The main gear over-center lock (on a LNC2) should lock regardless of whether
or not the hydro system is energized, since that that is what allows one to
land, with gear down-and-locked safely, after an emergency extension. On
earlier LNC2's, the coil springs pulling down on the over-center locking
struts provide the lock and on later models, the "rat-trap" springs do the
trick.

IMHO, if one has an occurrence as related by Hollis Helms, the problem isn't
in the hydro system (assuming the system is set up properly in the first
place, e.g., sufficient cylinder extension to allow the springs to pull the
strut over-center).

Cheers,

Dan Schaefer