A roll or pitch limit is too small to fly with

What ArduPilot says:

• PreArm: PTCH_LIM_MAX_DEG too small (N.N)
• PreArm: ROLL_LIMIT_DEG too small (N.N)
• PreArm: PTCH_LIM_MIN_DEG too large (N.N)

ROLL_LIMIT_DEG (the steepest bank), PTCH_LIM_MAX_DEG (nose up) and PTCH_LIM_MIN_DEG (nose down, a negative number) limit the attitude in every mode where the autopilot holds it: FBWA (fly-by-wire A: the sticks ask for an angle, not for a servo position), CRUISE, AUTO, RTL. Each must leave at least 3°: the roll and pitch-up limits 3 or more, the pitch-down limit -3 or lower. The message shows the value it found. With less, the plane could not turn, climb or descend. The defaults are 45, 20 and -25.

What to do, most likely first

1. PTCH_LIM_MIN_DEG was typed without its minus sign.

   CheckThe message reads “PTCH_LIM_MIN_DEG too large” and the number in brackets is positive or zero.

   FixSet it negative: -25 is the default, and most planes fly well with a value between -15 and -30.

2. A limit was set to 0 or to a tiny value, by hand or from another aircraft's parameter file.

   CheckRead the three values; Parameter Compare & Migrate shows what differs from the file you meant to load.

   FixStart from the defaults (ROLL_LIMIT_DEG 45, PTCH_LIM_MAX_DEG 20, PTCH_LIM_MIN_DEG -25). Lower the roll limit later only if the plane loses height or stalls in steep turns.

Parameters to look at

Where to do it:Parameter Compare & MigrateStarting Parameters