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Hopfner HM-1334 / HM.13/34
Hirtenberg HM-1334 / HM.13/34
In 1934 Flugzeugbau Hopfner GmbH began building the Hopfner HM.1334 (HM.13/34). This was done on a purely private basis because there was no corresponding request from the Austrian Air Force.
The machine was a two-seat, single-engine biplane in mixed construction with fixed tail wheel gear and normal tail. The fuselage consisted of a tubular steel structure covered with plywood and fabric around the stern. Only in the engine area were light metal sheets used.
The two open pilot seats were arranged one behind the other and had sloped windshields. As engine only a BMW VI with 750 HP was to be used, but there were procurement problems, so that Lampich had to resort to available Fiat A-20 series engines. As armament was a 7.9 mm machine gun Hotchkiss provided, installed in the upper wing and firing over the propeller circle. The biplane wings and the tail were wooden structures covered with plywood and fabric. All control surfaces were cloth-covered. The upper wing had a short wing center piece, which rested on each of two V-struts above the fuselage. The upper and lower wings were each connected by an N-strut and additionally with cables. The tailplane was supported by a strut to the fuselage. The undercarriage was on the engine frame of the fuselage and also backwards to the fuselage and the hull bottom. The wheel arches were aerodynamically shaped.
With the takeover of Hopfner by the Hirtenberger Patronen-, Zündhütchen- and Metallwarenfabrik AG in Hirtenberg, the semi-finished aircraft was brought to Hirtenberg, where it was completed in 1935 and received the designation HM.13/34 or HM.1334.
The first flight took place on June 6, 1935 and during the following flight testing there were no noteworthy incidents. The machine was then presented to the Austrian Air Force, but the interest was low, since several Fw 44J had been procured from Germany for fighter pilot training.
Finally, at the beginning of 1936, three machines were ordered by the Austrian Air Force (for Verwendungsgruppe B, Beanspruchungsgruppe II), which were delivered from the summer of 1936 and received the civil identifiers OE-FAH (factory number 52), OE-FEH (factory number 53) and OE-FIH (factory number 54). After the annexation of Austria to the German Reich in 1938, the three machines, like all Austrian military machines, were taken over by the Luftwaffe and passed on to fighter pilot schools in southern Germany.
The fate of HM.13/34 is unknown.
Hopfner / Hirtenberg HM.13/34
Engine: Fiat A-20, 410 hp (302 kW) max /
Continuous power: 355 hp (282 kW) at 3,000 m
Propeller: adjustable two-bladed wood
Propeller diameter: 2.50 m
Propeller disc: 4.91 m²
Wingspan upper: 10.21 m
Wingspan lower: 9,60 m
Upper wing dihedral: 2.33°
Lower wing dihedral: 2.66°
Wing area: 27.80 m²
Aspect ratio: 6.76
Wing chord: 1.08 m
Length: 8,45 m
Height: 3,03 m
Empty weight: 1,185 kg
Normal weight: 1,585 kg
Maximum TOW: 1,695 kg
Fuel tank capacity: 345 lt
Top speed SL: 258 km / h
Top speed at 3,000 m: 272 km / h
Cruise speed at 3,000 m: 245 km / h
Landing speed: 96 km / h
Ceiling: 6,000 m
Climb rate: 7.3 m / s
Time to 1,000 m: 2,4 min
Time to 3,000 m: 9.5 min
Range normal: 450 km
Maximum range: 600 km
Endurance: 2.5 hr
Wing loading: 60.97 kg / m²
Power load: 4.13 kg / hp (5.61 kg / kW)
Wheel track: 2,54 m
Crew: 1
Armament: 1 x 7.9 mm Hotchkiss machine gun / 500 rounds
Maximum bomb load: 40 kg

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