mentioned by bvcu, on the 16th, regarding Maintenance corrective action (deferral) of a BURNT Terminal Block for Pilots Windshield HEAT:
"... permitted discrepancies in the AMM which will normally have a repair limit i.e flight cycles or hours ... These are not MEL ... I assume in the case quoted the manufacturer believed the operation of the windshield heat was ok in this condition , so not an MEL item ..."
Not the manufacturer. From the NTSB report, it seems that UA had somehow migrated some wrong words into their company's customized-AMM -- but
nobody questioned the obvious err included in the company's AMM:
"... United Airlines AMM ... “When bus bar(s) show signs of ... burning, the condition is acceptable for continued service ..."
The next flight departed with the same problem, and with the defective HEATER still powered. Seems someone should have challenged the company's erroneous AMM, and especially that corrective action (deferral) done by company Mx.
No big deal in this case, but over the past seven decades, the
biggest risk during an inflight fire was LOSS OF CONTROL -- and this case could easily have progressed to a typical airliner upset.