Can't change to flight mode PrecLoiter using IR-Lock

Currently I’m using Pixhawk and Mission Planner V3.5.5

I’m using IR-Lock without beacon, I made my own circuit lighting IR light.

I connected IR-Lock sensor as document in

and set parameter
CH7_OPT = 39
(also checked ch7 radio parameter goes over 1800)

and also changed Ch7 Opt to PrecLoiter

HOWEVER, when testing in stabilized mode without propellers, it does not change flight mode to PrecLoiter

Can anyone help me with that?

You need good gps status.
Did you wait the GPS check at start ? Did you have enough gps precision ?

@khancyr yes, in Missionplaaner it said GPS: 3D Fix…

it also has rangefinder, however it just do not change to precloiter.

It is possible to change to LAND mode, but failed to PreLoiter.

Mission Planner saying you have a 3D Fix does not mean you can use GPS modes.

Yes, I know its confusing.

This anomaly was introduced with EKF, which may or may not be happy with the 3D Fix.
Before arming you need to change into your GPS modes and check the LED colour.
If the EKF is not happy then the LED will turn blue again.
If armed check Mission Planner flight mode to be sure it actually changes mode.

@mboland Thanks. I tested without props from Loiter to Precloiter and found that motor speed differ when IR led is in front of IRlock.

I guess it is working properly, right?

I thought the PrecLoiter function was supposed to be in lieu of the GPS. Would it still function if the GPS was jammed or otherwise had a loss of signal while in PrecLoiter?


No it won’t work without the GPS, as we need the GPS to have position estimation.