Event Summary
On September 29, 2014, an Embraer 170-200 (registration SP-LID) encountered a Traffic Collision Avoidance System (TCAS) Resolution Advisory (RA) while approaching runway 07L at Frankfurt Airport (FRA). The incident occurred during an Independent Parallel Approach (IPA) procedure. No injuries or damage were reported.
Sequence of Events
During the approach to runway 07L, at approximately 1600 feet, a TCAS Traffic Advisory (TA) activated. The crew observed conflicting traffic on instruments and visually, identified as LOT flight 379 (LO 379) approximately 600 feet above and behind their aircraft. At 1400 feet, a TCAS RA "DESCEND" was issued. The crew disconnected the autopilot and initiated a descent. At 1000 feet, the TCAS instructed "ADJUST VERTICAL SPEED ADJUST," followed by TCAS INHIBIT activation due to the system's minimum altitude limitations. The crew maintained visual contact with the conflicting traffic throughout the event. After landing, the captain secured the Cockpit Voice Recorder (CVR) by switching off the DVDR 1 circuit breaker. The crew informed Air Traffic Control (ATC) of the incident and filed an Air Safety Report (ASR) upon arrival at Warsaw Chopin Airport (WAW).
Analysis
Analysis of the Digital Voice and Data Recorder (DVDR) indicated that the TCAS RA began at 1145 feet AGL (radio altimeter) and concluded at 1000 feet. At approximately 900 feet, TCAS entered Inhibit mode as per its altitude-based design. This was the first such reported event in the preceding 12 months.
Cause
The TCAS RA was caused by insufficient separation between aircraft conducting independent parallel approaches to runway 07R and the significantly higher speed of the other aircraft approaching runway 07R.