Eurofighter's flight control system (FCS) software has been modified to counter transonic pitch-up automatically and reduce pilot workload.
All aircraft pitch up as they pass through Mach 1 because the centre of pressure - the point through which lift acts - shifts rearwards, creating a nose-up moment. In some aircraft this is countered by pumping fuel aft to maintain the relative distance between the centres of pressure and gravity, but this would potentially reduce the manoeuvrability of a fighter. While the phenomenon is well known, it can require unwelcome additional pilot inputs during combat manoeuvring or accelerating for battle positioning.
BAE Systems Eurofighter head Ross Bradley says FCS software to be delivered at the end of this year will include the ability to maintain the aircraft's attitude as it passes through M1. The load will also include an automated low- speed recovery capability. The latter will allow the aircraft to take over control if the speed becomes too low, perhaps during dogfighting.
Bradley says: "Controlling the transonic pitch-up through the FCS underlines the ability to manage a particular point [of the flight envelope]." Carefree handling has been a major driving point in Eurofighter flight control law design and implementation and is "a key element of lowering pilot workload", he adds.
Bradley says that delivery of the transonic pitch-up and low-speed recovery capabilities were originally planned for late next year. Eurofighter will probably enter service in September.
Source: Flight International