Estonia

Causal factors:
This accident results from the combination of the following factors:
• The intermittent THSA override mechanism malfunction allowing to cause the loss of pitch control by both ELACs. The repetitive triggering of the ELAC PITCH faults was caused by the non or late activations of the PTA micro-switches, which were due to the OVM piston insufficient stroke. The insufficient OVM stroke was caused by the THSA OVM clutch unit non-standard friction. The oil in the THSA OVM casing appeared to be with a higher viscosity than defined in the CMM. The higher viscosity might have reduced the friction of the OVM clutch unit, causing the THSA OVM nonstandard friction.
• SEC design flaw allowing for a single event, the left landing gear temporary dedecompression, to cause the loss of pitch control by both SECs. The absence of ground spoilers arming for landing in the context of touch and go's training may have contributed to the temporary decompression of the left main landing gear.
• The training instructor`s decision for continuation of the flight despite repetitive ELAC PITCH FAULT ECAM caution messages. The lack of clear framework of operational rules for training flights, especially concerning the application of the MEL, and the specific nature of operations that caused pressure to complete the training program may have impacted the crew decision-making process.

Contributory factors
• Smartlynx Estonia ATO TM does not clearly define the need for arming spoilers when performing touch-and-go training (ATO procedures not in accordance with Airbus SOP). The fact that there is no clear reference in the Smartlynx Estonia ATO TM Touch-And-Go air exercise section to additional procedures that should be used, in combination with lack of understanding of the importance for arming the spoilers during this type of flights contributed to TRI making a decision to disarm the spoilers during touch and go training enabling landing gear bounce on touch down.
• At the time of the event Airbus QRH did not define the maximum allowed number of resets for the flight control computers.
• At the time of the event Airbus FCTM did not require to consider MEL on touch-and-go and stop-and-go training.
• The oil in the THS OVM casing was with higher viscosity than defined in the CMM. The higher viscosity might have reduced the friction of the OVM clutch unit.
• The aircraft maintenance documentation does not require any test of the OVM during aircraft regular maintenance checks.
• Smartlynx Estonia ATO OM does not clearly specify the role in the cockpit for the Safety Pilot. The lack of task sharing during the event caused the ECAM warnings to be left unnoticed and unannounced for a long period.
• The crew not resetting the ELAC 1. The fact that ELAC 1 PITCH FAULT was left unreset lead to the degradation of the redundancy of the system. Considering the remoteness of the loss control of both elevators, there is no specific crew training for MECHANICAL BACKUP in pitch during approach, landing and take-off. This condition of the aircraft occurred for the crew in a sudden manner on rotation and during training flight, where the experienced TRI is not in PF role and cannot get immediate feedback of the aircraft behaviour and condition. Despite these difficult conditions the crew managed to stabilize and land the aircraft with no major damage to the persons on board. The crew performance factors that contributed to the safe landing of the aircraft are the following:
• The TRI followed the golden rule of airmanship (fly, navigate, communicate), by stabilizing the aircraft pitch by using the trim wheel and by keeping the aircraft engine power as long as possible;
• The Safety Pilot started to play a role in the cockpit by assisting the TRI and student by informing them about the status of the aircraft and later on taking the role of the PM.

The investigation determined the inadequate action of the flight engineer, consisting in early and uncommanded landing gear retraction, as a cause of the accident.
Contributing factors to the accident were:
1. Inadequate crew recourse management and insufficient experience in cooperation and coordination between crewmembers.
2. Start of aircraft rotation at low speed and with fast elevator movement to 17˚, which resulted in:
Lifting the aircraft sufficiently to close the WOW switch and allow the retraction of the landing gear at the speed not sufficient for the climb.
Providing misleading information to FE about the aerodynamic status of the aircraft.
3. Inadequate adjustment of the WOW switch, which allowed the gear retraction to be activated before the aircraft was airborne. The position of the landing gear selector on the central console is not considered as a contributing factor to the accident. However, investigation finds necessary to point it out as a safety concern, specifically in situations, where crewmembers are trained and/or used to operate the aircrafts with gear selector location according to the EASA Certification Standards CS-25. Positioning of the gear lever to the location which is compliant to EASA document CS-25, would create additional safety barrier to avoid similar occurrences, specifically in aircrafts where landing gear is operated by FE.

Causes of the accident:
1. The failure of the left engine lubrication oil system, leading to the failure of the rear compressor bearing and inflight engine failure.
2. The failure of the crew to maintain the approach path and adhere to single engine landing procedures.
Factors contributing to the accident:
1. Improper and insufficient crew training, inter alia complete absence of simulator training.
2. The lack of effective coordination between crewmembers.
3. The failure of the crew to start RU19A-300 (APU).
4. Adverse weather conditions.
5. Inadequate company supervision by Polish CAA, consisting in not noticing the lack.
of flight crew training and companies generally pour safety culture.
6. Inadequate company maintenance practices, leaving preexisting breather duct failure unnoticed.

The investigation established the following causes of the accident:
1. The pilot could not maintain safe flight altitude when approaching Ruhnu aerodrome.
2. The pilot continued the descent in spite of IMC.
Contributing factors to the accident:
The investigation established the following factors contributing to the accident:
1. High motivation to perform the flight.
2. Inadequate weather information from ground services of Ruhnu aerodrome.
3. Inadequate aeronautical oversight in the destination airport.

The following findings were identified:
- Pilot’s inability to maintain necessary altitude and terrain clearance due to the spatial disorientation type 1 (unrecognized).
- Dark terrain, the absence of visual horizon and ambient light, the long duty time of the pilot and unfamiliarity with the airport can be considered as contributing factors to the accident.

It was determined that the right engine failed during initial climb following the rupture of a turbine ball bearing due to poor lubrication.

The accident was the consequence of an incorrect assessment of the situation by the commander of the aircraft during the approach, which resulted in errors in the piloting techniques, expressed in:
- Transition from intense icing conditions to active descent with a transition from the originally planned instrument approach to a visual approach;
- Failure to take into account the possibility of complex meteorological conditions in preparation for the approach and during the approach - the crew did not consider the possibility of going around or returning to the point of departure;
- Maintaining an unjustified low airspeed and high vertical descent speed during an approach with poor altitude control;
Associated factors were:
- Difficult weather conditions due to severe icing conditions;
- Reassessment by the aircraft commander of his knowledge and experience in controlling the An-28 aircraft in adverse weather conditions;
- Failure to comply with the requirements of the Airplane Flight Manual of the An-28 aircraft for the operation of aircraft systems and crew resource management;
- Failure to comply with the Airplane Flight Manual in terms of timely termination of the approach and transition to climb;
- The copilot, taking into account the large flying experience of the aircraft commander and overestimating his flight and navigation skills, behaved passively and did not provide him with adequate assistance in difficult conditions during the approach;
- Transition from an instrument approach to a visual approach without ATC clearance;
- The lack of 32 visual assessment of the angle of the descent trajectory (PAPI system) on the runway.

Engine failure, maybe due to icing.

Poor planned approach on part of the flying crew.

Hijacked and set on fire.