In Air Failures
When the general public look at what we do, they think that it is so easy to to our job that the systems are so reliable and that the human is not doing much. The truth is that these systems have failure, and they have failures regularly. A small list of the actual failures (not pilot error) that have occurred during some of our operations:
- Gyro Failure (in the Z Axis);
- Command and Control Failure;
- Battery Cell Failures;
- Telemetry Failures;
- Barometric Sensor Failures;
- Power Distribution System Failure;
- Lights failure;
- GNSS Failure;
- Motor Failures;
- Servo Failures;
From all the issues above (and many others), only 1 resulted in the loss of an air frame and payload. All others were controlled and brought back to the ground in a safe manner. During our RPAS Training we get the students to start thinking about what happens during a single system failure and to observe the situation, act on the situation, this is very different from reacting to the situation. The most common scenario that we have the new students experience is the GNSS Failure, this is due to the easy of simulation, and there are real world situations that are GNSS Denied. This is also one of the easiest to recover from in a training exercise with a simple flick of a switch, the system is back under control and fully stabilised.
In all situations, they pose serious increase in workloads for the pilot in command, below we will explore the first one on the list.
Unpacking the aircraft from the box, nothing is noted as abnormal, all equipment was in order, all hardware was clean in good repair, the maintenance was up to date. There was nothing to suggest that a failure would be about to happen. The aircraft started up and as part of the startup process, the Gyros were calibrated. The finishing tones sang out and it was ready to go. The pilots moved the aircraft to a better location ready for the photography mission.
The motors started up and made a normal grunt noise as the props scraped the cowling and the air flow increases through the ducts. The aircraft takes off and climbs skyward, seconds after take off, the aircraft starts to yaw heavily to the left. This is where the pilot training starts to come in.
The pilot observed the situation and responded to the failure, they didn’t react but responded. The first action was to add throttle, the aircraft was stable but needed space not to hit anything else. Then full opposite yaw input, this slowed the yaw down, but it did not stop the adverse yaw completely. This is where knowing your autopilot is critical, a central theme throughout our RPAS training. An autopilot mode was enabled called Intelligent Orientation Control (IOC), this allows the aircraft to lock onto the direction of home and be flown as though it was still facing the same way that it took off. The pilot could now use just cyclic inputs to bring it back in and control the throttle to land the aircraft.
The aircraft was not damaged, and the system was removed from service until repairs on the gyro could take place. With the proper training and knowledge, the pilot was able to bring the system home when it had a single failure.