Overview
On the day of the accident, a Learjet 35A, registration N521PA, operating as a public use aircraft under the call sign Dart 21, crashed on an avenue in Fresno, California, at approximately 1146 Pacific Standard Time. The flightcrew had declared an emergency while inbound to Fresno Air Terminal after receiving engine fire indications.
Emergency Declaration and Sequence
After declaring the emergency, the flightcrew flew the aircraft toward a right base for their requested runway. However, the airplane continued past the airport. Air traffic control tower frequency recordings captured the flightcrew attempting to diagnose the emergency conditions and control the airplane. The landing gear was observed down at the time of the crash.
Accident Details
The aircraft crashed on an avenue in Fresno, resulting in fatal injuries to both pilots. Twenty-one persons on the ground sustained injuries. Impact and subsequent fire destroyed or substantially damaged 12 apartment units within two buildings.
Investigation Findings
Investigation revealed that special mission wiring was not properly installed, leading to a lack of overload current protection. The in-flight fire most likely originated from a short circuit of the special mission power supply wires in an area unprotected by current limiters. This fire produced false engine fire warning indications, prompting the pilots to shut down the left engine. An intense fire subsequently burned through the aft engine support beam, damaging the aircraft structure and systems in the aft fuselage, which may have precluded a successful emergency landing.
Probable Cause
The probable cause of the accident, as determined by the official investigation, is a combination of the following factors: improperly installed electrical wiring for special mission operations that led to an in-flight fire, which caused airplane systems and structural damage and subsequent airplane control difficulties; improper maintenance and inspection procedures followed by the operator; and inadequate oversight and approval of the maintenance and inspection practices by the operator in the installation of the special mission systems.