CANT Z.515

10* built 1939-43

The Z.515 was another CANT CRDA project ruined by bad timing. This Zapatta's reycling of its Z.514 Leone bomber, rejected by the Regia Aeronautica, was a modified floatplane variant with inline engines. It answered a 1937 specification for a replacement to the obsolescent Z.501 Gabbiano. It was ready by 1939 but its first flight was delayed until 1940 when it competed against Fiat with its own CR.14. The latter won by a slight margin and was adopted for production. But after delivery in 1941, its issues prompted the Regia Aeronautica to turn back to CANT and asked to resume production after the order for 100 was cancelled. Only two of the 15 ordered again at Montfalcone were delivered (under German control after September 1943), with the factory destroyed in 1944 by three RAF raids. The Z.515 never was operational, but it was an interesting model, albeit unusual for its air-cooled inline engines.

Development

The CANT Z.515 was a twin engine monoplane floatplane designed and built for maritime reconnaissance in Italy shortly before World War II that was never mass produded and remained in limited service. The The Z.515 ("Z" as it was another Zappata design) resulted from an Italian Regia Marina requirement, passed on to the Regia Aeronautica for a reconnaissance seaplane with light bombing capability. This was to be a smaller and lighter model compared to the CANT Z.506 Airone tri-motor, in 1937. The Regia Aeronautica also looked for a successor to its small Z.501 Gabbiano parasol patrol flying boat which was becoming obsolete due to rapid advances in technology. Like the Z.501, the new model would perform reconnaissance and patrol but also anti-submarine warfare. But the specs precised many points, notably that it was to be a floatplane, not flying boat, and otherwise other details.

CANT Z1018 Leone

At the time, if the Regia Aeronautica submitted a tender, Filippo Zappata, proposed to military authorities a project of light seaplane based on the CANT Z.1018 Leone, a projected twin-engine medium long range fast bomber. It eventually received the company designation Z.514, and after its First flight on 9 October 1939 did not attract interest (15 were built). Indeed, the fuselage was too narrow to accommodate its defensive armament, had excessive tailplane vibration had its cockpit way back, plagued by poorly visibility for landing, its proposed copilot was unjustified. Besides this, it had frequent mechanical failures and not enough room to absorb the needed modifications requested by Regia Aeronautica. Als its new engines were not reliable.

The Regia Aeronautica looked at the time for a replacement for the CANT Z.501 in fast maritime reconnaissance. Zappata adapted the Leone to these new requirements, adding floats, making the fuselage shorter, adding a H-shaped tail, and ended with a draft that looked partly similar to the CANT Z.1018 with its two engines, low-wing cantiliver, and fuselage shape, glassed nose. The same year in 1939, the Italian Royal Air Force showed this time interested and asked CANT to suppy a wooden flying mock-up made of wood. It was Zappata's preferred technology, and preferred solution before a production with all-metal.

Filippo Zappata as chief designer of C.R.d.A. (Cantieri Riuniti dell'Adriatico, Monfalcone aeronautical division) or "CANT" designed this all-wood mockup floatplane, with metal floats however, like the Airone. The Italian Aviation preferred floatplanes at the time, as if the floatplane version was successful, it could also be declined into a land-based versions with undercarriage. He really devised a model that would be easy to produce in wartime but planned for the start that all cells would mix aluminium and duralumin. He kept however the same types of floats already used by the Z.506. Attention to the powerplant was also made in order to spare common aero engines of the time. One suggestion on the ministry he considered indeed the line-line Isotta-Fraschini "Delta" RC.35-I engine, rated for 710 hp. It was not overly powerful, but between the lightweight fuselage and generally very aerodynamic profile, it would procure the desired speed and be less susceptible to water spray, a common issue for radial engines on seaplanes at the time. It was also recoignised as reliable.

He devised an oval-section fuselage, with a narrow beam, heavily glazed nose for an excellent visibility. Behind the forward observer and pilot sat a radio operator/gunner under the glassed canopy that followed. Defence rested on a single 12.7 mm Scotti machine gun in the dorsal turret. There was an option for additional gunners with two Breda 7.7 mm in side turrets. External hardpoints enabled a limited load (960 kg) of depth charges or small bombs. In the nose were mounted two cameras AGR 90 and APR. Production models could be optionally all-metal if the ministry required.

Construction of the first Z.515 prototype MM.466 was completed in 1939, and it was practically airworthy, but needed minor modifications for over almost a year, so that its maiden flight was pushed back to July 8, 1940 without armament, to test speed, as it was reserved for production aircraft. Tests were quite successful. The prototype Z.515 in its first run, flew from the Adriatic coast off Monfalcone, under control of ttest pilot, Commander Mario Stoppani. The pilot noted about the limited power from the pair of Isotta Fraschini Delta RC.35s but his trials confirmed the validity of the design. CANT then sent it to the Centro Sperimentale Idrovolanti, in Vigna di Valle. There, Regia Aero personnel examined it alongside the competing Fiat R.S.14 as it came from an open tender. This was from December 3, 1940, and the Seaplane Experimental Center made a serie of acceptance trials before delivering its greenlight.

The rival Fiat RS.14 tested in 1940 and adopted for service. Only 15 were delivered before cancellation.

Comparative tests revealed however in 1941 the superiority of the design supplied by the CRDA. Upon completion of these tests however, it was judged that the CANT model was closely matched and promising anyway, the Regia Aeronautica issued on May 19, 1941, an initial supply contract for three aircraft, supplemented on December 6, by a second and a total order of 50 units. The May 19 contract also assigned the Sicilian Air Force a contract fo 52 more under license, and a second for 14 from CRDA, then 52 aircraft to S.A. Piaggio. Still, the general opinion was that the CMASA (Fiat) RS.14 had slightly better performance and the Regoa Aeronautica eventually picked it up for production, not the CANT model. In the early months of 1942, CRDA delivered an initial batch of 15 RS.14 which first flew on October 7, 1942. In November 1942, orders were cancelled altogether for the Fiat floatplane as well. Mussolini decided bomber production should have all priority given the limited means of the country. They were deemed more necessary. Thus the winner Fiat R.S.14 from CMASA at Marina di Pisa ended in short supply just like its rival. The planned production of hunded Z.515 series aircraft order was cancelled as well.

Soon, the R.S.14s assigned to flight units soon revealed operational limitations. The Regia Aeronautica deemed it necessary to restart production of the Z.515, and its second prototype was on the verge of being withdrawn when the Armistice of Cassibile caused a new production halt as it fell under German administration. The Luftwaffe estimated still the project interesting enough and authorized completion of the intended batch. By March 1944 the first seven Z.515s were completed at Monfalcone but before deployment, they were destroyed by three bombing raids of the RAF on 19 March, 4 and 20 April. Today, records agrees on a total of 15, but they never entered service. Logs postwar shows a production originally split between 64 from CANT, and 50 from Aeronautica Sicula in Palermo. Some sources states only ten were completed before the German takeover, leaving perhaps 3 almost completed after (for seven total) plus the two prototypes.

Design

General Layout

The Z.515 was typical of Zapatta's design of the time and shared many elemùents with the Leone. The design of the fuselage was modern and echoed the design of the Z.1018, very similar in overall shapes. Although the prototype was built of wood, the production version was planned as all-metal. This differed from that of the Z.1018 by a lack of a ventral nacelle. It had large windows positioned at the front apex, enclosing the observer's station. Behind was a two-seat cockpit for the pilot and his co-pilot enclosed by a large canopy. Behind them was the radio operator's station. He also acted a gunner and could reach the rear dorsal gun post behind. Access inside was via a hinged ladder in the central section, after the wingtip joined the fuselage. The graceful lines ended in a narrow, pointed tail terminated the two-fin empennage. Aerodynamic attention was paid in the nose shape and way it received windows, for a better visibility when landing compared to the Leone and more space for a pilot and co-pilot side by side.

It was a cantilever low wing monoplane, with straight tapered wings that had a noticeable dihedral, and rounded tips. Flaps were inboard of the ailerons. The engine thrust line was in the wing plane. Their fairings behind engine mountings, on the wing undersiden extended short of the trailing edge. The rear engine mounting supported forward attachment points for the rearward and sloping "N" shaped struts down to single stepped floats similar to thes used on the Z.506 and Z.511 Idrogigante. They were the smallest of the three and in all-metal from the start. These floats were laterally braced, by inverted-V struts at the bottom of the fuselage. The "H" style tailplane was mounted on top of the fuselage had a greater dihedral than the wing. They carried endplate fins. The horizontal surfaces were straight but tapered, and the elevators like the rudders had all trim tabs. Vertical surfaces were almost elliptical elbeit their were split roughly equally between fin and had an unbalanced rudder each.

Powerplant

The two 560 kW (750 hp) V-12 inverted air-cooled Isotta-Fraschini Delta RC.35 engines. They were mounted well forward of the leading edge. They were coupled to three-bladed propellers, with fixed pitch, all metal. The Isotta Fraschini Delta was designed in 1927 and c3300 were made total. They ere remarkable as being rare example of sucessful large air-cooled inline engine, as normally liquid was used for cooling, notably for the rearmost cylinders. 750 hp was for common versions, with examples rated up to 900 hp. It was used in a number of production aircraft and advanced prototypes. Its valves were powered by dual overhead cams, driven by power shafts, at the rear of the engine.

Exhaust ports were arranged to exit toward the middle of the engine, with a cylinder bank being the mirror of the other so that piping be ganged below the engine nacelle. It was provided to the proposed emergency wooden fighter Ambrosini SAI.107, SAI.207 and 403 prototypes, the Caproni Ca.313, 314, 331, French Caudron C.714 prototype fighter alternative to the Renault V12, Henschel Hs 129 prototype, Reggiane Re.2001 prototype and Savoia-Marchetti SM.86. Only the CANT Z.515 adopted it for seaplane applications.

Performances were not stellar in 1940 but conform with the drag endured by any floatplane: Top speed was 237 mph (381 kph) for the light, wooden prototype at 14,108 ft (4,300 m), for a cruise Speed of 186 mph (300 kph), 17,75 min to climb to 16,404 ft (5000 m) and a range of 1,181 miles (1,900 km). See data for the production model below.

Armament

The defensive armament rested on the dorsal turret 12.7 mm Scotti/Isotta Fraschini machine gun on board a Caproni-Lanciani Delta E mount. A second 12.7 mm Breda-SAFAT mount was added for the pilot, fixed at the starboard wing. There were two 7.7 mm Breda-SAFAT machine guns posed on either side of the fuselage as well with flexible mounts and from small pistol ports close to the wing's end. The lower nose of the Z.515, completely glazed was provisioned also to mount another 7.7 m Breda LMG. The dorsal machine gun turret at mid-chord was however criticized by its lack of visibility. The droppable military payload consisted of six underwing positions for bombs weighing up to 100 kg (221 lb) or depht charges so a total of 600 kg (1,320 lb).

Japanese Order

Unlucky with Italy, CANT had the prospect of a Japanese order however. Due to the Imperial Japanese Navy's need for that same role, a production license for the Z.515 was transferred in 1941. The documentation was sent via a Rome-Tokyo-Rome run in a Savoia-Marchetti SM.75 GA (Grande Autonomia) three-engined aircraft. It Took off from the Zaporoskje airfield, now in Ukraine, after a 21-hour non-stop flight, and reached Japanese-occupied Manchukuo after 6,000 km, much of it over Soviet airspace. However Japan never started production.

⚙ spec.
Empty Weight	6,390 kg
Gross Weight	8,482 kg (18,700 lb)
Max TO Weight	8,640 kg
Lenght	16.04 m (52 ft 7 in)
Wingspan	22.50 m (73 ft 10 in)
Height	5.86 m (19 ft 3 in)
Wing Area	63.10 m2 (679.2 sq ft)
Engines	2× Isotta Fraschini Delta III R.C.40 LC IV-12 560 kW (750 hp)
Top Speed	383 km/h (238 mph, 207 kn) at 4,300 m
Cruise Speed	304-310 km/h (190 mph, 170 kn)
Range	1,800 km (1,100 mi, 960 nmi)
Climb Rate	Unknown
Ceiling	7,200 m
Range	1,900 km
Armament	1× 12.7 mm (0.5 in)MG +dorsal turret, 3× 7.7 mm hand controlled MGs
Armament (Bombs)	6x 100 kg bombs (1,323 lb total)
Crew	5

Fate

Once in service, the rival FIAT R.S. 14 proved to be disappointing so the Regia Aeronautica wanted to revive the cancelled Z.515 and resume construction with a first order for 15 awarded to CRDA CANT in early 1942. The first of these production model (in all metalpreumably) flew on 7 October 1942. The second was close to delivery by 8 September 1943 when the armistice of Cassibile was signed. After CRDA came under German administration, completion was authorised so a further 7 were completed by March 1944, until three RAF bombing raids on 19 March, 4 and 20 April completely destroyed the Workshops and all aircraft under construction burned. This left a grand total of 10, not 15 in most sources: 1 prototype, 2 production models, 7 destroyed in the factory. Officially the Z.515 never entered service as apart the prototype tested, the two first production models fate is unknown. There were not enough to be of any use in a regular unit. It's possible they were burned during the same RAF raids. Photos are rare also, alsways showing the prototype being tested. As for the potential livery,

Construction detais shows the following:
-Wooden flying mock-up MM.466. First flight Monfalcone on 08/07/40 (Mario Stoppani), tested Vigna di Valle.
-Delays in production with 50 ordered, contract No. 621 for £. 102,600,000, MM. 35789-35838.
-19/05/41 order to Aer Sicula for 53 more (MM.35875-35926), contract No. 1739 19/01/43 for £25,000,000, cancelled.
-11/42 order canceled, 15 approved instead, MM. 35789-35803, to maintain construction skills.
-Order for 14 to CRDA (MM.35927-35938) cancelled 11/42.
-Order for 52 to Piaggio (MM.35939-359090) also cancelled 11/42.
-31/07/43, order for three experimental variants, two reconnaissance ones.
-MM. 35790 accepted on 08/09/43.
-German control: Work resumes on MM. 35791-35803, 80% complete at the time of the first raid.
-MM.35790-35797 destroyed. Remaining aircraft likely scrapped.