NTSB · Safety Recommendation
Safety Recommendation A-17-035
Recommendation
TO THE FEDERAL AVIATION ADMINISTRATION: Implement ways to provide effective terrain awareness and warning system (TAWS) protections while mitigating nuisance alerts for single-engine airplanes operated under 14 Code of Federal Regulations Part 135 that frequently operate at altitudes below their respective TAWS class design alerting threshold.
Safety Issue and Context
On June 25, 2015, about 1215 Alaska daylight time, a single-engine, turbine-powered, float-equipped de Havilland DHC-3 (Otter) airplane, N270PA, collided with mountainous, tree-covered terrain about 24 miles east-northeast of Ketchikan, Alaska. The commercial pilot and eight passengers sustained fatal injuries, and the airplane was destroyed. The airplane was owned by Pantechnicon Aviation, of Minden, Nevada, and operated by Promech Air, Inc., of Ketchikan.
The flight was conducted under the provisions of 14 Code of Federal Regulations (CFR) Part 135 as an on-demand sightseeing flight; a company visual flight rules flight plan (by which the company performed its own flight-following) was in effect. Marginal visual flight rules conditions were reported in the area at the time of the accident. The flight departed about 1207 from Rudyerd Bay about 44 miles east-northeast of Ketchikan and was en route to the operator’s base at the Ketchikan Harbor Seaplane Base, Ketchikan.
Response History
August 10, 2026 · Recipient Response · FAA
-Bryan Bedford, Administrator: In June 2025, the Federal Aviation Administration’s (FAA) Radio Technical Commission for Aeronautics (RTCA) Special Committee 231 (SC-231), Terrain Awareness Warning System (TAWS), delivered its internal report to the RTCA Program Management Committee (PMC). SC-231 concluded the PMC should update the requirements for Class B and C TAWS in DO-367, Minimum Operational Performance Standards (MOPS) for Terrain Awareness and Warning Systems, to address the issue of permanent inhibition of the Forward Looking Terrain Avoidance (FLTA) function in conjunction with the addition of the Ground Collision Avoidance System (GCAS) requirements.
The PMC pointed out that any changes to DO-367 that preclude permanent inhibition of FLTA should allow the function to be implemented in either the TSO-approved TAWS unit or at the installation level. SC-231 converted the internal report into an external report for the public, published September 9, 2025, and can be found at:
https://my.rtca.org/productdetails?id=a1BPP00000JNp5K2AT
The PMC will set the schedule for updating DO-367 when the revised GCAS requirements are complete. Once RTCA updates DO-367, the FAA will provide an anticipated publication date for the revised TSO-C151d, Terrain Awareness and Warning Systems, which will invoke the updated DO-367. Resource constraints among industry and government participants during this process have delayed the development of the PMC’s deliverables. As a result, RTCA has advised the FAA that the anticipated completion of the GCAS requirements is now expected in December 2028. SC 231 will use these requirements in developing the next version of DO-367.
Lastly, the FAA extended Exemption No. 18544B to April 30, 2031, granting relief from § 135.154(b)(2), Terrain Awareness and Warning System, while we continue to develop and implement the GCAS requirements. Exemption No. 18544C allows operators to apply the exemption as an interim Controlled Flight into Terrain risk mitigation until GCAS can be implemented for aircraft operating at low altitude near proximate terrain.