To the west of the World Conference building lay the Academy, flanked by a cluster of research wings.
One of these was the Aviation Research Lab.
"It's almost lunchtime, so they should still be in the lab right now," Fione Fias said.
The time was 11:30 AM.
The student cafeteria was quite popular, so if one didn't line up early, their meal of choice would sell out.
"Over there is the Factory, and the lab is right here."
The Factory was a large, single-story building, and the Aviation Research Lab had been built right alongside it.
When Fione knocked on the door, it was opened from within almost immediately. Word of their arrival had apparently already reached them.
"We have been expecting you, Magi Craft Meister Lord Jin Nidou!"
"H-Hello."
Inside the lab were about ten students and a single middle-aged man who appeared to be an instructor.
"I am the Aviation Research Lab chief, Roa Eisker."
"I am the deputy laboratory chief, Zora Himmel."
"I'm Ciel Azur."
"Ina Kouki."
"Tainer Vito."
"..."
After everyone introduced themselves, the gathering immediately transitioned into an informal discussion.
As invited, Jin took a seat at a conference table in a corner of the lab, upon which a blueprint was spread out.
"This is..."
"This is the small aircraft we are currently considering," Lab Chief Roa Eisker said.
"...It's an interesting design."
Jin could not help but comment.
After all, what was drawn there was a biplane-style circular wing aircraft.
"I see. So you designed it like this to keep the overall length and wingspan down?"
"As expected of Lord Jin, you saw through our intention at a single glance," Roa Eisker said in admiration.
"Designing it this way should improve its lateral maneuverability."
"Oh, precisely!"
Most fighter planes during the First World War were biplanes.
They could keep the wingspan narrower than monoplanes and were therefore more agile... Jin seemed to recall reading something along those lines in a book.
While that was a somewhat one-sided perspective, in reality, securing sufficient wing area to generate the necessary lift relative to engine output was also a major factor.
By the time of the Second World War, as engine output rose and speeds increased, most fighters shifted to metal monoplanes, more than doubling their top speeds.
Naturally, objects that are large or long are harder to rotate.
For that reason, the Aviation Research Lab had come up with the idea of stacking circular wings in two tiers to reduce their overall diameter.
"Standard circular wings seem to have a diameter of about five to ten meters," Deputy Lab Chief Zora Himmel chimed in.
"That affects the load capacity—in other words, the passenger count. And this 'biplane' is intended to seat four."
For a four-passenger craft, a single circular wing would fall into the six- to seven-meter class.
Assuming a diameter of six meters, the surface area would be 3 × 3 × pi. Taking pi as 3.14, that amounted to 28.26 square meters.
What would happen if that area were split between two wings?
Dividing the halved value of 14.13 by pi and then taking the square root of that result...
The answer was roughly 2.12. In meters, this was the radius, so doubling it gave a diameter of 4.24 meters.
Factoring in a slight drop in aerodynamic efficiency, the current blueprint specified a diameter of 4.5 meters.
Since the circular wings of the Taube and Eagle Unit 1 were seven meters across, this design looked remarkably compact.
In exchange, its overall height was about thirty percent greater.
"Are you planning for it to operate at low speeds?" Jin asked to make sure.
Because aerodynamic drag would increase, it wouldn't be suited for high-speed flight.
"Yes. It is primarily intended for short-range transit within and around town. Specifically, inside Avalon."
"In that case, there shouldn't be any problem."
When the intended use and performance targets were clearly defined, designing became far simpler.
"We were just discussing building a one-fourth scale working prototype model."
"I see. That sounds like a great idea," Jin agreed.
Miniaturized models exhibit different characteristics from full-scale craft due to fluid dynamic constants like air resistance, but at one-fourth scale, that discrepancy would likely remain relatively minor.
"Oh, hearing you say that is very encouraging!" Zora Himmel said, looking delighted.
"We've already gathered all the materials."
"I look forward to seeing it, then."
"We're finally about to start processing the parts!"
Ciel Azur chimed in cheerfully. Since they were going to begin fabricating the components today, Jin decided to stay and observe the process.
"Having you present, Lord Jin, gives us the strength of a thousand men."
...Or so they said, but Jin had no intention of intervening for the time being.
First, let's see what they can do on their own.
Though if any danger arose, he and Reiko would not hesitate to step in.
"Let us begin by processing the parts."
They began shaping the prepared ingots of 64 light silver according to the blueprint.
First came the basic fabrication.
Bars of specific cross-sections and plates of specific thicknesses were quickly produced one after another.
Yeah, they're quite skilled.
It seemed they practiced hands-on crafting rather than just studying theory, which brought a satisfied smile to Jin's face.
The day wrapped up with the fabrication of the components.
Fione Fias guided Jin and Elsa to the guest dining hall.
Tomax Bertman was not present, and a quiet private room had been arranged so Jin and Elsa could enjoy their meal at a leisurely pace.
With Reiko waiting attentively behind them and Elsa seated across the table, it was a relaxing dinner spent together as family.
The menu was prepared in the style of the Shouro Empire, fully satisfying in both quality and portion size.
Jin and Elsa relaxed, sipping their post-meal tea.
"...Jin-nii, did you have fun?"
"Yeah, I did. I got to see the people who will shape the coming era, after all."
Hearing his words, Elsa giggled softly.
"Fufu, you sound like an old man."
"...I suppose I do."
Jin scratched his head, then murmured quietly to himself:
"I still have plenty of things left to do, too."
Upon hearing that, Elsa smiled gently.
"Mm. The journey is only halfway through....Let's do our best, okay?"
"Yeah, absolutely," Jin replied with a smile.