The LOS rule comes from a not too distant past, when all RC planes and copters flew without any FPV. I recently bought a RC plane with no FPV and a flight simulator package that works off the actual controller. Within about 1 minute on the flight Sim I realised that: a) flying a Spark is insanely easy, b) that if the plane is more than about 100m away then you can't tell it's orientation, and C) that if it goes out of LOS then it's bye bye plane and hopefully it doesn't hit anything or anyone.
Some of us have experience from the time prior to quads and FPV video feeds. I wanted to fly a helicopter as far back as age 20 or so, and I eventually had the money to spare to get a nitro size 30 heli. (raptor, with futaba remote) And I quickly learned that knowing your orientation was key to staying in the air. A few years prior to that a friend of mine got a piper cub model and we flew that in the parks, and even with that, orientation was important when inputting controls. Fortunately for that aircraft however, if it was flying straight and level you could take your hands off the sticks and hand the remote to someone else and they had plenty of time to "get settled in" before assuming control, the plane would just "coast" fairly well.
NOT the case with a helicopter of the day. Even with my large rotopod safety landing gear, it was still quite possible to have it go doing its own thing within a few seconds of losing control. With the big gear off and it not nearly so bottom-heavy, I liked to describe it like balancing a broom upside down on your finger. It required
constant attention, and would come crashing down within a few seconds if you ignored it.
Unfortunately, my stereo eyesight isn't so good, and I was terribly disappointed to find that I couldn't fly it out more than 150-200ft from myself without starting to lose orientation, despite the colorful tail etc that everyone had on their heli for just that reason. Once you lose track of which way it's facing, you are in
serious trouble because any control input you make (and you need to make them constantly) risks creating a severe pitch or roll that will send it to the turf in a matter of seconds if not corrected. (which you can't do unless you know the orientation)
My skills at repairing the helicopter got pretty good but my flight skills couldn't improve much past the limits imposed by my vision, so eventually it got shelved as any crash was $150 to repair
at a minimum and it was just getting too expensive for me to fly.
I've really enjoyed quads recently, because of how stable they are and "safe to let go of the sticks", giving me time to figure out orientation or just plain stop it from continuing on an undesired course. My first year of flights were without FPV or any serious attitude/position control, as I was testing the waters with cheap quads like the Syma X10, so by the time I got my Spark I was already familiar with quad piloting. And I must admit that considering the ease of flying a syma compared to a raptor, I saw again that much more ease when I got my Spark, with its automatic attitude and position controls plus FPV. It's almost effortless now, and is a joy to fly. Everything and more that I had hoped my Raptor would be year ago.
I realize the Spark was designed to be a "selfie-drone" and a stable camera platform, but I really get the most enjoyment out of it in sport mode, racing around the local airspace. I don't really have any desire though to get into the smaller racing quads, that's just too stressful. The Spark is well-suited to my comfort-zone.
So for me it used to all be about much more than "line of sight" because I would never
survive long enough to get out of sight...
