NTSB investigating cause of helicopter crash
The National Transportation Safety Board says it is investigating whether the radio tower that an Air Angels helicopter clipped last night was properly lit, whether the pilot was flying high enough and whether there were any mechanical problems.
John Brannen, of the NTSB, said at a press conference Thursday morning the helicopter's rotor blade may have separated during flight, but he would not speculate on the cause. The agency will issue a preliminary report within a week, he said.
Brannen said the helicopter was flying about 50 feet below the top of the tower when the wire was clipped. He said NTSB was investigating whether lights on the tower were on at the time or could have been knocked out during the incident.
"I can say that when I was out here last night after the accident that the lights on the tower were not lit," Brannen said Thursday.
Air Angels CEO Jim Adams said the pilot did not report mechanical problems, and weather was not an issue.
Brannen said the helicopter "fragmented," and pieces were found scattered around the area. Parts of the main blade were found in a nearby apartment complex, he said.
The Air Angels crew was in communication with a tower at the DuPage Airport, but there was no indication of a distress call, Brannen said. The wreckage of the chopper will be removed this afternoon, he said.
Three crew members and a 14-month-old girl were killed in the crash when the helicopter went down in a cornfield late Wednesday near Eola Road in Aurora.
In January 2003, an Air Angels helicopter crashed in West Chicago during a training flight, killing the pilot. Investigators determined pilot error and weather caused the accident. Mechanical problems were blamed for an August 2007 Sugar Grove emergency landing in which there were no injuries.
A medical helicopter has crashed near Chicago, Illinois killing three crew members and the patient, a thirteen-month-old baby girl. The crew aboard the helicopter included the pilot, a nurse and a paramedic.

The helicopter, operated by Air Angels Inc., was transporting the baby to Children's Memorial Hospital from Valley West Hospital, when it hit a wire connected to a 734-foot (224-meter) radio tower in Aurora and burst into flames around 12:00 a.m. (EDT). The baby was suffering from epileptic seizures. 

The cause of the crash is not known, and there were no reported problems with the helicopter before it took off. An investigation by the National Transportation Safety Board (NTSB) is ongoing.

This is the third crash which involved an Air Angels helicopter. In 2003, a pilot was killed when his chopper crashed. An investigation concluded that the cause was pilot error, and bad weather. Another chopper crashed in 2007, but there were no injuries.