Hi , I’m experiencing an unintended landing detection during the RTL phase of an auto mission and would appreciate any insights from the community.
Flight Summary :
Mission type: Auto Mission with RTL as final waypoint
RTL initiated at: ~80m AGL
Descent rate: 1.3 m/s vertical speed
Unexpected landing detected at: ~35m AGL
As per Log Observations: During RTL descent, the flight controller triggered a landing detection at 35m AGL. Reviewing the logs, I found that the collective pitch held at -1° blade angle continuously for 3–4 seconds prior to the detection event. It appears the land detector interpreted this sustained minimum collective as ground contact.
Should i put more than -2 or -0.7 in collective blade pitch angle minimum when landed or Is there a parameter to increase the minimum duration or add altitude gating to the landing detection logic during RTL?
I would check that configuration and reality match with regard to blade angles. AFAIK you shouldn’t be getting negative blade angles during the descent.
I looked over the log. During the descent, the collective is at the lower limit. That along with the slow descent rate (< 1m/s) caused the landing detector to meet the criteria to declare the aircraft landed. It is odd that you have a collective value of -1 deg that produced a descent rate of only 1 m/s. I agree with @LupusTheCanine that you should check your collective values to ensure they are accurate. Are you using asymmetric airfoil blades? Based on your hover collective setting, you are hovering with only 2.5 deg of collective. so you either have a very light heli or you are using a high rotor speed, or both.
Sorry again about the crash. please adjust your lower collective limit and the land collective min value to lower values so you don’t get into this situation again.
Hi, thank you for the detailed analysis and feedback.
Yes, I’m using cambered (asymmetric airfoil) blades, which is likely why I’m able to hover at around 2.5° collective with the current rotor speed.
I’ll review and recalibrate my collective pitch range to ensure the values are accurate. As you pointed out, the low descent rate combined with the lower collective limit seems to have triggered the landing detector prematurely.
Could you please suggest suitable values for:
Lower collective angle limit
H_COL_MIN (or equivalent land collective minimum)
so I can tune them appropriately and avoid this issue going forward?
Appreciate your support, and thanks again for the guidance.
@Karan_S you probably want to set the H_COL_MIN to have enough negative collective to achieve at least 3 m/s descent rate which is what the auto mode is probably set to. I would probably set it so I get at least 5 m/s descent rate. As long as you don’t have a lot of vibration when on the ground with rotors turning, I would set the H_LAND_COL_MIN to the H_COL_MIN_ANG. As for the zero thrust collective, it is probably just a guess if you don’t have any data on the airfoil or manufacturer data. Setting it to -2 deg might be fine.
