Passive Vibration Isolator
project name

Passive Vibration Isolator

Isolating the Avionics Rack from Aircraft Induced Vibration


Isolating the avionics rack from aircraft induced vibration and mechanical shocks in a rotary wing aircraft.

Problem Statement
The avionics rack is fixed to the aircraft decking through traditional isolation mounts. However, to control and limit the displacement of the vertically cantilevered mass created by the avionics rack design, a passive travel limiter with an integral damper is needed.

A machined spring was placed between, and connected to two stainless steel slip-fit cylinders. A novel spring mount design connects each end of the spring to the respective end of each cylinder. Each cylinder is closed ended to which adjustable rod ends are installed to allow a custom fit up to the airframe structure.

Results & Outcome
The original concept was developed around an elastomeric material directly molded between the two slip-fit cylinders. However, the low quantity production rate did not justify the cost of developing a custom elastomeric compound to meet the required stiffness (spring rate) and deflection limits. Numerous in-house tests of economical and commercially available elastomers for the passive damper did not provide acceptable results. An alternate solution was needed. Ingenium Aerospace engineers designed the passive vibration isolator and sized a machined coil spring by specifying the number of coils, slot width, spring cross section, and material. The Ingenium design also allowed for the integration of machined mounting features and geometric shapes into the spring body and ends. The machined mechanical spring was sized to meet the aircraft performance demands (stiffness and deflection limits) as well as aircraft environmental conditions.