STEVI Instruments and parts

The Sperry Turbine Engine Vibration Indicator (STEVI) range of products was acquired from Atlantic Inertial Systems (formerly BAE Systems Inertial Products).

STEVI is a two-inch (50mm) panel-mounted instrument that combines in a single package all the system functions engine vibration monitoring (except the engine-mounted vibration pick-ups). The signal from the vibration pick-ups is wired directly to STEVI, which contains the entire amplifier, indicator, filter selection, system test, and warning light functions. The result is substantial savings in aircraft wiring weight and initial installation costs. For multi-engine systems, one STEVI per power plant is recommended. The only aircraft wiring required is a power cable and dual-conductor shielded cable from each vibration pick-up.

Both high and low frequencies are monitored by STEVI, with high frequency being indicated continuously and low frequency being shown when the low filter button is pressed. An auxiliary unit to monitor the low filter separately and continuously is also available.


  • simplicity  self-contained amplifier only needs power and pick-ups points
  • low installation costs   there are fewer components to mount
  • ease of operation   all controls are in one location
  • ease of maintenance
  • ease of integration with AIDS or recorder system
  • lightweight construction  indicator weighs less than 0.45 kg
  • low power   consumes less than 1.5 watts
  • high accuracy maintained throughout severe environmental conditions
  • built-in self test   for complete system ‘short-circuit’, ‘open-circuit’, and ‘correct’ by depressing test button
  • dual filter advantage   the dual filter feature of the STEVI is extremely important for twin-rotor engines. It provides a means for detecting high-speed rotor failures in early stages. Other equipment (with simple-filter provisions to measure overall vibration) cannot detect progressive high-speed rotor failures. This is due to the averaging characteristics of all vibration amplifiers. For example a typical engine failure may progress as follows:
Low Speed +(N1) High Speed =(N2) Overall Vibration Level
1.0 1.0 Relative units of vibration
0.3 1.0*  
1.03 (normal) 1.1 (N2 failure progressing)  

*Note that the N2 vibration level has been increased threefold but the overall vibration level has increased less than 10% which would appear negligible. This equipment is fitted to the Airbus Military C160 Transall Transport Aircraft and the Dassault ATL 1 & 2 (Atlantique) Maritime Reconnaissance Aircraft among others. We are always happy to help. If you have a query you can Contact us for a prompt response.