Application of visual and instrument flight rules to remotely piloted aircraft systems: A conceptual approach

The non-segregated participation of remotely piloted aircraft systems (RPAS) into civil air traffic is still a big challenge with many open questions, especially in terms of airspace integration, traffic handling and aircraft certification. One of the most basic and most natural regulatory requirements in aviation is the application of flight rules as written down in ICAO Annex II. This existing regulation is on one hand per definition not restricted to manned aviation, on the other hand it points to the need of finding a way to apply these flight rules also to RPAS, which has already been a known key issue for a long period of time, but which is not yet completely solved by now. Many ANSPs impose only few requirements for RPAS operations under instrument flight rules, but the application of visual flight rules to RPAS operations is more demanding, e.g. in terms of detect-and-avoid capabilities, navigation, right-of-way, aerodrome operations and others. Many of the worldwide research activities related to RPAS set the focus on developing technical solutions to reproduce these pilot-typical capabilities such as the see & avoid capability, and it should be just a question of time, until such a sensor-based technology will be available. But the introduction of these devices will most probably imply a significant change in terms of navigation, perception of the aircraft environment and decision making compared to manned aviation. The question how to apply visual and instrument flight rules to RPAS will still not be completely answered. Starting from ICAO's Manual on Remotely Piloted Aircraft Systems (ICAO Doc 10019), this paper looks beyond required technical capabilities and gives a renewed definition of flight rules. This definition is especially designed for both manned and unmanned aviation without significantly changing or lowering the standards for manned aviation. Based on several conceptual studies, which were performed within the scope of the DLR research activities for traffic management and integration of unmanned aircraft, this paper provides a simple guideline for the application of these re-defined - or modernized - flight rules in analogy to the existing rules. It discusses manned and unmanned flight operations in non-segregated and segregated airspace as well as unmanned visual-line-of-sight operations in terms of navigation, surveillance, tactical ATM decision making and flight pre-notification, following existing procedures as far as possible. The basic ideas behind these procedures are outlined, but separately from aspects resulting from distinct technical solutions (such as secondary radar and transponders) or human factors (such as visibility minima) in order to cover the whole bandwidth of manned and unmanned flight operations. In this context, basic terms are also redefined.