The motor layout this copter is set up for

What ArduPilot says:

• Frame: …/…
• Frame: …

At start-up, and at the top of every log, the copter names its frame: the class (FRAME_CLASS: QUAD, HEXA, OCTA, OCTAQUAD, Y6, TRI and others) and, after the slash, the type (FRAME_TYPE), which fixes the order of the motors and the way each one turns: X, PLUS, V, H, BF_X (X in Betaflight's motor order), BF_X_REV (the same with every motor reversed, “props out”), DJI_X and so on. “Frame: QUAD/BF_X” is four motors in Betaflight's order. Nothing to fix, as long as it is the frame you built: with the wrong class or type the copter flips at take-off.

A changed FRAME_CLASS takes effect only after a reboot. Before the first flight check the line against the copter with the motor test, props off: each motor must be the one the test names and must turn the way the frame's diagram shows.

Parameters to look at

Where to do it:Setup & Tuning GuideSetup & Tuning Guide