When I test my drone for the first time and I run the throttle up form my remote with the props off the motors keep spinning even when I bring my throttle back down. Will my quad flip out if I put the props on and try to fly it? Why does this happen? It seems fine when I spin the motors up from the motors tab.
This is a result of I term windup from the PID controller. It's completely expected and normal with props off, and will be fine when you put props on and go fly! Almost everyone new to RC multirotors asks this question on their first build, so don't feel bad!
The detailed answer to this question is related to how multirotors maintain stability in flight. Multirotors use a control system called a PID controller. This is a feedback loop control that takes information from the sensors onboard the flight controller and then executes change via the motors based on how the commanded input is different from what it is sensing. For more information check this white paper from the national instruments lab.
To understand this problem, the component of the PID controller we need to examine is the I constant, often referred to as Ki. Essentially this is based on the integral calculation between the sensed value and the setpoint or target value. What this means is that I get stronger the longer there is a difference between the sensed value and the target value. Hence change over time. What you're seeing as the motors slowly spin-up is the buildup of that Ki value getting stronger and stronger as flight controller is trying harder and harder to execute a change that it can sense, but can't impact. No props means no force to execute change, hence the windup. This is often referred to as I term windup.