david.p.mann
 Second Officer
Flight distance : 18669501 ft
Canada
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I upgraded to 1.1.411 firmware 10 days ago and, with one exception, have had very good flying and video performance. I first tested flight stability in low (3 feet) and high hover (80 feet), forward and backward high-speed flight segments, and left and right high-speed flight segments with 410 firmware, then upgraded to 411, performed IMU calibration and compass calibration. For me flight stability was excellent and the same on both 410 and 411 firmware. For both firmware versions, the P4 will climb 4-8 feet as it decelerates to a full stop, then immediately descend to original altitude (before the 4-8 foot deceleration climb) and, quite frequently descend another 1-4 feet below original altitude before slowly climbing back to original altitude. I'm sure some P4 owners still consider this a "loss of altitude on stopping" and a "problem", but I DO NOT. I consider this completely acceptable performance of complicated flight electronics.
I also flew my P4 extensively over water last weekend - mostly flooded fields and parks in the Houston, TX area. The stability of the P4 for 98% of the time was excellent. Slow pans at low altitude, low-level P-mode flights several feet above water filming ducks, the P4 was rock steady.
However, at one point near the end of a 15-minute flight with the P4 ~150 feet away from me and hovering ~6 feet above very still standing water (glass smooth - no current) under the shade of several trees while I was shooting video of some baby ducklings, the P4 started climbing with no stick input! In fact, I had to immediately apply 30-50% down stick to keep my P4 from climbing up into tree branches and to maintain altitude. It got a little exciting for about 30 seconds as I had fight to keep my P4 from crashing either into tree branches a few feet above or standing water a few feet below the aircraft.
As soon as I got back out into sunlight, the P4 started behaving normally - hovering stably at 4-8 feet above water with no up/down stick input. I have no idea what caused the barometer and/or VPS sensors to read erroneously and to cause the P4 to try to climb unnecessarily. The flight record shows altitude jumping from 3.3 to 6.6 feet when it first started climbing and then going negative 10 to negative 16 feet as I was applying down stick to keep it from climbing. These sudden negative altitude readings were, obviously, completely erroneous. If they were real, my P4 would have been a submarine. A negative altitude reading of -16.4 feet persisted for the remainder of my low-level flight 8 feet above very calm water as I brought it back to where I was standing on the shore. Even aOfter I descended ~ 8 feet and landed at home point, the barometer still read -16.4 feet. There was zero wind but it was 98 F and very humid that day. Perhaps the barometer sensor was affected by the heat and/or humidity? When I flew again several days later, the barometer was behaving normally and temperatures were again 98 degrees and humidity was just as high.
This experience reinforces the need to ALWAYS be ready to assume manual control of your aircraft - particularly when flying over water. |
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