So the aviation industry in my science-fantasy world with intelligent animals is dominated by hovercrafts. They levitate and move by manipulating gravitational fields, and can move freely in any direction, are very quick to respond to control inputs, can hover in place or go as slow as they want since they don’t have a stall speed. Basically, if regular planes are like an eagle soaring in the clouds, a hovercraft is like a hummingbird darting around with absolute precision. However, hovercrafts can also be very fast, with the ones used in commercial aviation having a similar top speed as today’s airliners, with the benefit of course that they can slow way down on takeoff and landing (both of which are done vertically onto a landing pad) and only hit their top speed in cruise.
But, they also have birds and other flying animals in this world, and obviously safety is extremely important. The gravitational slipstream engines of hovercraft are considered safe for flying animals to approach at low speeds, as they do not have spinning blades or create strong air currents, that’s why they are the norm for aircraft and the only type allowed in populated areas. So really the only real thing to worry about is a collision.
For the brunt of collision avoidance, my solution is to have to stratified airspaces: Animal-prioritized airspace starts from the ground and extends to some predetermined level above either the average tree line in a forest, or above an absolute altitude value, depending on jurisdiction, it would be set based on how high birds and other animals can actually fly on their wings (which according to this is apparently about 5500 m being the highest typical altitude, but some of the highest recorded being over 7000 m. For reference a 737 has a max altitude of 41000 ft, or about 12500 m), above which the airspace is designated for aircraft. Basically, in airspace where you’d expect to run into flying animals, they get absolute priority because they are extremely vulnerable in a collision. Their cruising altitudes are similar to our planes, because they absolutely need to be well above any animal when traveling at high speeds. To quote one of my avian characters: “Back when cats still ate prey, if you got caught your death rate was, what? 50 percent? 60? And that’s pretty bad. An animal on aircraft collision is more like a 99.9% death rate.”
However, hovercrafts still need to descend into the forest canopy to land and drop off/pick up passengers. I envision landing pads both on the ground, inside tree cover, and on the roofs of buildings providing last-mile transportation in a city. They don’t have to deal with bumper to bumper traffic like we do with private cars because they only have essentially aerial busses and public transit, but that only means a hovercraft would only come every few minutes, and the rest of the time its path would be invisible. We have a static safety measure in road vehicles or trains because the infrastructure is clearly visible and you know if you see a part of the ground that looks like that, there will be cars or trains coming. But in the sky, the aircraft corridors and approach areas for landing pads are on maps only. The hovercrafts will have navigation and automatic flight path following capabilities, but if you’re a bird flying through the forest, there is nothing to hint that you’re in the path of a busy flight corridor unless you actually see a hovercraft, and even then it could turn and change directions, you’d have no way of knowing what their path will be unless you’ve memorized the charts and have really good spatial awareness and ability to translate a set of coordinates denoting waypoints into where around you that actually would be. If they were unfamiliar with the part of the city they’re in, they would disrupt hovercraft traffic by blocking their path at best, or end up in an instantly fatal collision at worst.
Birds in this world would definitely be smart enough to actively avoid hovercrafts and wouldn’t place themselves in the path of one if they can help it, but the issue is having the information to do that in advance, and I really don’t want to make this world cyberpunk and have glowing holographic tubes denoting every flight corridor and animal-restricted airspace. Actually, in-universe they really prefer to have cities, which are mostly inside forests, look as natural as possible even with their very advanced technology.
Does anyone have any ideas how I might be able to rectify this? Anyone else have naturally flying members of their society flying next to powered aircraft? How do you deal with it? Have you come up with any other aviation safety mechanisms that I might not have thought of? I’d love to hear your thoughts!
It kinda sounds like you just need your cities to have a “VTOL only” policy. No need to worry about complicated flight paths and sudden changes of direction if the aircraft is only going (roughly) straight up or down. Of course, with or without this kind of policy, no sane city planner would put a hovercraft terminal below tree cover such that pedestrians could not see descending hovercraft (or descending hovercraft couldn’t see ascending ones) until the last minute. Fortunately, many city planners and city councils in real life are bat shit insane, so it’s not exactly an immersion-breaking decision to have that still be an element of your cities.
Thinking more about it, I think the hazard would mostly be mitigated once the hovercraft lifts above the tree line, since then it would be easily visible, and assuming a reasonable speed limit until it gets above the altitude where birds fly. There’s no real need to fly laterally through the canopy either. Thank you!
Typically, from what I know there are very few birds that fly more than a few thousand feet off the ground. So I’d extrapolate to that to flying critters.
I’d restrict the airspace around ANY airport as controlled airspace. Where small airports are similar to Class D airspace defined by the FAA. Any vehicle or creature in that air space needs to have two way communication to talk to both ATC and each other.
Cross-country travel over 200 knots outside airports would be done at an altitude above say 5000 feet. Below that there would need to be a speed limit, nav lights, and enhanced anti-collision lights to enter uncontrolled airspace less than 5000 feet.
Mix all that with common published approaches and departures, airways and ATC you could have a safe airspace I think.
I actually have more lore around the proper airports in the city, where the approach/departure area is absolutely restricted and everyone flying around there needs to have radio contact with the tower and wear a transponder. But I had not developed the lore around small urban landing pads. Though, speed limits and vertical movement only until it’s above the tree line would help a lot imagine. Not perfect obviously, but I’m still actively developing this.
So yeah, pretty similar to what you suggested. Thank you!
