Date: 12th December 2024
Location: 70 nautical miles ESE of Zagreb, Croatia
Aircraft: ATR-72-200 Freighter, registration SP-SPG
Operator: SprintAir
Flight Number: SAR-7802
Route: Cologne, Germany to Sofia, Bulgaria
Occupants: Unknown
Injuries: None reported
Summary of Events
On 12th December 2024, SprintAir Flight SAR-7802, an ATR-72-200 freighter, was operating a cargo flight from Cologne, Germany, to Sofia, Bulgaria, when it experienced a series of critical failures mid-flight. While cruising at FL210, approximately 70 nautical miles east-southeast of Zagreb, the crew reported:
1. Loss of cabin pressurisation,
2. Temporary loss of engine control, and
3. Failure of basic flight instruments.
Faced with multiple system failures, the crew declared an emergency and made the decision to divert to Zagreb Airport (LDZA). The aircraft descended and landed safely on runway 04 about 30 minutes later. There were no reported injuries.
Poland’s PKBWL (State Commission on Aircraft Accident Investigation) classified the event as a serious incident and opened a formal investigation.
Aircraft Details
The ATR-72-200 is a twin-turboprop regional freighter designed for short- to medium-range operations. Known for its reliability, the aircraft is equipped with systems designed to ensure redundancy and safety during flight.
• Registration: SP-SPG
• Type: ATR-72-200 Freighter
• Engines: 2x Pratt & Whitney Canada PW124
• Operator: SprintAir
Sequence of Events
1. Cruise Phase:
• The aircraft was at FL210 when the flight crew observed:
• A cabin pressurisation loss, requiring immediate descent,
• Momentary engine instability, reducing thrust and control,
• Loss of basic flight instruments, affecting situational awareness.
2. Emergency Decision:
• The crew declared an emergency and diverted to Zagreb Airport, the nearest suitable diversion point.
3. Descent and Diversion:
• The aircraft performed an emergency descent to a lower, safer altitude to mitigate hypoxia risks.
• The crew stabilised engine control and regained partial functionality of flight instruments during descent.
4. Landing:
• The aircraft landed safely on runway 04 at Zagreb without further incident. Emergency services were on standby but not required.
Initial Findings
The investigation into the incident is focused on identifying the root cause of the failures. Early analysis suggests the following areas for examination:
1. Cabin Pressurisation System:
• Possible malfunction of outflow valves or cabin pressure controllers.
2. Engine Control Issues:
• Temporary loss of engine parameters due to electrical anomalies or sensor faults.
3. Flight Instrument Failures:
• Potential faults in pitot-static systems, Air Data Inertial Reference Units (ADIRU), or other critical avionics systems.
4. Electrical System Integrity:
• Investigation into whether electrical faults or single-point failures caused cascading system issues.
Safety Risks
1. Loss of Pressurisation:
• Cabin pressure loss requires immediate descent to avoid hypoxia, posing a safety risk to crew in prolonged incidents.
2. Engine Control Instability:
• Loss of thrust can compromise flight safety, particularly in adverse conditions or during critical phases of flight.
3. Instrumentation Failures:
• Loss of basic flight instruments reduces situational awareness and increases workload during emergencies.
4. Operational Risks:
• Simultaneous system failures pose significant operational challenges for the crew, requiring prioritisation of responses.
Recommendations
1. System Diagnostics:
• Conduct thorough diagnostics of the cabin pressurisation system, engine control systems, and flight instruments to identify root causes.
2. Electrical System Inspection:
• Examine electrical systems for anomalies that could contribute to multiple simultaneous failures.
3. Crew Training:
• Reinforce crew training for handling multiple system failures under emergency conditions, focusing on prioritisation and communication.
4. Maintenance Enhancements:
• Review and enhance preventive maintenance procedures for pressurisation systems, avionics, and engine controls.
5. Flight Data Analysis:
• Analyse flight data to better understand the sequence of events and the interactions between failed systems.
Safety Lessons
This serious incident highlights the importance of:
• Robust system redundancy to mitigate simultaneous failures,
• Effective crew resource management (CRM) to handle complex emergencies, and
• Thorough maintenance protocols to prevent cascading failures of critical aircraft systems.
The crew’s prompt decision to divert and their professional handling of multiple failures ensured the safety of the flight.
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Our investigation reports are based on all the evidence and facts we have at the time of writing and posting. We apologise if any details are missed or are not fully accurate.
