The Black Hawk helicopter that crashed in Leesburg killing four onboard was conducting a test flight with a newly installed piece of firefighting equipment when a piece came off and swung into the blades, the preliminary crash report from the National Transportation Safety Board shows. The Black Hawk helicopter crashed during a training exercise May 25 near the Leesburg airport. Leesburg city officials said all four crew members died. Their bodies were recovered in the wreckage but officials have yet to release their names. The aircraft was registered to Brainerd Helicopters Inc./Firehawk Helicopters, which contracts with the federal government for firefighting and other services. The Federal Aviation Administration and the NTSB are investigating the crash. On Wednesday, the NTSB released its aviation accident preliminary report.