A derivative of the Hopfner HS-5/28 via the Hopfner HS-8/29, the Hirtenberg HS.9 two-seat touring or training aircraft of the late 1920s and early 1930s was an Austrian parasol wing monoplane with a fixed tailskid landing gear and room for two occupants in tandem open cockpits.
Designed by Theodor Hopfner, it had a metal fuselage (front covered with duralumin sheets, the rest – with a cloth) and a wooden wing lined with linen. In the center section there was a fuel tank for 132 liters. The wing consoles, for more convenient storage in the hangar, could be folded along the fuselage.
It first flew as the Hopfner HS-9/32 in 1932, powered by a 120 hp de Havilland Gipsy Major I engine. Prototypes HS-9 had civil registration codes A-124 (then changed to OE-ANA) and A-144 (OE-DJH). Later the second prototype was sent to the UK and received the G-AGAK registration there.
Production versions were produced under the designation HS-9/32 (sometimes called the HS-932) and had 150 hp Siemens Sh 14 engines with NACA cowlings and two-bladed screws. As Hopfner’s production facilities were insufficient, HS-9/32 was produced by Hirtenberg Patronen (Hirtenberg), where 9 aircraft were built.
In 1935, four were transferred to the Austrian Air Force for use as training. They were given military registration codes OE-TOH, OE-TUH, OE-TAO and OE-TEO and numbers (Dienst Nummer, DNr.) 426 – 429.
After the annexation of Austria in 1938, several aircraft were still in service. The Germans included captured aircraft in their own air force and left them on Austrian territory, where they were handed over to Nationalsozialistisches Fliegerkorps (NSFK). As of 1939, Gruppe 17 still had five machines of two types: four HS-9/35 with numbers 425-428 and one HS-9 with number 434. As for HS 8/29 (number 412), this aircraft was destroyed in Zeugamt Erding.
A single example of a refined version with an uncowled 125 hp Siemens engine was flown in 1935 as the Hopfner HS-9/35, shortly before the Hopfner company went bankrupt.
When Hopfner’s assets were purchased by Otto Eberhardt Patronenfabrik, production continued of both de Havilland- and Siemens-powered (designated HS-9A) aircraft under the Hirtenberg brand.
Twelve Hopfner HS.932 (HS.9/32) were built from 1932 (2 prototypes + 10 series), including one aircraft with modified ailerons and undercarriage designated as HS.935 / HS.9/35.
In 1935, a significantly modified version of HS-9 \ 35 then in the Fliegertruppen des Osterreichischen Bundesheeres received the code OE-TAR (DNr. 434). With an uncooled Siemens engine it was flown shortly before the Hopfner company went bankrupt.
About 40 were built in total. They were operated by the Austrian Air Force during 1927-1938.
Variants
HS-9/32 – Original version by Hopfner
HS-9/35 – developed version of HS-9/32
HS.9 – Production aircraft with a Siemens Sh 14a piston engine.
HS.9A – Production aircraft with a de Havilland Gipsy Major piston engine.
HS.16 – military trainer version of HS.9
HS.9A
Engine: 1 × de Havilland Gipsy Major, 90 kW (120 hp)
Length: 8.05 m (26 ft 5 in)
Wingspan: 10.972 m (36 ft 0 in)
Empty weight: 568.8 kg (1254 lb)
Gross weight: 948 kg (2090 lb)
Maximum speed: 190 km/h (118 mph)
Crew: 2
HS.932
Engine: Siemens Sh 14A, 150 hp
Wing span: 10.96 m
Length: 8.02 m
Height: 2.39 m
Wing area: 18.00 sq.m
Empty weight: 570 kg
Maximum take-off weight: 860 kg
Maximum speed: 190 km / h
Cruising speed: 170 km / h
Practical range: 400 km
Service ceiling: 4400 m
Crew: 2
Hopfner HS-9\35
Engine: Siemens Sh.9, 150 hp
Prop: two-bladed wooden
Wingspan: 10.96 m
Length: 8,02 m
Wing area: 18,00 sq.m
Height: 2.39 m
Empty weight: 570 kg
Takeoff weight: 860 kg
Maximum speed: 190 km / h
Range: 400 km
Ceiling: 4400 m
Crew: 2
