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Cretan AU random FD drawing
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Author:  raafif [ November 28th, 2022, 4:40 am ]
Post subject:  Re: Cretan AU random FD drawing
really like the ICAR tt-01 & ICAR A-39 ... but then I'm weird :D
Author:  waritem [ February 4th, 2024, 11:20 pm ]
Post subject:  Re: Cretan AU random FD drawing
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.

[ img ]
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.

[ img ]
These operations were the occasion of one of the worst Cretan setbacks of the war:
Refusing to leave the Vercors maquisards to their fate after the abandonment of the “Montagnards” plan, the Cretan command (without any support from the allies) set up the operation Vendôme.
On the night of July 15 to 16, 1944, 10 θ-37b transport seaplanes loaded with weapons, ammunition and 120 paratroopers from the first airmobile brigade headed for Vassieux-en-Vercors accompanied by 6 ICAR π-39 fighters. The modest escort was to be compensated for by the weakness of the Luftwaffe in the sector and the element of surprise.
There was quite a surprise, but not in the expected way. As they approached their objective the formation was assaulted by no less than 30 German interceptors. The Cretans, at one against 5, couldn’t prevent the destruction of all the seaplanes. Only around thirty survivors managed to join the Free Republic of Vercors.
It is unlikely that such a large hunting party could have found themselves in the area by chance.
Although the origin of the leak was never established, the plan had undoubtedly been revealed.

[ img ]
This failure did not put an end to the operational career of the θ-37. He continued to be employed until the end of the conflict. As for the airborne part of the Corfu landings.

The version which remained the latest  in service was the θ-37c. It incorporated a retractable landing gear which made it an amphibious aircraft. Some were retrofitted with twin turboprops instead of their former piston engines, making them the most powerful and advanced model of the type.

[ img ]
[ img ]
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.
Author:  waritem [ February 7th, 2024, 11:57 pm ]
Post subject:  Re: Cretan AU random FD drawing
I've hadded the turboprop water bomber version of the θ-37 flying boat.
Author:  odysseus1980 [ February 8th, 2024, 11:30 am ]
Post subject:  Re: Cretan AU random FD drawing
Very curious and unusual shape. I am not sure if this plane could fly.
Author:  reytuerto [ February 8th, 2024, 6:23 pm ]
Post subject:  Re: Cretan AU random FD drawing
Hi, Odysseus. I think that the ICAR seaplane will be able to fly, but it will be a wet aircraft, specially in the tail section. And with corrosion problems. And with a tricky take off and landing (I don´t know if "landing" is the correct term for a seaplane touching the water). It is an unusual design, but in the air, it could behave well, the wings are very "clean" for a seaplane of the era. Of course, from a dentist´s point of view :lol: ! Cheers.
Author:  waritem [ February 9th, 2024, 7:51 am ]
Post subject:  Re: Cretan AU random FD drawing
I don't get why it would be a "wet" aircraft. The shape of the hull is similar to contemporary flying boats.
I would even say that the tail stabilisators they deport the spray in the wake of the device.

To me, as Charguizard pointed before, the main niptick would be that the spray fouls propellers very quickly.
This is what I tried to solve with an articulated propeller shaft (I really need to draw it taking off.....)

By the way, i've added a landed picture.
Author:  acelanceloet [ February 9th, 2024, 12:55 pm ]
Post subject:  Re: Cretan AU random FD drawing
I do wonder how wide the tail would have to be (or how fat the vertical tails) to give enough stability when floating at low speed. I also wonder how you solve the issue of the tail increasing in drag in the water when the aircraft speeds up and the main wing starts gathering lift, lifting the nose up.
Author:  waritem [ February 9th, 2024, 1:17 pm ]
Post subject:  Re: Cretan AU random FD drawing
acelanceloet wrote: *February 9th, 2024, 12:55 pm
I do wonder how wide the tail would have to be (or how fat the vertical tails) to give enough stability when floating at low speed. I also wonder how you solve the issue of the tail increasing in drag in the water when the aircraft speeds up and the main wing starts gathering lift, lifting the nose up.
I have to check the top view i've started a few years ago, but i'm quite sure i drawed a quite wide tail to increase the rear wing lift in order to compensat the engines weight.

I don't think the fins will sink any further into the water during the pitch-up. A classic seaplane rests on the rear part of its hull which is quite slender and it does not sink particularly.
Author:  The_Sprinklez [ February 9th, 2024, 3:22 pm ]
Post subject:  Re: Cretan AU random FD drawing
Horizontal stabilizers do not generate lift in the upwards direction. Instead, it's inverted relative to the wing to create "Tail-Down Force" and compensate for CG. [ img ]
Author:  waritem [ February 9th, 2024, 3:29 pm ]
Post subject:  Re: Cretan AU random FD drawing
The_Sprinklez wrote: *February 9th, 2024, 3:22 pm
Horizontal stabilizers do not generate lift in the upwards direction. Instead, it's inverted relative to the wing to create "Tail-Down Force" and compensate for CG. [ img ]
Exept if it's a tandem wing......
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