Covering form of preliminary or final report
| Date of event : | 2021-02-27 |
| Incident number : | CZ-21-0059 |
| Report : | Final report |
| Place of event : | Field south of Hostim village |
| Registration mark : | Accident |
| Weight category MTOM: : | <2250 kg |
| Type of operation : | Recreational and sport aviation |
| Plane / SFM : | Airplanes |
| Type of plane / SFM : | Cessna 150L |
| Health effects of event : | Without injury |
| PDF document : | 
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Description:
Summary
On 27 February 2021, the AAII was notified of an air accident of the Cessna 150L aircraft in the vicinity of the village Hostim. The pilot with another person on board of the aircraft was carrying out a recreational flight with touch-and-go landing at the Plzeň‑Líně airport and planned return to the Sazená airport. During his flight near the SIERRA point (entry point to CTR Ruzyně), the performance of the aircraft power unit was gradually decreasing. The pilot was trying to power up the engine, but failed, so he identified an area for emergency landing. After the aircraft landed on a water-logged ground, it overturned and remained lying upside down. Nobody was injured during the air accident.
The Police of the Czech Republic, the FRS unit, the Emergency Medical Service and then the AAII inspector arrived at the location of the air accident and the AAII inspector performed professional investigation of the location and the wreckage.
The flight
Given the weather situation, having taken off from the Sazená airport, the pilot switched on the carburettor heating and continued flying to the Plzeň-Líně airport where he carried out a touch-and-go landing. As it is not recommended to heat the carburettor during take-off, he switched it off so that full thrust of the power unit was available for departure from the Plzeň-Líně airport. He did not switch carburettor heating on afterwards and continued flying to LKPR.
The critical situation occurred at the moment when the aircraft was located near the SIERRA point as the power unit performance started decreasing and was not restored even when powering up. The pilot announced the situation to the air traffic controller and was heading, as agreed, towards the Bubovice airport where he wanted to make an emergency landing. From the moment when the power unit performance started decreasing until the moment of emergency landing, the pilot did not use any aircraft procedures or documentation to resolve the emergency situation. According to the pilot’s statement, he was focusing only on the goal of reaching the Bubovice airport.
During his flight towards the Bubovice airport, the pilot made a right decision to land in the field as he was concerned about overcoming a terrain obstacle – a wooded hill. Landing took place in a slight counterslope, and the pilot landed on all undercarriage wheels (three-point landing), the aircraft bounced and after the second contact (again on three points), the front undercarriage leg collapsed, and the aircraft then overturned.
In the area of the air accident, there were low clouds, air humidity was high, and the temperature was slightly above freezing. Such conditions are suitable for the occurrence of a phenomenon known as carburettor icing when in spite of the ambient air temperature being above zero, due to the speed of air flow and humidity, carburettor icing may occur.
Based on the analysis of weather conditions according to the information provided by the Czech Hydrometeorological Institute, it was found out that there were conditions in the area under which the probability of carburettor icing occurrence was very high.
Conclusion
The cause of the air accident was a negative effect of the carburettor icing formation on the power unit performance due to a flight under conditions which were favourable for the formation of carburettor icing together with the fact that the carburettor heater was switched off.
Safety recommendations
Recommendations for the operator
The AAII recommends CZ ATO-22 to revise the risk identification and assessment process and extend the risk register to make identified hazards and resulting risks more specific and recommendations mentioned in risk management targeted.
Recommendations for the CAA
Given the results of the investigation of this occurrence and the CZ-19-0385 occurrence, the AAII recommends the Civil Aviation Authority, when carrying out its audit activity with approved training organisations, to place more emphasis on the content of management system documentation (e.g. risk libraries) in order to guarantee that it contains relevant data and can be really used to manage the risks that the organisation could face.
Attached final report in PDF file is in original Czech language.