The Hirtenberg HS.9 was an Austrian two-seat touring or training aircraft of the late 1920s and early 1930s. A derivative of the Hopfner HS-5/28 via the Hopfner HS-8/29, it was a parasol wing monoplane with a fixed tailskid landing gear and room for two occupants in tandem open cockpits, and first flew as the Hopfner HS-9/32 in 1932, powered by a de Havilland Gipsy I engine. Production versions had Siemens Sh 14 engines with NACA cowlings.

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Training and mocking aircraft "Hirtenberg HS 9".
This aircraft model, now manufactured by the Hirtenbetget Patronenfabrik A.-G., Aircraft Construction Department, in Setie, is a further development of the well-known Hopfner sports aircraft, a braced high-wing aircraft in mixed construction, equipped with a 150 hp Siemens SH 14 A engine, which is geared in particular to aerobatic capability  The proven construction principles of the previous type were retained and all the experience gained with it during more than ten years of testing in civil and military schools was taken into account. Construction safety, flight characteristics and flight performance have been largely improved.
With good speed performance and maneuverability, the model is characterized above all by its harmless flight characteristics, especially in the coated state and in briefs. Great stability even in slow flight, no tendency to spin unintentionally or slip over the wing. The aircraft can only be brought into a spin with rough control deflections. However, it spins excellently in
both directions and ends this movement immediately after the normal position of the stick, without the need for countersteering with the rudder.
All other aerobatic manoeuvres can also be performed easily. Steering forces low, rudder effects, well coordinated. Seats spacious and comfortable, excellent visibility, can be left quickly and safely by parachute. The aircraft type is to be used for courier flights in group S4K with a flight weight of 810 kg (payload 240 kg) and for cruising flights in group R3 with a flight weight of 900 kg (payload 330 kg).
For operational reasons, operational series engines of domestic origin were selected and all frequently stressed parts, such as landing gear, spur,
steering mechanism, rudder bearings, etc., were dimensioned in such a way that they could withstand the continuous and peak stresses even of a forced school operation. Due to the easy
folding of the supporting structure - it can be carried out within two minutes without tools - only a small storage space (8X3.5X3 m) is required. During external landings, the folded aircraft
can be towed along any path at least 3.5 m wide without dismantling work. In the event of an emergency landing, a v/oak spring-loaded
chassis with high energy destruction capability protects the airframe, strong damping in the oil air struts prevents the machine from jumping and wheels that can be easily braked
increase landing safety.
Harmless flight characteristics, simplicity of control and low landing speed make it easy for even those who are less capable of flying to learn to fly with this
type of aircraft.
Wings covered with fabric, rectangular outline rounded at the ends and slight arrow and V shape. Wooden construction with internal bracing, divided. V-stem made of
profile tubular steel supported against the lower fuselage chord. Wing around the handle connection and rear Holman connection on the canopy can be folded backwards. Front spar v/ird connected to the canopy by a double-secured bolt quick-release fastener. Holm belts laminated, ribs partly truss, partly stegrippen. Connection fittings
chrome-moleybden blech, internal bracing steel cables and steel tubes. The ailerons, which pass through the foldability, are designed as split ailerons with
aerodynamic internal compensation and are dimensionally balanced.
Fuselage: welded hull without wire crossing, fabric covering, back covered with easily removable light alloy skin. Strong, shatterproof
canopy, braced with profile wires. Brackets and flutter strips achieve an aerodynamically favourable outer shape. Fabric-covered tubular steel frame seats,
spacious, with v/oak leather cushions and back cushions. It is possible to take seats and back parachutes with you. A comfortable,
lockable boarding door leads to the passenger seat.
In both seats stick steering and adjustable rudder logs. All components steel tube. Elevator is operated by bumpers. Steering cables to rudder
and aileron guided by ball bearing pulleys. Control pressure regulator in the driver's seat.
In front of each seat there is an elastically mounted equipment board in which the flight, tracking and engine instruments are clearly arranged.
Tail: Zv/eiholmige. Height fin built in wood, braced and braced, adjustable at the bottom. Tubular steel elevator with lateral compensation. Keel fin steel tube,
organically connected to the hull. Rudder steel tube, with lateral compensation.
Wide-gauge chassis, split, consists of strong steel axles connected to a 4-frame gimbal and oil
air spring struts supported against the fuselage upper chords. Dunlop low-pressure wheels 4.75X7.5, Bendix brakes, by foot pedals, also to be operated individually. Spur lying outside the fuselage, articulated leaf spring battery and swivelling sanding pad with Percite support.
The normally compressed Siemens SH 14 A engine with a maximum output of 150 hp and a continuous output of 130 hp is fitted as standard. Wooden propeller of 2.3 m diameter
and 1.2 m pitch. Throttle lever on the left side of the ship, transmission through rods. The pre-ignition is automatically activated by a
Bosch pre-ignition switch that is dragged along when accelerating. For starting, snap-off magnet, a hand crank magnet and outboard compressed air connection. Aluminum welded fuel tank
(132 1) elastically attached to the canopy. Fuel delivery by motor-driven double-acting DBU pump. Pipe network throughout Aviotub hoses with
anodized light alloy connections. In front of the carburetor there is a generously sized fuel cleaner. Lubrication tank (16 1) attached to the engine stem above the oil pump.
Wingspan 11 m, length 8 m, height 2.4 m, wing 18 m2, equipment 570 kg, payload 330 kg for cruising and 240 kg for aerobatics, flight weight 900 kg for
cruising and 810 kg for aerobatics, maximum speed 190 km/h, cruising speed 165 km/h, landing speed 70 km/h, service ceiling 4400 m, climb time to 1000 m 4.5 min., Flight time 580 km