P.Grosz, G.Haddow, P.Shiemer Austro-Hungarian Army Aircraft of World War One

Lohner 10.21 (new) and 10.22

  The Fliegerarsenal (Flars - aviation arsenal) issued specifications in July 1916 for a long-range reconnaissance aircraft and requested Lohner to submit project drawings for two aircraft powered by the experimental 300 hp Daimler V-12 engine and capable of carrying a crew of three, including two observer-machine gunners in the rear cockpit. Lohner proposed the Type F [Fernerkundungs Flugzeug - long-range reconnaissance aircraft). Before much progress was made, the project was cancelled in favor of a 350 hp aircraft designed by Ingenieurleutnant Karl Saliger and Dr Richard von Mises of the Flars construction bureau.
  Structural drawings for the Saliger-Mises design had been completed in September 1916. From the outset Flars had planned to assign the construction to Aviatik, a company with spare manpower, but Aviatik suddenly had its hands full with C.I and D.I aircraft production. Consequently, on 11 December 1916, the LFT command shifted the project to Lohner. The Saliger-Mises specifications called for a top speed of 200 km/h (124 mph) with a rate of climb of 1000 meters (3281 ft) in 4 minutes, a duration of two hours, an armored seat for the pilot, a common cockpit for the crew, one fixed machine gun, and a rear gun located to fire a 180-degree traverse. Parts assembly began in the Lohner shops in January 1917. The first prototype, numbered 10.21 (w/n 33/438), stood assembled at the factory on 24 April 1917. Since the 350 hp engine was not ready, the experimental 300 hp Daimler V-12 engine was installed. The second machine, 10.22 (Type F-w/n 33/439), was completed but not assembled.
  The Lohner flight log shows that the 10.21 was at Aspern ready for flight trials on 2 May 1917. Now began a year-long program, delayed by problems with the new Daimler V-12 engine. From the record it is clear that the 10.21 was used primarily as a test-bed for engine trials. Ground tests were performed on 7 May. During taxi trials on 11 May, the undercarriage shock cords tore apart. On the maiden flight, performed on 12 May, Lohner test pilot Karl Kriger reported severe engine vibrations and tail skid failure. On 16 May, the tailplane broke while taxiing. The "nose and tail heaviness" was reported solved by structural modifications in June 1917. Work was also underway to design a new tail skid and widen the rear cockpit to hold a third crew member. The task of finding a suitable propeller to match the engine-airframe characteristics consumed much of the test program.
  The 10.21 prototype was turned over to the Flars test group on 4 June 1917 and Karl Kriger continued the flight investigation through October 1917, during the course of which the climb rate to 1000 meters (3281 ft) had been lowered from 15 to 3:45 minutes as a result of engine and propeller improvements. On 28 October the engine was removed to install aluminum pistons which, among other modifications, increased the engine rating to 345 horsepower. The 10.21 continued sporadic flights at Aspern to evaluate engine performance up to 4000 meters (13,123 ft) altitude. When last reported in October 1918, the 10.21 prototype was based at Aspern in flying condition.
  In February 1918, preparations were underway to install the experimental 360 hp Daimler six-cylinder engine in 10.22, the second Type F prototype. The 10.22 appeared at Aspern on 14 May 1918 and performed its maiden flight on 27 May. Returned to the factory owing to a minor mishap on 8 June 1918, the 10.22 was last reported at Aspern in August 1918.

Lohner 10.21 Specifications (new)
Engine: 300 hp Daimler
Wing: Span Upper 15.0 m (49.21 ft)
Span Lower 15.0 m (49.21 ft)
Chord Upper 1.96 m (6.43 ft)
Chord Lower 1.96 m (6.43 ft)
Total Wing Area 50.0 sq m (538 sq ft)
General: Length 10.3 m (33.79 ft)
Height 3.50 m (11.48 ft)
Empty Weight 1150 kg (2536 lb)
Loaded Weight 1800 kg (3969 lb)
Maximum Speed: 157 km/hr (97.5 mph)
Climb: 1000m (3,281 ft) in 15 min

E.Hauke, W.Schroeder, B.Totschinger Die Flugzeuge der k.u.k. Luftfahrtruppe und Seeflieger 1914-1918

10. Flugzeuge der Fabrik Jacob Löhner & Co. Wien, Floridsdorf
10.21 Löhner DD Type F Dm 300
10.22 Löhner DD Type F Dm 300