Tethered unmanned aerial platforms (tUAVs) possess significant advantages over autonomous drones, primarily due to their capability for prolonged continuous operation, making them suitable for diverse applications. Ensuring the reliability of such platforms is paramount, particularly in scenarios where satellite navigation signals are degraded. This study investigates a laser-based local navigation system (LNS) as a novel solution. This study investigates the reliability of such a LNS for tUAVs using risk tree construction and analysis methodology.