Standards Development

Scope

This project specifies the requirements for design, material, construction, manufacture, testing, and inspection of a refillable fuel system for liquid hydrogen used in the hydrogenpowered aerial vehicle, including manned and unmanned aerial vehicles.

This work will consider an appropriate fuelling protocol that reflects conditions during the liquid hydrogen fuelling process. The suggested standard will specify test procedures and requirements for verifying performances of a safe fuel storage system mounted on liquid hydrogen powered aerial vehicles.

This document considers the universal fueling protocols for liquid hydrogen such as the subcooled liquid hydrogen protocol as well as the normal (conventional) liquid hydrogen fueling protocol.

It applies to all parts of permanently attached fuel storage system for aerial vehicles as installed, from the liquid hydrogen fuel tank to the fuel gas supply system (FGSS). In case of UAV, a detachable fuel storage system can be adopted. The following elements of liquid hydrogen fuel system for aerial vehicles are:

- Liquid hydrogen fuel tank

- Fuel Gas Supply System (including Heaters and/or Heat Exchanger)

- Fuel Gauge Sensor Unit

- Valves and Lines (or Pipes)

The international standards to be developed through this project will be developed in close cooperation with relevant Task Groups of EuroCAE and SAE. We will harmonize the ISO standard with their standard documents under development (AS6679/ED-XXX; Liquid Hydrogen Storage for Aviation and AIR8466; Hydrogen Fueling of Aircraft, in both Gaseous and Liquid Form).

Purpose

Aviation is no exception to the global effort to combat the climate change crisis. The estimated emission of CO2 and greenhouse gas (GHG) from commercial aircrafts are 2% and 3% in global, respectively. Those values are expected to rise to 4% and 5% as long as the status quo continues. Compared to a train, which is a large-scale transportation in land, CO2 emission per passenger on airplanes is about 20 times higher. Combined with an increasing demand for cargo and passenger traffic by aircraft, the action for CO2 emission reduction is inevitable in aviation.

In response to the suggested agenda, the International Civil Aviation Organization (ICAO) introduced the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) in 2016 to freeze GHG emission at a 2020 level.

In a bid to mitigate GHG emission, a hydrogen propellant technology has been paid attention, especially for an unmanned aerial vehicle (UAV) and an advanced air mobility (AAM). In that system, a state of stored hydrogen in aircraft is one of the important factor for determining its mission capabilities. To increase payload and mission range, a liquid hydrogen, which is a denser state that gaseous hydrogen is much practical.

However, the technology of a liquid hydrogen fuel tank is less mature in aerial vehicles compared to tanks for land usage. It is urgently required to specify a related standard and guideline for navigating development of a safe and reliable storage system in the future.

The suggested international standard includes test standards and guidelines for production of a safe and reliable liquid hydrogen fuel tank. This standard will also introduce a specification of fuel tank peripherals (i.e. balance of tanks, BOTs). It means that this project will standardize the requirements on a fuel storage system for liquid hydrogen in aerial vehicles.