Complex sentence: For a variety of reasons, the triplane's combat career was comparatively brief; it proved difficult to repair and the fuel and oil tanks were inaccessible without substantial disassembly of the wings and fuselage.
Split into simpler sentences: For a variety of reasons, the Triplane's combat career was comparatively brief. The fuel and oil tanks were inaccessible without substantial disassembly of the wings and fuselage.