Manufactured by the Società Leonar¬do da Vinci in Milan, the ‘Forlanini’ class airships (designed by Enrico Forlanini and the firm’s engineer Luigi Crescentini) may be regarded as the most successful of the Italian semi¬rigid vessels, winning a number of re¬cords during the years immediately preceding World War 1. Early versions had carried their structural girder externally, but this was eventually placed within the hull as a truss from which the central car with its crew compartment, motors and flotation bags protruded, the leading edge being glazed and an unusual tri¬plane set of control surfaces being car¬ried at each side of the F.3. To the rear of the car the propellers, arranged as pushers, were carried on outriggers with an extended linkage to the en¬gines, the reversible propellers being capable of variable pitch.

An interesting design feature of the envelope was its double surface with a space between the inner and outer fabric, which served as a ballonet to maintain the shape of the envelope. In addition a climbing well was included together with a ladder by which to gain access to a platform on top of the hull.

There were five initial ‘Forlanini’ airships with progressively improved performance, the best showing a rate of climb of 1000 m (3,300 ft) per minute. One such airship setting up an endur¬ance record of eight hours, in the course of which the average altitude maintained was 3960 m (12,992 ft) although at one time 5335 m (17,503 ft) was attained.

Perhaps the most unusual feature of the Forlanini was the construction of the tail. This did not terminate in the conventional cruciform pattern but had instead a robust ventral fin of thick section. To each side of this and below the centreline a series of high aspect ratio rudders was carried (five to a side) with biplane horizontal surfaces above and below.

A Forlanini F.3 was built to a British Admiralty order in 1913, and to be known as Naval Airship No.11, but ws appropriated by the Italian Government at the outbreak of war in 1914. Two further airships of this design, No.12 and No.13, were to be built under licence by Armstrong Whitworth but were not proceeded with due to pressures of other war work.

A considerably smaller Forlanini airship was the ‘P’ class (Piccolo, or small) with a fixed vertical fin and out rigged rudders at the ends of very wide span elevators. This model was 63.0 m (206 ft 8.3 in) in length, with a diameter of 12.0 m (39 ft 4.4 in).

P Class
Propulsion: Four FIAT S.54-A, 80 hp
Volume: 13,790 cu.m
Maximum speed: 80 km/h
Flight endurance: 24 hr
Useful payload: 6 tonne

Forlanini F.3
Type: sea patrol and bombing airship
Powerplant: two 74. 6-kW (100-hp) Fiat A six-cylinder water-cooled piston
Maximum speed 80 kph (50 mph)
Service ceiling 5480 m (17979 ft)
Range 650 km (404 miles)
Useful lift 2720 kg (5997 lb)
Diameter 20.34 m (66 ft 8.8 in)
Length 95.1 m (296 ft 11.4 in)
Volume 13800 cu.m (487,343 cu ft)

Forlanini F.3
Engines: 2 x Isotta Fraschini V5 8-cyl, 180 hp
Envelope: 421,000 cu.ft
Length: 234 ft
Diameter: 58 ft
Height: 73 ft
Gross lift: 11.5 ton
Disposable load: 4.2 ton
Speed: 40 mph
Range: 600 miles
Crew: 10

Enrico Forlanini designed and built a series of dirigibles, notably, in 1912, the Città di Milano, dedicated to his beloved home town. It showed exceptionally good characteristics of stability and controllability that won Forlanini international renown.

The F.2’s gondola was divided in three compartments: the command cabin, passenger cabin, and machine room. For safety all the material was treated with a fire suppressant and the envelope was double-skinned.

A coning tower was situated at the bow connected to a deep, V-shaped keel, which allowed access to the eight separate gas bags and the engine cars in a similar arrangement to the Zeppelins. The gass bags were in turn enclosed within an annular air ballonet positioned between the gas bags and outer cove. The 2 inch air space served the double purpose of acting as a ballonet and as an insulating air cushion to minimisw the effects of external temperature changes on the hydrogen gas.

Owned by the Royal Italian Army (Regio Esercito) and first flown on 17 August 1913, the Città di Milano completed 43 flights.

On 9 April 1914 the Città di Milano made an emergency landing during a storm, then was damaged by trees and terrain while moored. While attempting to deflate gas cells, it caught fire and was destroyed.

Propulsion: Two Isotta Fraschini petrol engine, 80 hp
Volume: 12,000 cu.m / 421,000 cu.ft
Length: 72 m
Gas cells: 12
Maximum speed: 70 km/h / 40 mph
Flight ceiling: 2400 m
Useful payload: 5 tonne