By William Pearce

In late 1930s, FIAT developed the CR.42 Falco (Falcon), one of the last biplane fighter aircraft. The CR.42 was powered by an 840 hp (626 kW) FIAT A 74 RC38 radial engine. With good performance and excellent maneuverability, the CR.42 was one of the best biplane fighters ever built. However, frontline fighters had adopted new tactics in which speed controlled the fight, so the maneuverability of the biplane was traded for the speed of a monoplane. Looking to maximize a combination of speed and maneuverability, the Italian Air Ministry asked FIAT to re-engine the CR.42 with a 1,000 hp (746 kW) Daimler-Benz DB 601A engine. The resulting aircraft was designated CR.42 DB.

The FIAT CR.42 DB undergoing an engine run. Its Daimler-Benz DB 601 engine made the aircraft the fastest biplane ever built. However, its performance could not match contemporary monoplane fighters.

Some sources incorrectly list the DB 601-powered aircraft as the CR.42 B, which was a trainer built from a standard CR.42 by moving the engine forward, elongating the fuselage, and adding a second cockpit. Additionally, some sources claim the CR.42 DB’s engine was an Alfa Romeo RA 1000 RC41, which was a DB 601A built under license in Italy. However, the Alfa Romeo RA 1000 engine had not proceeded beyond initial testing by late 1941, after the CR.42 DB had already flown. It is unlikely that an untried RA 1000 test engine was installed in the CR.42 DB.

The FIAT CR.42 DB project was underway by early 1941. The aircraft was assigned serial number MM 469. In the span of a few weeks, a standard CR.42 was re-engined with the DB 601 power plant. Switching from a large, air-cooled, 14-cylnder radial engine to a long, liquid-cooled, V-12 engine necessitated many changes to the aircraft.

Like all CR.42s, the CR.42 DB consisted of a welded steel tube and alloy airframe. The fuselage was skinned in aluminum with the exception of the rear fuselage’s sides and bottom, which were covered with fabric. The wings and tail had a duralumin frame. The wings’ leading and trailing edges were aluminum, and fabric covered the rest of the surface. The horizontal and vertical stabilizers were aluminum-skinned. All control surfaces were had a duralumin frame and were covered in fabric.

The CR.42 DB with its lower wing removed. The removed bottom panel exposes some of the aircraft’s structure.

The entire front of the CR.42 DB was redesigned to accommodate the DB 601A engine and its radiator. The DB 601A was encased in a close-fitting, streamlined cowling. Positioned on the left side of the cowling was the engine’s air intake. Faired into the cowling’s upper deck were the blast tubes for the aircraft’s two 12.7 mm guns—each had 400 rounds of ammunition. A housing for the radiator was located under the engine. Scoops for oil coolers were placed in the wing roots of the lower wing (in the same location as a standard CR.42).

The CR.42 DB had the same 31.8 ft (9.70 m) upper and 21.3 ft (6.50m) lower wingspans as the standard CR.42, but those were the only specifications the two aircraft shared. The CR.42 DB was 1.8 ft (.54 m) longer at 28.9 ft (8.80 m). The aircraft was 507 lb (230 kg) heavier at an empty weight of 4,299 lb (1,950 kg). The CR.42 DB’s performance improved substantially over the standard CR.42. The CR.42 DB had a top speed of 323 mph (520 km/h) at 17,388 ft (5,300 m) and could climb to 16,404 ft (5,000 m) in 5:40. The aircraft had a ceiling of 34,777 ft (10,600 m) and a range of 715 mi (1,150 km). The standard CR.42 was 56 mph (90 km/h) slower, took an additional 1:40 to reach 16,404 ft (5,000 m), and had a 1,312 ft (400 m) lower ceiling.

This image shows the wing root scoop for the oil cooler and the induction scoop for the DB 601 engine. The CR.42 DB is shown at Caselle airfield in May 1941.

The CR.42 DB’s first flight was in March 1941, piloted by Commander Valentino Cus. The aircraft was delivered to the Centro Sperimentale (Experimental Center) at Guidonia Airfield (near Rome) for military tests in the summer of 1941. The CR.42 DB proved to be an exceptional aircraft; it was (and still is) the world’s fastest biplane. While not much slower than monoplane fighters then in service, the CR.42 DB’s speed could not be improved, whereas the speed of monoplane fighters would continue to increase as advancements were made.

Although an order for 150 aircraft was placed on 10 April 1941, series production was never started. The short supply of DB 601 engines available to Italy and the engine’s priority use in the more advanced Macchi MC.202 Folgore (Lightening) and Re.2001 Falco II (Falcon II) monoplane fighters left no DB 601s available for the CR.42 DB. Only one CR.42 DB was built. Some consideration was given to lengthening the CR.42 DB to 30.8 ft (9.38 m) and modifying it into a two-place training or reconnaissance aircraft. However, this project never proceeded beyond the initial design phase. Although the FIAT CR.42 DB was the pinnacle of biplane fighter performance, it was outclassed by frontline monoplane fighters as the era of biplane fighters came to an end.

The two-place, DB 601-powered CR.42. Some sources refer to the aircraft as the CR.42 R. However, the drawing appears to be labeled “R.42 P”. The “CR” stood for Caccia (Fighter) Rosatelli. Rosatelli was the aircraft’s designer, Celestino Rosatelli. Since the two-place aircraft was not a fighter, it makes sense that the “Caccia” designation would not be used.

Sources:
– The FIAT Fighters 1930–1945 by Piero Vergnano (1969)
– Italian Civil and Military Aircraft 1930–1945 by Jonathan W. Thompson (1963)
– Aeronuatica Militare Museo Storico Catalogo Motori by Oscar Marchi (1980)
– Tutti gli aerie del Re by Max Vinerba (2011)
– “Fantasmi di aerie e motori Fiat dal 1935 al 1945 (prime parte)” by Giovanni Masino Ali Antiche 106 (2011)
– Fiat CR.42 Falco by Przemyslaw Skulski (2007)