GM6 Article 3(1) U-space airspace

AIRSPACE RISK ASSESSMENT — ACCEPTABLE LEVEL OF SAFETY (ALS)

(a)     One of the main objectives of the implementation of the U-space is to increase the level of safety of the introduction of UAS operations to an acceptable level. In aviation, the acceptable level of safety is generally defined in terms of the probability of an aircraft accident occurring and the consequences being acceptable to the society, i.e. the society is ready to accept or be subjected to the risk that the event might involve. The role of Member States in this regard is to translate the societal perception into qualitative or quantitative criteria addressing the probability and consequences of occurrences.

(b)     The acceptable level of safety is defined by Member States, which should consider the inputs from UAS operators and USSPs regarding their needs and capacities. In order to set acceptable levels of safety for the U-space airspace, it is proposed to set safety criteria as per Regulation (EU) 2017/373 considering the singularities and specificities of the different types of risks posed by unmanned traffic in the U-space.

(c)      The defined set of safety criteria should cover all possible identified risks. Each criterion should be verifiable and expressed in terms of an explicit level of safety risk or another measure that relates to a specific safety risk. In the absence of sufficient data related to U-space operations to take as a reference to determine the safety criteria, safety indicators from manned aviation operations may be used.

(d)     It is worth remarking that when setting safety criteria for the U-space airspace, the goal is to maintain at least the safety levels attained over years of experience in manned aviation. However, considering the specificities of UAS operations in the U-space, this might mean a higher rate of mid-air collisions than for manned aviation. Nevertheless, considering the mitigation means that ensure separation between manned and unmanned aircraft, the mid-air collision between two unmanned aircraft will not result in casualties in the air. The ground risk is likely to be higher in populated areas, particularly when comparing high density of unmanned operations with traditional manned aviation. The definition of safety criteria should take these factors into account, as well as the presence of critical infrastructures in the vicinity which could be negatively impacted by UAS operations.

(e)     With reference to units of measurement, the most common unit of measurement applied to manage aviation risks is generally the reference to ‘aircraft per flight hours’. Nevertheless, there are other units that could be used in the framework of an airspace risk assessment. In general, it is considered that the most appropriate unit of measurement to assess U-space safety risks refers to ‘per flight hour’ for en-route phases of flight, while for the take-off, approach and landing phases of flight, reference to ‘per movement’ over a period of time (e.g. ‘per year’) is the most convenient.

(f)      The airspace safety specification at operational level will define what must happen at operational level in the airspace for the specified acceptable level of safety to be met. Different factors can be adjusted, like for instance the type of traffic, aircraft and system performance, equipment, procedures, aircraft speed, type of operation, maximum capacity, the number of people overflown (population density), among others, to comply with the airspace safety specification at operational level. Once the U-space is operational, comparative approaches to determine the appropriate level of safety to be attained by the changes in the functional system (reassessments) may be useful. In these cases, the rationale of ‘maintaining or improving’ the current safety level of operations in the U-space may be used to define the new safety criteria associated to the changes made to the functional system. Such an approach is convenient for the consolidation of the U-space where incremental improvements are applied, while planning safety in the long term in terms of procedures and system design can produce additional quantitative figures.

(g)     Finally, the acceptable level of safety should be materialised through the definition of the U‑space airspace safety requirements, such as the set of U-space services, performance requirements, as well as the operational conditions and constraints, describing the high-level design characteristics of the functional system to ensure that the system operates as specified, thus satisfying the airspace safety specification at operational level.