Definition
A condition in which warning indications — such as a low-voltage light, a discharging ammeter, abnormal generator or alternator readings, or flickering avionics — show that the aircraft's electrical generating system is no longer reliably supplying power and a complete loss of electrical power is likely if action is not taken. The aircraft is still operating on residual generator output and battery reserves, giving the pilot a limited window to load-shed, troubleshoot, and plan a course of action before total electrical failure occurs.
Plain English
Signs in the cockpit are telling the pilot that the system that makes electricity for the aircraft is failing, and the battery alone will not last long. The pilot has a short window to turn off non-essential equipment and decide what to do before the electrics quit completely.
Context Anchor
Seen in abnormal procedures and instrument flying discussions, especially when a generator or alternator warning appears and the pilot must prepare for loss of electrical power.
Derivation
‘Impending’ comes from the Latin impendere, meaning ‘to hang over’ — something hanging over you, about to happen. So an impending electrical failure is one that is hanging over the flight, not yet here but clearly on the way.
Why Pilots Care
Requires immediate use of backup power sources and prompt diversion or landing to prevent loss of flight instruments and avionics.
Intuition Check
Do not read impending electrical failure as “the electrical system has already completely failed.” It means the system is showing signs that a failure may be about to happen.
Example Sentence 1
When the low-voltage light illuminated and the ammeter showed a discharge, the pilot recognised an impending electrical failure and began shedding non-essential loads.
Example Sentence 2
After the generator warning light illuminated, the checklist directed the pilot to prepare for impending electrical failure.