Dropping altitude quickly.

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I work for a surveying firm, and we fly often to acquire data for projects, usually 2-3 times a week. However yesterday we ran into a situation none of us had previously encountered and the discussion was started within the office about procedures in the future. We encountered a situation at the end of our flight (was in the process of landing) a low flying plane coming into our flight area. Low flying plane in context was a crop duster. We use Pix4D to set our flight path and was flying at 300 feet yesterday. However at the time of the incident our drone was 75-50 feet above ground in a controlled descent. Typically that is not our procedure, but I was instructing a new pilot on how to control the drone manually.

I mentioned to my second set of eyes and two crew members (surveyors) on site that if I tried to drop my altitude quickly I don't think we would have been out of the way in time. Is this because of the program we were tied too, or a setting within the DJI app that will allow for a quicker (controlled) descent?
 

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First WELCOME to the forum :)

The Decent Rate is hard coded in the aircraft to attempt to not allow it to get into what's called Vortex Ring State (VRS) which can lead to total loss of lift/control in the blink of an eye. We experienced this with earlier models and the software was changed to reduce decent rate to avoid VRS and it works splendidly.

In a Real World situation where you're actions could endanger a manned aircraft your best hope might be to kill the motors and let the aircraft tumble down at the fastest rates physics will allow. Yes it's going to destroy your sUAS but if it impacts a manned aircraft the status of your sUAS (and probably company as well) will be the least of your worries. It's our ultimate responsibility to do whatever is necessary to avoid ANY sUAS to manned aircraft conflicts.
 
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First WELCOME to the forum :)

The Decent Rate is hard coded in the aircraft to attempt to not allow it to get into what's called Vortex Ring State (VRS) which can lead to total loss of lift/control in the blink of an eye. We experienced this with earlier models and the software was changed to reduce decent rate to avoid VRS and it works splendidly.

In a Real World situation where you're actions could endanger a manned aircraft your best hope might be to kill the motors and let the aircraft tumble down at the fastest rates physics will allow. Yes it's going to destroy your sUAS but if it impacts a manned aircraft the status of your sUAS (and probably company as well) will be the least of your worries. It's our ultimate responsibility to do whatever is necessary to avoid ANY sUAS to manned aircraft conflicts.

Thank you!

I was fairly certain that the decent rate was set to avoid a rapid decent, but wasn't aware it could not be changed. I'm afraid your solution would be the only solution if we are in that situation. Hopefully it never comes to that, but a life is more valuable than a drone.

Thanks again!
 

ianzone

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I work for a surveying firm, and we fly often to acquire data for projects, usually 2-3 times a week. However yesterday we ran into a situation none of us had previously encountered and the discussion was started within the office about procedures in the future. We encountered a situation at the end of our flight (was in the process of landing) a low flying plane coming into our flight area. Low flying plane in context was a crop duster. We use Pix4D to set our flight path and was flying at 300 feet yesterday. However at the time of the incident our drone was 75-50 feet above ground in a controlled descent. Typically that is not our procedure, but I was instructing a new pilot on how to control the drone manually.

I mentioned to my second set of eyes and two crew members (surveyors) on site that if I tried to drop my altitude quickly I don't think we would have been out of the way in time. Is this because of the program we were tied too, or a setting within the DJI app that will allow for a quicker (controlled) descent?
Quicker decent in app I would exit pgps mode to sport mode
 
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Just a comment ...

Back in UK - one club I flew with used a Royal Navy Airstation for models .... Lee on Solent. Based there were two Seaking Air-Sea Rescue heli's.
Those boys were on instant call out and boy when they went out - they went between the buildings LOOOOOWWW ! and fast.

The Club had to agree to a policy of Dump model in event of alarm going off ... no come round to a landing ... its was shut throttle - nose down and into the ground ... no ifs or buts.

I have odd low flying stuff come over my house ... including Nato Patrols ... if I was up and one came over low enough - its a CSC and pick up the pieces.
 
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I have also noticed that in some of the DJI autonomous models that controls seem to be dampened a little more than usual. Not sure about other software like you were using.
 

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In a Real World situation where you're actions could endanger a manned aircraft your best hope might be to kill the motors and let the aircraft tumble down at the fastest rates physics will allow. Yes it's going to destroy your sUAS but if it impacts a manned aircraft the status of your sUAS (and probably company as well) will be the least of your worries. It's our ultimate responsibility to do whatever is necessary to avoid ANY sUAS to manned aircraft conflicts.
That's the drone equivalent of the pilot going down with the plane to be certain to fly it away from a populated area. Tough choices.
 

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That's the drone equivalent of the pilot going down with the plane to be certain to fly it away from a populated area. Tough choices.

In a manned aircraft I agree it's a very tough choice. With sUAS not nearly as tough. If I am not certain I can clear the airspace I will ditch in a heart beat.
 
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GadgetGuy

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In a manned aircraft I agree it's a very tough choice. With sUAS not nearly as tough. If I am not certain I can clear the airspace I will ditch in a heart beat.
Biggest advantage of a sUAS over a manned aircraft is that you aren't in it, if it goes down, or you have to take it down! My uncle died in his own private plane flying in Alaska. I loved the views, but prefer them vicariously through my drones, while I am always still safe on the ground (except the one time when my P3P came crashing straight down from 215 feet, directly above me, when the battery shut off 15 seconds into the flight, landing 12 feet away from me, smashed to bits on the concrete, which, but for luck, could have been the top of my head! :oops:
 
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I thought I saw a video where someone restarted the motors in free fall and it recovered.
 

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I thought I saw a video where someone restarted the motors in free fall and it recovered.
Not when the battery had already shut itself off on its own, causing the motors to stop in the air! However, yes, if you execute a CSC to shut the motors off with the battery still on, the potential exists that you could still restart them on the way down. Depends upon the height AGL at the time of motor shutoff, and when you try restarting them. Earlier attempts with the P3P were not successful, but made for great crash videos!
 
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Not when the battery had already shut itself off on its own, causing the motors to stop in the air! ...
Agreed. But I don’t think that’s the scenario being discussed here.
 
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it happened to me this last weekend, suddenly a low flying Robinson light helo appeared from nowhere and at some point we were unconfortably close to him. It does not take too much to bring a Robinson down . We had several spots to take off from and we probably chose the one with the poorest 360º visibility. I mean, if you foreseee incoming aircrafts the best course of actions is that you choose a taking off spot with real 360º far away visibility, even if this takes you a long way from your operational site. Anticipation and visibility are paramount. Also consider equiping your bird with a strobe light. Last moment saving manoeuvres are just that.
 
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GadgetGuy

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it happened to me this last weekend, suddenly a low flying Robinson light helo appeared from nowhere and at some point we were unconfortably close to him. It does not take too much to bring a Robinson down . We had several spots to take off from and we probably chose the one with the poorest 360º visibility. I mean, if you foreseee incoming aircrafts the best course of actions is that you choose a taking off spot with real 360º far away visibility, even if this takes you a long way from your operational site. Anticipation and visibility are paramount. Also consider equiping your bird with a strobe light. Last moment saving manoeuvres are just that.
360° visibility generally requires an elevated launch point, which makes it ideal for signal and safety, whether VLOS or LOS! Drones can also safely fly much lower to the ground than manned aircraft, especially when flying from an elevated launch point, so hug the ground and avoid surprises!
 
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Yes, in fact the fast spiralling descent is compulsory manoeuvre for getting certified here, with combined forward down and coordinated turn. But the question is that you should avoid getting in that situation in the first place. In theory any close encounter is reported and you never know whether the other part is going to report it.
 
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Yes, in fact the fast spiralling descent is compulsory manoeuvre for getting certified here, with combined forward down and coordinated turn. But the question is that you should avoid getting in that situation in the first place. In theory any close encounter is reported and you never know whether the other part is going to report it.
Can you explain that maneuver? I am guessing it has to do with stability issues with descending too fast?
 

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