Not having human life on board an RPA makes a big difference to safety and risk considerations. Manned aviation safety has evolved over the last hundred years or so with the main focus on preserving human life on board the aircraft. This meant that any risk of incident, either with other air users or with terrain or bad weather had to be mitigated to the required extent - to an acceptable level of risk. This means not only that the airworthiness of the aircraft has to be to a very high standard but also that the risk to other airspace users and people on the earth’s surface is very low. The majority of manned aircraft, once they have received safety certification, are authorised to fly in most environments, such as over centres of population.
Since there is no risk to human life on board an unmanned RPA, the risk assessment focuses on the risk to other airspace users and those on the surface. The risk in remote areas with negligible air traffic and terrestial population density is therefore hugely lower than in the proximity of a major commercial aviation hub in a densely populated area. The operational risk for an unmanned RPA is a function of the RPAS and, crucially, the operational environment (which includes many factors). This enables optimising RPAS for specific operational scenarios delivering not only the required level of safety but also economic efficiency. The greater the operational risk, the greater the safety mitigation required from the RPAS.
The widely variable requirement for airworthiness, depending on operational risk in any given case, and the need to address airworthiness on a full system basis (eg communications, remote pilot station) pose challenges. An additional consideration is that manned airworthiness certification typically leads to a type certificate for a given specification of aircraft, which may endure for many years. With rapid technological development and system change in the RPAS sector, the costs involved with a ‘traditional’ approach to airworthiness certification seem to be unacceptable.
Further Reading
Statement of Issue. A short paper summarising some of the particular features of UAS in relation to the well established manned aircraft certification processes is available as a dowloadable .pdf at: UAS Airworthiness Statement of Issue.
RPAS Airworthiness Considerations. NB Working paper - Not Final. The purpose of this paper is to describe an outline approach to structure airworthiness considerations in the context of RPAS. RPAS, UAS and other sectors, such as Urban and Advanced Air Mobility (UAM & AAM), all call for special considerations as to if and how ‘traditional’ airworthiness practices can be applied or adapted. While anticipating that airworthiness can evolve to deal with these sectors, it might be that other regimes of safety assurance and mitigation wil have to be developed. One example might be that an Unmanned Traffic Management (UTM) ‘ecosystem’ might require some form of ‘certification’ unlike the current ATM domain.