The Bf109 Tropical was unique due to its air intake filter, hydraulic seals and protective covers. In addition, an umbrella was extendable over the cockpit to help keep the pilot from overheating when on the ground. The plane was equipped with a special emergency kit including a gun for self-defence and a supply of food and water.
Following the experiences of the E-4, the E-7 was the next major production variant, entering service and seeing combat at the end of August 1940. One of the limitations of the earlier Bf109E interceptor fighter was the short range of 660km (410 miles). The E-7 rectified this problem as it was the first to carry a drop tank.