A whitepaper from the Dutch Association of Certified RPAS Operators (DCRO) has addressed the probability of a flyaway with an uncrewed aerial system (UAS) operated by professional operators. DCRO uses the term flyaway to describe a situation in which the UAS leaves the intended operational volume due to a loss of control and the flight ends outside the operational volume.
In 2025, the updated Specific Operations Risk Assessment (SORA) 2.5 will come into effect across all EASA member states. One key difference between SORA 2.0 and SORA 2.5 is that the ground risk for adjacent areas must now be considered when determining the level of containment for UAS operations. DCRO says that there are various pros and cons of using the new methodology to determine containment levels, but that one clear consensus from discussions with manufacturers and operators is that the current assumptions on the probability of a flyaway are not based on real data and are unrealistic.
“When assessing the probability of a flyaway it is very important to make the distinction between professional and non-professional operators,” the whitepaper states. “A professional operator is an operator that operates according to audited procedures from an operational manual and is trained to control a UAS under normal, abnormal and emergency conditions. In addition, the UAS flown are maintained by trained professionals. The professional operator is trained and capable of executing predefined contingency procedures in the event of an off-nominal condition.”
DCRO’s research – based on over 1.4m hours of flight logs from skilled operators – found that the odds of a drone leaving the operational area was approximately one in 100,000 flight hours – not the one in 1,000 hour figure currently indicated in guidelines published by the Joint Authorities for Rulemaking on Unmanned Systems (JARUS), on which SORA methodology is based. The team found that the chance of a drone flyaway was around one in a million flight hours, not the one in 10,000 hour figure currently indicated in JARUS guidelines.
Drone manufacturer DJI submitted its own research which supported DCRO’s findings. In fact, DCRO says “the data from DJI is based on a much higher number of flight hours so we should assume this number to better express the probability.” For example, results for the Dock 1 are based on 5.4 million flights whereas approximately several thousand flights have been executed using the Dock 1 by DCRO members.
DCRO believes that the current containment requirements for ground risk are disproportionate. “The risk of a UAS experiencing a flyaway and causing a ground risk are negligible for operators in the Specific Category in our opinion. The requirements to comply with a medium or high level of containment are excessive and only create a false sense of security since the chance of this happening is negligible. We would even argue that adding an Flight Termination System (FTS) makes the UAS less safe as the chance of these failing are far bigger than the probability of the UAS exiting the operational volume.”
DCRO is recommending that safety statistics are collected across all EU member states in a uniform manner. “The collection of this data should not be voluntary,” the whitepaper states. “Statistics should also not be limited to just flyways but also include crashes, personal injury and look at the cause if this is human or a technical error. The first step would be to harmonise the definitions behind the figures, such as the exact definition of a flyaway, a crash, an incident etc. At DCRO we believe this the responsibility of the definitions to come from EASA and the collection of the data from the national CAAs. In this manner the submission of safety data can be made mandatory.”
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