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FAA NTSB Report

Date: 18 MAR 2006
Time: ca 14:48
Type: Beechcraft C.99
Operator: Ameriflight
Registration: N54RP
C/n / msn: U-218
First flight: 1983
Engines: 2 Pratt & Whitney Canada PT6A-36
Crew: Fatalities: 2 / Occupants: 2
Passengers: Fatalities: 0 / Occupants: 0
Total: Fatalities: 2 / Occupants: 2
Airplane damage: Written off
Location: 13 km (8.1 mls) SW of Butte, MT (USA)
Phase: En route
Nature: Cargo
Departure airport: Helena Airport, MT (HLN/KHLN), USA
Destination airport: Butte (Bert Mooney) Airport, MT (BTM/KBTM), USA
Flightnumber: 2591

Narrative:

The Beech 99 departed Helena (HLN) at 14:35 on flight to Butte (Bert
Mooney, BTM) and was carrying only about 10 pounds of freight. The
aircraft was cleared for the VOR B approach to Butte at 14:48. Butte
controllers noted that a weather front that included icing conditions
and heavy snow had been approaching the area from the south to the
north/northeast even though a UNICOM-based Digiwx AWOS reported clear
skies with good visibility and gentle winds in the mountains. During the
descent, the airplane collided with trees and subsequently the terrain.
Search crews found the wreckage of the plane on March 20. Upon
investigation, one of the cockpit radio was found to be tuned to 123.0
MHz which is the airport's CTAF/UNICOM.

Preliminary results strongly suggest that the Beechcraft pilot received
incorrect and faulty data from a Digiwx AWOS weather reporting station
on the field at Butte (BTM) airport. FAA and NTSB continue to probe the
weather data being disseminated from this Belfort Instruments Digiwx
AWOS which has never been formally FAA commissioned. Cary Gates from the
Northwest Mountain Region of the FAA in Helena, MT notes that the
barometer setting is the only FAA Approved weather sensor on the Digiwx
AWOS weather station; all remaining weather sensors on the Digiwx AWOS
(wind direction, wind speed, temperature, dewpoint, relative humidity,
visibility, ceilometer, density altitude, condensation altitude) are
all "advisory." According to the FAA, "Advisory Use ONLY" means not for
actual in-flight aviation use. It should be noted that Belfort
Instruments website even makes mention in a disclaimer that "weather
readings shown on the Internet are advisory only."

Sources: 2 killed in crash of cargo plane (Billings Gazette 20-3-2006);
FAA NTSB