What happened
On June 12, 2018, an AWHERO unmanned helicopter, registration I-UASF, was conducting experimental research and development flight tests at the Nettuno military range in Italy. The flight was part of an authorized program to test specific flight control gains.
During the third test flight of the day, the aircraft was performing a maneuver to return to the takeoff/landing pad. While executing a coordinated turn, the aircraft drifted toward the coastline and struck tall vegetation, causing it to crash. The impact resulted in significant damage to the front, the main rotor, the tail rotor, and the tail boom. There were no injuries to the ground crew or occupants, as the aircraft was unmanned.
The investigation
The ANSV investigation examined the flight sequence, the ground control station (GCS) operations, and the technical capabilities of the aircraft. The investigation established that the crew was executing a test card that required transitioning the flight mode from heading-based control to course-based control. This transition required the pilot to momentarily halt the turn, input new data via an alphanumeric keyboard, and then restart the turn.
Investigators found that the sequence of testing performed that day differed from the original plan, which led to the decision to perform the mode transition during the return turn. During this period of manual data entry, the aircraft drifted closer to the coast. While a backup operator positioned outside the GCS noticed the aircraft crossing the coastline and warned the crew of its low altitude, the crew inside the GCS did not immediately perceive the proximity of the trees through the onboard camera feed.
Findings
- The primary cause of the accident was a design factor related to the limited field of view provided by the onboard camera, which prevented the crew from maintaining adequate situational awareness during maneuvers where the aircraft's heading differed significantly from its ground track.
- The lack of a Terrain Awareness and Warning System (TAWS) on the aircraft contributed to the crew's inability to detect the approaching obstacle.
- A secondary contributing factor was the difficulty in monitoring radar altimeter data within the ground control station, as the crew only became aware of the rapid descent after the backup operator's radio warning.
- The investigation confirmed that no mechanical failures or structural defects contributed to the crash, and weather conditions were favorable.