Vibration Transducer Test Set

Aircraft operators – both military and commercial – can reduce the number of maintenance runs associated with Functional Check Flights (FCF’s) required after repair or balancing job by verifying the proper calibration of vibration sensors with The Modal Shop’s Portable Vibration Calibrators.

Reducing maintenance runs, which are required to achieve FCF release, is a crucial means to save time and money. By utilizing known good velocity sensors on a C-130 aircraft, the USAF can balance the aircraft more quickly, with improved confidence in both measurements and adjustments. Completing the balancing job with fewer maintenance runs associated with FCF’s not only saves time and money, but improves fleet readiness and ensures repeat FCF failures do not send the aircraft to impound.

Normally reliable, piezoelectric sensors permanently installed on aircraft endure the harshest of operating conditions causing drift in output sensitivity. Errors often occur at specific frequencies of interest on the extremes of the sensor’s frequency response, making it important to test for early resonances or reduced output throughout the range of the transducer. The output of two sensors is utilized in most balancing jobs. Amplified output from one of the two sensors will produce a false imbalance condition.

Hanger bearing sensors are relied upon to detect high frequency faults, providing early warning of an impending part replacement. But accelerometers with early resonance issues produce amplified output which can lead to an unnecessary $50,000 to $70,000 bearing replacement.

Phase inspection is an ideal opportunity to utilize a Portable Vibration Calibrator to reduce costs. Often vibration sensors are considered “consumable” and are thus thrown away and replaced during phase inspection. Replacing all accelerometers on the V-22 Osprey would cost over $50,000. Using a Portable Vibration Calibrator from The Modal Shop with pass or fail notification after each test point, aircraft maintenance specialists do not need to be vibration experts to re-certify sensors and avoid throwing away expensive instrumentation that is still in good working order.

The Modal Shop Models 9110F and 9110D Portable Vibration Calibrators are identical except that the 9110F features an internal charge amplifier and is supplied with the following suite of accessories to better suit aviation applications:

• Turn-key power supply for Honeywell (formerly Chadwick Helmuth) Model 7310 and 8866-1 velocity sensors used on C-130 aircraft
• Turn-key power supply for Wilcoxon 991D and 991D-1 helicopter accelerometers
• Power supply for Constant Voltage Line Drive (CVLD) accelerometers also known as Modulated Current sensors
• Tri-axial and bi-axial mating cables and right-angle mounting bracket for Dytran airborne accelerometer Models 3303A, 3302A and other sensors within airborne series
• Tri-axial mating cable, 4-socket Bendix connector to three BNC’s

*The appearance of U.S. Department of Defense (DoD) visual information does not imply or constitute DoD endorsement. Photo taken by Lance Cpl. Julian Elliott-Drouin.