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On October 2, 2016, about 1157 Alaska daylight time, Ravn Connect flight 3153, a turbine-powered Cessna 208B Grand Caravan airplane, N208SD, collided with steep, mountainous terrain about 10 nautical miles northwest of Togiak Airport (PATG), Togiak, Alaska. The two commercial pilots and the passenger were killed, and the airplane was destroyed. The scheduled commuter flight was operated under visual flight rules (VFR) by Hageland Aviation Services, Inc., Anchorage, Alaska, under the provisions of Title 14 Code of Federal Regulations (CFR) Part 135. The National Transportation Safety Board’s (NTSB) investigation determined that instrument meteorological conditions (IMC) were likely in the vicinity of the accident site at the time of the accident. The flight departed Quinhagak Airport, Quinhagak, Alaska, at 1133 and was en route to PATG. Data available for the accident flight showed that, after departure in visual meteorological conditions, the airplane proceeded along a generally direct route toward the destination at an altitude of about 1,000 ft mean sea level (msl), which resulted in terrain clearances between 500 and 700 ft above ground level (agl). During the last 4 minutes of the flight, the airplane climbed as it approached the mountain ridge that it eventually struck at an elevation of about 2,300 ft msl after having likely entered IMC. The airplane was equipped with a Class B terrain awareness and warning system (TAWS) that had an en route required terrain clearance (RTC) of 700 ft agl; flight at altitudes below the RTC (and not within 15 miles of an airport, given certain criteria) would result in TAWS terrain alerts. Hageland flights operated under VFR were allowed to fly as low as 500 ft agl, as was seen with this flight, which was flown en route below the TAWS alerting threshold. The system was equipped with a terrain inhibit switch that allowed the pilot to manually inhibit all TAWS aural and visual caution and warning alerts. A TAWS simulation that used an estimated flightpath for the accident airplane (assuming a level cruise altitude between known data points and a climb after the last data point to the accident elevation) showed that, if the alerts were not inhibited, the TAWS would have provided continuous alerts for most of the assumed flight. The investigation concluded that the TAWS alerts were likely inhibited for most, if not all, of the flight, eliminating a margin of safety.
TO THE FEDERAL AVIATION ADMINISTRATION: Although controlled flight into terrain (CFIT)-avoidance training programs are not required by federal regulation for Title 14 Code of Federal Regulations Part 135 fixed-wing operations, work with Part 135 operators in Alaska to improve any voluntarily implemented training programs aimed at reducing the risk of CFIT accidents involving continuation of flight under visual flight rules (VFR) into instrument meteorological conditions, with special attention paid to the human factors issues identified in recent Alaska accident investigations, including, but not limited to, (1) the challenges of flying in mountainous terrain in Alaska and low-altitude VFR flight in an area subject to rapid changes in weather; and (2) limitations of the Alaska infrastructure, particularly weather observations, communications, and navigation aids.
Original recommendation transmittal letter:
Open - Acceptable Response
Togiak, AK, United States
Collision with Terrain Hageland Aviation Services, Inc. dba Ravn Connect Flight 3153 Cessna 208B, N208SD
Addressee(s) and Addressee Status:
FAA (Open - Acceptable Response)
Safety Recommendation History
We note that a team of FAA aviation safety inspectors is working with the General Aviation Joint Steering Committee (GAJSC) on the CFIT workgroup to improve voluntary training programs aimed at reducing the risk of CFIT accidents. As part of this effort, the workgroup plans to focus on the human factors issues identified in previous accident investigations in Alaska. Please periodically update us regarding the workgroup’s progress. Pending completion of the recommended action, Safety Recommendation A-18-13 is classified OPEN--ACCEPTABLE RESPONSE.
-From Daniel K. Elwell, Acting Administrator: FAA Comment. I n December 2017, the Federal Aviation Administration (FAA) and its team of Aviation Safety Inspectors (the Team) partnered with the General Aviation Joint Steering Committee (GAJSC) on the CFiT workgroup. The Team in conjunct ion with its joint efforts with GAJSC will focus on improving voluntary program s implemented by part 135 operators/certificate holders to reduce CFIT accidents. Special emphasis will be placed on Alaska and the human factors identified by the Board. As part of this effort, the Team will conduct discussions with the FAA's General Aviation Safety Assurance Division and Offices with oversight of part 135 operators/certificate holders in Alaska that voluntarily incorporated CFiT training into their 17 AA-approved training programs. This will ensure the Team has the most current understanding of part 135 operators in Alaska. Furthermore, the Team will ensure that early communications with FAA offices and units responsible for continued operational safety is accomplished, and that FAA offices with oversight of part 135 operations relay the content of this safety recommendation.
On April 17, 2018, the NTSB adopted its report, Collision with Terrain, Hageland Aviation Services, Inc., dba Ravn Connect Flight 3153, Cessna 208B, N208SD, Togiak, Alaska, October 2, 2016, NTSB/AAR-18/02. The details of this accident investigation and the resulting safety recommendations may be found in the attached report, which can also be accessed at http://www.ntsb.gov. Among the Safety Recommendations, five are issued to Federal Aviation Administration (FAA) and can be found on page 71 of the report; eight are reiterated to the FAA and can be found on pages 72-73 of the report. The NTSB is vitally interested in these recommendations because they are designed to prevent accidents and save lives. We would appreciate a response within 90 days, detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendations by number. We encourage you to submit your response.
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