Our inside secrets

A lot of folks we talk to believe that programming an autopilot to land a plane is magic. Well we're gonna break the first rule of magic and talk about how its done.

Welcome to the first post! We've been talking about this for some time so I'm excited to finally see it happen. Let's jump right to the most important thing about auto landing. Energy management.

“That's a fantastic goal but in the real world that's not always practical.”

When you first learn to land a plane, the instructor hammers on one thing, airspeed, airspeed, airspeed. If you fly the right airspeed, the airplane will practically land itself. Sounds easy right? Well it is with an autopilot because the computer is doing it for you. So what's the point of this post?

Flying the right airspeed is easy. Knowing what that speed is can be hard

The way aircraft manufacturers do this is the same way we do it. Calculate stall speed, then test fly to verify stall speed. Once we know stall speed we can fly the approach at the right airspeed relative to our stall speed. For most aircraft, this is around 1.5x stall speed. For instance, if the airplane stalls at 40 knots, we should fly our pattern at 60 knots.

That's great but what about touchdown? Glad you asked! Back to your instructor. "The perfect touchdown happens when the plane stops flying at the exact moment the wheels touch the ground." That's a fantastic goal but in the real world that's not always practical. So instead of of always insisting we be exactly at the same speed we set a small range for ourselves. The slowest we should go is whatever speed will allow us to deal with wind gusts with a margin of safety. The fastest we should go, is whatever speed we can touch the ground at and reduce the angle of attack to stop flying.

This isn't a huge spread. But even with a five knot window, we can aim for the middle and expect the autopilot to reliably touchdown with an airspeed that's in the window.

By not demanding airspeed perfection, we significantly increase the reliability of landing and coming to a controlled full stop every single time.