Technical Advances may be moving the SST closer to reality
EASA takes regulatory to setting noise and CO standards
Environmental Groups likely to oppose
The European Union Aviation Safety Agency (EASA) has issued an Advance Notice of Proposed Amendment 2022-05 –-Environmental protection requirements for supersonic transport aeroplanes. The document is a preliminary first step, perhaps tentative, towards “development of environmental protection requirements for SST aeroplanes, with the objective of ensuring a high, uniform level of environmental protection in Europe…”
Thirty-eight pages describe the EASA formulated the ANPA, define objectives, describe a range of landing and take-off (LTO) noise and CO2 standards, suggest how these standards could be established in regulations and then thoughts on how testing of the aircraft might be implemented.
Given the heavy political influence of the Green Party within the EU, this is a dramatic action by EASA in that the safety agency might face a strong response from its Commission and Parliament bosses (expectations in US).
Both EASA and FAA [contrary view] must deal with conflicting directions. Certification of new aircraft is one of the most prominent statutory responsibilities; experts are employed to assess the airworthiness of airplanes like this new SST. The same organizations are charged with protecting the environment from aeronautical noise and CO pollution. The SST poses even greater challenges because of the sonic boom that their speed creates.
The US Congress, which must assume that it speaks Ex Congressus (the governmental equivalent of papal Ex Cathedra), in one bill (a) mandated that the FAA “ must exercise leadership in the creation of Federal and international policies, regulations, and standards relating to the certification and safe and efficient operation of civil supersonic aircraft” and (b) ordered the same organization to develop more rigorous noise restrictions.
[SST certification is a daunting multi-layer maze.]
Another point of background is found in The Washington Post May 28 article Inside the race to master supersonic air travel. The reporter captures some of the confusion surrounding the SST as an attractive nuisance:
“…Now, however, plane-makers and airlines are trying to revive that dream, and pouring millions into efforts to build better, cleaner and more cost-effective jets that can fly at supersonic speeds, meaning faster than the speed of sound. They are hoping to succeed by 2029, when travelers could fly business class between New York and London in just over three hours — all for $5,000 to $10,000 round-trip…
Meanwhile, technical challenges remain. Jet engine technology, noise regulations and the shortage of clean and alternative aviation fuel will make it difficult for airlines to get government approvals on aircraft and keep ticket prices low, critics said. Bold corporate claims of bringing back supersonic travel will run headlong into scientific challenges for years to come, they added.
“These manufacturers are trying to reinvent supersonic aircraft,” said Dan Rutherford, director of the aviation program at the International Council on Clean Transportation. “But they can’t reinvent the science — and the science is actually pretty damning.”
“…Over the past decade, numerous start-ups have cropped up promising a better, more cost-effective supersonic jet for commercial air travel. Earlier this week, Canadian business jet manufacturer Bombardier announced it had successfully tested a smaller private jet at supersonic speeds, called the Global 8000. Cost: $78 million per jet.
Scholl added that his company’s supersonic jet, which could seat 65 to 88 passengers and fly at just under twice the speed of sound, will cost airlines $200 million a piece[sic]. United Airlines has a firm order for 15 planes, he said, which could increase by up to 35 more. Japan Airlines has said it could purchase up to 20 aircraft, Scholl added.”
He said that the company won’t replicate the failures of the Concorde for multiple reasons. Carbon fiber technology has improved since the 1960s, allowing the Overture to be lighter and more fuel efficient than the Concorde. Software is better, allowing his team to build a more aerodynamic plane. And his company plans on using sustainable aviation fuel — which is an alternative fuel derived from plant waste and other organic matter — allowing Boom to be more environmentally conscious.
“All of that put together means that for Overture One, airlines will be profitable,” he said.
But some scientists and aerospace engineers are skeptical, pointing out that the claims plane-makers and airlines make sound promising, but are difficult to create.
[Professor Iain] Boyd, of the University of Colorado, said noise will be the biggest challenge. He notes that sonic booms could be less of an issue due to advances NASA has made on muffling the sound, but planes will still be able to fly at their maximum velocity only over water — making supersonic travel between cities in the United States difficult.
Meeting FAA and international noise regulations also will be difficult, he said. Supersonic aircraft require narrow, aerodynamic engines, experts said, but those are harder to keep quiet enough to meet government sound limits. Public debates on aircraft noise are also fraught with political issues, Boyd added.
“The inconvenience and discomfort of extra noisy aircraft just for a relatively small number of rich people, that doesn’t sound good,” he said. (Boom spokesperson Aubrey Scanlan said she’s “confident” the Overture will meet FAA regulations around noise.)
And Rutherford, of the International Council on Clean Transportation, said fuel costs will make it tough for supersonic air travel to become a viable business. Supersonic aircraft will burn seven to nine times more fuel compared to normal “subsonic” aircraft, he said.
Rutherford added that companies like United and Boom are aware of that, and pledging to use sustainable aviation fuel. But the supply of sustainable fuel is limited and the cost is high — two to five times costlier than fossil jet fuel.
“That is honestly a dealbreaker, I would guess,” he said.
The battle lines have been drawn. The history of aviation is a long trail of innovation improving safety, reducing travel times and creating new forms of commerce. For those reasons, hopefully the Scholl forecast is closer to the mark that the Rutherford /Boyd/Green party pessimism.
By David Kaminski-Morrow26 May 2022
European regulators are preparing an initial environmental-protection certification framework aimed at addressing the emergence of new supersonic transport aircraft designs towards the end of this decade.
EASA states that a new generation of supersonic commercial and business aircraft is expected to become operational from the late 2020s.
Noise and carbon emission requirements for such aircraft are topics that “need to be addressed”, it says, to ensure a “high, uniform level” of environmental protection.
EASA points out that no ICAO standards exist for landing and take-off noise, or emissions, that would apply to supersonic aircraft – and that it intends to develop detailed requirements which would apply until ICAO draws up its own.
“Pending ongoing work towards establishing an appropriate [carbon dioxide] limit for [supersonic aircraft], provisions for the standardised measurement and reporting of [carbon] emissions are proposed as an interim step,” it adds.
Source: Boom Supersonic
Supersonic projects under development include the Overture commercial transport
Its preliminary draft noise requirements would apply to all supersonic aircraft regardless of maximum take-off weight, number of engines, maximum operating Mach or required runway length.
ICAO defines maximum noise limits for subsonic aircraft and EASA is proposing to “apply the same noise limits” to supersonic types.
The effective perceived noise level for subsonic jet aircraft as well as the same noise measurement reference points can be “reused”, it says, as the noise evaluation measure.
“Considering the specifics of [supersonic aircraft] designs, meeting those limits appears to be challenging but technologically feasible, as indicated by results from research studies,” adds EASA.
The regulator says that, without limits in place, the “significantly” increased noise exposure around airports would potentially outweigh the advantages of quieter subsonic models.
Its proposal also outlines the complexities of translating subsonic emissions measurements for certification, based on three reference points, to the supersonic regime, given the specific performance and fuel characteristics of such high-speed designs.
EASA says the proposals “represent a first step” towards environmental protection requirements for supersonic models and will be “further developed” in subsequent rulemaking steps. It is seeking comments on the measures by 25 July.
 Andrea Castillo, the program manager for the Technology Policy Program at the Mercatus Center at George Mason University, wrote a scholarly journal which concludes:“If not for Federal Aviation Administration (FAA) meddling in supersonic flight innovation, we could zip around the world in a fraction of the time…
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