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Full Parameter PDF

Overview

The GLIDE parameter group (often appearing as LAND_GLIDE_ in the full parameter list) configures the Autonomous Landing Glide Slope for ArduPlane.

The glide slope is the imaginary path (usually 3 to 10 degrees) that the plane follows from the start of the landing sequence to the touchdown point.

Key Concepts

1. Glide Slope Rebuilding (GLIDE_SLOPE_THR)

If the plane is pushed off its planned path by a gust of wind, should it dive back to the original line?

  • Threshold: If the plane is higher than this value (meters) above the planned slope, the autopilot will "rebuild" the slope from its current position to the target, ensuring a smoother descent.

2. Minimum Slope (GLIDE_SLOPE_MIN)

Defines the shallowest angle the plane is allowed to fly during a landing approach. This prevents the autopilot from trying to "float" indefinitely if it has too much energy.

Parameter Breakdown

  • GLIDE_SLOPE_THR: Altitude error threshold for slope recalculation.
  • GLIDE_SLOPE_MIN: Minimum allowable glide angle (degrees).

Integration Guide

  • Landing Issues: If your plane dives aggressively during landing, check if GLIDE_SLOPE_THR is too low.
  • Floating: If your plane consistently overshoots the runway, increase GLIDE_SLOPE_MIN.

Developer Notes

  • Library: ArduPlane/mode_landing.cpp.
  • TECS: Works in tight coordination with the TECS_ (Total Energy) library to manage the trade-off between altitude and airspeed.

GLIDE_SLOPE_MIN

m
Default 15
Range 0 1000

Glide Slope Minimum Altitude (GLIDE_SLOPE_MIN)

Description

GLIDE_SLOPE_MIN controls how "Smoothly" your plane changes altitude between mission waypoints.

If you have two waypoints with a very small altitude difference (e.g. 5 meters), it might be better to just climb instantly rather than calculating a long, shallow glide slope. This parameter sets that cutoff point.

  • 0: Glide slope logic is always used (or disabled, depending on vehicle).
  • 15 (Default): If the altitude change is less than 15 meters, the plane will try to reach the new altitude as quickly as possible. If it's more than 15 meters, it will calculate a straight line (slope) between the points and follow it precisely.

Tuning & Behavior

  • Usage: Increase this value if you find your plane "hunting" for altitude during slight variations in terrain-following or waypoint missions.
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GLIDE_SLOPE_THR

m
Default 5.0
Range 0 100

Glide slope threshold (GLIDE_SLOPE_THR)

Description

This parameter sets the "re-calculation threshold" for the auto-takeoff and auto-landing glide slopes. If the aircraft finds itself significantly above the planned path (e.g., due to a thermal or overshoot), rather than diving aggressively to regain the original line, the autopilot will compute a new, smoother path from its current location to the target if the error exceeds this threshold.

The Mathematics

$$ \text{If } (\text{Current Alt} - \text{Path Alt}) > \text{GLIDE\_SLOPE\_THR} \implies \text{Recalculate Slope} $$

The Engineer's View

Defined in ArduPlane/Parameters.cpp.

  • Benefit: Prevents "porpoising" or aggressive pitch-down commands during takeoff climb-out or landing approach.

Tuning & Behavior

  • Default Value: 5.0 m
  • Behavior: Higher values force the plane to stick closer to the original path; lower values allow it to adapt (shallow out) the path more easily.
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Generator Configuration (GEN) Ground Effect Compensation (GND)