Normally...such damage is the result of the pilots inability to take corrective (IE: disconnect) action in a timely fashion.
Some might just sit there and think
that...hmmm, IDG low oil pressure, and reach for the appropriate checklist, as though this was not an immediate actionable item.
Meanwhile, said IDG is rapidly grinding itself to bits...
At one airline where I worked, the individual responsible for IDG status (the Flight Engineer) was charged (salary deduction) for his
inability to recognise the problem, and take timely corrective action (IE: IDG disconnect, pronto).
For example, with many L1011 operators, IDG disconnect actions are a memory item (for the F/E)...after a quick word to the Commander, who promptly will say...'disconnect NOW, you fool.'
IDG's are a hugely important item...especially on a two engine transport airplane.
IE: treat with utmost respect, and be prepared for the necessary action in the event of problems.
In addition...for charter opertators, many carry an extra IDG in the fly-away kit (as we do)...a sensible precaution, make no mistake.
NB.
Modern transport jet airplanes are....
electric by their design so...make absolutely
sure that you have the electrics available, to complete the flight properly, otherwise, you might find yourself up the creek without a paddle.
Was this true of old(er) time designs?
Yup, sure was.
The Lockheed ELECTRA, comes to mind.
Big time.
The name 'Electra' was not without some thought, and systems design, accordingly..
Elecrtrics?
Yup, and if not, dead as a doornail was a distinct possibility
