Novakovic, N., "Hardware Design and Implementation of the Landing Gear Control Algorithm," SAE Technical Paper 2014-01-2186, 2014, doi:10.4271/2014-01-2186.
Since the early 1970s, when microprocessors became commercially available, they quickly became a common part of all aircraft control and indication systems. With an ever-increasing number of microprocessor-based airborne applications, safety regulations and software standards like RTCA DO-178 evolved, demanding rigorous requirements and processes for software development, testing, life cycle, and certification. Over the years, as development of aerospace software applications increased, engineering costs of development and product certification costs exponentially increased, having a significant impact on the market.Landing Gear Actuation system is one of many aircraft systems whose control functions are based on microprocessors and software application. Considering that Landing Gear Actuation control algorithm can be defined in a form of the State Machine, this article intends to demonstrate that such controller can be realized as wired logic hardware, without software implementation. Control algorithm and logic structures were defined based on generic aircraft Landing Gear Actuation system, which is common for many midsize commercial aircraft. A full functionality of the control algorithm was defined and simulated together with the initial conditions, power up recovery states, and reverse commands.Although Landing Gear Actuation control is an aircraft safety critical function, the presented design and hardware implementation in accordance with RTCA DO-254 can qualify as “Simple Electronic Hardware.” With such design concept, cost of development, implementation, and certification can be significantly reduced compared with the same controller realized with microprocessors and software.