Alternator failure over the escarpment
While cruising VFR at 9,500 ft from Keetmanshoop to Windhoek in a Cessna 172, 80 nm south of Hosea Kutako, the alternator warning light illuminates. The ammeter shows a steady discharge. The engine is running normally, the vacuum-driven attitude indicator and directional gyro are still erect, and the electric turn coordinator is available. The aircraft has two VHF radios, a transponder, GPS and an intercom. The battery was replaced eight months ago. You are in day VMC, but the terrain ahead rises and there are few suitable forced-landing areas. You have 2 hours 10 minutes of fuel remaining and a passenger on board. The next suitable aerodrome behind you is 25 nm back; ahead, a private strip is 35 nm away, and Hosea Kutako is 80 nm. The pilot has a handheld VHF in the flight bag but its battery is not fully charged.
1. Diagnose the likely fault and state your immediate actions.
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A steady discharge with the alternator warning light points to alternator failure, a broken alternator belt or a failed alternator control circuit. The engine is still running, so this is an electrical-system failure, not an engine failure. Immediately reduce electrical load: switch off unnecessary lights, pitot heat in day VMC, and non-essential avionics; keep one radio and the transponder. If the aircraft has an alternator reset or field switch, try it once according to the checklist, but do not keep resetting a failed system. Monitor the ammeter and engine gauges. Plan to land as soon as practicable because battery endurance is limited and the battery is powering the radios, transponder, intercom and electric turn coordinator. Do not continue over rising terrain on the assumption that the battery will last.
2. Choose between the aerodrome 25 nm behind, the private strip 35 nm ahead and Hosea Kutako 80 nm ahead. Justify the decision with time and risk.
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Turn back to the aerodrome 25 nm behind. At about 100 kt ground speed that is roughly 15 minutes, which is well within the reduced-load battery endurance and keeps the aircraft over known terrain with a serviceable runway and emergency services. The private strip 35 nm ahead is about 21 minutes away, may be unlicensed, may have no services and its condition is uncertain; using it adds landing risk after an electrical failure. Hosea Kutako is 80 nm ahead, about 48 minutes, and the route crosses rising terrain; that is likely beyond safe battery endurance and increases the consequence of a subsequent radio or electrical loss. The safest option is the known aerodrome behind. Declare urgency if needed, request priority and land.
3. What systems are affected, and how does the failure change your navigation and communication plan?
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The alternator failure will eventually remove the VHF radios, transponder, intercom, landing and navigation lights, and the electric turn coordinator. The vacuum-driven attitude indicator and directional gyro remain available because they are engine-driven, so basic attitude and heading information is not lost. Navigation should shift to GPS with a chart and compass as backup, and the pilot should note time and fuel manually. Communication should be minimised: one radio, short transmissions, and use the handheld on 121.5 only if needed. If the destination is controlled, do not expect to enter without a radio unless a clearance has already been received. The plan should be to land before battery depletion, not to diagnose the fault in the air.