Final answer:
When operating a multi-engined aircraft under night VFR, the weight of the aircraft must be such that it can at least maintain an altitude of at least 1000 feet above the highest obstacle within 3 NM of the route being flown with any engine inoperative.
Step-by-step explanation:
When operating a multi-engined aircraft under night VFR, the weight of the aircraft must be such that it can at least maintain an altitude of at least 1000 feet above the highest obstacle within 3 NM of the route being flown with any engine inoperative. This is necessary to ensure the safety of the aircraft and its occupants in case of engine failure. By maintaining this altitude, the aircraft has a buffer zone to clear any obstacles and continue flying safely.