Worst fears realized yesterday!! . . . I'm a pretty experienced flyer . . . retired career helicopter pilot with thousands of hours flying low level . . and now 250+ UAV missions in the past year . . you'd think I would know. Coming back to shore from a run in SPORT mode out over the bay, at what I knew and could see by the display was around 120ft+ Altitude. . . . as it crossed right to left about 20-30min front of me . . . I was blinded momentarily by the sun so . . . I looked down at the display quickly to see what the altitude actually was . . Knowing I was fairly low but expecting to be high enough to clear the 1 tall tree to my left . . .before I could focus on the DJIGO4 screen . . WHACK! . . just clipped the top bare branches of the only tall tree around . . and with at least 2 maybe 3 blades blown off it tumbled and hit the ground hard . . . broke just about everything. . . and continued to spin the bladeless motors. . . finally I issued a CSC and it stopped vibrating as I picked it up . .in pieces
HOW COULD THAT HAPPEN ?. . .The telemetry says it hit at 94.5 ft so I obviously was not above 120ft like I thought. The angle looked like I was passing behind and above the tree . . but depth perception is pretty low especially when looking upSun, into a bright sky.
CONTRIBUTING FACTORS:
1. It was cold and I was wearing special touch sensitive gloves but may NOT have been been able to feel the light pressure if I was exerting by resting my left thumb on the stick . . even a slight back pressure probably caused the bird to drop 10-20 ft in the 30-40 second prior to the event.
2. I was VLOS (Visual Line of Sight) not FPV (First Person View) . . if I had been flying just using the FPV camera view I would have noticed I was heading directly toward the tree not passing by it. . . here in Canada FPV flying is not allowed . . it means "no goggles" . . but technically means you should be VLOS looking at the drone not the display at all times.
3. Lack of a pre-planned IMMEDIATE RESPONSE. Flying helicopters in the military we often practiced what is the first automatic reaction to an emergency. . . like if you have an engine failure your immediate response should be to lower the collective and preserve rotor rpm . . you should not have to think about it . . it should be just an instinctive reaction. . . . .
4. Depth perception when looking into the sun or bright sky. Lack of shadows and a bright featureless sky background gives little visual aid in estimating distance or height.
5. Poor path panning. High rate of angular movement (due to close-in pass) leads to lack of situational awareness if you're visual field passes through 180 degrees in less than a second. It takes more than a second or two to become familiar of a rapidly changed scene . . unless your brain gets there before the aircraft as it should.
Being unexpectedly blinded by the sun but fully aware I was approaching obstacles at speed what is the best reaction? . . slow down yes . . but that takes time when not anticipated. You could instinctively turn away from the shoreline but at a critical moment you might just as likely hit something else. The only likely safe place is above you and so the immediate response SHOULD have been to slow down but immediately apply FULL UP command and head for the sky. . . . I waited barely a second too long by thinking "hey that looks a bit low . . woah! sun in the eyes . . . let's look at the display and see what it says" . . WRONG! . . .immediate reaction to my perception of a threat should have been back on the right stick and FULL POWER.on the left . . just for a full second or 2, so I would head for clean air above and give myself time to think and confirm there may be a potential threat here.
Yes this would likely not have happened anyway, had my decision to fly back towards home in SPORT mode been better thought out before I executed it . . . But even though I instinctively knew I was getting too close to the tree . . the only tall tree near me . . I had the presence of mind to be checking my altitude before arriving . . .but failed to account for a couple of seconds of sun in my eyes . . .This is now an rapid reaction I will practice until it is instilled as automatic. . . If I am ever unsure I am high enough . . my first instinct should be UP! . . not "I wonder if I'm high enough?"
The ONLY TREE! . . from where I was standing as it passed right to left at 94.5ft
HOW COULD THAT HAPPEN ?. . .The telemetry says it hit at 94.5 ft so I obviously was not above 120ft like I thought. The angle looked like I was passing behind and above the tree . . but depth perception is pretty low especially when looking upSun, into a bright sky.
CONTRIBUTING FACTORS:
1. It was cold and I was wearing special touch sensitive gloves but may NOT have been been able to feel the light pressure if I was exerting by resting my left thumb on the stick . . even a slight back pressure probably caused the bird to drop 10-20 ft in the 30-40 second prior to the event.
2. I was VLOS (Visual Line of Sight) not FPV (First Person View) . . if I had been flying just using the FPV camera view I would have noticed I was heading directly toward the tree not passing by it. . . here in Canada FPV flying is not allowed . . it means "no goggles" . . but technically means you should be VLOS looking at the drone not the display at all times.
3. Lack of a pre-planned IMMEDIATE RESPONSE. Flying helicopters in the military we often practiced what is the first automatic reaction to an emergency. . . like if you have an engine failure your immediate response should be to lower the collective and preserve rotor rpm . . you should not have to think about it . . it should be just an instinctive reaction. . . . .
4. Depth perception when looking into the sun or bright sky. Lack of shadows and a bright featureless sky background gives little visual aid in estimating distance or height.
5. Poor path panning. High rate of angular movement (due to close-in pass) leads to lack of situational awareness if you're visual field passes through 180 degrees in less than a second. It takes more than a second or two to become familiar of a rapidly changed scene . . unless your brain gets there before the aircraft as it should.
Being unexpectedly blinded by the sun but fully aware I was approaching obstacles at speed what is the best reaction? . . slow down yes . . but that takes time when not anticipated. You could instinctively turn away from the shoreline but at a critical moment you might just as likely hit something else. The only likely safe place is above you and so the immediate response SHOULD have been to slow down but immediately apply FULL UP command and head for the sky. . . . I waited barely a second too long by thinking "hey that looks a bit low . . woah! sun in the eyes . . . let's look at the display and see what it says" . . WRONG! . . .immediate reaction to my perception of a threat should have been back on the right stick and FULL POWER.on the left . . just for a full second or 2, so I would head for clean air above and give myself time to think and confirm there may be a potential threat here.
Yes this would likely not have happened anyway, had my decision to fly back towards home in SPORT mode been better thought out before I executed it . . . But even though I instinctively knew I was getting too close to the tree . . the only tall tree near me . . I had the presence of mind to be checking my altitude before arriving . . .but failed to account for a couple of seconds of sun in my eyes . . .This is now an rapid reaction I will practice until it is instilled as automatic. . . If I am ever unsure I am high enough . . my first instinct should be UP! . . not "I wonder if I'm high enough?"
The ONLY TREE! . . from where I was standing as it passed right to left at 94.5ft
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