Direct Lift Control: A review of its principles, merits, current and future implementations

Abstract

Direct Lift Control (DLC) is the capability to directly and intentionally influence lift on a fixed-wing aircraft by means of aerodynamic control devices, with minimum change of its angle of attack. Although several definitions exist, with various degrees of ambiguity, the combination of DLC and pitch attitude control has unambiguously proven to reduce pilot workload and improve flying comfort considerably. DLC has historically seen several applications on so-called inflight simulators and, recently, this capability has been rolled out over several aircraft types of the US Navy fleet, massively reducing pilot workload during carrier landings. On the civil front, only one aircraft type has been equipped with this capability, despite its very positive reception by flight crews and passengers. The intention of this paper is to revive interest in civil DLC applications, by reviewing in-depth its basic principles, characteristic features, benefits, and implementations so far. Several modern aircraft and disruptive wing configurations appear to be inherently capable of accommodating DLC functionality from a flight physical, systems, and software point of view. The proven benefits of DLC are likely to well outweigh the cost of the added functionality.