a tactical version with weapon pods, the SF.260W Warrior; and a surveillance and rescue variant with radar and photo-recon gear in wing-tip pods, the SF.260SW Sea Warrior. While you can still buy a purely civilian SF.260 from the SIAI Marchetti factory, the type has in truth become too expensive for the private owner, at some $140,000. (In 1975)

The SF.260 has the same fabulous handling and aerobatic capabilities as the Falco, and a 75% cruise at altitude of 165 knots in the civilian version; the useful load, though, is modest for a 260 hp airplane at 1,000 pounds. However, expect a long take off run and a very unstable plane at a gross weight of 2,800 lbs. until you get above 130 knots.

SF.260's imported into the United States were marketed as the "Waco Meteor"-a bizarre fantasy on the part of the importer, one Alexander Berger, for there was no possible connection with the fine old Waco airplanes of the 1930's. In recent years two of these "Waco Meteors" have been seen at U.S. air shows performing an aerobatic duet of synchronized maneuvers. Female racer Mary Knapp had one and used to come in second only to Judy Wagner's hot Bonanza-performance. Indeed the aircraft holds several world speed records in its class: 1,000 km closed circuit at 200.04 mph, 100 km at 229.6 mph, and Las Vegas to Los Angeles as a point-to-point record at 214.08 mph. The SF.260's book max is some thirty mph better than a stock Bonanza with the same power. Of course the truck like Bonanza is more comfortable to fly in.

Stelio Frati and the rest of General Avia ("My family", says Frati)
In 1970 Stelio Frati set up the General Avia company and bought a well-equipped shop where, with the help of a staff of two dozen, he now builds his own prototypes. The first of these was the F.20 Pegaso (Pegasus), a 5-6 seat twin with two big 300 hp Continentals. Though it gained Italian and FAA certification, the company that was to have built the Pegaso, Italair, was unable to find the necessary financing and has closed its doors.

Frati's latest is the F.600 Canguro (Kangaroo), a high-wing fixed-gear utility twin with two 310 hp Lycomings-a project much along the lines of the Britten-Norman Islander. In addition, he is continuing to develop the Picchio. The 1968 F.15E model of this had a structure completely re-engineered in metal, and 300 hp; the latest variant is the F.15F Delphino (Dolphin) with 200 hp and a sliding canopy like the Falco and the SF.260 instead of the Picchio's original hinged doors. However there are as yet no firm plans to manufacture the Delphino.


This brief canter through the different designs of Stelio Frati reads necessarily rather like a catalogue, for which my apologies. But even among European pilots the full range of his work is little-known; and any discussion of one of his designs (the Falco, for instance) invariably starts someone wondering aloud what else he has done. My account here is, I think, the first listing in English of Frati's designs.

If you are surprised that so many of his excellent designs never made it into production, that, I'm sorry to say, is the European way. The market for general aviation craft in Europe is far smaller than in the USA, and Stelio Frati's record of some 750 fine lightplanes commercially manufactured and sold from his designs is one matched by few other European designers.

Signor Frati is, by the way, an excellent pilot, who qualified originally in one of his own designs--a Falco.

James Gilbert
London, July 1978

More details on the SF260 development.