Night Alternator Failure Over the Negev
You are flying a Piper PA-28-181 at night VFR from Beersheba (LLBS) to Ramon (LLER) at 8,500 ft with two passengers. The sky is clear, moonless, and the terrain below is dark. About 25 nm south of LLBS, the alternator warning light illuminates and the ammeter shows a steady discharge. The battery voltage falls from 24.5 V to 23.8 V over the next 10 minutes. Your GPS, transponder, and one COM radio are on. The engine is running normally, fuel pressure is normal, and the standby attitude indicator is vacuum-driven. You have 1 h 20 min of fuel. LLER is 45 min ahead; LLBS is 20 min behind. The aircraft has a landing light, pitot heat, and an electric turn coordinator. You must decide whether to continue or divert, and what to shed.
1. Identify the most likely fault and list your immediate actions, including load-shedding priorities.
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The most likely fault is an alternator failure: the warning light is on, the ammeter shows discharge, and battery voltage is decaying. First, check the alternator circuit breaker and the alternator switch; if the checklist allows one reset attempt, make it, but do not keep resetting a failed alternator. Reduce electrical load immediately: turn off unnecessary interior lights, the second COM, GPS if not required for navigation, and any non-essential equipment. Keep the transponder, one COM, and navigation equipment as long as needed, but be prepared to lose them. Pitot heat and the landing light are high-current items; use them only when required. The decision must be based on battery endurance, not on the hope that the alternator recovers, because at night over dark terrain a total electrical failure is a serious risk.
2. Decide whether to continue to LLER or divert to LLBS. Support your decision with time, battery endurance, and risk.
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Divert to LLBS. LLBS is 20 minutes behind, while LLER is 45 minutes ahead. The battery is already falling and the alternator is not charging, so the remaining electrical endurance is uncertain and likely shorter than 45 minutes with the current load. Continuing to LLER would leave little or no margin for radio, transponder, or landing light at the destination, and a total failure over dark terrain would make navigation and traffic avoidance much harder. Turning back to LLBS keeps the flight short, keeps the aircraft near a suitable aerodrome, and allows ATC to be informed while the radio still works. Inform ATC of the alternator failure and the diversion before shedding the radio.
3. If the battery fails completely 5 nm from LLBS, what changes and what do you do?
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With a complete electrical failure, the transponder and aircraft radios are lost, so you must squawk 7600 only if the transponder still has power; if not, expect no radar identification. Use the handheld radio if available, but do not rely on it. Fly visually, use the landing light only if it still works, and watch for light signals from the tower. Approach on the normal circuit, keep separation visually, and land only when clear. After landing, stop safely and report to ATC. The priority changes from managing the electrical system to flying the aircraft and maintaining visual separation without radio; do not attempt a complex instrument procedure or continue to a distant aerodrome.