Located on each engine of the F/A-18 Super Hornet is the aircraft's Airframe Mounted Accessory Drive (AMAD), a device that acts as the brain of the electrical and hydraulic systems.
The AMAD is a gearbox, and through engine revolutions, powers the aircraft's hydraulic pump, fuel pump, generator, and starter.
AMAD maintenance and overhaul is handled by pneudraulics mechanics assigned to the hydraulics shop in Building 379 at Fleet Readiness Center Southwest (FRCSW).
AMADs are removed and examined when an F/A-18 is inducted for maintenance. Units are tested and those operating within specification are forwarded to supply as ready-for-issue (RFI), and flight-hour notifications are sent to engineering.
AMADs inducted for specific issues, like a failed generator, are overhauled.
Overhaul requires disassembly of the entire gearbox and inspection of all components. In all, about 200 parts are ordered for reassembly including gaskets, seals, bearings and gears.
Non-destructive testing (NDI) is used to identify cracks or flaws on the gearbox. Worn parts, such as thread inserts, are sent to the machine shop for replacement.
Once rebuilt, the units are tested using Automated Testing Equipment (ATE) prior to release as RFI to the fleet. The Navy uses ATE to test all electronic and hydraulic aircraft components.
FRCSW installed an upgraded AMAD gearbox test stand for the Super Hornet five years ago.
The test stand includes a data acquisition (DA) system that operates the test cycles, and measures and records the data. The data is stored and displayed so the operator can verify that the unit is within safe operating specifications.
The stand also simulates varying loads in horsepower to test the gearbox at different speeds, load conditions and vibrations.
The test stand features three screens: The first indicates calibration, the second, which tests are running and the outcome, and the third screen connects to a camera showing the AMAD stand. The operator may also use a joystick to identify and query specific areas and tests.
AMAD calibration tests include six tests in break in mode, six tests in calibration and ground maintenance mode, and an air-turbine start cycle test. The tests take about three hours to run per unit.
After testing, artisans inspect the gearbox and its magnetic plug for metal or debris.
FRCSW returns an average of 30 Super Hornet AMADs to the fleet yearly.