Background: Accumulation of security-related incidents
The problems particularly affect the most critical phases of a flight - the take-off and the first few minutes of the climb. As these events are difficult to reproduce, analysing the incidents is extremely complex.
Focus on possible causes
The analyses carried out so far by EASA, Rotax and other organisations involved have identified several possible causes:
- Soft-start function for Tecnam engines
Unintentional activation of this function can lead to a drop in propeller speed during flight. Previously published documents such as the Service Bulletin "SB_773_-CS-Rotax_912S_Engine_Soft_Start_Deactivation" are intended to address this. - Incorrect power selection and propeller adjustment
An incorrect combination of power settings and propeller configurations can lead to excessive load and possible malfunctions. - Use of unsuitable fuel types
Cases in which the wrong fuel quality was used occurred in particular with Bristell aircraft. Service bulletins have been published to specify the use of suitable fuels. - Carburettor icing and unfavourable operation
Problems such as engine knocking, triggered by full-load operation with carburettor preheating switched on, or sporadic events such as carburettor ice formation, contaminated fuel or vapour bubble formation were also documented. - Design-related influences
Differences in the quality of components such as carburettors or spark plugs as well as the integration of the engine into the available installation space of an aircraft influence the heat distribution and aerodynamic properties.
Co-operations and measures
Since the beginning of 2023, the LBA, EASA and other aviation authorities have been meeting regularly to share findings and discuss measures. The focus is on:
- Improving the reporting culture: The increasing reporting of security-related incidents enables a more comprehensive database for analyses.
- Communication with manufacturers and operators: Results and recommendations for action are exchanged with aircraft manufacturers, associations such as the DULV and DAeC, and pilots.
- Introduction of service bulletins and airworthiness directives (ADs): These documents define specific measures to minimise disruptions.
New developments and publications
Service Bulletin SB-912-079 and Revision R1
Service Bulletin SB-912-079, which was published in November 2024, initially led to considerable uncertainty. The current revision "R1" mitigates some of the measures:
- Implementation of the measures is now expressly recommended, but no longer mandatory.
- There is no longer a deadline for implementation within a certain engine running time.
Separation by aircraft type
An additional service bulletin has been published to differentiate more clearly between certified aircraft and microlight aircraft. This is intended to provide operators with more precise instructions.
Important information for pilots and operators
The LBA emphasises the importance of careful handling of aircraft in order to minimise problems:
- Careful operation: Pilots should avoid extreme operating conditions and respect the technical limits of the aircraft.
- Expert maintenance: All maintenance work must be carried out by qualified personnel in accordance with the manufacturer's instructions.
- Reporting of incidents: All safety-relevant incidents must be reported to the LBA via the "ECCAIRS2" system.
Outlook and further investigations
The LBA expects tangible results from the ongoing investigations in the coming months. Together with EASA and manufacturers such as Rotax, technical aspects will be re-examined and revised. A further version of the service bulletin is expected to be published at the end of 2024 or beginning of 2025.
Regular communication between authorities, manufacturers and affected parties remains a central component in order to sustainably improve the safety and reliability of Rotax engines. All relevant information is published on the LBA and EASA websites.
Source references:
LBA