The WM-23 Silver Arrow is a Hungarian-designed, closed cabin, single-seat fighter aircraft manufactured by Weiss Manfred Aircraft Factory.
The aircraft was designed by Béla Samu and his design team.
Planning began in the summer of 1939.
The WM-K-14B, Two-Wreath Star engine, (A copy of the French Gnome-Rhône 14Kfrs Mistral Major), was intended to be its production engine at the Weiss Manfred factory.
A single prototype was built, this aircraft was destroyed in a test flight accident in 1942.
The development of the WM-23 commenced during the summer of 1939 and was undertaken by a team of designers led by Samu Béla, alongside Marton Vilmos, Milcsevics Tibor, Pap Márton, Pavláth Jeno, and other skilled professionals.
The prototype was finalized by the conclusion of 1940.
The WM-23 was equipped with the Weiss Manfréd WM K-14B, a 1,030 horsepower (768 kW), 14-cylinder, two-row, air-cooled radial engine.
The WM K-14B was a licensed, modified variant of the Gnome-Rhône 14Kfrs Mistral-Major radial engine.
The WM-23’s engine was fitted with a NACA-type cowling that was closely fitted, and it was paired with a three-bladed variable-pitch metal VDM propeller.
The engine’s cooling was efficiently managed through the use of cowl flaps, which could be manually opened or closed by the pilot.
The aircraft’s canopy was designed to slide rearward, providing an excellent view from the cockpit.
An R-13 radio device, intended for a 24 V network, with a long antenna was planned for installation, although it was not included in the prototype to expedite testing and flight trials.
The WM-23 aircraft was designed with wooden, plywood skinned wings featuring a low-wing design and camber-changing Fowler flaps.
The wings possessed a subtle inverted-gull wing shape when viewed from the front and an elliptical shape when viewed from above.
The engineers’ calculations indicated that this design not only enhanced the wings’ durability but also significantly improved the aircraft’s flight performance and controllability, with excellent manoeuvrability.
The wing root had a chord length of 2.5 meters and an airfoil of NACA 23018, transitioning to a NACA 23012 main airfoil until the end of the wing, where it tapered to a NACA 23009 airfoil.
The conventional landing gear design featured main undercarriage legs that joined the lowest part of the wings and folded outwards to fully lie within the wing profile.
Originally, Samu Béla had planned for the landing gear to fold inwards to lie within the fuselage, but factory manager Korbuly László insisted on the landing gear folding outwards to avoid the heat from the engine damaging the rubber of the tyres.
The tailwheel was also retractable.
The fuselage was constructed with a welded steel tube structure and plywood skinning.
During the testing phase, several issues were encountered with the prototype.
Firstly, despite the utilization of modern mechanisms, the engine cooling system proved to be inefficient, resulting in the engine overheating rapidly.
Consequently, a redesign of a portion of the nose was necessary.
Additionally, complications arose with the landing gear retraction and the brake system, which required repair.
Lastly, the aircraft experienced significant vibrations in various areas, particularly the ailerons, especially at high speeds.
After extensive investigations and testing, the problem was partially resolved through the redesign of the exhaust system, which eliminated the vibrations at lower speeds.
However, the aircraft continued to experience vibrations at high speeds.
Specifications
Crew
One
Length
9.12 m
Span
9.6 m
Wing surface
18.5 m²
Height
3.3 m
Weight
2200/2600 kg
(Empty state/maximum take-off mass)
Engine
One WM-K-14B 14-cylinder air-cooled two-wreath star engine.
Maximum speed
Armament
2 x synchronized 12.7mm heavy machine guns in the fuselage,
2 x 8mm high-speed machine guns in the wing,
20kg bomb load.
Sources
Hungarian Fighter Colours, 1930-1945, Vol 2- Dénes Bernád & György Punka.
Hungarian Eagles, The Hungarian Air Forces 1920 – 1945-G Sarhidai, K Kozlik & Punka George.
Aero Historia Magazine.
