The E.4./M.15. was a further development with a stronger 160 hp twin-row Oberursel rotary engine and often fitted with twin guns, some with three guns.
Only 49 were built, partly because the increased gyroscopic effect that made the E.4. more difficult to fly than the Fokker E.3., partly because the aircraft became obsolete
The F.4. was a last-ditch effort on Fokker's behalf to prolong active life when the type was obsolescent, since the legend of the Fokker's invincibility had been shattered by the spring of 1916.
The E.4. was virtually an enlarged E.3. fitted with two machine-guns and with a 160 h.p. Oberursel U III engine.
This was a fourteen-cylinder, two-row, rotary and had not the reliability, or flexibility, of the less powerful rotaries.
Due to its weight it made the E.4. far less nimble than the E.2. and E.3..
Immelmann had one which had been especially equipped with three machine-guns, but performance was so poor, due to the increased weight, he reverted to the E.3., on which type he was eventually killed on 18th June 1916 during combat with an F.E. 2b of 25 Sqdn. R.F.C., flown by Lieut. G. R. McCubbin and his observer Cpl. J. H. Waller.
However, Oblt. Student of Fokkerstaffel der III Armee (later on Jasta 9) preferred the E.4. to the E.3. and operated with success in the Verdun sector.