While playing a MM game I was wondering how some people handle certain aspects of salvage in reference to equipment being destroyed for game purposes vs truly destroyed. We know a mech is destroyed when all IS in the CT is gone by damage. But a limb or other location can be destroyed and whatever occupies in the crits in that location can be salvaged. By my reading, even if equipment has been hit on all the crits it can still be salvaged from the wreckage of whatever it was mounted on.
SO p175 is the first logical argument:
’Mechs: A ’Mech is truly destroyed when its center torso internal structure is eliminated. Some components may be salvageable, but the ’Mech itself cannot be returned to service.
This implies that any/all components have a chance for recovery & repair, including those also in the CT. Reference auto-accidents where a vehicle becomes torn asunder, and the engine/transmission remain useable, sometimes not even damaged.
For the diagnosis effort, use of a Descartes can mean figuring out what's wrong vs a mis-diagnosis and scrapping an otherwise useable piece of gear; diagnosing on an 9+ with 2x, or an 8+ means 3x more return on damaged equipment than without its use.
With Diagnosis (SO pg177), we read the distinction between crit'd and 'destroyed by location destruction':
Players can attempt to repair weapons and equipment that have received a critical hit or are in a destroyed location
and along with the above wording:
Engine: An engine that has suffered a critical hit to every location or has exploded (see Engine Explosion, p. 77, TO) is considered truly destroyed and must be replaced.
tells us that engines can be repaired even if the CT has been blown out ('Mech as a unit remains no longer useable) and even if the engine has received up to 1-crit less than its total critical-count.
(all of this assuming the Quality rating wouldn't drop below an A).
Additionally, when using Expanded Critical Hits and Damage (TO p74), or Optional Critical Hits Table (Solaris: Teh Reaches, pg51), weapons and equipment can continue to function after receiving a critical hit - so "truly destroyed", still remains variable (IE, would a weapon having received a critical hit while using the Expanded Critical Hits rule be subject to "truly destroyed" without a "Diagnosis check"; or, would the diagnosis still be required, and a failed-roll indicate that it simply burnt-out or failed after being powered off... OR - Schroedinger's equipment - If the Diagnostics roll is never made, will it always continue to work with the damaged-crit?)
(These of course, would likely also require the use of Partial Repair rules, SO pg182, while still carrying the prior effect determined by Expanded Critical Hits and/or Optional Critical Hits.)
Regarding longevity of that MW who's piloting his great-great-grandfather's Centurion, along with whose father, and every father before him had died in that same cockpit - if the CT had continued to survive by 1 point of IS, it would/could still have been repaired ;)