Why serviceable shock absorbers will extend your engine lifecyle?
Are you worried about your engine stand utilization? In the workshop or in the engine shop, maintenance tooling like engine stands are being heavily used. To ensure their regular usage, shock absorbers are a very important key point. Let me explain you how taking care of your shock absorbers will extend your engine lifecycle.
Why serviceable shock absorbers will extend your engine lifecyle?
Are you worried about your engine stand utilization? In the workshop or in the engine shop, maintenance tooling like engine stands are being heavily used. To ensure their regular usage, shock absorbers are a very important key point. Let me explain you how taking care of your shock absorbers will extend your engine lifecycle.
Engine stands are critical assets since they are used for engine transportation. An engine stand is a maintenance tool from the engine tooling family. It is used to perform several maintenance operations: engine transportation, engine removal-installation, engine storage.
The engine stand called aero–transportable are engine stands you can transport on the ground, on road or in an aircraft.
The workshop engine stand is not aero-transportable because they cannot resist to airtransportation loadcases.
The engine stands are composed in 2 main subassemblies: the base or trolley and the cradle.
Between them, we find the shock absorbers.
An engine is one of the most expensive part of an aircraft. During the maintenance operation, it is necessary to have the best tooling approved by the Engine OEMs.
A qualified Engine Stand has been approved, tested and validated by the OEM. It ensures safety, reliability and guarantee.
Using a non-qualified engine stand exposes you to many risks. If you get an issue with the engine stand, the insurance claim won’t be applicable thus the liability transferred to the end users.
To protect your engine stand from environmental vibration and any damage, the shock absorbers — located on each side of the stand — are mechanical or hydraulic devices designed to absorb and damp shock impulses. It does this by converting the kinetic energy of the shock into another form of energy (typically heat) which is then dissipated.
Engine stand plus engine can be modelized by a mass-spring-damper system :
m = engine + cradle mass
k = vertical stiffness of shock absorbers and cradle
c= damping ratio
This target allows to avoid coupling mode with truck trailer natural frequency and the airfreighter thus avoiding the resonance problem.
Engine stands are designed using the latest FEM technology.
The resonance appears when the excitation frequency matches the natural frequency of the system, it can be very destructive :
The second purpose of shock absorbers is to protect the engine. During operation, engine and engine stand are subjected to shocks. To protect the engine, in particular bearings, shock absorber decreases maximum acceleration seen by the engine regard to the input acceleration.
Shock absorbers work by taking the kinetic energy (movement) of the engine stand and converting it to thermal energy (heat) that is then dissipated into the atmosphere through the mechanism of heat exchange.
Engine stand storage and utilization condition may modify the lifetime of shock absorbers, exposure of following substance reduce lifetime: humidity, chemical agent (oil, jet fuel, detergent, acids, …), direct sun light, ozone. Good storage and use can increase shock absorbers lifetime.
Time and external factor (see above) affect the rubber: the stiffness, the maximal resistance are modified. To guaranty the OEM specification we recommend to change shock absorbers every 5 years.
FEM simulation picture showing peak between unserviceable and serviceable shock absorbers: impact on frequency/ impact on shock absorbing/ Impact on engine protection.
The price of an engine stand represents approximatively less than 1% of the price of an engine. Any failure in an engine stand can be serious. Thus, engine stands must be regularly followed up, checked and maintained by engine stands manufacturers like Dedienne Aerospace.
We know what parts need to be periodically replaced and what checks are necessary to make your engine’s journey safer.
It is very important to choose qualified engine stand by an approved OEM manufacturer.
Thanks to a regular inspection and maintenance of your tooling and your equipments, you will avoid risks and incidents.
27 January 2022
