Like all post-E8 British E-class submarines, E27 had a displacement of 662LT at the surface and 807LT while submerged. She had a total length of 180feet[1] and a beam of 22feet. She was powered by two Vickers eight-cylinder two-stroke diesel engines and two electric motors.[2] [3] The submarine had a maximum surface speed of 16kn and a submerged speed of 10kn. British E-class submarines had fuel capacities of 50LT of diesel and ranges of 3255miles when travelling at 10kn.[1] E27 was capable of operating submerged for five hours when travelling at 5kn.
E27 was constructed with a 12-pounder 76mm QF gun mounted forward of the conning tower, although this was later removed. She had five 18 inch (450 mm) torpedo tubes, two in the bow, one either side amidships, and one in the stern; a total of 10 torpedoes were carried.[2]
E-Class submarines had wireless systems with power ratings; in some submarines, these were later upgraded to systems by removing a midship torpedo tube. Their maximum design depth was although in service some reached depths of below . Some submarines contained Fessenden oscillator systems.[1]
Her complement was three officers and 28 men.[1]