Type	GL 18	GL 18a	GL 18c
Engine	2 Junkers L1a	2 Siemens Sh 11	2 Siemens Sh 12
Dimensions	Length 8.50 m, height 2.60 m, span 16.00 m, wing area 32.00 m2	Length 9.10 m, height 2.60 m, span 16.00 m, wing area 32.00 m2
Weights	Empty 925 kg, flying weight 1450 kg		Empty 1194 kg, flying weight 1650 kg
Performance	Max. speed 135 km/h, cruising speed 125 km/h, landing speed 85 km/h, required runway for take off 115 m, for landing 85 m, climb to 1000 m 10 min., service ceiling 3400 m		Max. speed 140 km/h, cruising speed 125 km/h, landing speed 85 km/h, required runway for take off 160 m, for landing 100 m, climb to 1000 m 5.8 min., to 3000 m 15 min., service ceiling 3500 m, range 500 km

c got an incresed width  to make it more comfortable for the instructor and the trainee

Type	WerkNr.	Registration	History
	28	D-967	"Helgoland". First flight 9th of August 1926. To Junkers Luftverkehr AG, from 1926 to Lufthansa. 1929 to RLM, scrapped 1932
a	30	D-1066	Used by the DVS
c	31	D-1097	Built 1928. To DVS, Berlin-Staaken. Stored March 1932