The crash of a Mercy Flight King Air 200 on Feb. 6, 2007, near Bozeman, Mont., is believed to be the first CFIT (controlled flight into terrain) loss of a civil turbine-powered airplane equipped with an enhanced ground proximity warning system (EGPWS).
The NTSB last month blamed Metro Aviation pilot Vince Kirol, 59, for the crash about 13 nm north of Bozeman’s Gallatin Field, saying he failed to maintain altitude while descending for landing on a dark, overcast night. The King Air struck a 5,700-foot ridge about 80 feet below its peak, killing Kirol, a flight nurse and a paramedic.
Investigators said damage to the class-B EGPWS unit prevented post-accident testing. This particular model was capable of issuing audible warnings, but it did not include a cockpit display showing the location of terrain. The unit also included an audio-inhibit switch. EGPWS maker Honeywell noted that 40,000 aircraft are equipped with the safety device, which had flown more than 800 million hours without a CFIT accident. The company added that there is no evidence indicating the unit installed in King Air N45MF failed to perform as designed.
The King Air was on an IFR flight from Great Falls, Mont., about 100 nm north of Bozeman, to pick up a patient for transfer back to Benefis Healthcare. The pilot had flown the route many times and was said to be familiar with the terrain. About 42 nm from the destination ATC cleared the King Air to descend from 15,000 to 13,000 feet. A short time later, after the pilot reported he had Gallatin Field in sight, radar services were terminated and he was instructed to contact the tower.
Investigators faulted the pilot for descending below the 9,100-foot minimum obstruction clearance altitude for the area. The NTSB also issued a safety notice that stressed the importance of altitude awareness and preflight planning after identifying what it called “a noticeable number” of CFIT accidents that have occurred during night VFR operations. In the notice issued in late January the Safety Board wrote that in a number of instances pilots involved in recent crashes were in contact with ATC and receiving radar services, but they appear to have been oblivious to the danger.
Citing the Bozeman King Air crash and six others in the last four years, the NTSB said better planning “would likely have prevented all of these accidents.” An NTSB spokeswoman said the accidents “appear to be quite preventable,” but added that some were still under investigation. Of the seven accidents referenced in the alert, three were aeromedical transport flights. The spokeswoman said the Safety Board did not issue the alert “to identify any particular risk for medical transport aircraft,” but added, “By their very nature, these kinds of aircraft often operate in more remote or rural areas.”
Most U.S.-registered turbine-powered airplanes have been required to carry terrain awareness and warning systems since March 2005. Part 135 turbine airplanes with six to nine passenger seats must carry at least a class-B device, which is not required to include a terrain display. These systems issue audible warnings, but an audio-inhibit switch in N45MF allowed pilots to mute so-called “nuisance alerts.”
Because the King Air did not carry a cockpit voice recorder and the EGPWS unit was so badly damaged, investigators were unable to determine whether the pilot received a terrain alert or whether the unit was even turned on.
Jennifer Harrington contributed to this report.