What happened
On a morning in Fresno, California, a Learjet 35A, registered as N521PA, was operating as a public use aircraft when the flightcrew reported an emergency. While flying under the call sign Dart 21, the crew notified air traffic control of engine fire indications while inbound to the Fresno Air Terminal. The aircraft was attempting to establish a right base for the intended runway, but the descent continued past the airport boundaries.
During the final moments, the crew was heard on the tower frequency attempting to manage the emergency and diagnose the ongoing issues. The aircraft eventually impacted an avenue in Fresno with its landing gear extended. The accident resulted in two fatalities among the flightcrew. On the ground, the impact and subsequent fire caused significant damage to two apartment buildings, destroying or heavily damaging 12 units and causing 21 injuries to people on the ground.
Findings
An investigation into the crash identified that improper installation of special mission wiring was a primary factor. The wiring lacked necessary overload current protection, which allowed a short circuit in the special mission power supply wires to occur in an area without current limiters. This electrical fault triggered false engine fire warnings, prompting the crew to shut down the left engine. The resulting intense fire eventually compromised the structural integrity of the aircraft by burning through the aft engine support beam, which likely prevented the crew from completing a successful emergency landing.