3D-Printed Part Leads to Homebuilt Accident

British investigators released a report Thursday that linked an accident involving a Cozy Mk IV homebuilt aircraft to the use of a 3D-printed induction elbow. The aircraft was destroyed after losing engine power on final approach to Gloucestershire Airport in England.

Engine Failure on Final Approach

According to the U.K. Air Accidents Investigation Branch (AAIB), the single-seat flight was returning from a local outing on March 18 when the pilot initiated a GPS-based approach to Runway 09. The pilot advanced the throttle about 500 feet above ground to execute a planned go-around, but the engine was unresponsive and the aircraft landed short of the runway.

3D-Printed Component Found to Be the Cause

The AAIB report determined the loss of power resulted from a plastic, 3D-printed air-induction elbow that softened and collapsed in the engine compartment, severely restricting airflow. The aircraft’s previous owner purchased the part at an airshow in the U.S. and installed it during a 2019–2022 modification of the aircraft’s fuel-injection system.

Although the aircraft’s original plans specify a laminated fiberglass assembly reinforced with an aluminum inlet tube, the printed component did not include the metal support and was believed—incorrectly—to withstand higher temperatures. Lab testing later showed the part’s glass transition point was far lower than expected.

Oversight Gap and Planned Safety Actions

The previous owner had the modified fuel-injection system approved by the Light Aircraft Association (LAA), which oversees amateur-built aircraft approvals in the U.K. However, because the induction elbow was not listed on the modification’s parts sheet, the LAA did not evaluate the component during the system upgrade.

In the end, the AAIB report found that it was the material failure of the elbow that directly led to the engine’s power loss and the subsequent off-runway landing.

The final report said the LAA plans to issue an alert to inspectors outlining safety concerns with 3D-printed components and will ensure the guidance is referenced whenever a permit to fly is renewed.