WASHINGTON -- Almost two years after a medical helicopter crashed outside Brownsville, Tenn., killing its pilot and two nurses, the National Transportation Safety Board is expected to release the probable cause of the accident next month.
A voluminous docket of documents on the March 25, 2010, Medical Wing accident indicates much attention has been paid to the weather as a factor in the predawn crash as pilot William D. Phillips, a retired Memphis police officer from Bartlett, raced west from Jackson into an oncoming, intense cold front.
Witness statements indicate several heard something like thunder at the time of the crash, but a preliminary report a month after the crash said the French-built chopper showed no signs of a lightning strike.
Ida May Clark, who lived on the road near the wheat field into which the helicopter plummeted, told investigators she heard "woo, woo, woo -- like a train," then felt her whole house shake. Witness Wayne Tritt told the NTSB that the flash of lightning he saw as he drove that morning was "blue-white light," as if a transformer had blown out.
"The sound he heard was 'explosive' and not like regular thunder," the investigator reported.
Twenty-two months after the Memphis Medical Center Air Ambulance Service incident became the fourth medical helicopter crash in a six -month period, NTSB spokesman Peter C. Knudson said the probable cause is expected to be released in the latter half of January. The agency held four days of hearings on the increase in medical helicopter crashes in February 2009 to look at nine fatal accidents that had killed 35 people over the previous 12 months.
Phillips, 58, and nurses Cynthia A. Parker, 48, of Dyersburg and Misty L. Brogdon, 36, of Jackson had just transported a patient from Parsons to the Jackson-Madison County Hospital. All three in the helicopter returning to their base at Brownsville were aware of the severe weather ahead.
On the ground at Brownsville, pilot Robert Christopher Call, known as Chris, a Navy-trained pilot with just a month at Hospital Wing, had just come on duty at 5:30 a.m. He had been in touch with Phillips as he sat at the Jackson hospital heliport. Phillips estimated he had 18 minutes to make it back before the storm got to Brownsville.
A 32-page analysis of the weather on that morning indicates that a small-scale storm system was moving northeast through the southwest part of the state carrying pea-sized hail in some areas. "The accident site was located ahead of the low pressure system and the cold front in the warm-air section of the front," it says.
Weather radar imagery for the accident site at 5:59 a.m., seconds before the accident occurred, and 54 minutes before the sun would come up, showed a "bow echo," or bow-shaped line of cells often associated with straight-line winds and small tornadoes. Instruments indicated an intense storm with severe turbulence, lightning and hail along with "organized surface wind gusts."
The report notes that the "gust front" of an intense thunderstorm makes an area "prone to extreme low-level wind shear."
Regarding lightning, extremely detailed data showed that, within 15 miles of the accident site between 5:45 a.m. and 6:15 a.m., there were six cloud-to-ground lightning strikes and 12 intra-cloud strikes, but "none occurred within 90 seconds of the accident."
NTSB investigator Ralph E. Hicks interviewed Call, other Medical Wing pilots and some flight nurses in the course of the probe. According to his notes, one of the nurses expressed "an industry concern: Do you really need that type of transportation. Couldn't you go by ground?"
Another flight RN-EMT said the rural counties of West Tennessee don't have enough ground ambulances and she expressed frustration that "routine transports" by air are being done "for convenience."