NBAA Safety Committee Works to Reduce Controlled Flight Into Terrain Accidents

In business aviation, there are no shortages of scenarios that can lead to trouble, including maintenance failures, weather events and even pilot error such as controlled flight into terrain, or CFIT.

CFIT occurs when an airworthy aircraft under pilot control unintentionally collides with terrain, water or obstacles, often with the crew unaware of imminent impact.

The NBAA Safety Committee seeks to better understand the human factors involved in terrain awareness and warning systems (TAWS) alert compliance by conducting a survey for pilots at nbaa.org/cfit. Results will be used to provide recommendations to system manufacturers.

Trouble occurs when situational awareness is compromised. Thankfully, mitigation strategies can help.

Richard Meikle, NBAA Safety Committee CFIT project leader, shared his expertise to raise awareness and help prevent these rare, but typically fatal events.

Persistent Factors

Because the rate of CFIT events in business aviation is low, there isn’t a large data set from which to draw conclusions about persistent factors, Meikle said. Modern jets often have advanced avionics systems, including head-up displays (HUD), fly by wire and fully integrated auto flight systems that were unavailable years ago. Outdated/inoperative equipment, or failure to appropriately respond to alerts in a timely manner, are the biggest contributors.

Technology Awareness Impact

TAWS and Ground Proximity Warning Systems (GPWS) have contributed to CFIT reduction. Regulators, including the FAA, have mandated installation on turbine aircraft with six or more seats.

Look-ahead modes using GPS improved the advance warning, and statistics prove its effectiveness. Synthetic vision, HUD and other tech improve situational awareness of threatening terrain, but GPWS/TAWS is the chief contributor.

Current designs provide sufficient warning to ensure safe operation, although the primary “limitation” is crew response to warnings, Meikle said. The survey seeks to learn what’s behind the low response rate.

Best Practices

Meikle offered these strategies to reduce risk:

• Maintain the TAWS with the current operating system and obstacle database.
• Have a clear policy or SOP related to responses to alerts and warnings.
• Train crewmembers to understand the appropriate response.

NBAA is also stewarding an industry SOP. Operators should refer to their own published SOPs for guidance. Otherwise, the SOP recommendations include:

CFIT Escape Maneuvers

Attending to an Enhanced Ground Proximity Warning System (EGPWS)/TAWS caution or warning takes precedence over a TCAS alert.

Cautions: Crew Actions

• Evaluate the situation to determine if subsequent action is required. Consider surrounding terrain, phase of flight and aircraft configuration.
• Adjust flight path to eliminate the caution.

Warnings: Crew Actions

• Immediately initiate a missed approach procedure/go-around (on approach).
• Take immediate corrective action by adjusting aircraft flight to eliminate the warning.

Immediately inform ATC of any maneuver based on an EGPWS/TAWS alert, especially if crew action contradicts ATC clearance. EGPWS/TAWS escape maneuvers are performed in accordance with OEM/aircraft-specific guidance and procedures.

Review NBAA’s Safety Committee resources at nbaa.org/safety.