RTL_ALTITUDE – 30m?

[werhof (Werner Hofmann)]

A question for the experts!
When triggering an RTL via FS_LONG_ACTN = 1, the model (glider) should circle in a controlled manner (without motor power) until it reaches the emergency landing field (start altitude minus 20m).
Can this be achieved by setting RTL_ALTITUDE to minus 30 meters (or ALT_OFFSET -30 and RTL_ALTITUDE = 0)?
Is this possible in the software version 4.6.3?

[LupusTheCanine]

You should be able to program such behavior using landing sequence, if you had speed brakes you could even try automatic landing.

[werhof (Werner Hofmann)]

Thanks!
A colleague experienced a fully automated crash with his model.
At an altitude of 300 meters, the RC receiver failed.
FS_LONG_ACTN = 1 / Rally Point
The flight phase down to the launch altitude proceeded in a very controlled manner,
albeit taking a considerable amount of time (approx. one hour, thanks to good thermals).
However, below the launch altitude, the model exhibited highly uncontrolled behavior all the way down to the emergency landing field (at -20 meters).
Hence the question I posed above.

[LupusTheCanine]

If you have a .bin log file could you ease post it.

[werhof (Werner Hofmann)]

Sorry, my colleague didn’t have an SD card installed. There’s only the parameter file.

It’s a shame you can’t configure automatic landing. A DO_LAND_START from 300m (or 700m) upon arrival at the RTL position makes no sense.

[Allister (Allister Schreiber)]

Have a read through this post. It may help:

New Fixed Wing AUTOLAND mode

Using an autoland mission sequence with RTL_AUTOLAND is highly recommmended to prevent failsafes simply returning and loitering at home until battery or fuel runs out and the plane glides randomly down to earth on the loiter path. But that means you have to know and program a mission with the correct landing approach direction. ArduPiot has just merged into “master”, or also know as “dev or 4.7dev”, code a new flight mode: AUTOLAND. If an automatic takeoff has occurred, either by a mission NAV_…

[LupusTheCanine]

DO_LAND_START can be used for arbitrarily long and complex (within the limits of mission storage) landing sequence.

[werhof (Werner Hofmann)]

Thank you for your feedback on this topic.
I consider it highly unrealistic to execute a DO_LAND_START immediately following an FS_LONG_ACTN = 1. After all, a DO_LAND_START could potentially be triggered at a distance
of 150 meters or 750 meters. This would necessitate a very large number of waypoints—a process that is extremely cumbersome.

Our 25-year-old autopilot—originally developed by a glider pilot—solves this problem more simply and safely. In the event of an RC signal failure, our older autopilot would guide the model back to the Home position (much like ARDUPILOT). Subsequently, the old autopilot initiates a steep descent to a reasonable, user-selectable altitude suitable for commencing the landing sequence (a capability not available in ARDUPILOT). Only once this safe altitude is reached does the autopilot initiate the automatic landing approach—a process that has consistently functioned flawlessly.