msinger
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My P3P crashed, DJI not cooperating
- Thread starter Chris_P
- Start date
The answer is not to turn off auto RTH in all cases. You can be interrupted, get distracted or anything else that can happen to a pilot that shouldn't. You can always cancel RTH very quickly.I reiterate my strong suggestion to turn Smart Return Home OFF. This entire incident would never have occurred with Smart Return Home disabled. It is a very annoying function, when left on, and won't tell you anything you aren't aready fully aware of, if you are paying any attention to the telemetry. Now, we see that it can also lead to crashes during landing, even if only because the pilot misinterprets what is happening. Shut it OFF!
HOWEVER, all that being said there are times where you might want to turn it off like when you are moving around on a boat and changing positions. This would seem like the smart thing to do. Every pilot should have a pre-flight checklist. You better believe that every pilot of a plane has a pre-flight checklist. If you are not using one then either you have done it so many times that it has become automatic, or you have never been a pilot. Pilots use pre-flight, pre-takeoff, takeoff, climbing, cruising, descent and landing checklists. Many small plane crashes are the result of not following these checklists whether they are written or mental.
I would also have to ask the pilot who lost his drone whether he ever went to a large field and practiced all of these maneuvers like moving around the field, turning off the auto RTH or resetting the RTH point and checking the map to make sure it worked aside from the audio cue from the mobile device. Did he do this until the battery was low and the smart RTH kicked in?
Finally, 12 or 15 seconds is enough time to hit the throttle and climb. If it was not enough time then the pilot simply did not have enough experience to be flying under at least 200 feet. How much time did he spend on the simulator practicing.
I posted earlier about a situation where I almost crashed into some trees but for hitting the throttle and climbing. I had another incident yesterday. I forgot to do an Advanced Unlocking before flying near an airport. I will need to add that to my checklist. The app informed me that is was landing automatically. My heart dropped as I saw the altitude dropping on the screen. What is that rule again? CLIMB. I hit the throttle and it started to climb. After a few seconds, with time to understand what was happening I started to fly away from the airport. A notice came up on the app asking if I wanted to cancel the auto landing. I hit it and came running home.
The point here? Climb. Get on the simulator or at least out on a field and practice. Simulate a potential emergency and get used to climbing as your first reaction.
GadgetGuy
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The default single distance displayed in the app is the distance to the Home Point (which will also be the controller's location, if you haven't moved during the flight, or have successfully reset the Home Point to your current location, by using a GPS enabled tablet or controller), which is recorded before launch by the GPS in the aircraft, and stored on the aircraft, which is how it knows where to go when the controller signal is lost. The aircraft continuously updates this measured distance away from the Home Point during flight through the controller, and passes it on to the app for your viewing pleasure.
GadgetGuy
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I was simply passing along bladestrike's sage advice, regarding increasing the accuracy of the barometer zero point, by letting it "warm up" and calibrate for some 3 minutes. He didn't say anything about temperature. Barometer readings are based upon pressure, and, with all due respect, I fail to see how a pressure calibration process would be shortened by an increase in temperature. GPS accuracy is enhanced with time if you stand in place, but has no temperature correlation to my knowledge. IMU's are different from barometers. IMU warmups before launch are based upon temperature, which is why the aircraft won't allow takeoff until the original IMU calibration temperature has been reached. There is no requirement before takeoff of a proper barometer calibration. The barometer needs time to accurately calibrate the zero elevation takeoff point, based upon the current air pressure. I doubt that higher temperatures will shorten that time.
I welcome validation of either statement (neither of which I claim credit for), whether time or temperature, is the real controlling factor behind a proper barometer calibration.
I went to the crash site and flew the phantom around the area, near the trees and near where I recalled it impacting. Have a look at these logs and compare to the crash logs on Google maps or Bing. I also took a video of the flight with my phone, its uploading to dropbox now, I'll post a link when its done.
These are great. I have several of them. I use one at work and no one notices because they are so discrete. Some are louder than others, but at home and outside they are plenty loud. You can put an earplug in your other ear to help with ambient noise as you an only use one of these at a time.The range is incredible for such a small and cheap earbud. I can get well over 100 feet away from my ipod when listening to music.
Looks like you flew around various areas there. At what point in the log were you hovering over the spot where it crashed? There's a lot of path data and I want to be sure.
Mike
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I think the 3-minute thing needs to be tested before it's accepted as valid.
It's come from someone that isn't very scientific and not everything he recommends is necessarily true.
I have heard of a few Phantoms with poorly calibrated barometers giving wrong readings but I haven't observed it with any that I've flown.
The specs for the P3 state 0.5m vertical accuracy and the kind of inaccuracies that have been mentioned above is well outside that.
Because I do a lot of flying above the surface of the sea at not very high altitudes, it is important that my altitude reading is reliable and so far it has been on all my birds.
It's easy to do a quick check of your flight records to see if there is any substantial difference between start and landing altitudes and get an idea of whether your altitude accuracy drifts during a flight.
Yeah, I'm going to repeat my testing and more, but I'll try to do the 3 minute test today or tomorrow to compare with my previous findings. For me, it's just about testing and seeing for myself particularly since that was a claim I hadn't heard before. I'll definitely post results. Even if it's not the 3 minute warmup, I'd like to get to the bottom of why mine was off about 15 feet on landing and more while I was flying. If you can't depend on the accuracy to be better than maybe 10 or 15 meters (at times), I can accept that. I'll just work that into my flight routine. It's not a big deal as long as I'm aware of it. I just like tinkering and testing I guess.
Mike
I flew over the area back and forth, I was thinking the lat.lon will match the crash site. Clearly if I'm flying over it at 6-10' altitude, there are no trees there. When you overlay on Google maps / Bing, you should see the same coordinates from both flights.... It should be easy to confirm where there are trees or no trees.
I tool a video of the drone flying but its still uploading to dropbox.
What I was getting at is that I wish you had hovered for say 60 seconds over the spot where you think the impact occurred so we could compare that. The path looks like spaghetti so it's hard to tell where you actually saw it impact. I wanted to see if that spot lined up on the map.
Mike
I did hover there for about 10 seconds, not 60 though. It's not one of the points when I'm moving. I did hover there for sure.
I do see a very straight line going from off shore (about where the boat would have been) directly toward the edge of the rock. You did stop right at the edge of the rock just a few feet where the rock meets the water. You then flew off in different patterns, so I guess the end of that straight line would be where you saw the impact. That lines up almost exactly with the path from the crash log. So that's pretty good evidence that Google Maps is accurate there.
Mike
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Yes ! That was me trying to the best of my ability to recreate the line to impact from where I was on the boat offshore.
GadgetGuy
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I fully agree.
However, allowing a barometer to properly calibrate itself before expecting its best accuracy makes intuitive sense. Whether that takes 3 minutes or 2 minutes or a minute remains to be seen, but it should be a constant. I still doubt that it is dependent upon temperature. I am not aware of any check of proper barometer calibration in the app, before launch. However, some research on barometer calibration, in general, is clearly in order. The 10-15 foot drops the P4 still exhibits under old firmware, after letting off the throttle, are of far more concern than the .5m vertical inaccuracy of the P3 barometer. To its credit, the P4 barometer clearly shows those altitude drops, even from 3 miles away! Kind of scary, flying low over the surf! Back inside from my 3 minute warmup test. Differences from my non-warmup flight were pretty negligible. Palm tree height was reported as 53 feet this time compared to 60 feet the first time. I brought it back down to eye level twice. The first time after just a few minutes and it registered 14.8 feet. Second time was at the end of the ~9 minute flight and it registered 19.7 feet the second time. Actual in both cases was about 5'4". The error seemed to increase a bit toward the end of the flight and as I rose higher. Even though the error was just a little less this time with it reading only 10-15 feet higher than actual, I'm not convinced the 3 minute warmup did a lot. Might try an even longer warmup next time and see what happens. And personally, if it doesn't vary more than 15-20 feet, that's probably accurate enough. I just wonder if I'm able to measure a 15-20 foot discrepancy on two rough tests, what factors could contribute to that error being more (as it appears to be in Chris' case)? I don't know the answer to that as I don't know what causes the "drift".
Mike
Mike
The full video of the area was 8 mins long and 1.2G. I edited out the beginning that basically shows the main relevant content. As Mike pointed out, this is my fly out and back simulating the direction of the crash. I hover before and after in the area. This video should put some perspective on the logs I posted earlier. I think this totally disproves the hitting a tree scenario.
Dropbox - Phantom Crash Site Video.mp4
Dropbox - Phantom Crash Site Video.mp4
I think the map from your log proves you didn't hit a tree and that the GPS is accurate to the Google map in that location. But that's probably a moot point by now. There were some pilot errors and the altitude error that contributed. I think if I were you, I might make a final argument that the (significant) altitude error, which I believe has been proven, was a contributor that resulted in less time to react... and maybe try to talk them up to a 30% discount? The basis is a "faulty" barometer that resulted in errant telemetry.
Mike
Mike
