Vibration requirements in helicopter certification
Helicopter certification is a very demanding process requiring, among other things, a solid background in structural dynamics and in-flight testing. Vicoter supports both manufacturers and operators in such activity. Our services cover both new helicopter platforms and modifications to existing models, backed by in-depth knowledge of various regulatory frameworks and technical requirements.
Working in close coordination with Design Organisations (DOA), Vicoter provides comprehensive, end-to-end technical support—from the planning and execution of tests to the preparation of compliance reports required for certification approvals.
Vicoter operates on two main fronts in the certification of rotary-wing aircraft:
For larger helicopters, falling under CS-27 (Small Rotorcraft) and CS-29 (Large Rotorcraft), our core activities include:
- execution of Ground Vibration Tests (GVT) on the entire structure,
- vibration transmission measurements,
- bonk tests (impulse excitation of the structure to identify modal characteristics) on various installations,
- in-flight vibration testing, aimed at verifying compliance with the vibratory criteria set by certification authorities.
A significant part of our work involves the experimental certification of external installations—such as sensors, antennas, cameras, or mission equipment—typically carried out at the client’s site.
In accordance with EASA Certification Memorandum CM-21.A-D-002, we pay special attention to ensuring that the resonance frequencies of the installed equipment remain outside the excitation frequency ranges of the rotorcraft, across all variants and rotor speed configurations, to avoid overlapping with structural resonances.
Before flight testing begins, Vicoter performs the required modal analyses— Bonk/RAP/Impact/Hammer tests—with the equipment already mounted. Results are compiled and submitted to EASA Panels 1 and 3 to obtain Flight Test Authorisation.
During subsequent in-flight trials, Vicoter instruments the external equipment with accelerometers to ensure that no critical vibration levels are reached that could compromise the structural integrity or mounting of the installed components.
If any local vibration issues are identified, our extensive experience enables us to support the client in finding effective and practical solutions.
For light and ultralight helicopters, typically certified under CS-VLR or LTF-ULH, Vicoter offers a complete service that extends beyond vibration testing to include in-flight load and stress measurements on critical components like rotor blades, control rods, tail boom …. These measurements are crucial for demonstrating structural compliance, especially when analytical methods are unavailable or unreliable.
General aviation authorities require applicants to demonstrate by tests the structural strength and quality of critical parts under fatigue conditions. To perform a valid experimental campaign correct loads encountered during the flight must be applied or, at least, known to validate assumptions made during the design phase.
While measuring loads on non-rotating parts can be performed with standard instrumentation, capturing the forces on rotating elements like the rotor hub and blades presents unique technical challenges—mainly due to the difficulty of powering sensors and transmitting data from rotating parts.
To overcome these issues, we have developed the VR-DAQ (Vicoter Rotating Data Acquisition) system, an innovative, self-contained unit capable of powering, amplifying, acquiring, and storing data from multiple Wheatstone bridges directly on the rotating system. Battery-powered and mounted on the rotor mast via a custom interface, it records data onto an internal SD card, removing the need for cumbersome, not-customizable slip-ring systems and improving signal quality and reliability.
This technology, already successfully applied during certification processes, can be furthermore fully integrated with other instruments to obtain a 360° knowledge of the structural response of the helicopter during the various phases of the flight.
Thanks to its advanced methods and equipment, Vicoter provides clients with all the necessary data and support to satisfy the most stringent certification requirements for rotary-wing aircraft, even in the most complex configurations.
Why choose Vicoter?
Vibration and load measurements for helicopter certification demand not only precision, but deep expertise—both in execution and in interpreting complex dynamic data. To meet these challenges, Vicoter offers:
- Over 15 years of hands-on experience in structural dynamics applied across a wide range of sectors—including aerospace, automotive, household appliances, and renewable energy—with a strong specialization in rotorcraft applications.
- Several already performed activities on different models of helicopters.
- State-of-the-art instrumentation, fully equipped to handle the unique demands of helicopter testing, whether for in-flight vibration compliance, blade loads, or fuselage stress analysis.
- Strong theoretical foundations, allowing us to fully understand the physical phenomena involved and provide technically sound recommendations and solutions.
- An agile and efficient company structure, capable of responding quickly to project needs and adapting to evolving certification requirements.
Here are some brief articles where you can find more information about real cases we have dealt with:
