Change Speed under Action tab

What does change speed parameter in the Action tab do? its default at 100, is it 100% throttle? I have used the change Alt option to guide my plane once but never seen much difference in the flight while changing this option.
Thanks in advance!!!

@Michael_Oborne Any suggestions?

According to code

This value changes TRIM_ARSPD_CM value if You have airspeed sensor.

Airspeed in cm/s to aim for when airspeed is enabled in auto mode. This is a calibrated (apparent) airspeed.

And change TRIM_THROTTLE if You dont have it.

The target percentage of throttle to apply for normal flight

@Michael_Oborne As I can see there is no WP_SPEED_MAX param in quad param list, WPNAV_SPEED should be used instead?

I do think this need an update, as pram names have changed since I added those buttons

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Regarding that “change speed” button there’s something confusing. There’s three controls in a column: “change alt”, change speed and “change loiter radius”. And they behavior in different way: “change alt” uses “MAV_CMD_DO_CHANGE_ALTITUDE” while others use changing corresponding parameters. Also “change alt” button is effective until the next WP reached and other have constant effect. And this is most confusing. While “change loiter radius” is more about mission planning, the first two are really affecting flight control.

Once we had controversy on whether operator changed parameters or not, and it seems that he changed it via "change speed’ and didn’t noted it as permanent parameter change.

May it be more clear to use MAV_CMD_DO_CHANGE_SPEED for “change speed” button?

Also there’s some confusion that values in numeric up/down are of different units and while changing units for altitude measurement affects “change alt”, “change speed” is not affected by changing speed unit and always in m/s. Also as far as I remember target speed is TAS and indication on HUD is IAS that is confusing too.’’

I thing we need to do something with "change speed’ controls and maybe with “change alt” too. At least it needs to show units and measurement reference (ASL/rel/AGL for alt and TAS/IAS for speed).