Aircraft Flight Operation Regulations Article 92
In the case of airplane having three or more powered-units, the aircraft shall be able, in the event of any two power units becoming inoperative at any point of a route, to continue the flight to an en-route alternate aerodrome and land.
中文原文 航空器飛航作業管理規則第92條
三具以上發動機之飛機於航路中，發生二具發動機失效時，其性能應能確保其繼續飛航至適當機場降落。