What happened
On 14 February 2025, a Tekever AR5 Evolution MK 2.3 (registration G-TEKG) was being operated remotely from Lydd (London Ashford) Airport when an electrical failure occurred at the Command Unit (CU). The incident began when the Uninterrupt to Interruptible Power Supply (UPS) issued an audible warning indicating that mains power had been lost.
Although a petrol generator was quickly deployed, the UPS indicated it had less than six minutes of battery life remaining. The pilot declared a "PAN" call to Air Traffic Control (ATC). In an attempt to restore power, the crew attempted to swap the existing UPS with one from an adjacent unit. However, this process was delayed by a lack of clear labelling on cables and plugs. It took approximately 18 minutes from the start of the event to restore enough power to achieve a downgraded level of emergency control.
Because the aircraft was still receiving a communications 'heartbeat' signal, it did not trigger its automated return-to-base protocol. Instead, it remained in a programmed holding pattern. Once sufficient control was re-established, the pilot manoeuvred the aircraft for a safe landing at the base. There were no injuries and no damage to the aircraft.
The investigation
The investigation focused on the electrical failure at the Command Unit. It was determined that the input power to the UPS had tripped, an event believed to have been triggered by the disconnection of a laptop power supply. The investigation found that while the external mains power remained available, the crew was unable to quickly restore the link due to difficulties navigating the electrical setup.
Findings
- The primary cause of the power loss was the tripping of the UPS input circuit breaker following the disconnection of a laptop charger.
- The process of restoring power was hindered by sub-optimal cable labelling and inadequate wiring schematics, which made it difficult to identify which plugs powered specific components.
- The limited battery endurance of the existing UPS left a very narrow window for corrective action.
- The aircraft continued to fly in a holding pattern because the communications link 'heartbeat' remained active, preventing the activation of automated emergency return procedures.
Safety action
Following an internal review, the operator has implemented several improvements, including:
- Upgrading the UPS capacity within the Command Unit.
- Enhancing the clarity of cable labelling and wiring diagrams.
- Updating internal procedures to prevent a recurrence of similar power interruptions.