In 1928, Theodor Hopfner began designing a new light passenger aircraft, designated Hopfner HV.4 / 28. The aircraft retained the power plant from its predecessors – one Hiero engine with a power of 230 hp. The passenger capacity of the aircraft also did not change – one passenger was located near the pilot, and three more were in the cabin.

The first flight of the aircraft (board number A-49) took place on July 25, 1929. The Hopfner HV-4/28 saw heavy use by the airline that year.

In 1929, it received a major refurbishment that included a change or powerplant from the original Heiro to a Gnome et Rhône 9A Jupiter engine and was sold to a private owner under the new designation HV-8/29GR. This aircraft was still flying at the time of the Anschluß, after which it received a new German registration.

Hopfner HV-4/28
Engine: 1 × Hiero 6, 170 kW (230 hp)
Wingspan: 16.20 m (53 ft 2 in)
Wing area: 42.0 sq.m (452 sq.ft)
Length: 11.00 m (36 ft 1 in)
Height: 3.30 m (10 ft 10 in
Empty weight: 1,390 kg (3,060 lb)
Gross weight: 1,970 kg (4,340 lb)
Maximum speed: 125 km/h (78 mph)
Cruising speed: 108 km/h
Endurance: 6 hours 30 min
Crew: One pilot
Capacity: 4 passengers

The Hopfner HV-3/27 (also written as HV.3/27) development of the HV-2 was a small airliner built in Austria. It was a conventional, single-engine high-wing cantilever monoplane with a fully enclosed cabin and fixed undercarriage.

A single example was built in 1927 and used by Hopfner’s own airline until 1934.

Engine: 1 × Heiro, 170 kW (230 hp)
Wingspan: 16.40 m (53 ft 10 in)
Wing area: 36.0 sq.m (388 sq.ft)
Length: 10.50 m (34 ft 5 in)
Height: 3.30 m (10 ft 10 in)
Empty weight: 1,380 kg (3,040 lb)
Gross weight: 2,080 kg (4,580 lb)
Endurance: 6 hours
Crew: One pilot
Capacity: 4 passengers

After the release of the light multi-purpose S.1, Theodor Hopfner began developing a five-seater passenger aircraft equipped with a 240 hp Hiero engine. The first flight of the aircraft, designated HV.2 (board number A-19), took place in early 1925.

After several test flights, the aircraft was reconstructed. In this form, it transported about 3,000 passengers in two years.

Engine: Hiero, 240 hp
Wing span: 15.00 m
Wing area: 10.55 m
Length: 3.15 m
Height: 38.00 sq.m
Empty weight: 1500 kg
Normal take-off weight: 2200 kg
Maximum speed: 150 km / h
Cruising speed: 121 km / h
Range: 500 km
Ceiling: 4000 m
Crew: 1
Passengers: 4

The Hopfner HV-6/28 (HV.628), designrd by Theodor Hopfner, was a small airliner built in Austria for Swiss use.

Unrelated to Hopfner’s other airliners of the period, the HV-6/28 was a conventional, high-wing, single engine, strut-braced monoplane with a fully enclosed cabin. The main units of the fixed tailskid undercarriage were divided. The single example built, CH-186, was handed over on April 19, 1929 and was flown by Ostschweizer Aero Gesellschaft St. Gallen between 1929 and 1931, and then scrapped.

The aircraft was a high-end engine equipped with a 240 hp Walter Castor engine, with a passenger cabin for 6 people.

Engine: 1 × Walter Castor, 180 kW (240 hp)
Length: 10.00 m (32 ft 10 in)
Wingspan: 16.00 m (52 ft 6 in)
Height: 2.90 m (9 ft 6 in)
Wing area: 36.4 sq.m (392 ft2)
Empty weight: 1,113 kg (2,449 lb)
Gross weight: 1,950 kg (4,290 lb)
Maximum speed: 194 km/h (123 mph)
Range: 250 km (160 miles)
Service ceiling: 3,500 m (11,500 ft)
Crew: One pilot
Capacity: 6 passengers

The light transport aircraft Hopfner HS.10/32 (HS.1032) was developed based on the successful light multipurpose aircraft HS.9. The 1932 HS.1032 was a sport und utility aircraft, two-seat, single-engine high-wing monoplane with enclosed cockpit and fixed undercarriage.

The first flight of the aircraft prototype (A-130 / registration – OE-DGL), equipped with a Siemens Sh 14A engine with a power of 150 hp, took place in the second half of 1932. Following it, two more aircraft were manufactured – A-131 and A-132 / OE-DIS.

Four were built (including one slightly modified and designated as HS.1033 / HS.10/33.

An Austrian mail pilot during the summer months, Hubert Kleinhaus gave joyrides in the winter from Kitzkeuhl and with a HS.10/32, and ran a service, when necessary, to St. Petersburg. Moritz. His machine, is a Hopfner “Superfly” with a Walter “Gamma” engine. Kleinhaus learnt to fly in Germany and took an aerobatic course in this country.

HS.1032
Engine: Siemens Sh 14A, 150 hp
Wing span: 10.96 m
Wing area: 18.00 sq.m
Length: 8.02 m
Height: 2.39 m
Empty weight: 640 kg
Normal take-off weight: 1000 kg
Maximum speed: 190 km / h
Cruising speed: 170 km / h
Practical range: 840 km
Practical ceiling: 4500 m
Seats: 2

In 1922, Austrian pilot Theodore Hopfner began construction of his first aircraft. The aircraft was built in the workshops near the Aspern Vienna airfield. In parallel, Hopfner establishes his aircraft construction firm Flugzeugbau Hopfner GmbH. The result of this activity is the light multipurpose aircraft Hopfner S.1.

The first flight took place in the spring of 1923. The plane flew until September 1924, after which it was destroyed in an accident.

Engine: Fiat-Mercedes, 100 hp
Wing span: 12.00 m
Wing area: 27.00 sq.m
Length: 7.53 m
Height: 2.56 m
Empty weight: 800 kg
Maximum take-off weight: 1150 kg
Maximum speed: 150 km / h
Cruising speed: 122 km / h
Range: 400 km
Seats: 1