The problem has also become more relevant in other countries due to improved reporting cultures. Originally noticed in Germany, cases reported across Europe are now included in statistical analyses. The accumulation of incidents has led to intensive discussions between authorities, manufacturers and operators.
Cooperation to analyse problems
Since the beginning of 2023, the LBA, EASA and other stakeholders have been meeting regularly to exchange information and develop solution strategies. The focus is on identifying the causes and developing technical and organisational measures. The implementation of service bulletins and airworthiness directives (AD) is also discussed in order to increase flight safety.
The investigations to date suggest the following possible causes:
- Soft start function: On certain aircraft types such as Tecnam, this function can unintentionally lead to a drop in propeller speed. Already published Service Bulletins such as the SB_773_-CS-Rotax_912S address this issue.
- Incorrect fuel selectionLack of clarity on suitable fuel grades, such as UL91, has also led to problems, which are addressed by service bulletins on certain types such as Bristell.
- Carburettor icing and vapour bubble formationUnfavourable operating conditions can cause sporadic motor faults.
- Constructive integrationThe design of the installation space and heat distribution have a significant influence on the performance and reliability of the motors.
Quality issues and technical focus
The LBA has identified quality differences in the carburettor series, the calorific values of the spark plugs and the effects of the dynamic pressure below the cowling at full load as critical aspects. Inconsistencies between the engine manuals and the aircraft manuals regarding the recommended power selection further exacerbate the situation.
Event messages as the key to the solution
Affected operators and pilots make a significant contribution to researching the causes by submitting detailed reports. The LBA works closely with reporters and associations such as the German Aeroclub (DAeC) and the German Ultralight Flying Association (DULV) to gather and pass on findings. The results are promptly forwarded to the EASA for inclusion in the regular meetings.
Publications and measures
In addition to service bulletins from manufacturers such as Tecnam, Bristell and Aquila, the service bulletin SB-912-079 from Rotax. This has caused uncertainty among pilots, which is why a revision is being worked on. The LBA expects further findings in the coming months and will communicate these publicly.
Practical tips for operators
The LBA emphasises the following aspects that support safe operation:
- Careful operation: Avoidance of operating states that place unnecessary strain on the technology.
- Professional maintenance: Work should only be carried out by qualified personnel in accordance with the maintenance instructions.
- Obligation to report: Errors and faults must be reported as "event messages" via ECCAIRS2 be reported to the LBA.
Outlook
The investigations into Rotax engines are continuing. The LBA is working intensively with manufacturers, owners and flight schools to find long-term solutions. The dissemination of new findings to EASA and the public remains a central concern.
Source references:
LBA
