Background
On 29 January 2015, a Boeing 737-800 registered EI-EMK, operated by Ryanair, was conducting a scheduled commercial flight from London Stansted Airport to Bergerac-Roumanière Airport (Dordogne, France). The first officer was pilot flying (PF), and the captain was pilot monitoring (PM). The aircraft carried 6 crew and 166 passengers.
Flight History
At 13:03 UTC, the crew received clearance to descend to FL70. The Aquitaine-Approach controller inquired about the crew's ability to perform an RNAV approach; the first officer responded ambiguously and requested weather information. At 13:05, the captain stated they would conduct an NDB approach. The controller cleared them for the NDB Y approach to runway 28 and directed them to the BGC beacon, descending to 2,500 ft.
At 13:17:48, the aircraft overflew the BGC beacon at 2,723 ft with autopilot engaged in LNAV and V/S modes, descending to the selected altitude of 2,500 ft. The heading was 213°, speed 216 kt. At 13:18:23, flap 1 was selected, and the aircraft began a left turn. At 13:19:42, it leveled at 2,500 ft on heading 097° in ALT HOLD mode, with flaps extended to position 5.
At 13:20:05, during a left turn in LNAV mode, the first officer selected an altitude of 900 ft, engaged V/S mode, and set a descent rate of -900 ft/min. The aircraft descended below the minimum safe altitude. A Minimum Safe Altitude Warning (MSAW) activated in the Aquitaine-Approach control room. The descent continued for nearly two minutes in instrument meteorological conditions (IMC) until the Enhanced Ground Proximity Warning System (E-GPWS) issued a "TERRAIN" alert. At that point, the aircraft was more than 8 NM from the runway threshold, left of the final approach path, at 1,054 ft altitude (842 ft radio altimeter height). The crew initiated a missed approach; simultaneously, the "PULL UP" warning activated.
Findings
The investigation identified several factors likely contributed to the event: insufficiently precise and complete approach preparation; the holding pattern not being performed after a late change; misunderstanding between pilots regarding autopilot modes; progressive loss of situational awareness; the first officer's limited experience with NDB approaches; controllers' unfamiliarity with NDB procedures; and the absence of a MSAW system at Bergerac or emergency coordination procedures between Aquitaine-Approach and Bergerac.
Safety Actions
Following the incident, the operator prohibited the performance of timed approaches in V/S mode, considering the additional risk. The air navigation service provider (DSNA) also undertook measures and reflections regarding MSAW deployment.