Staff Writer (Updated: 5/31/2016):
Using the large, existing Zeppelin hangars, the Germans worked on their own multi-engine bomber forms and one ultimately realized product became the Zeppelin-Staaken R-series. These bombers incorporated enclosed cockpits, which were rather novel for the time, multiple engine nacelles and a network of machine guns for local defense. Bomb loads reached over 4,000 lb. The aircraft offered the operational ranges required in reaching the enemy while also providing the needed bomb-carrying capability that light and medium bomber models lacked.
The first available mark was R.VI which arrived in late-June of 1917 and were pressed into service as night bombers against the Russians over the Eastern Front from August onwards. By September, they began operations in the West when stationed in German-held Belgium territory. Raids against the British mainland followed and lasted into May of the following year with none were lost to enemy action. Four aircraft were ultimately destroyed by enemy action during the course of the war with six lost to accidents.
Five major variants of the R-bomber were conceived beginning with the aforementioned R.VI. These marked the first true production versions of the line and were outfitted with 4 x Maybach Mb IV engines of 245 horsepower each. An alternative engine configuration became 4 x Mercedes D.IVa engines of 260 horsepower each. Eighteen examples made up this mark with one reserved as an engine testbed.
The R.VII mark came next - though with only one example built - and added a revised tail unit for improved stability. This sole aircraft was lost while in transit to the frontline. Variant R.XIV was outfitted with 5 x Maybach Mb IV engines, four arranged in paired "push-pull" nacelles and the fifth set in the nose as a puller engine. Three were ultimately built with one being lost to enemy action. R.XV appeared with the same five engine arrangement debuted in the R.XIV and was produced in three examples. A primary physical difference of this mark was a large tail fin added at the center of the tail unit arrangement. This group did not see formal combat service in the war.
The Type L was a large floatplane conversion of the land-based bomber to operate from water for the German Navy. Large floats were appropriately added in place of a traditional wheeled undercarriage and a sole prototype was completed. However, this example crashed while being tested. The Type 8301 followed suit as a possible seaplane conversion but introduced an all-new fuselage while retaining the wing elements of the previous bomber design. Again a float undercarriage allowed for waterborne take-off and landing and this design netted three examples in all.
Only two German Air Service squadrons were ever equipped with the R-bomber - Riesenflugzeugabteilung 500 (Rfa500) and 501 (Rfa501). As stated, the bomber also saw some limited service with the Imperial German Navy for a time.
Twenty-nine of these large bombers were built.