Date: 6th June 2023
Location: Skyros Airport, Greece
Aircraft: Boeing 737-700, registration OK-SWW
Operator: Smartwings
Flight Number: QS-2298
Route: Chios, Greece, to Skyros, Greece
Passengers and Crew: Not disclosed
Injuries: None
Summary of Events
On 6th June 2023, Smartwings Flight QS-2298, a Boeing 737-700, encountered a Ground Proximity Warning System (GPWS) “PULL UP!” alert during its descent into Skyros Airport. While descending through approximately 1,500 feet MSL south of the aerodrome, the aircraft entered cloud cover in proximity to terrain rising to 1,322 feet MSL.
The crew promptly responded to the GPWS warning, initiating a climb to 5,000 feet before realigning for a safe landing on Runway 17 approximately 10 minutes later. Czechia’s Civil Aviation Authority (CAA) attributed the incident to a breach of operational procedures but acknowledged the crew’s immediate and correct response to the GPWS alert, which prevented a potential collision with terrain.
Aircraft and Crew Information
Aircraft
The Boeing 737-700 is a member of the Next-Generation 737 family, equipped with a Terrain Awareness and Warning System (TAWS) integrated into the GPWS. These systems are designed to provide immediate alerts when terrain poses a collision risk, enabling crews to take evasive action.
Crew
The flight was operated by an experienced crew who successfully executed the corrective actions necessary to avoid terrain impact, despite procedural deviations leading up to the incident.
Sequence of Events
1. Approach:
• The aircraft was descending in a westerly direction south of Skyros Airport.
• During the descent, the aircraft entered cloud cover in close proximity to rising terrain.
2. GPWS Activation:
• The GPWS issued a “PULL UP!” alert as the aircraft approached terrain rising to 1,322 feet MSL.
3. Crew Response:
• The crew immediately complied with the GPWS warning, initiating an evasive climb to 5,000 feet.
4. Safe Landing:
• After stabilizing the aircraft, the crew rejoined the pattern for Runway 17, landing without further incident approximately 10 minutes after the GPWS activation.
Investigation Findings
Causes and Contributing Factors
1. Breach of Operational Procedures:
• The flight crew entered cloud cover during the visual approach, contrary to standard operational guidelines.
2. Proximity to Terrain:
• The aircraft descended to an altitude that brought it into proximity with rising terrain, triggering the GPWS warning.
3. Effective Safety Barriers:
• The GPWS functioned as designed, providing a timely alert to the crew, which prevented terrain collision.
Crew Performance
While the crew violated operational procedures by descending into cloud cover, their immediate response to the GPWS alert demonstrated professionalism and adherence to safety protocols in an emergency.
Safety Risks and Potential Outcomes
1. Terrain Collision:
• Failure to respond promptly to the GPWS alert could have resulted in a controlled flight into terrain (CFIT), a leading cause of aviation accidents.
2. Reduced Safety Margins:
• Entering cloud cover without proper situational awareness significantly reduced the safety margin during the approach phase.
3. Passenger Safety:
• The incident posed potential risks to the safety and confidence of passengers onboard.
Recommendations
1. Adherence to Visual Approach Guidelines:
• Crews must strictly adhere to visual approach procedures, avoiding cloud cover and maintaining situational awareness of terrain.
2. Enhanced Training for Terrain Awareness:
• Reinforce training on terrain awareness and the critical importance of maintaining prescribed minimum altitudes.
3. Operational Procedure Reviews:
• Review and update operational procedures to emphasize terrain clearance during visual approaches, particularly at airports with challenging topography.
4. Proactive Use of Navigation Systems:
• Encourage the use of terrain display functions on navigation systems to enhance situational awareness in areas with significant elevation changes.
5. Incident Reporting and Analysis:
• Share findings from this incident with other operators to improve industry-wide awareness and prevent similar occurrences.
Conclusions
This incident underscores the critical role of automated safety systems like GPWS in preventing accidents caused by human error or lapses in situational awareness. While the crew’s initial procedural deviation contributed to the GPWS activation, their immediate and appropriate response ensured a safe outcome.
The findings from this investigation serve as a valuable reminder of the importance of strict adherence to operational guidelines and the effectiveness of advanced warning systems in mitigating risks during critical flight phases.
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