In fact, the artwork shows the AGPU hooked to the aircraft for applying external hydraulics.
To briefly restate what the article should have said concerning the AGPU and aircraft: Electrical power from the AGPU can move systems like the stabilator and other electrically-driven systems.
The AGPU provides electrical and hydraulic power for testing and other maintenance tasks.
For the latest AGPU information check out TM 1-1730-229-13 on: NSN 1730-01-144-1897, NSN 1730-01-466-9371 and NSN 1730-01-552-2313.
There seem to be all kinds of causes, but the best solution to this problem is simple--Never back the AGPU with any vehicle
The AGPU is self-propelled, but it's quicker to pull it with a tug to those distant aircraft on the flight line.
As a reminder, stencil a CAUTION-DO NOT BACK WITH VEHICLE on the front, upper-left side of the AGPU on the opposite side from the fire extinguisher.
When the AGPU is hitched up to the M-Gator, one wrong turn or cramp when backing can break or bend the tow bar and damage the axle.
So when you take your AGPU for a ride to the flight line, keep your eyes on the turn.