On 4 December 1956, an Italian test pilot pointed a small silver aeroplane downhill from above 40,000 feet and became the first man to take an Italian-designed, Italian-built aircraft through the sound barrier.

The aircraft was the Aerfer Sagittario 2. Two were built. It had already lost the competition it was designed for, and it was flying on the wrong engine because the right one did not exist yet.

Its successor would carry a second jet engine on a retractable mast behind the cockpit. Both are now in a museum on a lake north of Rome, and almost nobody outside Italy has heard of either.

A Trainer With New Wings

Sergio Stefanutti had a problem that shaped everything he built: post-war Italy had no usable wind tunnels. If you wanted to know how a swept wing behaved, you had to go and fly one.

So in 1951 he took an Ambrosini S.7 — a two-seat piston trainer — and gave it wooden swept wings and tail, with 45 degrees of leading-edge sweep. More sweep than an F-86 Sabre. It first flew in that form on 5 January 1953. Then he pulled the piston engine out and put in a Turboméca Marboré turbojet of about 840 lbf, with a nose intake and the exhaust under the fuselage ahead of the tailwheel, which had to be heat-shielded. One was built.

That was the Sagittario 1: a wooden aerodynamic testbed, flown because there was no other way to find out.

The Sagittario 2 that followed was a real fighter. Rolls-Royce Derwent 9 in the nose, inclined about twenty degrees, exhausting under the mid-fuselage — which left the entire rear fuselage free for fuel and gave it unusually good endurance for its size. Two 30 mm Hispano-Suiza cannon. Pressurised cockpit, ejection seat, bubble canopy, braking parachute.

The engine was a compromise and everyone knew it. Stefanutti had designed the aircraft around the Bristol Siddeley Orpheus — the same engine the Fiat G.91 would use. The Orpheus was still in development. So the prototypes flew on Derwents.

Nineteen Minutes of Terror, Then a Fence

Costantino Petrosellini made the first flight on 19 May 1956, and half a century later wrote down what it was like. It is one of the better first-flight accounts in aviation, partly because so much went wrong before the aircraft ever left the ground.

On 1 May, at Pratica di Mare, a crane dropped it.

On 18 May, with the entire air staff assembled to watch, Petrosellini scrubbed the flight over a single fuel-pressure warning lamp. The Chief of Staff of the Italian Air Force, General Raffaelli, walked over and put a hand on his shoulder.

He flew it at first light the next morning. Take-off at 120 knots, 2,900 kg, landing run about 1,800 metres.

Five weeks later he flew it past the presidential tribune at the Fiumicino air display at around 550 knots and pulled a 360-degree turn at about five g. Foreign air attachés came to Pratica di Mare the next day for a private look.

Then on 20 July an engine failure forced him to put the aircraft down on the runway then under construction at Fiumicino, damaging it. Petrosellini left for Alitalia. Lieutenant Colonel Giovanni Franchini took over the test programme.

The Istituto Luce newsreel from 1956 — the only period film of the aircraft in general circulation.

Mach 1.1, Downhill

On 4 December 1956, Franchini took the Sagittario 2 above 40,000 feet over Pratica di Mare and put the nose down. It reached Mach 1.1.

It is worth being precise about what that means, because the claim gets inflated. The Aeronautica Militare’s own formulation is the careful one: the first aircraft designed and built in Italy to exceed the speed of sound. Italian pilots had already gone supersonic in foreign aircraft — Petrosellini himself had reached Mach 1.06 in a Super Mystère at Brétigny before the Sagittario’s flight. And it was a dive, not level flight.

Franchini was born at Varana di Monfestino in 1918, was a decorated wartime combat pilot, and ended his career as a four-star general. A bronze monument to him was unveiled in his home village in 2002. No words of his about the flight itself appear to survive; the only moving-image record is RAI footage held in the Quirinale archive.

The Competition Was Already Over

Here is the part that makes the whole story faintly tragic.

NATO had issued NBMR-1 in December 1953 — a specification for a lightweight tactical strike fighter able to operate from grass and roads, hit Mach 0.95, and weigh under 4,700 kg loaded. Ten submissions came in. Nine of them were built around the Orpheus, whose development the Americans were funding.

The first results were announced on 30 June 1955: Breguet Br.1001 Taon, Fiat G.91, Dassault Mystère XXVI. The Sagittario 2 was not among them. After comparative trials at Brétigny in September 1957, the G.91 was declared the winner in January 1958.

So Italy’s first supersonic aircraft flew supersonic eighteen months after losing the competition it was built for — and lost it to another Italian aircraft.

The Ariete and Its Retractable Engine

Stefanutti kept going. The Aerfer Ariete — Ram — first flew on 27 March 1958, and its solution to the thrust problem is the reason anyone should remember it.

It kept the Derwent 9 as the main engine. Behind the cockpit, a dorsal intake could be raised into the airflow to feed a second engine: a Rolls-Royce Soar of 8 kN, exhausting at the tail. For take-off, climb and combat sprint you put the mast up and had two engines. The rest of the time you retracted it and flew clean.

Jane’s and Air Enthusiast credit the Ariete with 227 m/s of climb and 12,000 metres in 4 minutes 20 seconds. Those figures appear in no Italian source, including the Aeronautica Militare’s own museum page, and 227 m/s from 24 kN of total thrust on a 3,535 kg aircraft is extraordinary. Treat them as a single-source claim, plausible as an instantaneous zoom figure and implausible as a sustained rate.

The retractable intake was also the aircraft’s worst feature: it repeatedly failed to deploy cleanly, or deployed on its own during manoeuvres. Two Arietes were completed; only one is documented as having flown. Test results fell short and the Aeronautica Militare declined to buy.

An Italian-language survey of Stefanutti’s Ariete, the unbuilt Leone and the rest of the line.

The Lion That Was Never Finished

The last of them was to be the Aerfer Leone — a genuinely supersonic interceptor with a 50-degree wing, a supersonic intake with a radar-carrying centrebody, an Orpheus main engine and a de Havilland Spectre rocket, throttleable and restartable in flight, in place of the Soar.

It was never completed. Italian sources say the prototype was around 80 per cent built when funding was diverted in 1960 to licence-production of the American Hawk surface-to-air missile, which required building up an Italian electronics industry and led to the creation of Selenia. Another account says the programme was simply abandoned in 1958 in favour of the G.91. A third says it was cancelled under American pressure. One source says only a wooden mock-up ever existed. Petrosellini himself called the cancellation political and industrial.

They cannot all be right, and there is no way to settle it from the published record.

What is not disputed is the epitaph. The Aeronautica Militare’s own museum catalogue introduces the Ariete as part of a series, and does not soften the adjective.

A colleague of Stefanutti’s from the Naples design team put it more sharply still. Asked years later what the Sagittario programme had achieved, Professor Mario Calcara is recalled as saying that they had worked like artists — for the museums.

Which is exactly where both aircraft are. Hangar Skema, Vigna di Valle, on the shore of Lake Bracciano. Two of the four aeroplanes Italy built to prove it could still design fighters, sitting a few metres apart, one of them the first Italian machine ever to go faster than sound.

Sources: Aeronautica Militare / Museo Storico dell’Aeronautica Militare; Costantino Petrosellini, “Dieci lustri”, Aeronautica (AAA), July 2006; Leonardo corporate history; Italian and English Wikipedia; Aeromedia; Francesco Fortunato / fremmauno.com; Archivio Storico della Presidenza della Repubblica.