Reference

Approach Aviation Coupling Tool

• What is included in the Alternator Drive Coupling Tool Kit?

  The tool kit consists of a zinc-coated coupling spanner wrench and unique coupling gear socket with steel housing and aluminum gear engagement, designed to protect the steel coupling gear from damage during maintenance. Together, these tools allow the coupling to be held in place (mounted on the alternator or free-standing) while the coupling gear slippage is checked with a calibrated 3/8” torque wrench (as specified in the engine maintenance manual).

• Why should every mechanic have an Alternator Drive Coupling Tool?

  The coupling provides a shear point, protecting the engine from damage should the alternator fail. However, it is imperative that the coupling be installed properly and inspected every 500 hours or any time that the alternator is removed from the aircraft. This critical component has been the subject of several Service Bulletins (SBs) and Special Airworthiness Information Bulletins (SAIBs) because an out-of-tolerance or improperly installed coupling can lead to catastrophic engine failure. The lack of specialized tools to perform these tasks has made compliance difficult for many shops, increasing the risk that these critical inspections are not being performed in the field. In addition, alternator coupling slippage is a frequent cause of low alternator output. Without the tools to properly inspect the coupling, these failures are often misdiagnosed as a failure of the alternator, resulting in wasted time and money for both shops and owners.