CHICAGO (AP) — A medical helicopter was flying at least 100 feet lower than the company's standard procedure before it hit a radio tower and crashed in suburban Chicago, killing a toddler and three others on board, according to a federal report released Thursday.

The "factual" report from the National Transportation Safety Board does not discuss a probable cause for the accident, which is expected to come in a final report later this year.

NTSB's report said nothing seemed amiss with 69-year-old pilot, Del Waugh, of Carmel, Ind., who spoke to an air traffic controller minutes before the helicopter clipped a tower guy wire, crashed into a field and burst into flames around midnight Oct. 15.

Waugh told the controller his altitude over Aurora was about 1,400 feet above sea level, according to the report.

Three minutes later as the Air Angels helicopter hit the tower, the top of which is about 1,450 feet above sea level, a voice could be heard over the radio making an unintelligible sound, which the report said "sounded similar to, 'ahhhhhhhh.'"

"There were no further contacts with the aircraft," it adds.

According to the highly technical report, Air Angels' usual procedure for the same route is for helicopters to fly at an altitude of between 1,500 feet and 1,700 feet at night.

A brief statement Thursday from Air Angels did not address any specifics of the NTSB report, saying only that it is a preliminary finding and that the company is reviewing it.

The report confirms earlier NTSB findings that there appeared to be no mechanical failures on the Bell 222 helicopter, that the radio tower's lights were flashing before the crash and that there were no severe weather conditions.

While the NTSB has not drawn a conclusion, safety experts have said the agency's finding that the helicopter's flight controls, engines and drive system showed no evidence of malfunction suggests pilot error is to blame.

The new report noted Waugh was regarded as "conscientious" and "meticulous," and cites colleagues as saying the pilot appeared well-rested and his demeanor normal when he reported for work on the day of the accident. An autopsy that included toxicology tests came back "negative for all substances."

The Air Angels helicopter was carrying 1-year-old Kirstin Blockinger from Valley West Hospital in Sandwich, where she was taken after suffering seizures, to Children's Memorial Hospital in Chicago. She was killed, along with Waugh, paramedic Ronald Battiato, 41, and nurse William Mann, 31.

The toddler's parents filed a wrongful death lawsuit last week, claiming known safety measures could have prevented the girl's death. Brooke and Robert Blockinger, the girl's parents, want new federal safety rules for such flights and hope to spur faster action by the Federal Aviation Administration, their attorney has said.

Thursday's NTSB report noted the Air Angels helicopter did not have a Terrain Awareness Warning System (TAWS), which warns pilots when helicopters are in danger of crashing into the ground or obstacles. The agency has recommended operators install TAWS, but some companies have said they're waiting for the FAA to act.

Safety issues have come to the forefront after 28 deaths in seven fatal medical helicopter crashes accidents last year. According to the NTSB, there were seven deaths in two fatal crashes in 2007.

The board will hold a hearing on the topic beginning Feb. 3 in Washington, D.C.

The NTSB on Thursday also released information on four other medical helicopter accidents, and gave the probable cause of four crashes. Investigators say flying at night in poor weather contributed to three crashes in which 12 people died; it blamed a fourth crash in Alabama on flying too low over trees as the EMS helicopter searched for a lost hunter.

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National Transportation Safety Board: http://www.ntsb.gov

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