slop-stuff / Drones & FPV

ArduPilot

Autopilot for anything that flies — pin Copter 4.6.

Copter 4.6: modes, failsafes, params, EKF, tune order, maiden ladder, and AI-slop kill-list.

droneCopterfailsafeEKFMission Planner

ArduPilot Copter 4.6.x (stable 4.6.3). Units are cm / cm/s / cdeg unless noted. Wiki pages that show RTL_ALT_M, LAND_SPD_MS, PSC_NE_*, ARMING_SKIPCHK are 4.7 — do not copy them onto a 4.6 craft.

Quick reference

Topic	4.6 truth
GCS	`Mission Planner` (Windows, `.BIN` logs, CompassMot) · `QGroundControl` (cross-platform flash) — don’t dual-write params
Cal order	Frame reboot → AHRS → accel 6-face → compass → radio + `FS_THR_VALUE` → ESC → motor test → level → battery FS → modes → outdoor GPS
Maiden	Stabilize → AltHold → Loiter → test RTL → Auto
Radio FS	`FS_THR_ENABLE=1` RTL · `FS_THR_VALUE` ≥10µs below `RC3_MIN`, >910
Battery FS	Stock `BATT_FS_LOW_ACT=0` = warn only → set `2` RTL; `BATT_LOW_VOLT` default 10.5V is 3S
EKF FS	Two variances > `FS_EKF_THRESH` (0.8) → Land · don’t raise thresh
RTL climb	`RTL_ALT=1500` = 15 m (cm!) · home = arm point · straight line
Arm	Throttle low + yaw right if `ARMING_RUDDER=2` · `ARMING_CHECK=1` never 0
Tune order	Linear motors → hover → harmonic notch → rate P/D → AutoTune → angle/pos later

GCS

	Mission Planner	QGroundControl
Best at	Param bitmasks, CompassMot, `.BIN` log analysis	Flash, cross-platform UI
Trap	Dual-open with QGC = param fights	Weak CompassMot / log workflow

Flash Copter 4.6.x for your board target — not Plane, not “latest 4.7 beta”.

Frame & arming

Param	Default / note	Pitfall
`FRAME_CLASS`	1 Quad typical · reboot	0 = pre-arm; Heli class on multicopter firmware = invalid
`FRAME_TYPE`	1 X typical · reboot	BF/DJI X ≠ ArduPilot X → flip on takeoff
`ARMING_CHECK`	1 All	Never 0 “to make it arm”
`ARMING_RUDDER`	Copter 2 ArmOrDisarm	Plane default 1 ArmOnly — don’t copy
`BRD_SAFETY_DEFLT`	1 on Pixhawk-class	Was `BRD_SAFETYENABLE`; press safety or set 0 + reboot
`DISARM_DELAY`	10 s	0 + crash on side = motors stay live

Calibration order

Props off until maiden. Battery off during RC cal if USB can power the FC.

FRAME_CLASS / FRAME_TYPE → reboot · Motor Test map
AHRS_ORIENTATION if not arrow-forward → reboot
Accel — all 6 faces, level → reboot
Compass — prefer external mast mag; disable internal (COMPASS_USEn=0) if inconsistent; CompassMot = last resort
Radio — Mode 2; Copter wants throttle low on center dialog; set FS_THR_VALUE from numbers
ESC — DShot: set MOT_PWM_TYPE, no analog cal · Analog: ESC_CALIBRATION=3, props off, reboot, wait tones — not high-throttle-then-power
Motor Test → set MOT_SPIN_ARM < MOT_SPIN_MIN
Level horizon · BATT_MONITOR + capacity · BATT_FS_LOW_ACT=2
FLTMODE_CH=5 with Stabilize/AltHold + RTL on throws
Outdoor: 3D fix, HDOP ≤ GPS_HDOP_GOOD (default 1.40)

Flight mode matrix

Mode	GPS	Alt	Sticks	Use
Stabilize	N	manual thr	lean; center levels	maiden + bailout
Acro	N	manual	rate; center ≠ level	after tune
AltHold	N	baro	Stab + mid holds alt	2nd flight
Loiter	Y	baro+GPS	velocity; center stops	daily GPS hover
PosHold	Y	baro	lean like Stab; release brakes	prefer Loiter
RTL	Y	baro/terrain opt	auto	home switch
Auto	Y	mission	auto	missions
Guided	Y	GCS	GCS	click-to-fly
Land	N*	baro	descent `LAND_SPEED`	FS fallback
Brake	Y	baro	ignores sticks	flyaway
SmartRTL	Y	baro	breadcrumb	obstacles to home
FlowHold	flow cam	baro	Loiter-like	only if FLOW set up
Sport	N	baro	rate + hold attitude	often compiled out in 4.6

*Land uses position if healthy. Only Stabilize/Acro save a bad EKF — RTL will not.

FLTMODE1–6 PWM slots on FLTMODE_CH (Copter 5, Plane 8). Never put only GPS modes on a 3-pos with no Stab/AltHold bailout.

Failsafe matrix

Triggers debounce; actions don’t auto-clear — flick the mode switch.

FS	Trigger	Rec action	Misconfig
Radio	no pulses or ch3 < `FS_THR_VALUE` (~1s)	`FS_THR_ENABLE=1` RTL	VALUE inside stick range; RX hold-last; RX forcing ch5=RTL (wiki: do not)
Batt low	V < `BATT_LOW_VOLT` 10s or mAh	`BATT_FS_LOW_ACT=2` RTL	stock 0 warn-only; 10.5V is 3S; reboot to clear
Batt crit	lower V/mAh	Land (`1`)	CRT≥LOW pre-arm; Terminate=motors off
GCS	no heartbeat 5s, after GCS connected	`1` RTL if telem; else leave `0`	closing MP mid-flight; bit4 continues pilot modes
EKF	any two variances >0.8 ~1s	Land (`1`); don’t raise thresh	raising lengthens flyaways
Dead-reckon (4.6)	lost pos/vel	`FS_DR_ENABLE` RTL then EKF after ~30s	≠ EKF FS
Fence	alt/circle/polygon	RTL/Land	enable with none defined; no position+fence = no arm

Pre-4.0 names FS_BATT_* are slop — use BATT_FS_LOW_ACT, BATT_LOW_VOLT, BATT_CRT_*.

Must-have params

GPS / EKF

Param	4.6 note	Pitfall
`GPS1_TYPE`	was `GPS_TYPE`	`0` + EKF wants GPS = cannot arm
`GPS_HDOP_GOOD`	140 (=1.40)	raising under trees → Loiter toiletbowl
`EK3_ENABLE`	1 (EKF3)	EKF2 gone from default builds
`EK3_SRC1_POSXY/VELXY`	GPS	match sources to hardware
`EK3_SRC1_YAW`	Compass	Copter ≠ Plane auto-GSF
`FS_EKF_THRESH`	0.8	don’t raise to “stop landing”

Motors / ESC

Param	Note	Pitfall
`MOT_SPIN_ARM`	< `MOT_SPIN_MIN`	find with Motor Test
`MOT_THST_HOVER`	learns ~0.2–0.5	hover >0.7 unsafe for AltHold
`MOT_PWM_TYPE`	DShot 4–7	DShot → skip analog ESC cal
`ESC_CALIBRATION`	set 3, props off	not high-throttle plug-in

RTL / Land (cm!)

Param	Default meaning	Pitfall
`RTL_ALT`	1500 = 15 m	`15` = 15 cm → tree
`RTL_ALT_FINAL`	0 = land	non-zero = hover and wait
`LAND_SPEED`	50 cm/s	4.7 name `LAND_SPD_MS`
`ANGLE_MAX`	3000 cdeg = 30°	4.7 → `ATC_ANGLE_MAX` in degrees

Tune order (not a PID dump)

Linear motors / expo (MOT_THST_EXPO)
Stable hover
Harmonic notch (INS_HNTCH_*) — before AutoTune
Rate P/D (ATC_RAT_*) — I≈P on multicopters
AutoTune (rate only)
Angle / position later (ATC_ANG_*, PSC_*)

PSC_ACCZ_*: keep I ≈ 2×P; never raise on a vibey craft (climb-to-the-moon). Toiletbowl in Loiter = compass, not PSC_POSXY_P.

EKF / vibes

Check	Target
`VIBE`	< ~30; Clip = 0
XKF4 variances	< `FS_EKF_THRESH`
Mag vs throttle	walk = relocate mag, not CompassMot first

KEY: Raising FS_EKF_THRESH extends flyaways. Fix mount, props, mag, GPS — don’t paper over variances.

Maiden ladder

Props on, outdoor clear, HDOP ≤ 1.4
Stabilize — hover ~mid stick, practice bailout
AltHold — mid holds height; watch climb on vibe
Loiter — center stops; watch toiletbowl
RTL at altitude — confirm climb, home, land behavior
Auto — only with a real mission loaded

Logs: CTUN alt track · VIBE/Clip · MAG · XKF variances.

Plane landmines

Don’t paste onto Copter	Why
`THR_FAILSAFE`, `RTL_ALTITUDE`	Plane names
`MODE_CH=8` / `FLTMODE_CH=8`	Copter default 5
`Q_*` VTOL	Plane/QuadPlane
`ARMING_RUDDER=1`	Copter wants 2 for yaw disarm
Wiki `_M` / `_MS` / `PSC_NE_*`	4.7

AI-slop kill-list

Slop	Reality
BF rates = `ATC_RAT_*`	Ardu has rate + angle + pos + ACCZ
`FS_THR_VALUE` near stick low	Must sit below `RC3_MIN`
`ARMING_CHECK=0`	Not a fix
Raise `FS_EKF_THRESH`	Extends flyaways
CompassMot first	Disable internal mag first
Plane params on Copter	See landmines
MP + QGC both writing	Pick one writer
GPS modes without 3D / HDOP	Toiletbowl / FS
Disarm vs Land vs Terminate	AirMode keeps motors up — RC-loss won’t disarm
`RTL_ALT=1500` as “1500 m”	It’s 15 m (cm)
`GPS_TYPE`	Use `GPS1_TYPE`
AutoTune flight 1	Notch first
Default battery FS = RTL	Stock is warn only
Sport/FlowHold as universal	Often missing / needs hardware
Home = launch pad vibe	Home = arm point
RX forces mode-ch to RTL	Wiki do not
Teach 4.7 names on 4.6	`RTL_ALT_M`, `ARMING_SKIPCHK`, `PSC_NE_*`

4.5→4.6 teach: GPS1_TYPE, ARMING_NEED_LOC, FS_DR_*, ATC_LAND_*_MULT, PID bit in LOG_BITMASK, Sport often gone.

Refs

Flight modes
Radio failsafe · Battery · GCS · EKF
ESC calibration · Tuning process · IMU notch
Param name changes — translate wiki 4.7 → 4.6
Copter-4.6.3 Parameters.cpp — 4.6 truth