What happened
On 17 January 2023, a Tekever AR5 Evolution Mk 2, registration G-TEKV, was conducting a commercial unmanned aircraft system (UAS) operation over the English Channel. The flight was being performed in support of UK Border Force activities within the Temporary Danger Area EG D098. The aircraft was being operated via a Ground Control Station using satellite communications (Satcom) to maintain a Beyond Radio Line of Sight (BRLOS) connection.
At approximately 1346 UTC, the primary Satcom command and control (C2) link failed. Following its programmed contingency protocols, the aircraft activated its Return to Home (RTH) flight mode and began a pre-defined route designed to maintain safety within the danger area. For several minutes, the aircraft was not under the direct manual control of the remote pilot.
By 1348 UTC, the aircraft's Satcom backup channel transitioned from standby to active, allowing the pilot to regain a C2 link. The pilot then maneuvered the aircraft closer to the ground station to re-establish Radio Line of Sight (RLOS) and 4G connectivity. Once multiple links were restored, the primary Satcom link was eventually recovered, and the aircraft completed its mission, landing without further incident at 1521 UTC.
The investigation
The AAIB examined the aircraft's log files and coordinated with the Satcom service provider. While there was no evidence of planned maintenance or external service degradation, the analysis revealed that the Satcom terminal logged out due to faults in the transmit block upconverter (TXB) reported by the antenna control unit.
Investigators investigated potential causes such as excessive antenna temperature or a loss of the 10 MHz reference signal. While temperatures were within normal limits and replacing the signal cable did not resolve the issue, subsequent ground testing confirmed that the fault persisted. The Satcom antenna was subsequently replaced. Post-incident monitoring of subsequent flights showed no further communication dropouts.
Findings
- The loss of the primary C2 link was caused by a fault within the Satcom antenna.
- The aircraft's automated contingency procedures, including the RTH mode and the use of a backup Satcom channel, functioned as intended.
- The operator's risk assessments had previously identified the loss of C2 link as a known hazard, with mitigations such as redundancy and automatic flight modes already in place.
Safety action
Following the incident, the operator announced that future versions of the Tekever AR5 will include a feature that automatically activates the Satcom backup whenever the aircraft has fewer than two active communication links available.