P.Z.L. P.46 Sum (Sheat-fish)

The P.Z.L. P.46 Sum (Sheat-fish) was to have been a more advanced version of the P.23 light bomber and reconnaissance aircraft, but it hadn’t entered production by the time the Germans invaded Poland in 1939.

Work on the P.46 began in 1936. The aim was to produce a new aircraft stressed to use radial engines of up to 1,200hp, with the same basic structure as the P.23, but with aerodynamic improvements. 

P.Z.L. P.46 Sum from the left
P.Z.L. P.46 Sum from the left

The first of the Karas B production aircraft was modified on the production line to help with the development of the P.46. The normal gondola was removed and replaced with a retractable version that was to be operated by the weight of the bomb aimer/ gunner. It was given a new twin tail and was powered by a PZL Pegasus VIIIA and made its maiden flight in April 1936, as the P.Z.L. P.42. The weight operated gondola wasn’t a great success, so work began on a hydraulically operated version.

In 1937 another Karas B was given a 925hp Bristol Pegasus XX engine with a three blade variable pitch Hamilton metal airscrew. After tests were completed with this engine it was returned to the normal Karas B standard and returned to the Air Force.

By the time the P.46 was entering production, the Polish air force had changed its doctrines. The idea of multi-purpose ‘liniowe’ (front line aircraft) squadrons was replaced by a split between an attack force, which was to use new aircraft, and an armed-reconnaissance force, which was to be made up of separate light bombing and reconnaissance squadrons. As a result each P.46 was to be completed either as a bomber or a reconnaissance aircraft. The existing P.23 Karas squadrons were allocated to one or the other task and began to training in their new role.

The production version of the P.46 would have used a hydraulically operated gondola, and had a twin fin and rudder tail. It kept the three man cockpit of the P.23, with the pilot in an enclosed cockpit in the front, the observer just behind with access to the gondola, and a rear gunner. The open rear gunner’s position on the P.23 was replaced with a version covered by a canopy.

In the middle of 1937 work began on three flying prototypes and one static test aircraft.

The first prototype, P.46/I, was completed in time to take part in the Salon International de l’Aeronautique in Paris late in 1938. It was armed with four fixed guns in the wing and two rear firing flexibly mounted guns, one above and one below the fuselage. The quick construction meant that there wasn’t time to neatly shape the duralumin panels on the forward fuselage, so the gaps had to be covered with metal strips, which caused some confusion at the air show. The aircraft made its first flight in late October 1938, just before it was sent to Paris. After the air show was over it returned home and began a series of flight trials. When the Germans invaded it was grounded by damage caused by a burst tyre.

The second prototype, P.46/II, was completed in the spring of 1939. This time the duralumin was properly shaped, so the metal strips weren’t needed. In September 1939 it was flown to Romania, where it was seized by the Romanian government. On 26 September Captain Stanisalw Riess managed to take off in the prototype and flew it back to Warsaw, with orders from the C-in-C of the Polish Armed Forces to the defenders, including the orders to form the underground army. The aircraft then flew to Latvia and was interned.

The third prototype, P.46/ III, was close to completion when the Germans invaded in September 1939. It was powered by a 1,030hp Gnome-Rhone 14N21 engine, and was the development version for an export version, the Sum B, which had been ordered by Bulgaria.

Plans of P.Z.L. P.46 Sum
Plans of P.Z.L. P.46 Sum

The P.46 passed its airworthiness trials during 1939, and in the summer the prototypes went to the Experimental Squadron for service evaluation. An order for 300 P.47A Sum As was placed. These were to be powered by the Pegasus XX, and would have been similar to the prototypes apart from using two dorsal guns. Production was to begin in July and a production rate of 15-20 aircraft per month was expected by the winter of 1939-40. However in August 1939 it was decided to postpone production of the P.46 and use all of the materials at the factory to produce fighters.

In the winter of 1938-39 work began on a related aircraft, the Losos (Salmon), which would have been a dive bomber similar to the P.46, but with a crew of two, no gondola and a retractable undercarriage. Work on this version was underway when the Germans invaded.

Engine: Pegasus XX/ Gnome Rhone 14N21
Crew: 3
Span: 47ft 11in
Length: 34ft 5.5in
Height: 10ft 10.25in
Empty Weight: 4,398lb
Loaded Weight: 7,827lb
Maximum Speed (Pegasus): 264mph at 11,811ft; 217.4mph at sea level
Maximum Speed (Gnome Rhone): 292mpg at 18,500ft; 229.9mph at sea level
Service Ceiling: 25,261ft/ 28,214ft
Range: 807 miles/ 683 miles
Guns: Four fixed guns in wing, one dorsal gun, one ventral gun

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How to cite this article: Rickard, J (5 October 2021), P.Z.L. P.46 Sum (Sheat-fish) , http://www.historyofwar.org/articles/weapons_PZL_P46_sum.html

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