PUP_ENABLE: Enable pullup after altitude wait

Description

Enable pullup after altitude wait.

Values

• Default: 0

Description

This parameter activates the special "Pull-Up" sequence for high-altitude glider drops (e.g., from a balloon).

• Function: When the mission command NAV_ALTITUDE_WAIT completes (meaning the balloon has burst or the release altitude is reached), the plane will execute a controlled pull-up maneuver to transition from a vertical dive to level flight without over-stressing the airframe.
• Safety: Prevents structural failure by limiting the G-force (PUP_NG_LIM) during the recovery.

Source Code

ardupilot/ArduPlane/pullup.cpp

PUP_ARSPD_START: Pullup target airspeed

Description

Target airspeed for initial airspeed wait.

Values

• Range: 0 to 100
• Units: m/s
• Default: 30

Description

This parameter sets the Minimum Airspeed Trigger for the pull-up maneuver.

• Function: If an airspeed sensor is available, the autopilot will wait until the vehicle reaches this speed during the freefall before attempting to pull up.
• Purpose: Prevents stalling the control surfaces. The control surfaces need airflow to be effective; pulling up at 0 airspeed does nothing but stall the servos.

PUP_ELEV_OFS: Elevator deflection used before starting pullup

Description

Elevator deflection offset from -1 to 1 while waiting for airspeed to rise before starting close loop control of the pullup.

Values

• Range: -1.0 to 1.0
• Units: % (Normalized)
• Default: 0

Description

This parameter applies a fixed elevator offset during the "Freefall" phase.

• Function: While the aircraft is diving to gain speed (before the high-G pull-up begins), this offset is applied to the elevator.
• Usage: Typically set to 0. Can be used to trim the aircraft for a specific dive angle if it has a tendency to pitch up or down naturally.

PUP_NG_JERK_LIM: Maximum normal load factor rate of change during pullup

Description

The maximum rate of change of normal load factor (Jerk) allowed during the pullup maneuver.

Values

• Range: 1.0 to 10.0
• Units: 1/s
• Default: 5.0

Description

This parameter controls how smoothly the G-force is applied.

• Function: Instead of snapping instantly from 1G to 4G (which could snap the wing spar), this parameter ramps the G-load up gradually.
• Physics: It limits the "Jerk" (the derivative of acceleration).
• Effect: A lower value makes the onset of the pull-up smoother but takes longer to reach the maximum turn rate, requiring more altitude. A higher value initiates the turn faster but puts a sudden shock load on the airframe.

PUP_NG_LIM: Maximum normal load factor during pullup

Description

This is the nominal maximum value of normal load factor used during the closed loop pitch rate control of the pullup.

Values

• Range: 1.0 to 4.0
• Units: G (Gravities)
• Default: 2.0

Description

This parameter sets the G-force limit for the autonomous pull-up.

• Function: During the recovery from a vertical dive, the autopilot calculates a pitch rate that will produce this specific Normal Acceleration (G-load).
• Safety: It prevents the autopilot from pulling up so hard that it snaps the wings off the glider.
• Tuning: Set this according to your airframe's structural limits (e.g., 2.0 G is generally safe for foamies, 4.0 G requires composite reinforcement).

Custom pitch (PUP_PITCH)

Description

This parameter defines the Pitch component of a custom user-defined rotation. It is part of the CUSTOM_ORIENTATION system, allowing you to define arbitrary sensor mounting angles that do not fit the standard 90-degree increments (e.g., a GPS mounted on a 15-degree slope).

The Mathematics

The rotation is applied as an intrinsic Euler sequence (Yaw -> Pitch -> Roll).
$$ R\_{\text{total}} = R\_z(\text{PUP\_YAW}) \cdot R\_y(\text{PUP\_PITCH}) \cdot R\_x(\text{PUP\_ROLL}) $$

The Engineer's View

Defined in libraries/AP_CustomRotations/AP_CustomRotations_params.cpp.

Tuning & Behavior

• Default Value: 0 deg
• Usage: Set AHRS_ORIENTATION (or sensor specific orientation) to 100 (Custom) to use these values.

PUP_PITCH_START: Pullup target pitch

Description

Target pitch for initial pullup.

Values

• Range: -80 to 0
• Units: deg
• Default: -60

Description

This parameter defines the Pitch Angle Trigger for the pull-up maneuver.

• Function: After the altitude wait finishes (e.g., balloon burst), the autopilot assumes the vehicle is tumbling or diving vertically. It waits for the nose to stabilize at this pitch angle (e.g., -60 degrees, nose down) before initiating the high-G pull-up.
• Purpose: Ensures the aircraft has gained sufficient airspeed and aerodynamic authority before attempting to pull out of the dive.