Concept and Objectives:
The long-term, ultimate goal of the consortium carrying out this project is to introduce new and innovative technologies into the small aircraft aviation segment; everything from avionics, navigation up to aircraft manufacturing. This will be a completely new transportation system for small aircraft which will make it more available to everyone and should provide safe, “green” and affordable air transportation even under denser air traffic and more complex ATC in the future.
SAFAR will focus on the development of a future avionics architecture for small aircraft providing easy and safe control of the aircraft. SAFAR aims at a significant reduction of pilot workload and an increase of safety during all phases of flight and ground operations including take-off and landing. In order to achieve this, SAFAR will provide the aircraft with easy handling characteristics and flight envelope protection at any time. The pilot flies the aircraft mainly via a stick controller and throttle lever. Switching between flight control and flight guidance modes will be performed automatically by the system: transparent for the pilot.
Within the SAFAR project the consortium will set first steps in the direction of design, development and validation of an avionics architecture for future small aircraft (safe, cost efficient, extentable and scalable) which will lead the way for advanced low capacity air transportation (LCAT) systems.
Baseline of the SAFAR architecture will be an advanced safety critical, fault tolerant fly-by-wire platform applicable to LCAT aircraft. The platform will comprise computing resources, a human machine interface, a mainly satellite based fault tolerant attitude/navigation system and a safety critical electric power supply with all-electric actuators. In order to keep the handling characteristics of the aircraft as easy as possible and to avoid any pilot training cases, the fly-by-wire platform must maintain the same handling characteristics and flight protection features even in cases of platform failures. Significant functional degradations in the handling characteristics such as degradation to “direct law” are not acceptable. This requires an all time / full performance / full authority fly-by-wire platform without any mechanical backup. In order to cope with the challenge of “low-cost” for the LCAT category, synergies with advanced absolutely safety critical drive-by-wire platforms with 10E-9 safety capability from automotive developments based on fly-by-wire experience will be used.
The fly-by-wire platform will be developed as a safety critical all electric platform including all electric actuation. Therefore, new absolute safety critical electric power generation / distribution including strategies providing safe E-powerstorage in cases of emergency descent due to total engine loss (no ram air turbine will be used) including mechanisms for continuous accurate diagnostics of energy storage will be investigated. Energy management will provide sufficient emergency E-power-storage at any time. Electric fault tolerant actuation system complying with specific requirements of small A/C will have to be designed.
Reliable and accurate position and attitude information is a fundamental requirement to enable autonomous control. For the SAFAR project a primarily GNSS based solution is identified as a promising solution to create a cost efficient and failure tolerant position and attitude sensor.
Future operation in environments of much increased traffic densities will need advances in ATM capabilities and operational practices. It will be mandatory that the present practice of tactical instructions by Air Traffic controlers using very busy radio channels is to be replaced by a strategic trajectory based ATM system. The recommendations of SESAR will be considered here.
The objectives of making A/C more affordable, reliable and greener, will be supported both directly and indirectly by SAFAR. It will allow advanced A/C design relying fully on active control, monitor and diagnostics functions. This will allow A/C designers to utilise mechanical safety margins optimally and thus to design more flexible and lighter structures. Also, natural dynamic stability will not be a constraint for A/C design any more. The design of a dynamically instable A/C allows a reduction of the induced drag due to an aft centre of gravity which results in a lower noise level and lower fuel consumption.
The fly-by-wire platform developed in this project will be the first to be certified according to CS23. Therefore a certification guideline for fly-by-wire / all electric small aircraft will be established in close cooperation with EASA. Up to now CS23 relevant for A/C considered here is not adapted for fly-by-wire control. So, clear criteria about the application of design assurance levels (DAL) as they are given in CS25 do not exist in CS23 and will be proposed.
Beyond the current research objectives it is the intention of the SAFAR consortium to provide a generic, enhanced and proven avionics architecture to the aeronautics community with a high degree of reuse of generic hardware and software components which will allow the implementation of advanced functionalities to small aircraft such as automatic takeoff and landing or automatic go-home and auto-land functionalities in case of emergency in the future. Advanced ATC and even ATM will be supported by maximum on-board automatism. Four dimensional flight vectoring as a result of the onboard ATM/FM shall be executed automatically.