From September 1943, Typhoons were also armed with four "60 lb" RP-3 rockets under each wing. In October 1943, No. 181 Squadron made the first Typhoon rocket attacks. Although the rocket projectiles were inaccurate and took considerable skill to aim and allow for ballistic drop after firing, "the sheer firepower of just one Typhoon was equivalent to a destroyer's broadside." By the end of 1943, eighteen rocket-equipped Typhoon squadrons formed the basis of the RAF Second Tactical Air Force (2nd TAF) ground attack arm in Europe. In theory, the rocket rails and bomb-racks were interchangeable; in practice, to simplify supply, some 2nd TAF Typhoon squadrons (such as 198 Squadron) used the rockets only, while other squadrons were armed exclusively with bombs (this also allowed individual units to more finely hone their skills with their assigned weapons).