Since 2002, Brüel & Kjær has been working very closely with Turbomeca to develop dedicated Vibration Check systems for helicopter engines, measured on the aircraft on the ground during engine run-up. This has resulted in a range of standard systems that can be used for measurements on virtually all Turbomeca engines used on helicopters.
Turbomeca has issued Service Letters to over4300 owners of ARRIEL, MAKILA, and ARRIUS engines stating that the Brüel & Kjær PULSE based Vibration Check Systems Types3641-A/B, 3648-A/B and 3649-A/B have now been validated and certified to perform vibration checks in compliance with the Turbomeca Engine Maintenance Manuals.
Measurements are made on the first order of the vibration signal with reference to two tacho signals – one from the generator and one from the free turbine of the helicopter engine. Only one run-up is required for all measurements.
The simple user interface leads the technician from identification of the engine, via monitoring of the signals and comparison with threshold levels (the verification). The signal is stored in a database and a service report is produced immediately, clearly indicating the results as ‘Passed’ or ‘Limit Exceeded’. The report can be sent directly to the engine manufacturer along with the results and a copy of the time signal for further analysis. A contour plot (frequency, speed, level) is included to aid in fault diagnosis. At present, engine-specific systems are available for MAKILA, ARRIEL, ARRIUS,RTM322, TM333, and TURMO engines. Other engine-specific systems are in preparation. The systems perform filtered processing of the signal, controlled by the tachometer signals from the generator and the turbine in the frequency band 80 to 1000 Hz. They process both sensor signals simultaneously relative to the first order of the two tacho signals and show the evolution of the signals over time. The results are displayed in real-time and a report is produced in a predefined format.
Managers of helicopter Service and Maintenance Centres have realised that the PULSE system can be used for many other applications, not just Vibration Check. The whole suite of PULSE applications is at their disposal. Main gearbox and tail rotor gearbox vibration on the ground, vibrational comfort during flight and trend analysis are some of the important areas of interest for owners of helicopters.