What happened
On October 15, 2008, a Bell 222 helicopter, operating as N992AA, was performing an emergency medical services (EMS) transport flight from Sandwich, Illinois, to Chicago, Illinois. The flight was transporting a 14-month-old patient along with a pilot, a flight nurse, and a flight paramedic.
At approximately 23:55, the pilot contacted the DuPage Airport air traffic control tower, reporting the aircraft's position over Aurora at 1,400 feet MSL. Shortly thereafter, at 23:58, the helicopter struck a 734-foot radio station tower and the ground in a forest preserve. The impact caused a post-crash fire that severely fragmented the aircraft. All 4 occupants were fatally injured.
The investigation
Investigators examined radar data, which showed the helicopter maintained a steady course and altitude of 1,300 to 1,400 feet MSL until the radar track ended at the location of the radio tower. While the tower's strobe lights were operational earlier in the night, video evidence indicated the lights ceased functioning at the time of the accident.
The helicopter was not equipped with a terrain awareness and warning system (TAWS). A simulation performed by Honeywell International indicated that a helicopter terrain awareness warning system (H-TAWS) could have provided a "Caution Obstacle" prompt 34 seconds before impact and a "Warning Obstacle" prompt 23 seconds before impact.
The air traffic controller on duty was engaged in administrative duties at the time of the accident. Although the tower was an obstruction that controllers were required to memorize, the controller did not issue a safety alert. The investigation found that the controller failed to monitor the aircraft's progress sufficiently to recognize the hazard and issue the required alert.
Findings
- The pilot failed to maintain clearance from the 734-foot lighted tower due to inadequate preflight planning, insufficient altitude, and a flight route that was too low to clear the structure.
- The air traffic controller failed to issue a safety alert as required by FAA Order 7110.65.