Hydrogen Airships: Potential International Difficulties

Hydrogen Airships: Potential International Difficulties

Hydrogen Airships: Potential International Difficulties

Airships have yet to reemerge as commercial transport, despite their numerous ecological, humanitarian, security, and business applications. A barrier for some business models is the regulation of lifting gasses. Regulations in many countries require airships to use helium to generate vertical movement, or lift. As supplies diminish, helium gas has become dramatically more expensive.

When the last batch of legal writers on airships were writing, helium was only eight times more expensive than hydrogen, but its non-flammable nature meant it was perceived as safer and therefore desirable. Hydrogen offers a potential business solution to the problem of rising fuel costs and carbon emissions, but the legal landscape for hydrogen as a lifting gas, around the world, is not well harmonized.

Business and governmental interest has resurfaced for airships because of increased scrutiny being given to aviation carbon emissions. The International Civil Aviation Organization (ICAO), a specialized agency of the United Nations in charge of international air navigation, has promulgated the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) regime. CORSIA “is the first global market-based measure for any sector and represents a cooperative approach that moves away from a “patchwork” of national or regional regulatory initiatives,” and instead into an international harmonization of initiatives to reduce carbon in international aviation.

Airships are largely situated within the existing international legal framework. ICAO Standards, Recommended Practices and Procedures (SARPs) that govern aircraft generally govern airships. Therefore, “[i]t flows from what has been said earlier that also airships will have to conform to general rules applicable to aircraft. However, it seems logical that for airships in analogy to the various SARPS, rules will have to be created which take into account the specifics of airships.”

Legal review on the viability of airships in the early 2000s concluded that: “the existing juridical framework in place on a national as well as an international level does not seem to hamper the development of airships towards this new mode of air transportation of persons and goods.” This is generally true with respect to national and international conduct of airships but may be untrue with respect to lift agents of airships.

At the time of this was written, helium was the exclusive lift gas of airships. In the same legal paper, the author speculated that future airships would use helium which is only eight percent less efficient for lift, nonflammable, and cost only eight times as much. The increased cost was a business expense that reduced risks of fire, while only marginally reducing lift. Also, it helped assuage negative public perceptions of hydrogen associated with the Hindenburg accident.

This comparison of helium and hydrogen overlooks an important point of economics. Rigid airships are approximately 50% deadweight. For a 200-ton gross lift, a hydrogen airship would carry 100 tons of freight. The same airship filled with helium would carry only 84 tons. Assuming other costs to be the same, the helium airship gives up “16-tons of profit.” Given that the price of helium is 67 times the price of hydrogen, operating costs are not the same. Contemporary legal analysis must explore the possibility of hydrogen as a lifting gas, with respect to international law.

Hydrogen is unable to be used as a lifting gas because it is perceived as unsafe. A United States Federal Aviation Administration advisory circular issued in 1992 states “hydrogen is not an acceptable lifting gas for use in airships.” Further, the FAA’s 1995 Airship Design Criteria report, which still governs current airship design, states that “[t]he lifting gas must be non-flammable.” This FAA design criteria excludes hydrogen because hydrogen is flammable. Inventions in chemistry have produced a chemical additive that renders hydrogen less flammable, but it is still currently flammable and so is excluded from use. Currently, then, airships in the United States designed for hydrogen as a lift gas cannot be issued a certificate of airworthiness from the FAA.

Flying without a valid certificate of airworthiness violates a Federal Aviation Regulation. So, while no statute or regulation prohibits the use of a hydrogen-based lift gas, it is functionally illegal to do so – either a pilot would be illegally operating a vehicle without a valid airworthiness certificate, or they would have fraudulently secured a certificate in violation of design criteria.

In Canada, hydrogen is also illegal as a lifting gas. The Canadian Air Regulation 541.7 states that “Hydrogen is not an acceptable lifting gas for use in airships.” This is unusual because Canada has never had an airship industry but could benefit from airship transportation as climate change affects ice roads.

An unusual conceptual outcome results where hydrogen as a lifting gas is illegal. That is, while hydrogen cannot be used to lift the airship, it can be transported on the airship or used to power the airship. In other words, it is legal to carry hydrogen in a high-pressure container to power any vehicle including an airship – but not if it is carried in a zero-pressure container (gas cell) to lift the airship. Any risk associated with hydrogen as a lift gas is exacerbated by creating high-pressure containers, including risks of flammability, leakage, and explosion. Yet, an airship could legally have more hydrogen as cargo than would be needed to lift the craft, while still being barred from use to lift the craft.

The European Union, however, has begun reviewing relevant regulations for purposes of airship reemergence. In early 2021, the EU Aviation Safety Agency (EASA) proposed a set of airworthiness specifications for the issuance and modification of type certificates for gas airships. A 30-day public comment period resulted in 425 submissions, and EASA issued its final specifications document in 2022. The lifting gas specification reads:

  • (a) Lifting gas systems required for the safe operation of the Airship must:
    • (1) withstand all loading conditions expected in operation including emergency conditions;
    • (2) monitor and control lifting performance and degradation;
  • (b) If the lifting gas is toxic, irritant or flammable, adequate measures must be taken in design and operation to ensure the safety of the occupants and people on the ground in all envisaged ground and flight conditions including emergency conditions.

This specification would allow for hydrogen if adequate measures were taken with respect to safety. This provides a basis for hydrogen-based airships or LTA technology in the European Union to obtain a valid airworthiness certificate both with respect to EU law and to ICAO, but whose certificate may not be valid in the United States because the use of hydrogen as a lift agent violates FAA advisory positions. Although Germany, The Netherlands, and the United States have signed a mutual airworthiness requirements agreement for transport category airships such that the lifting gas for large airships must be “non-flammable, non-toxic and non-irritant,”

Germany and The Netherlands, as EU Member States, may produce hydrogen lift gas airships if “adequate measures” have been “taken in design and operation to ensure . . . safety . . . .” However, this potentially could result in conflict between these two EU countries and the United States if a German or Dutch manufacturer obtained EU certification for a hydrogen lift gas airship and wished to fly it into the United States.

Currently, no such problem exists. However, situations where one country confers a certificate of airworthiness to a hydrogen-lift gas airship and its airworthiness certificate is invalid in another nation could create tensions between States and might even lead to ICAO involvement, as Article 33 of the Chicago Convention requires States mutually to recognize as valid other States’ certificates of airworthiness.

Internationally, the ICAO secretariat should initiate a proposal for SARPs with respect to either contemporary airship airworthiness requirements or the lift gas agent in airships. The development of SARPs through the Air Navigation Commission (ANC) would help to reaffirm the safety of hydrogen as a lift agent. The ANC is composed of technical experts who would be suitable for making such a determination. During the review phase, the United States and Canada would have the ability to submit comments against hydrogen as a lift agent. More likely, these States would not comment or file a difference.

On publication of the SARP, member States would be bound to align domestic regulations to ensure the interoperability of air trade systems. Through this method, all States that constrain the use of hydrogen as a lift agent would be compelled either to align with the international standard established in the SARP, or to file a difference (which may or not be recognized). The value of this approach, while slow, would compel all ICAO member States to reciprocally review and standardize regulations associated with lift agents and/or airship certifications. Given that the economic utility of airships is in their ability to ship cargo trans-continentally or over very large distances, ICAO’s updating of SARPs with respect to airships would help secure standardization and relieve the risks identified above.

In the last ten years, public interest in airships has dramatically increased. Nations are globally working to reduce the pace of climate change. Jet airplanes are difficult to decarbonize because the only logical fuel, hydrogen, requires so much space for its fuel tanks. Rigid airships can easily store such fuel tanks in their hull and have ample room for passengers or freight. Interest in airships has never gone away, but as helium’s scarcity raises prices, the economics worsen. The regulation requiring the use of helium as a lifting gas creates business doubt: will helium be affordable? will helium even be available?

While increased business interest emerged, legal research interest appears largely unchanged. No major revisions have occurred with laws that directly govern airships. The stagnant legal circumscription of airships has created a functional legal problem. Innovative airship newcomers are considering hydrogen as a lift gas amid an incongruent regulatory environment. As climate change progresses, use of hydrogen for fuel in airships, and as lifting gas, seems inevitable. The aviation regulators in Canada and the United States will have to run to catch up.

For more information, see: the Spring 2023 edition of DuPaul’s Issues in Aviation Law and Policy.

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