We assembled all our components together and realised that we had a problem with our 6 dimensions of freedom sensor (6DOF) that we had seen once or twice before but not paid enough attention to. The sensor had a habit of locking up randomly: sometimes after a few seconds, sometimes after a few minutes. There was no obvious pattern or triggering event. The sensor was simply preventing us from controlling the glider for no obvious reason. We spent several hours investigating. We tried several MPU6050 sensors, different libraries and even used an I2C protocol analyser to try and identify a problem before deciding that we needed to find an alternative solution. Fortunately, we had access to a different 6DOF sensor (LSM6DS3 breakout boards) that we could easily adapt our boards for. Modifying the code was harder as we had to abandon a lot of our earlier code. We decided to base our readings mostly based on the gyroscope rather than the accelerometer and wrote code to convert angles into a 10 bit value that could be passed reliably to the simulator software.
After resolving these 6DOF sensor issues, we gave the airframe a good vacuum cleaning and got on we more angle grinding! We finished removing parts of the frame that protruded or would prevent us from installing plexiglass panels to close holes in the sides.
We created the bottom and top rear shelves, covering the top shelf with insulating cork before securing the power supplies and enclosures to shelf. We also installed the bolts to secure the rear enclosures to the bottom shelf.
We fixed back panel to frame and adjusted rear air brake spring before adjusting the trim cables and rear pivoting plates.
We spend a lot of time finding the optimal place for the release cable sensors. We had initially thought of placing the sensors in the nose of the glider, attached to the remaining release cable, but decided on a different solution today. When we took over the airframe, the nose hook (aerotow hook) of the aircraft was still there but the belly hook (winch hook) had been removed and, presumably, sold or re-used elsewhere. The cable connecting the nose and belly hooks was lying on the floor of the glider. When cleaning the airframe and removing unnecessary cables and fittings, we had decided to leave this connecting cable “just in case” it would be useful later. This proved to be a very wise decision and allowed us to clean and re-use the cable for the release sensors. We connected the connecting cable to a spring attached to the front plate where the front springs holding the stick are attached (albeit facing towards the nose of the airframe). This allowed us to put a little bit of tension in the release cable and provided a convenient place to attach a magnet and the 2 release sensors. Once the front floor of the glider is put back in place, the cable, magnet and sensors will disappear from view and should be well protected.
We installed the wiring on the top rear shelf: black cables for 230V AC and white cables for 5V DC. We will need to add the cabling for the LEDs when these are fitted, most likely fitting a connection box behind the lighting controller enclosure.