Preliminary Safety Analysis of Liquid Hydrogen Aircraft Refu- elling and Its Operational Con- sequences for Airports

Abstract

Liquid hydrogen (LH2) is a promising option for deep aviation decarbonisation and could be deployed at airports within the next decade. Compared with Jet-A1, LH2 refuelling may require larger safety and exclusion zones that reduce stand availability and constrain apron access. Operational studies often assume these zones, while safety studies rarely turn consequence-driven distances into enforceable apron constraints and quantify delay impacts. This work provides an integrated safety-to-operations assessment for LH2 refuelling at compact airports. The objective is to identify the main safety distance drivers for open- apron LH2 releases during refuelling through a qualitative safety assessment and quantify how zone size and enforcement, refuelling logistics, and resource capacity affect departure delays as LH2 penetration increases.
A qualitative hazard and accident-pathway assessment (HAZID/HAZOP supported by bow-tie logic) was conducted to identify the main LH2 refuelling hazards and accident path- ways, and to determine how these hazards drive conservative safety-distance requirements. The outcomes were then used to select representative scenarios and define zoning modes for the operational analysis. These modes are translated into operational rules (e.g., stand closures and route restrictions) and implemented in a stochastic discrete-event simulation of a regional airport apron with LH2-specific turnaround processes. Experiments vary penetra- tion rate, stand layouts, refuelling logistics and transfer duration (S1–S5), and LH2/Jet-A1 truck-fleet sizing. Performance is assessed via statistical comparison of departure-delay met- rics.
The safety assessment identifies dispersion-and-ignition outcomes (flash fire and jet fire) as the dominant safety distance drivers for open-apron LH2 releases and motivates practical distance scales that define the zoning modes. In the operational simulation, zoning has lit- tle effect at low LH2 adoption, but delays increase sharply once conservative zones remove neighbouring stand capacity and push the apron into a capacity-limited regime. For smaller zones, performance is driven mainly by refuelling logistics and refueller availability rather than by routing restrictions. Undersized service fleets primarily worsen the tail of very late departures, with the binding constraint shifting between the LH2 and Jet-A1 fleets depend- ing on demand. Overall, safe scale-up requires joint design of zoning rules and refuelling resources to prevent structural apron bottlenecks.