Auto launch is applying throttle immediately after arming in 2.6-RC2

[avsaase]

Current Behavior

Today I noticed that with 2.6-RC2, auto launch permanently enabled (and some idle throttle configured), the motor starts spinning directly when you arm the board, instead of after raising the throttle stick. This is potentially dangerous if you don't expect this and is a significant change from previous behavior.

Steps to Reproduce

1. Have auto launch permanently enabled.
2. Not sure if this is required to reproduce, but I have some idle throttle configured.
3. Arm
4. Motor starts spinning
5. You still need to raise the throttle stick, otherwise the launch will not be detected.

Expected behavior

Don't spin motor until throttle stick is raised.

Suggested solution(s)

Could it be a problem with recent changes to auto launch?

Additional context

diff all

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• FC Board name and vendor: MATEKF411SE
• INAV version string: INAV/MATEKF411SE 2.6.0 Nov 17 2020 / 10:46:27 (1a490f4)

[digitalentity]

I noticed this as well. This is NOT how launch mode is designed to operate and needs fixing.

[avsaase]

This seems similar to the bug you found in RC1, but other than the motor spinning up the flight controller performed normally.

[digitalentity]

@dragnea, as you recently touched the launch mode code, can you please look into fixing this? If you're busy - I can have a look later this week.

[dragnea]

@avsaase I did not intend to change the old behaviour. It is tested on my main planes, but not using permanent autolaunch. So I have to see what happens. Do you had a chance to test with autolaunch on a stick? At least we will know more. Here is
with some idle throttle: https://www.youtube.com/watch?v=Lh1rxddKeyU&ab_channel=DragneaMihai
@digitalentity I will have a look tonight or tomorrow after work. Thanks

[b14ckyy]

Found the reason:

nav_overrides_motor_stop causes this. If it is OFF > all good. If it is set to AUTO_ONLY or ALL_NAV, motor spins at IDLE throttle when armed.

If throttle stick pushed up > motor spins up to Launch Idle.

Update: It has nothing to do with navl launch idle throttle. If set to 1000 motor stop is still not working when armed.

[dragnea]

@b14ckyy yep. I don't know if it's ok using the idle settings for wings

[b14ckyy]

before the RC phase nav_overrides_motor_stop worked differently with just ON and OFF. And that seemed to work with your code. Maybe it's easier to fix there? @digitalentity

[dragnea]

@b14ckyy Yep. I'm working on it. The actual implementation is using getThrottleIdleValue(). What if we use the min_command value to keep the motors off for the autolaunch. On the wings we don't need the idle throttle, right?

[b14ckyy]

@dragnea launch idle throttle is absolutely important for a lot of planes! If you talk about motor idle, I'd prefer to keep it. I like to keep props spinning on planes with props that are clear from the ground. Esspecially scale planes.

[dragnea]

@b14ckyy that's another thing. it's only about of the autolaunch sequence. When you arm the plane, you want the motors to be off. Using getThrottleIdleValue() now will get the motors running. By usgin the min_command value, the autolaunch will don't care about the idle settings. but just in autolaunch. I have tested already

[dragnea]

@digitalentity what do you think? dragnea@b672f53

[b14ckyy]

OK I don't get it. The nav_launch_idle_thr is important. We can't remove that.

If I arm now, the motor will spin at throttle_idle and NOT on nav_launch_idle_thr. When I then raise the throttle stick, the motor speed goes to nav_launch_idle_thr, that's correct.

so throttle_idle must not be used when plane is armed and AUTOLAUNCH is active. But that's what is happening right now.
If nav_overrides_motor_stop is set to OFF then it works fine. so here the new nav_overrides_motor_stop settings cause the motor to spin at idle as soon as nav launch is active.