Lost the Skywalker with the Gopro 3 Black and Mobius cameras a-blazing yesterday.    The first indication I was having a problem was the LCD screen on the monitor blacking out.  At this point the plane was not flying very high nor far.. probably not more than 80′ up. The control response were also squishy but I was able to manage to align the plane on the field for a landing but was coming in too high and decided to make another round which was a mistake, at this point even the EzUHF transmitter shut down. This could mean 2 things either the 12v BEC I used for power distribution for the EzUHF transmitter, monitor, DVR and VRx has failed or the LiPO has discharged.  Running back to the field tent to get a spare battery I saw the plane do an RTL and do at least one circle over the launch area.. so far so good.  Couldnt find the spare battery for the transmitter and decided to disconnect the rest of the electronics and just power the ezuhf, at this point I can still the hear the buzzing plane above.. then silence.

Went around surrounding area for a couple of hours but couldn’t find it.

Lessons for this one:

1)  VERIFY, VERIFY that the transmitter battery is at least at 90%.. this is the 3rd flight I made for the day and I remember starting with about 80% (I’m using a Tiger 4S 2800), usually I charge this the night before but not yesterday =(  Checking the battery after showed it was only generating 11.1v.  I completely under-estimated the power drain by the system.
2) Nevertheless, the APM2.6 seems to have gone on a fail safe which dropped to the RTL. I was expecting the plane to loiter above after reaching ‘home’ waiting for a signal (or the battery drains) but this did not happen.  The correct behaviour should have been with long RC signal loss, the APM 2.6 should loiter or RTL and Circle and not make do a hardware fail safe, either that OR the ESC has fail-safe’d, and finally;
3)  At the first sign of power and control issues…land!

G R O A N.

Last saturday was a great day for flying FPV.. I flew several relatively long flights (ie at least 15 minutes anyway), the first flight was at dawn, 6:30AM and I flew more than 1.4km before turning back and chickening out =)  altitude was about 250m.   I noticed the that the APM2.6+minimosd is heating up quite quickly.. positioned in the compartment under the wings it seems like there’s not much ventilation there in the Skywalker.

After lunch, I used a plastic spoon to create an air scoop and glued that to a small hole in the fuselage to ventilate the APM system.. it proved to be very effective, lowering the temperature from 39.2C (while on the ground) to 36.9C (while cruising).

Took a couple of longer flights and was able to get to 560m in altitude and 1.5+km out.

Had a successful checkout flight of the on-board FPV equipment:

1)  2014 1.9m Skywalker (very much already a crash veteran even at a tender age of 2 months)
2) ImmersionRC EzUHF with diversity for the R/C
3) 700TVL sony ccd camera
4) 2w VTX mounted on the tail boom just before the tail assembly
5) APM2.6 (with 2.78b firmware) and minimOSD for the auto-pilot and OSD respectively
6) 80A Hobbywing ESC (previous 60A ESC was damaged after a crash)
7) 4S 5000mah battery

A week before, during a first test, I had an issue with the GPS and experienced TBE’s during loiter and auto modes.. turns out the external GPS was being affected by the APM power supply.. moved the UBlox GPS and APM to another location (in the compartment under the wing)  and the problem just disappeared.

The day before this test, I upgraded to the APM 2.78 firmware which unfortunately had a bug rendering one of the servos params to be uneditable..a big problem for me since my Ailerons needs to be reversed with the auto-pilot is engaged. Fortunately 24 hours after releasing the software, the developers released a patch 2.78b which solved the problem.

The auto mode in particular is pretty good, as there was a 23kph crosswind.  The APM was able to compensate for the wind and made automatic adjustments in the final approach landing the plane a few meters from the target.  Though in the future, when setting waypoints, one has to give allowance for the typical crosswind direction of a known field and set the waypoints several meters opposite the wind direction.