Synopsis
On 4 June 2023 at 12:55 hours UTC, an MNA GEN 3.8 unmanned aircraft (UA) was conducting a routine delivery flight in Balbriggan, Co. Dublin. While descending to the delivery height, the UA struck a building. The impact triggered the aircraft's flight termination protocol, which included deployment of a ballistic parachute. The UA then descended and struck the ground in a clear area near the building, sustaining substantial damage. No injuries were reported.
History of the Flight
The UA departed from its operating base in Balbriggan at 12:53 hours on a delivery flight to a customer's address in an urban area, approximately one kilometer northeast of the base. The climb and cruise phases were uneventful. Upon reaching the delivery location, the UA began a descent to the pre-defined normal delivery height of 14 meters. It initially descended to 12.29 meters, then used a LiDAR system to recalculate height above ground before adjusting to 14 meters. During this adjustment, the propellers on the left side contacted a building estimated by the operator to be 12.99 meters tall. Immediately after impact, the UA's control system detected a critical failure and activated the Flight Termination System (FTS). The FTS shut down the electric motors and deployed the ballistic parachute. At that time, the UA was below the minimum effective deployment height of 47 meters. The UA hit the ground 1.1 seconds after parachute deployment, coming to rest in a concreted area between apartment buildings near the planned delivery location. A Visual Observer was present at the site prior to delivery to ensure it was clear of obstacles and people. The operator activated its Emergency Response Procedure and deployed a team to the site, who recovered the UA.
Injuries to Persons
No injuries were reported to the Investigation.
Damage to Aircraft
The UA was substantially damaged, including multiple cracks in the frame, a cracked bracket connecting the right frame to the right arm, a sheared bolt in the front left bracket, cracks in all four front propeller blades, minor scrapes and cracks in the four rear propeller blades, bending of the front arm, detachment of the parachute tube from its mount, and other dents and cracks.
Personnel Information
The operating crew consisted of a Mission Controller, a Remote Pilot, and a Visual Observer. The Mission Controller and Visual Observer had completed role-specific training and held current authorizations from the operator. The Remote Pilot, aged 26, held an EASA Remote Pilot Certificate of Theoretical Knowledge (A1/A3 and STS certification) issued by the Irish Aviation Authority, and had completed a practical skills assessment on 1 December 2022. The Remote Pilot had 27.81 hours (406 flights) of flying experience at the time of the occurrence.
Aircraft Information
The MNA GEN 3.8 is a lightweight coaxial octorotor UA constructed from plastics and carbon fiber, with a maximum take-off weight of 23.6 kg. It uses eight T-Motor U8 electric motors. Components include off-the-shelf parts and bespoke elements designed to the operator's specifications. Final assembly occurs in County Offaly, Ireland. Maximum payload is 2.25 kg, carried in a cargo compartment. During urban deliveries, packages are lowered on a thread from approximately 14 meters. A ballistic parachute is fitted for automatic deployment upon loss of control or critical malfunction, and can also be deployed manually. The subject UA, serial number MNA-1630, was manufactured in April 2023, with 30.5 hours and 512 cycles total time. It did not require a Certificate of Airworthiness. The UA had no automatic obstacle collision avoidance system fitted, nor was one required.
Meteorological Information
Met Éireann provided estimated meteorological conditions for the Balbriggan area at approximately 12:54 hours on 4 June 2023. Ireland was under high pressure with a light to moderate easterly flow. Surface wind was east-northeast at 8-12 knots. Between surface and 300 feet, wind varied from northeast to southeast at 10-12 knots. Visibility was 40+ km. Weather was dry and sunny with few fair-weather cumulus clouds at 2,500-3,000 feet. Surface temperature was 18°C, dew point 8°C, and mean sea level pressure 1026 hPa. The operator reported similar conditions at its base.