Frati's New Airplanes



This article was published in Volare magazine in Italy.


Frati's New Airplanes
by Fabrizio S. Bovi

If you think that 84-year-old Stelio Frati, the world-renown airplane designer, can rest on laurels, you are wrong. He, along with some other designers of his generation is very special people. Designing, creating is their source of energy. Mr. Frati is working from home now, and two new different airplanes are coming to life on his drawing board in his apartment in downtown Milan. They are a transport twin turboprop (F.2500) and a small two-seat jet (F.1000).

As usual, Mr. Frati preferred understatement. He pointed out that his new planes are "The evolution of ideas I already had in the past." But he fails to point out that they were such leading-edge ideas that much time was needed to push them forward. It is on the other hand true that the F.2500 and F.1000 show the same sleekness and grace as all his previous creations.



We gave the airplane three-views to Bruno Giardino, who works with the car designers Giugiaro and Pininfarina, and asked him to give us artist's renderings. You can see the results in these pages.

"The F.1000 twin-turboprop derives from the 19-seat F.3000 twin jet developed some 15 years ago" Mr. Frati explained. "The F.3000 had to be powered by two 3,000-lb thrust Garrett TPE 731 engines. It was meant to compete with the Dornier 328. The cabin was the roomiest in its class, with seats arranged on three rows, overhead bins and toilets. Unluckily, success did not smile on this aircraft: SIAI Marchetti scrapped its production from its programs, and General Avia, another company in the loop, which had already started manufacturing the first engineering mock-up, also gave up."



The F.2500 commuter maintains the general architecture of the F.3000, but it has been modified to transport freight from and to small airports. Those whose runways are shorter than 1,200 meters, are becoming more and more important, due to the increasing congestion at the larger ones. And, in fact, the US government's SATS project calls for the building of 5,400 new facilities within 2010.

Frati told us about his new airplane: "In order to meet the new demands, I have conceived a twin turboprop in the 1,200 shp class. The installed power and the not supercritical airfoil (series NACA 63) give the aircraft good STOL characteristics and a satisfactory cruise speed without increasing the moment coefficients too much".



The airplane will be able to operate from grass strips, and is fitted with a large rear ramp equipped with an electrically operated winch. The winch will be used to load as many as nine different types of containers according to the IATA standard (the size of model 17 is 148x148x107 cm), for a total payload of up to 3,200 kg."

Mr. Frati also underscored that the cargo hold volume is 20 cu.m while the floor area is 11.70 sq.m. The large access door and the need to have a hold entirely free from obstacles, resulted in the installation of cable-operated controls for the rudder and tail plane. They run on the cabin ceiling and have large pulleys that provide for the rigid transmission.



The solutions adopted to simplify the airframe construction as much as possible are particularly interesting. Based on the experience gained in the past with the F.600 Canguro, the structure of the F.2500 is square and consists of a number of identical frames resulting from the assembling of four L-shaped members. The pressurization (up to 25,000 feet) could be limited to the cockpit, which is isolated from the cargo hold.

"These features make the F.2500 suitable for manufacture also in the countries where the experience in aeronautical constructions is limited, like the developing ones", Mr. Frati explained. "You do not need a computer program to draw the fuselage sections; a ruler, a triangle and the applicable frame tables are enough, like when we built models in the past."

The wing, designed with the safe life criterion in mind, that is for maximum safety and high structural margins, has a six-meter, single-piece center spar to which there connect two end spars from a lightened extrusion. The wet wing contains two tanks located in the area outboard of the engine-affected area.




"The F.2500 meets FAR 23 requirements applicable to commuters with weight up to 19,000 lb (8,620 kg), and is very close to the limits. It was in fact decided to avoid falling in the category covered by the more burdensome FAR 25", noted Stelio Frati. And added: "I do believe that this aircraft, if it is eventually built, might be a successful one. In the end, as many as 500 CASA Nurtanio C.212s have been sold. And the Aviocar is smaller than the F.2500".

Mr. Frati also told VOLARE that the small F.1000 two-seat jet is only a concept aircraft so far. It is a scion of the family that includes the F.4/F.7 Rondone, the F.8 Falco and the SF.260.

"The idea of the small jet is over 50 years old." noted Frati. "Back in 1952, I designed the F.5 Cobra for Caproni. Turboméca developed the Arbizon, a 200-kg thrust turbofan engine specifically for it. Despite its aggressive appearance, the F.1000 is only a lighter (nearly 100 kg) SF 260. If it is built by exploiting the currently available technologies, it will cost definitely less than the SF.260 TP". The F.1000 has been conceived around its engine. The dorsal air intake protects the engine from foreign object ingestion, especially on grass strips. Cruise speed should be about 500 km/h, the maneuverability characteristics should be similar to those of the SF.260.

"I look forward to the availability of the 750-lb thrust Williams engine powering the Eclipse prototype, the innovative twin-jet developed in the USA. The Eclipse has revolutionized the biz-jet sector. The F.1000 could do the same in the now fairly depressed sector of the private airplanes. I hope so."