Caproni Ca.135

Caproni

Industry	Aerospace, Defense
Founded	1908 (1908)
Founder	Giovanni Battista Caproni
Headquarters	Milan , Italy
Products	Aircraft, including Caproni Ca.135 bomber

Template:Infobox aircraft

The Caproni Ca.135 was a medium bomber developed in Italy by Cesare Pallavicino at Bergamo. Its maiden flight took place in 1936, and it was introduced into service with the Peruvian Aviation Corps in 1937, followed by the Regia Aeronautica in January 1938.

Origins

Template:Essay-like The "R-plan," initiated by General Valle (then Chief of Staff of the Regia Aeronautica), aimed to modernize Italy’s air force and expand its strength to 3,000 aircraft by 1940. In late 1934, a competition was organized for a new bomber meeting these criteria:

• Speed: 330 km/h (210 mph) at 4,500 m (14,800 ft) and 385 km/h (239 mph) at 5,000 m (16,000 ft).
• Climb rate: reaching 4,000 m (13,000 ft) within 12+1⁄2 minutes.
• Range: 1,000 km (620 mi) carrying a bombload of 1,200 kg (2,600 lb).
• Service ceiling: 8,000 m (26,000 ft).

While the speed requirements were surpassed by nearly all competitors, the ceiling and range goals remained unmet. The contest concluded with orders placed for several aircraft models: the Ca.135 (204 units), the Fiat BR.20 (204), the Savoia-Marchetti SM.79 (96), the CANT Z.1007 (49), and the Piaggio P.32 (12).

This assortment highlighted significant disorder, favoritism, and inefficiency within Italy’s aviation sector. Additionally, the Regia Aeronautica frequently squandered resources by commissioning aircraft that were already outdated. Notably, some winners in the competition were not necessarily superior designs—for example, the BR.20 was sidelined in favor of the SM.79, which had not even participated in the contest.

Design

The Ca.135 was intended for production at Caproni's primary facility in Taliedo, Milan, which explains its designation within Caproni’s main aircraft series rather than the Caproni-Bergamaschi Ca.300 line. Nevertheless, development remained at Ponte San Pietro, where the prototype—completed over 1934–35, a lengthy period for that era—undertook its initial flight on 1 April. Cesare Pallavicino of CAB (Caproni Aereonautica Bergamasca) led the design effort.

Though classified among Caproni’s "century series," the bomber bore resemblance to the Caproni Ca.310, featuring a rounded nose, twin engines, a low-mounted fuselage, and wings with an unusually long chord. Multiple variants were equipped with differing powerplants, resulting in varying performance characteristics.

The prototype utilized two 623 kW (835 hp) (at approximately 4,000 metres (13,000 ft) altitude) Isotta Fraschini Asso XI.RC V12 engines initially paired with two-bladed wooden propellers. Its dimensions included a length of 14.5 metres (48 ft), wingspan of 18.96 metres (62.2 ft), and wing area measuring 61.5 square metres (662 sq ft). The empty weight stood at 5,606 kilograms (12,359 lb), with a useful load capacity of 2,875 kilograms (6,338 lb). Construction combined materials: a stressed-skin forward fuselage with wood and fabric-covered steel tubing aft; wings composed of metal and wood covered by fabric and plywood; wooden spars numbering two per wing; and tail surfaces built from wood covered with metal and plywood. The wing structure accounted for more than one-third of total length with a strength coefficient rated at 7.5. Fuel capacity consisted of two tanks located in the inner wings holding a combined total of 2,200 L (581 US gallons).

In contrast to aircraft like the Fiat BR.20—which resembled the American B-25 Mitchell—the Ca.135’s low-profile fuselage bore greater similarity to the American B-26 Marauder. Its elongated nose housed both the bomb aimer's position and a forward turret akin to those found on aircraft such as the Piaggio P.108 and certain British bombers that followed. The nose front section was removable to facilitate rapid crew evacuation during emergencies; additionally, two cockpit roof hatches provided pilots an alternate escape route. The right pilot seat could fold upward to ease access to the nose compartment.

A mid-fuselage turret armed with a single 12.7 mm (0.5 in) machine gun was operated by the co-pilot, who also had an adjacent seat later adapted for a flight engineer's use. The wireless operator’s station located aft contained standard Italian bomber radio equipment including AR350/AR5 units, a P63N radiogoniometer, an OMI AGR.90 or similar AGR 61 photographic-planimetric camera, plus an APR 3 camera typically operated through a small window despite not being fixed permanently in place. The wireless operator also manned a ventral-mounted 12.7 mm (0.5 in) machine gun—a demanding workload that often necessitated carrying an additional crew member. The aircraft featured extensive glazed areas across nose, cockpit, central fuselage, and rear sections—far more expansive than those on many contemporary Italian designs.

Armament comprised three machine guns: two 12.7 mm (0.5 in) weapons positioned in dorsal turret and ventral stand respectively, plus one 7.7 mm (0.303 in) gun mounted in the nose—each supplied with ammunition counts of approximately 500 rounds for the larger calibers and 350 rounds for the smaller.

Its bomb-carrying capability—typical of Italian bombers—was modest but adaptable depending on mission type ranging from anti-ship strikes to close air support:

• Two × 800 kilograms (1,800 lb) bombs—the heaviest used by Regia Aeronautica—alongside two × 50 kilograms (110 lb), and two × 31 kilograms (68 lb), totaling approximately 1,862 kilograms (4,105 lb)
• Two × 500 kilograms (1,100 lb) bombs plus four × 100 kilograms (220 lb), and two × 31 kilograms (68 lb), summing nominally to 1,462 kilograms (3,223 lb)
• Four × 250 kilograms (550 lb)
• Eight × 100 kilograms (220 lb) plus eight × 50, and four × , totaling about
• Sixteen × plus eight × , amounting to roughly
• Twenty-four bombs ranging from , down to smaller sizes such as , , or even
• Up to 120 small bomblets weighing between one or two kilograms each
• Two torpedoes (though never operationally deployed but supported by hardpoints)

This bombload capacity surpassed many contemporaries—for instance, the SM.79 typically carried two × 500 kg/1,100 lb bombs or five × 250 kg bombs plus twelve smaller ones or hundreds of bomblets—but remained limited compared to larger strategic bombers of other nations.

Performance

The aircraft suffered from insufficient power, achieving a top speed of only 363 km/h (226 mph) at an altitude of 4,500 m (14,800 ft), and exhibited a relatively high stall speed of 130 km/h (81 mph). It lacked slats and possibly did not have flaps installed. The service ceiling was limited to 6,000 m (20,000 ft), while its endurance at 70% throttle was approximately 1,600 km (990 mi). The aircraft’s actual all-up weight was excessive, totaling 8,725 kg (19,235 lb), instead of the anticipated 7,375 kg (16,259 lb).

The payload capacity of 2,800 kg (6,200 lb) was distributed among the crew (around 320+ kg/705+ lb), armaments (200 kg (440 lb)), communication devices and additional equipment (100 kg (220 lb)), fuel (2,200 L/581 US gal), oil (1,500 kg (3,300 lb)), oxygen, and bombs. It was nearly impossible to carry a full fuel load alongside the maximum bomb load, especially when compared to other Italian bombers that typically managed payloads between 3,300–3,600 kg (7,300–7,900 lb). Due to the limited engine power, overloaded take-offs were unfeasible, and even standard take-offs presented difficulties.

Take-off and landing distances measured 418 and 430 m (1,371 and 1,411 ft), respectively. The operational range allowed for approximately 2,200 km (1,400 mi) when carrying 550 kg (1,210 lb) of bombs and about 1,200 km (750 mi) with a payload of 1,200 kg (2,600 lb).

The production models were equipped with two inline liquid-cooled Asso XI RC.40 engines, each delivering 671 kW (900 hp) at an altitude of 4,000 m (13,000 ft). Aerodynamic efficiency improved through the use of three-bladed metal propellers, which theoretically enhanced performance. These upgraded engines raised the maximum speed to 400 km/h (250 mph) at 4,000 m (13,000 ft). Climb rates included reaching 2,000 metres (6,600 ft) in 5.5 minutes, 4,000 metres (13,000 ft) in 12.1 minutes, and 5,000 metres (16,000 ft) in 16.9 minutes.

Nevertheless, power remained inadequate, prompting a 1939 retrofit of existing Ca.135 "Asso" aircraft with more powerful Piaggio P.XI engines rated at 746 kW (1,000 hp), leading to the designation Ca.135 Mod.

Operational service

The aircraft entered service later than comparable models such as the BR.20 and featured technology that was considered outdated upon introduction. Regardless, the Regia Aeronautica placed an order for 32 units on 19 June 1937. Deliveries began in January 1938, more than a year after the BR and SM bomber types had already been deployed.

Spanish Civil War

In 1938, eight aircraft were allocated to the Aviazione Legionaria for deployment during the Spanish Civil War. These versions, known as Tipo Spagna ("Spanish Type"), were fitted with Fiat A.80 R.C.41 engines rated at 746 kW (1,000 hp).

Personnel from 11 Wing traveled to Taliedo, near Milan, to prepare seven of these planes—designated Ca.135S—for transfer to Spain. One aircraft was damaged during take-off; six proceeded to Ciampino, near Rome, where two sustained landing damage. After undergoing repairs and modifications, the seven aircraft were not ready for departure until late 1938. During transit, two planes had to return to Italy due to icing conditions while three crashed into the sea. Ultimately, only two reached Palma de Mallorca, where they remained inactive for half a year.

Italy

The initial production run consisted of 32 aircraft, with eight converted into Ca.135 Ss variants and the remainder adapted to the Ca.135 Mod standard. The first Ca.135 Bis models were manufactured in 1938, featuring 746 kW (1,000 hp) Piaggio P.XI RC.40 engines paired with Piaggio P.1001 three-blade metal propellers. These aircraft measured 17.7 m (58 ft) in length, had a wingspan of 18.8 m (62 ft), and a wing area covering 60 m² (646 ft²). Their armament remained limited to two 12.7 mm (0.5 in) guns and one 7.7 mm (0.303 in) machine gun, although the nose was redesigned to improve aerodynamic efficiency. Between 1939 and June 1940, an additional 32 units were ordered and produced.

These aircraft were met with significant disapproval from Italian pilots due to their poor performance. As they proved unsuitable for active duty, they were reassigned to flight training schools before being exported to Hungary. By late 1938, the initial batch operated by the 11 Wing had been phased out. At the Jesi airfield, 25 remained, but only four were flight-ready; the remainder were likely undergoing engine maintenance or replacement. In 1940, at least 15 Ca.135Ss and Ca.135Mods were stationed at the Malpensa flying school, but their deteriorated condition led to their scrapping in November 1941. Ultimately, all 64 Ca.135 aircraft exited service within the Regia Aeronautica without having undertaken any operational missions.

Hungary

File:Caproni Ca 135.JPG

A Ca.135 Bis of the Hungarian Air Force in 1942.

The Magyar Királyi Honvéd Légierő (MKHL) procured Ca.135s delivered in two batches—36 aircraft in 1940 and 31 (initially planned as 32, but one was lost during delivery) in 1942—with considerations for licensed production of both planes and engines.

Hungary operated a total of 67 Ca.135bis bombers with moderate success on the Eastern Front against the Soviet Union during 1941 and 1942, following Hungary's military engagement in that theater during World War II.

These bombers formed nearly the entirety of Hungary's heavy bomber fleet. The decision to acquire them followed Hungary’s return of 33 out of 36 Caproni Ca.310 aircraft purchased between May and September 1939. Due to an Italian credit worth 300 million lire and the inability to secure modern German planes, the Hungarian Air Force opted for the newer and more powerful Ca.135bis, placing the order in December 1939. The first delivery occurred in May/June 1940, followed by a second shipment in May 1942 from an order placed in July 1941. While the Regia Aeronautica had dismissed the Ca.135s over technical deficiencies leading to halted production, these bombers performed satisfactorily within Hungarian service.

At Hungary’s declaration of war against the Soviet Union in June 1941, its air force was predominantly equipped with Italian-made aircraft. The Ca.135s saw combat for the first time on June 27, 1941—the day Hungary entered the conflict—when 1st Lt Istvan Szakonyi, piloting a Ca.135 from the 4/III Bomber Group, successfully destroyed a strategic bridge using a test drop of two bombs. The aircraft equipped the 3./III Group of the 3rd Bomber Wing stationed at Debrecen, which operated under Lt Col Béla Orosz’s command and was assigned to support the Hungarian Rapid Corps, subordinated to Germany’s 17th Army.

On August 11, six Capronis led by Lt Szakonyi undertook a mission targeting a two-kilometer (6,560 ft) bridge over the Bug River near Nikolayev, on the Black Sea coast. One aircraft aborted due to engine trouble; however, five continued eastward escorted by Hungarian Fiat CR.42s and MÁVAG Héja Is. Despite losing his port engine from anti-aircraft fire, Szakonyi pressed on with his attack run. Captain Eszenyi succeeded in destroying the bridge while Szakonyi bombed Nikolayev’s train station. On their return journey, Soviet Polikarpov I-16 fighters intercepted them but were met by Hungarian escorts that downed five I-16s; additionally, Szakonyi's damaged bomber shot down three more Polikarpovs. Following the German capture of Nikolayev on August 16, Luftflotte 4 commander Colonel General Lohr honored these Hungarian crews at Sutyska.

File:Ca.135 being armed.JPG

A Hungarian Air Force Ca.135 Bis being loaded with bombs, 1942.

Operating on the Eastern Front exposed the Ca.135 to frequent mechanical failures and its limited payload capacity imposed considerable strain on ground crews responsible for maintenance. Achieving a readiness rate of approximately fifty percent was regarded as commendable.

Hungary’s initial flying unit on this front withdrew in September 1941 for rest, re-equipment, and recuperation purposes. In June 1942, Hungary deployed its second Air Brigade to provide tactical support and reconnaissance missions for its Second Army stationed along the Don. The sole bombing unit within this formation—the 4/1 Bomber Squadron—was equipped with seventeen Ca.135s.

This squadron continued operating these bombers until late 1942 when remaining aircraft were relegated to training roles due to wear and tear. Despite their reservations about the Ca.135Bis model, Hungarian forces maximized its use given limited alternatives. The I/4 Squadron originally fielded eight aircraft but lost one during landing; it was subsequently replaced by four additional planes. From inception until October 1941, this squadron executed approximately 265 bombing raids comprising around 1,040 sorties and dropped roughly 1,450 tonnes (1,600 tons) of ordnance—a feat facilitated by short-range missions (approximately 200–300 km (120–190 mi)) allowing maximum payload utilization. Losses included two aircraft shot down and two more lost due to accidents with eleven crew casualties recorded during this period. Their operational tempo averaged over eight missions daily with about thirteen tonnes (14 tons) of bombs deployed each day over these four months.

Design and production

In early 1936, Caproni's representative based in Lima, Peru, initiated contact with the Peruvian Navy and the Ministry of Aviation concerning the potential acquisition of Ca.135 aircraft. Since 1935, Peru had been evaluating options to replace its unsatisfactory Caproni Ca.111 bombers. The Italian Air Ministry authorized the export of the Ca.135 model, leading to Peru placing an order for six units from Caproni in May 1936. A Peruvian delegation, headed by Ergasto Silva Guillen, Commander of the Peruvian Aviation Corps, traveled to Italy to assess the Ca.135 firsthand and to avoid a recurrence of what was remembered as the "Ca.111 fiasco." During a demonstration flight conducted by Caproni test pilot Ettore Wengi, Silva found the aircraft underpowered and inadequately armed defensively. He subsequently sent a letter to Caproni demanding modifications and warned that failure to comply could result in cancellation of the order. Gianni Caproni (1886–1957), founder of the company, personally assured that the requested changes would be implemented.

The modified aircraft, designated Ca.135 Tipo Peru ("Peruvian Type"), featured upgraded Isotta Fraschini Asso XI R.C.40 Spinto ("Driven") engines—enhanced variants of the Isotta Fraschini R.C.40 Asso ("Ace")—producing 559 kilowatts (750 horsepower) at sea level and 671 kilowatts (900 horsepower) at an altitude of 4,000 meters (13,123 ft). Engine cowlings were also redesigned with additional openings to accommodate increased air intake requirements for these new powerplants. These improvements enhanced performance to satisfy Peruvian specifications and allowed for an increased bomb payload capacity up to 2,000 kilograms (4,409 pounds). The defensive armament was upgraded by fitting a 12.7-millimeter (0.5-inch) machine gun within a semi-open dorsal turret equipped with a wind deflector shield protecting the gunner, as well as another 12.7-millimeter machine gun housed in a retractable ventral turret. Both turrets provided full 360-degree firing arcs; however, extending the ventral turret caused significant aerodynamic drag and was advised for emergency use only.

All six Ca.135 Tipo Peru units were completed by early July 1937. Following acceptance flights conducted by Wengi and approval from the Peruvian delegation, the aircraft were disassembled and transported to Callao, Peru. Employees of Caproni’s local subsidiary, Caproni Peruana S.A., promptly commenced reassembly operations at Las Palmas. The first bomber was reassembled within two weeks, and on 10 September 1937, all six aircraft were handed over to the newly formed 2nd Heavy Bomber Squadron of the Peruvian Aviation Corps for operational deployment.

Operational service

Following an intensive two-month training period conducted by Italian instructors, five Ca.135 bombers from the 2nd Heavy Bomber Squadron were deployed to their designated base, the Lieutenant Commander Ruiz airfield in Chiclayo, Peru, on 5 November 1937. The sixth bomber remained stationed at Las Palmas to facilitate further crew training. Upon arrival in Chiclayo, these five Ca.135 aircraft formed the 2nd Bombardment Group, integrating with the Ca.111 bombers of the 1st Bombardment Group under the umbrella of the 1st Aviation Squadron. A restructuring in 1940 reassigned the Ca.135s to the 13th, 14th, and 15th Escuadrillas alongside Ca.111 bombers; however, later that year the Ca.111s were re-designated as transport planes and transferred to transport units. Consequently, the 14th and 15th Escuadrillas were dissolved, consolidating all Ca.135s into the 13th Escuadrilla.

The Ca.135 Tipo Peru quickly attracted criticism from Peruvian aviators who reported that the aircraft exhibited a tendency to yaw right during takeoff and suffered from inadequate lateral stability. Additionally, engine reliability proved problematic in operational conditions, with numerous oil and hydraulic fluid leaks reported. Caproni Peruana S.A. acknowledged these deficiencies and intended to address them in a locally produced version of the Ca.135; nevertheless, no units were ultimately manufactured within Peru.

Amid escalating tensions along the border with Ecuador in 1941, Peruvian bomber squadrons were placed on heightened alert. Despite this readiness posture, persistent engine troubles limited operational availability to no more than two airworthy bombers per squadron out of their complement of five. Training exercises continued at a bombing range situated north of Chiclayo. When hostilities erupted during the Ecuadorian–Peruvian War on 5 July 1941, the Ca.135s remained stationed at Lieutenant Commander Ruiz base while other bombers relocated to forward airfields; their extended operational range negated the necessity for forward deployment. However, Peruvian bombing sorties were confined primarily to tactical strikes against front-line Ecuadorian forces and their immediate support installations—missions for which the Ca.135 was ill-suited. Instead, these bombers undertook unescorted reconnaissance patrols over Ecuadorian territory as well as transport flights servicing airfields at Piura and Talara, Peru. On 10 July 1941, one Ca.135 encountered engine failure during a transport mission approximately 50 kilometers (31 mi) from Piura in terrain inaccessible to ground recovery vehicles; although it sustained only minor damage, disassembly for repair transport was impractical, leading to its cannibalization and abandonment.

Following the conclusion of hostilities on 31 July 1942, the remaining five Ca.135 aircraft stayed at Chiclayo before being withdrawn from active duty. They were dismantled and transported away on flatbed trucks operated by U.S. military personnel from El Pato airbase. By October 1942, all Peruvian Ca.135s had vanished from service records. While rumors suggest they may have been incinerated in desert locations or interred near El Pato airbase, their ultimate disposition remains undocumented.

Modified aircraft

Caproni altered a single Ca.135 "Asso" model, equipping it with a dihedral tailplane and installing 1,044 kW (1,400 hp) Alfa Romeo 135 RC.32 Tornado radial engines. This variant was designated as the Ca.169. The integration of these more robust engines increased the aircraft's top speed to over 480 km/h (300 mph).

In 1937, a "Raid" version was conceptualized at the request of Peru for a proposed Roma-Lima aviation expedition. However, after several years of development, the initiative was abandoned, and by 1939, the Ca.310 was selected as its replacement.

Variants

Ca.135

Initial model produced in a batch of 32 units for the Regia Aeronautica, powered by I.F. Asso XI RC.40 engines.

Ca.135 Tipo Spagna

Eight units from the original series were re-equipped with 746 kW (1,000 hp) Fiat A.80 R.C.41 engines for deployment in Spain.

Ca.135 Mod.

The base Ca.135 "Asso" refitted with twin 746 kW (1,000 hp) Piaggio P.XI R.C.40 radial piston engines.

Ca.135 Bis.

Featuring a redesigned nose and engine nacelles, this version was powered by two 746 kW (1,000 hp) Piaggio P.XI R.C.40 radial piston engines and produced in a total of 68 units.

Ca.135 Tipo Peru

Exported to Peru, this variant included six aircraft equipped with twin 671 kW (900 hp) Isotta Fraschini Asso XI R.C.40 Spinto engines.

Ca.169

A singular aircraft featuring an extended fuselage, twin tail configuration, and powered by two 1,044 kW (1,400 hp) Alfa Romeo 135 R.C.32 Tornado radial piston engines.

Ca.135 Raid

A special long-range model that remained unbuilt, designed with additional fuel tanks and intended to use two 736 kW (987 hp) Isotta Fraschini Asso XI engines.

SABCA S.45

A license-built version planned for Belgium that never entered production.

Operators

Template:Flagcountry

• Royal Hungarian Air Force

Template:Flagcountry

• The Regia Aeronautica operated 64 units delivered starting August 1936

Template:PER

• Peruvian Aviation Corps

Template:ESP

• Spanish Air Force

Specifications (Ca.135 P.XI)

File:Caproni Ca 135 bis 3-view line drawing.svg

{{Aircraft specs |ref=Italian Civil & Military Aircraft 1930–1945 |prime units=met

|genhide=

|crew=4/5 |length ft=47 |length in=2 |span ft=61 |span in=8 |height ft=11 |height in=2 |empty weight lb=13340 |gross weight lb=21050

|eng1 number=2 |eng1 name=Piaggio P.XI R.C.40 |eng1 type=14-cylinder two-row air-cooled radial piston engines |eng1 kw=746

|max speed kmh=365 |max speed mph=227 |max speed note=at 4,800 m (15,700 ft) |cruise speed mph=217 |max range km=2000 |max ceiling m=6500 |climb rate ftmin=1100 |time to altitude=4,000 m (13,000 ft) in 11 min 36 s and to 5,000 m (16,000 ft) in 17 min 24 s

|guns=3 x 12.7 mm (0.50 in) Breda-SAFAT machine guns |bombs=1,474 kilograms (3,250 lb)

References

• Abate, Rosario. Gli aeroplani della Caproni Aeronautica Bergamasca - Volume I. Roma: Edizioni Bizzarri, 1975.
• Hagedorn, Dan. "Les Caproni Ca.135 péruviens." Avions: Toute l'Aéronautique et son histoire, no. 86, May 2000, pp. 44–49. (French)
• Lembo, Daniele. Caproni Ca.135. Aerei nella Storia magazine, September 2006. (Italian)
• Mondey, David. Axis Aircraft of World War II. Chancellor Press, 1996. ISBN 1-85152-966-7.
• Neulen, Hans Werner. In the Skies of Europe – Air Forces Allied to the Luftwaffe 1939–1945. Ramsbury, Marlborough: Crowood Press, 2000. ISBN 1-86126-799-1.
• Thompson, Jonathan. Italian Civil & Military Aircraft 1930–1945. New York: Aero Publishers, 1963, pp. 102–105. ISBN 0-8168-6500-0.

External links

• Comando Supremo – Italy At War (HTML) Accessed 14 August 2007.
• The Latin American Aviation Historical Society: South American Aviation: "The Caproni Bergamaschi Ca.135 in Peruvian Service" by Amaru Tincopa GallegosTemplate:Fix/category