Rogozarski SIM-X
One SIM-X prototype delivered in early 1937 for testing and evaluation. Parasol wing primary trainer. After preliminary testing two orders were placed for a total of 20 aircraft. The last airframes were delivered during 1938, with the final three being given to the Yugoslav Royal Aero Club. Production aircraft were slightly different from the prototype, mainly by having a deeper NACA cowling. 120 hp Vlajkovic Walter NZR radial engine, although one aircraft later received a 132 hp Gipsy Major I engine. The type was used by the JKRV as well as by local aero-clubs for glider towing.

The SIM-X prototype was modified in early 1940 to serve as an instrument flying trainer - with new cockpit instruments, a front cockpit cover and 120 hp Walter Major 4 engine. Designated Si-Xip, the new version was not a success. The original Walter NZR engine was re-installed in early 1941 and the aircraft redesignated SIM-Xa.

Just before the April 1941 attack, five civilian examples were impressed into JKRV service. The majority of the aircraft were destroyed on the ground during German aerial attacks, but three were captured by the Germans and one of these was passed to the Croatian Air Force.

(The prototype and first ten production aircraft were initially given civil registrations).

Serial	c/no.	Prev. Identity	Delivered	Fate/Notes
301	1	YU-PDY	1937	first reg'd 1936, to JKRV 1937
302	2	YU-PDZ	1937	first reg'd 1937, to JKRV June 1937
303			1937
304			1937
305			1937
306			1937
307			1937
308			1937
309			1937
310			1937
311			1937
312			1938
313			1938
314			1938
315			1938
316			1938
317			1938
318			1938
319	19	YU-PFJ	1938	to Yug. Royal Aero Club Aug 1938
320	20	YU-PFK	1938	to Yug. Royal Aero Club Aug 1938
321	21	YU-PFL	1938	to Yug. Royal Aero Club Aug 1938

References:

• LET No.1 (Yugoslav Aviation Museum)

Rogozarski SIM-XI
One SIM-XI prototype delivered in early 1938 for testing and evaluation. Single-seat parasol wing aerobatic trainer developed from the SIM-X. 150 hp Siemens Sh 14a engine. No production order. In April 1941 the prototype was captured by the Germans and passed to the Croatian Air Force.

Serial	c/no.	Prev. Identity	Delivered	Fate/Notes
			1938

References:

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