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Risk of Failsafe functions

PeRo

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I would like to raise a question reg. experience of true RC transmission outages. Described in my post "Mountains and Failsafe RTH", there was an almost fatal accident due to a combination of lost RC signal together with hovering at close distance (<5m/16ft) from HP. In this case, autolanding kicked in while in unsuitable terrain.

So far, I have not managed to identify any root cause of the temporary RC failure. It did never occure during <100 previous flights and several flights after the incident.
However, I am concerned that it might happen again. While it is easy to further avoid the described situation, another even more problematic scenario was brought up by @slup which would lead to a probable loss of the AC. Reason is, that "Failsafe - Autolanding" will also be initiated in case of Loss of GPS- together with loss of RC-Signal.

Quote @slup: "So when you lost the connection your craft had no place to go home to ... in fact it didn't know where on earth it was. With no horizontal hold the craft would simply just drift away with the winds. The DJI software doesn't let this happen ... if in ATTI mode & losing the connection, the failsafe action will be landing."

While its clear that Return to Home would not succeed without HP, question is whether Autolanding will be triggered immediately = within the usual 3 sec of signal absence - or only at low Battery RTH? Did not find a clear answer in the manual.

I am flying in Mountain Regions with often challenging Launch points (narrow, steep walls therefore weak GPS signal). So, to improve GPS reception, the AC needs to be moved in ATTI-Mode to a better position furthere away and uphill (VLOS at any time), which can last up to a couple of minutes. During this time period in ATTI, the AC seems to be extremely vulnerable reg. RC signal outage. In this case it would go into unstoppable Failsafe - Autolanding Mode whereever it is, which can mean: down into the gorge.

So my question is: how many real RC uplink outages (close distance, unobstructed view) have you experienced? From the posts, several claims have been raised but many were analyzed as pilots error rather than technical failure.

In the case, immediate attempt to restart the RC might help - if there is enough time. Any similar experience?

Thanks!
 

PhiliusFoggg

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I
question is whether Autolanding will be triggered immediately = within the usual 3 sec of signal absence - or only at low Battery RTH?
I would suggest the the thing to do is recreate or at least attempt to recreate the situation in a place that is safe to do so and see what happens. It might be possible to cover the top of the drone with aluminium foil etc. to obscure the GPS reciever. If that works then you can experiment as you choose.


There is one other point I think needs to be raised.
So, to improve GPS reception, the AC needs to be moved in ATTI-Mode to a better position furthere away and uphill (VLOS at any time), which can last up to a couple of minutes
The homepoint is set to the place where the drone first acquires enough satellites to satisfy its postioning requirements, in the quoted circumstances that may well mean that the drone is at some distance from you when the home point is set and thus so is the home point.
When flying from around my house I often have to take off with insufficient satellites and need to get the drone up and away from me so that it has a clear view of the sky. Once enough sateliites have been obtained i.e. it sets a home point, I bring the drone back over head ( the height is irrelevant) and reset the homepoint to where I am.
 
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PeRo

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I

I would suggest the the thing to do is recreate or at least attempt to recreate the situation in a place that is safe to do so and see what happens. It might be possible to cover the top of the drone with aluminium foil etc. to obscure the GPS reciever. If that works then you can experiment as you choose.


There is one other point I think needs to be raised.

The homepoint is set to the place where the drone first acquires enough satellites to satisfy its postioning requirements, in the quoted circumstances that may well mean that the drone is at some distance from you when the home point is set and thus so is the home point.
When flying from around my house I often have to take off with insufficient satellites and need to get the drone up and away from me so that it has a clear view of the sky. Once enough sateliites have been obtained i.e. it sets a home point, I bring the drone back over head ( the height is irrelevant) and reset the homepoint to where I am.
Thanks for your response.

i) You gave me an idea for experimenting. While aluminium foil might be a bit tricky to use, there should be a method to remap the mode switch positions on the M2P, i.e re-mapping Tripod to ATTI. I am using an MPP but should get access to M2P for testing purpose. While bringing it to ATTI, switching off the RC should give an indication for the Autolanding behaviour. Asumption: M2P Failsafe function is similar to MPP.

ii) You will face a similar risk than the described one if going out with no GPS coverage and hence no HP set. In case of a RC Signal lost incidence prior to an established HP, the AC might go into Autolanding mode as well, no matter whether it is above trees or a street.

So, I am still interested to get details about temporary RC outages (connection lost) - and if this points to aging or degradation of the equipment.
 

PhiliusFoggg

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The M2P has a different failsafe response process. Using it as a guinea pig to investgiate the response of your MPP is, I suspect, likely to be a waste of time.
Besides, would switching an M2P to ATTI mode actually mean that it switches off the GPS reciever? It wouldn't surprise me to find that GPS remains available for automated procedures. I have switched a Phantom 3 to ATTI mode and, as I recollect, it still reported its changing distance from the home point so it must have known where it was and where the homepoint was.
 
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Kilrah

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Manually switching to ATTI is not at all the same as not having GPS available.

As long as GPS is available it'll be used for the safety features regardless of anything in your control.
 
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PeRo

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The M2P has a different failsafe response process. Using it as a guinea pig to investgiate the response of your MPP is, I suspect, likely to be a waste of time.
Besides, would switching an M2P to ATTI mode actually mean that it switches off the GPS reciever? It wouldn't surprise me to find that GPS remains available for automated procedures. I have switched a Phantom 3 to ATTI mode and, as I recollect, it still reported its changing distance from the home point so it must have known where it was and where the homepoint was.

Thanks, good point!
 

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