Savoia-Marchetti S.55

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Savoia-Marchetti S.55
An S.55P of Aeroflot circa 1933
General information
Type	Flying boat
Manufacturer	Savoia-Marchetti
Designer	Alessandro Marchetti
Primary users	Società Idrovolanti Alto Italia (Savoia) Regia Aeronautica Spanish Air Force Royal Romanian Naval Aviation
Number built	243+
History
Introduction date	1926
First flight	August 1924
Retired	1945
Variants	Savoia-Marchetti S.66

The Savoia-Marchetti S.55 was a double-hulled monoplane flying boat designed and produced by the Italian aircraft manufacturer Savoia-Marchetti. It was designed to perform both commercial and military applications.

The S.55 featured numerous innovative design features. While the passengers and cargo were housed within the twin hulls, the flight crew controlled the aircraft from a cockpit located in the thicker section of the wing between the two hulls. The S.55 had two inline contra-rotating propellers, mounted in tandem. The engines were canted sharply at an upward angle. Two wire-braced booms connected the triple-finned tail structure to the twin hulls and wing.

During August 1924, the S.55 performed its maiden flight. Shortly after its introduction, the S.55 set multiple records for speed, payload, altitude and range. Numerous flying boats saw service with the Regia Aeronautica and export operators such as the Spanish Air Force and the Royal Romanian Naval Aviation as reconnaissance bombers and maritime patrol aircraft. While some examples were active by the outbreak of the Second World War, the type only played a marginal role in the conflict due to their age.

The Savoia-Marchetti S.55 was a double-hulled thick-section cantilever monoplane flying boat that was designed to perform both civilian and military operations, dependent upon equipment fitout. In general terms, its design was largely original and possessed numerous features that increased its practicality as a platform for naval military tasks such as minelaying and torpedo attacks.^[1] Various aspects of the flying boat eased aspects of its operation; it was relatively easy to dismantle for ground transport; the wings comprised three detachable sections while each of the hulls could be entirely detached from the centre section along with the tail unit. The engines could be readily inspected at all times, even during flight.^[2]

The twin hulls of the flying boat were spaced roughly 13 feet apart, ran for just over half of the total length of the flying boat, and had a single-step V-shaped bottom. They were constructed in a manner that permitted the internal space to be configured into a series of cabins, accommodating a maximum of 12 passengers, if so required.^[3] The flying boat's cockpit was positioned in the centre section of the leading edge, between the two hulls; a passageway permitted personnel movements between the cockpit and the cabin space.^[4] On militarised flying boats, the stern of each hull would accommodate a tail gunner from which a relatively favourable range of fire could be obtained.^[3] Underneath the middle of the flying boat's centre section was an intentionally clear space of roughly eight foot; this space was suitable for the mounting of either torpedoes or mine-laying apparatus.^[5]

The outer wing sections had a pronounced dihedral and sharply tapered from root to tip.^[6] The leading edge swept back about 15 degrees while the trailing edge was only slightly inclined. The wing was furnished with balanced ailerons that had an inclined axis. The tail surfaces were carried by two pairs of V-shaped outriggers; the top beam of each outrigger was attached to the upper surface of the centre section, near the rear main spar, while the lower beam was attached to the sternpost of the hull.^[3] They were cross-braced and each had a vertical strut at its forward and rear ends. Mounted on top of the rectangular horizontal stabilizing surface were three triangular vertical fins, the trailing edges of which were outfitted with hinged balanced rudders.^[3]

It was powered by a pair of Isotta Fraschini Asso 500 V-12 piston engines, each capable of providing up to 400 hp. These engines were arranged in tandem within a streamlined nacelle that was mounted high above the centre section of the aircraft, supported by a series of struts.^[5] The forward engine drove a tractor propeller while the rear engine had a pusher propeller. Cooling of both engines was achieved via a single radiator that was mounted in the nose of the nacelle.^[5] The engine nacelle was inclined, placing the line of thrust from the engines at roughly eight degrees off from the horizontal, this exerting a constant but slight upwards push throughout flight. A key reason for this arrangement was to direct the generated slipstream on to the tail surfaces.^[5] Level flight could be maintained with only the one operational engine.^[7]

During August 1924, the S.55P prototype conducted its maiden flight. Throughout 1926, this same prototype set 14 separate world records for speed, altitude and distance with a payload.^[8] The type's greatest successes, however, were its many flights between Europe and the Americas.

The First aerial crossing of the South Atlantic had been made in stages in 1922 using three different Fairey III machines, and a subsequent crossing was made by the Dornier Do J Plus Ultra in January 1926 with a single stop at the Cape Verde Islands. One year later, the first S.55 crossing was made by the Santa Maria under Francesco de Pinedo.^[9] After flying south to Bolama, at that time in Portuguese Guinea, they hoped to cross the ocean without another stop but were forced down at Cape Verde, reaching Brazil on 23 February 1927. After the crossing, the aircraft was traded to Brazil for coffee beans.^{[citation needed]}

The Brazilian João Ribeiro de Barros and his crew of three made another crossing in S.55 "Jahú" on 24 April 1927. Departing from Santiago Island, he crossed the Atlantic in "Jahú" and landed at Fernando de Noronha Island, Brazil.^[10][11]

Pilots Francesco de Pinedo and Carlo del Prete took off from Sesto Calende, Italy, in an S-55 on 13 February 1927. Four months later, on 16 June 1927, they arrived back in Italy, having flown nearly 48,280 km (30,000 mi) in 193 flying hours and having made just over 50 stops, including Rio de Janeiro, Buenos Aires and New York City.^[12]

On 20 June 1928, S.55 I-SAAT Santa Maria, piloted by Ten. Col. Umberto Maddalena of the Italian air force, located survivors of Arctic explorer Umberto Nobile's crashed airship Italia on an ice floe about 120 km (75 mi) northeast of Nordaustlandet, Svalbard.^[13]

The Italian Air Marshal of the time, Italo Balbo, became famous for organizing a squadron of S.55s for Atlantic crossings, culminating in his 1933 flight with 24 aircraft to Chicago's Century of Progress International Exposition. On 1 July 1933, General Balbo commanded a flight of S-55s from Orbetello, Italy, completing the flight in just over 48 hours, maintaining a tight "V" formation. These large fleets of aircraft were sometimes called a "Balbo".^[14][15]

Numerous aircraft were introduced by the Regia Aeronautica and served as a long-range bomber and patrol aircraft. By the Second World War, the service's S.55 fleet was no longer considered to be serviceable and the type was only ever held in reserve.^{[citation needed]}

S.55

Prototypes and original production model delivered from 1927 to 1930, 90 built, including two prototypes.

S.55C

Civil variant delivered from 1925 to 1926, eight built.

S.55P

Improved civil variant with enlarged hull for ten passengers and enclosed cockpits delivered from 1928 to 1932, 23 built.

S.55A

Military variant delivered with 418 kW (560 hp) Fiat A.22R engines, 16 built.

S.55M

Variant with some wood structures replaced by metal, seven built by Piaggio in 1930.

S.55 Scafo Allargato

Widened and deepened hull and enclosed cockpits, 16 built by Savoia-Marchetti and 16 built by CANT.

S.55 Scafo Allargatissimo

Variant with greatly enlarged hull, 20 built by Savoia-Marchetti, 16 built by Macchi and six built by CANT.

S.55X

Variant fitted with Isotta Fraschini Asso 750 engines for North Atlantic formation flights, later armed and used as a reconnaissance-bomber. 25 built.

 Kingdom of Italy

• Aero Espresso Italiana
• Società Aerea Mediterranea

 Soviet Union

• Aeroflot

 United States

• Aero Transport Company d.b.a. AirVia.
• Marine Air Transport Co.
• Alaska Airways^[16]

 Kingdom of Italy

• Regia Aeronautica

 Brazil

• Brazilian Navy (eight flying boats)

Spain (1937)

• Spanish Air Force

 Romania

• Royal Romanian Naval Aviation (seven flying boats)^[17]

The last remaining example is preserved in Brazil, at the TAM "Asas de um sonho" museum, at São Carlos, São Paulo. The aircraft, registered I-BAUQ and named "Jahú", was the S.55 used by Commander João Ribeiro de Barros in his crossing of the South Atlantic in 1927.^[18]

Data from Jane's all the World's Aircraft 1928,^[19] National Advisory Committee for Aeronautics^[20]

General characteristics

• Crew: Two pilots and 3-4 other crew members
• Length: 16.5 m (54 ft 2 in)
• Wingspan: 24 m (78 ft 9 in)
• Height: 5 m (16 ft 5 in)
• Wing area: 92 m² (990 sq ft)
• Empty weight: 5,750 kg (12,677 lb)
• Max takeoff weight: 8,260 kg (18,210 lb)
• Powerplant: 2 × Isotta Fraschini Asso 500 V-12 water-cooled piston engines, 370 kW (500 hp) each mounted in tandem, plus one Garelli piston engine driving oil distribution placed between the two main engines^[21]
• Propellers: 2-bladed fixed pitch tractor and pusher propellers

Performance

• Maximum speed: 205 km/h (127 mph, 111 kn)
• Stall speed: 105 km/h (65 mph, 57 kn)
• Range: 1,200 km (750 mi, 650 nmi) to 2,200 km (1,400 mi; 1,200 nmi)
• Time to altitude: 1,000 m (3,300 ft) in 9 minutes; 2,000 m (6,600 ft) in 25 minutes; 3,000 m (9,800 ft) in 45 minutes

Related lists

• List of interwar military aircraft
• List of flying boats and floatplanes

• Axworthy, Mark (September–October 1999). "Flank Guard: Romania's Advance on Stalingrad, Part Two". Air Enthusiast (65): 72–75. ISSN 0143-5450.
• Boyne, Walter J. (2002). Air warfare: an international encyclopedia, Volume 1. ABC-CLIO. ISBN 978-1-57607-345-2.
• Garello, Giancarlo (October 2000). "Courrier des Lecteurs" [Readers' Letters]. Avions: Toute l'Aéronautique et son histoire (in French) (91): 3. ISSN 1243-8650.
• Grey, C.G., ed. (1928). Jane's all the World's Aircraft 1928. London, UK: Sampson Low, Marston & company, ltd.
• Yenne, Bill (1997). Batchelor, John (illustrations) (ed.). Seaplanes & flying boats. New York, US: BCL Press. ISBN 1-932302-03-4.
• Sicolo, C. (2017). Le onde smarrite della Tenda rossa (in Italian). Albino, Italy: Sandit Libri. ISBN 978-88-6928-259-1.
• Tucker, Spencer C. (2011). World War II at Sea: An Encyclopedia (2 volumes): An Encyclopedia. ABC-CLIO. ISBN 978-1-5988-4458-0.
• "Savoia seaplane S.55 : military or commercial" National Advisory Committee for Aeronautics, 1 March 1927. NACA-AC-33, 93R19117.

• Savoia-Marchetti S-55 Archived 17 March 2017 at the Wayback Machine