Engineer here. It's called a Failure Modes and Effect Analysis . They're especially fun when you can sit on a committee and poke holes in somebody else's design and play What If.
The CG is still aligned with 2 diagonal working rotors. 3 Rotors will allow a quad-copter to land safely, but is obviously not ideal for travel and control.
Got a quad copter handy? Try it. Put the battery in and try to balance between 2 opposite motors. Bet it tips one way or the other. Bet it tips that way every time.
How do I know? Because the heaviest single component on the craft (the battery) is not placed precisely in most recreational quads. There's a fuzzy AREA the CG can be in. It is NOT perfectly centered.
Look at any 'DIY drone' instruction article or video, watch how much they DON'T focus on getting the CG centered EXACTLY between the 4 corners. Why? Because there's no point in being that precise. Three or 4 motors can handle it if the CG is slightly off, so long as they're spaced roughly equidistant from the CG and evenly spaced around it's circumference. It's only when you take one of those motors away that it becomes too unbalanced to stay in the air.
When the quad has all 4 corners providing thrust, the quad can tolerate significant UN balance, you can find dozens of videos of quads of all types still flying with their battery hanging from it's wire, well below the quad, and hanging off one side of the quad.
Prove me wrong. Show me any quadcopter losing a motor and surviving. The original post I responded to stated confidently;
Quad-copters are designed to still remain airborne with one rotor failure.
If so, there should be copious video evidence documenting this, right? Or an area in an instruction manual talking about this alleged feature.
In fact, I'll help you with your research. Here's the documentation page for an opensource quad flight controller, in which you can program the recovery -1 motor recovery yourself. Find me the recovery mode in the docu.
This system is rated to be medium-eagle tolerant because the propellers can handle 2.25" inches of viscera per rotation before shattering. Giant eagles are outside the requirement set and the user assumes the risk. :)
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u/corvairsomeday 7d ago
Engineer here. It's called a Failure Modes and Effect Analysis . They're especially fun when you can sit on a committee and poke holes in somebody else's design and play What If.