What happened
On March 28, 2016, a Boeing 737-400 was performing an approach to the LERJ aerodrome. While flying in Visual Meteorological Conditions (VMC), the aircraft's Ground Proximity Warning System (GPWS) issued a "PULL UP TERRAIN" alert. The flight crew, maintaining visual contact with the approach path, responded by correcting the flight path and increasing the altitude by approximately 1,000 feet. Following this maneuver, the crew continued the approach and landed the aircraft without further incident.
The investigation
The investigation examined the flight parameters and the configuration of the aircraft's navigation systems. The analysis focused on why the GPWS triggered the terrain warning during a standard approach procedure.
Findings
- The investigation established that the GPWS alert was triggered because the descent was initiated too early after passing the Initial Approach Fix (IAF).
- This premature descent was caused by the failure to input the minimum approach altitude for that specific segment of the procedure into the Flight Management Computer (FMC).
- The incident was attributed to human error, specifically the failure to adhere to all required parameters of the established approach procedure.