What happened
On December 24, 2017, at approximately 18:08 PST, SkyWest Airlines Flight 3567, a Bombardier CRJ9 with registration N162PQ, was conducting an instrument approach to Rogue Valley International – Medford Airport (MFR) in Medford, Oregon. The flight was operating under instrument meteorological conditions (IMC) with a visibility of 10 statute miles.
The aircraft was cleared by the Medford sector controller to cross the initial approach fix, CEGAN, at or above 7,800 feet for the VOR/DME-C approach. While established on the 27 DME arc, the flight crew descended from 12,000 feet. At 18:04:59, the aircraft''s altitude indicated a descent below 10,000 feet. As the aircraft approached the fix BRKET, it entered an area with a minimum vectoring altitude (MVA) of 8,700 feet, while the aircraft was at 8,300 feet.
At 18:08:20, the pilot notified the controller of an obstacle indication. Five seconds later, the crew initiated a climb after receiving an alert from the Enhanced Ground Proximity Warning System (EGPWS). The crew and passengers were not injured, and there was no damage to the aircraft.
The investigation
Investigators found that the controller assigned an altitude of 7,800 feet for the crossing of CEGAN, despite the published procedure requiring an altitude of 10,000 feet for the segment from CEGAN until the aircraft was established on the arc. While the MVA for the area containing CEGAN was 7,800 feet, the MVA increased to 8,700 feet near the fix BRKET. The controller had an expectation that the crew would stop their descent at the published 10,000-foot altitude despite the 7,800-foot clearance.
Additionally, the investigation revealed that an antenna near the BRKET fix was not depicted on the Jeppesen approach chart in use at the time of the incident. Following the investigation, Jeppesen updated the charts to reflect the antenna and a new obstacle height of 7,614 feet.
Findings
- The air traffic controller assigned an altitude below the published procedure altitude for the approach segment before the aircraft was established on a published portion of the approach.
- The flight crew failed to identify the correct altitude for the approach segment and did not query the controller before descending below the published minimum altitude.
- The controller introduced risk by assigning the lowest possible altitude in the MVA area while expecting the crew to maintain a higher altitude.