ICAR θ-37b
Because of its insular location, the Cretan Republic was an intensive user of flyingboat in the interwar period, both for local and intercontinental connections. As with the rest of the national aeronautical sector, it initially made extensive use of foreign designs via production licenses.
In the early 30's, Dispite the introduction of θ-55 (licenced built version of S.66), it seemed obvious that the derivative of Savoia-Marchetti S.55 had reached their obsolesence limits. A new desing was required.
I.C.A.R., the national aeronautical producer, issued a call for tenders for a mid-sized flyingboat with accommodation for at least 25 passengers or 12 berths (night service). Several study offices submitted a project ranging from the most conventional to the most atypical. Against all expectations, it was precisely one of the latter that was selected. It was the first production of the newly founded S.E.M.A. ( Συνεταιριστική Εταιρεία Μηχανικών Αεροναυπηγών, Solidarity cooperative of aeronautical engineers), and not the last.
Completed in August 1936, the first θ-37 was successfully tested. It was a an all-metal high-wing monoplane with fabric covered control surfaces. Smooth sheet metal skin was used except on the forward two-thirds of the wing which had corrugated skin. The hull was of the two-step type and the rear twin tail acted as stabilizer.
The most original layout was the powertrain. power was supplied by two 900 hp H.S.K. (Hispano-Suiza-Krítis) 12Y26 and 12Y27 (opposite rotation to each over) located in the far rear part of the fuselage. They drived two contratotatives three-blades constant-speed propellers at the back of the tail. Accommodation was for a maximum of 32 passengers in four eight-seat compartments and for night service the normal seating could be replaced by 16 berths. The crew of five consisted of pilot, co-pilot, navigator, mechanic and stewardess. The aircraft was equipped with galleys, two lavatories, and a dorsal cargo hold.
Its extremely streamlined shape gaved it good speed and range for its class, and the plane became quickly a commercial success. The main market was naturally the domestics cretans airlines companies. But, in addition to consular companies, exports were particularly successful to the Caribbean and South America, with more mixed success on the European market.
The main issue with the first production aircraft was the rear section which carried most of the unusual features. Several accidents were caused by tail ruptures during takeoff or landing. This part, which concentrated significant mechanical stresses during these phases, required structural reinforcement.
The pusher layout implied that water spray fouled propellers very quickly. An articulated propeller shaft was designed. It was maneuvered by the mechanic to maintain a minimum distance between blades and water.
These developments (accompanied by more powerful engines) led to the θ-37b version, a standard to which the majority of first series aircraft were brought.
From the outset, a goods transport version was proposed. The Republican Navy ordered around forty copies for its supply needs, to which were added during the conflict the requisitioned machines. But no militarized versions were designed.
However, this did not prevent the seaplane from being used in combat missions: assault transport, parachuting, dropping of clandestine agents, supplying resistance movements....
The version which remained the latest in service was the θ-37c. It incorporated a retractable landing gear which made it an amphibious aircraft
The last military θ-37s served until the 1980s. As of 2021, 85 years after its first flight, the aircraft continues to fly as a waterbomber (or airtanker) in aerial firefighting operations in some parts of the world.
To learn more about this aircraft follow the link:
viewtopic.php?f=27&t=9839&p=210627#p210627
