Alternator Failure and Cockpit Lighting on a Baron at Night
A Baron 58 is cruising at FL100 on a night IFR flight from Walvis Bay to Windhoek, 40 nm to run, at 22:55. Nine minutes ago the left alternator tripped offline; the right alternator is now showing a fluctuating output and the battery has fallen to 22.0 V and is still dropping. The pilot has shed the pitot heat on the non-flying side, the cabin floodlight and the standby vacuum pump, and is running on the essential bus. The red cockpit floodlight is washing out the printed approach plate and the yoke-mounted EFB is at full brightness. The standby attitude indicator is not internally lit. The pilot reports the runway lights at 5 nm as 'a blur'. Windhoek is CAVOK, wind 09008KT, and ATC has offered radar vectors for a visual approach to runway 08.
1. Rank the load shedding and state what must be kept, with your reasoning.
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Keep, in priority order: pitot heat on the flying pilot's side (an unreliable airspeed indicator at night in cloud is a trap with no recovery); the attitude and heading instruments and their lighting; one VHF; the transponder; the position and anti-collision lights, which are legally required at night; and the gear and flap circuits.
Shed: the second VHF/NAV, duplicated DME, the standby vacuum pump, cabin and flood lighting, the EFB charger and any comfort loads. The autopilot is a judgement call - it draws continuous current, but shedding it adds pilot workload at the worst moment, so shed it last, after the aircraft is trimmed.
Defer: the landing light draws around 10 A and should be selected only on final, so it does not consume the last of the battery before the flare.
Reasoning. Order by 'what do I need in the next five minutes, then the next fifteen' and by legal requirement. A battery at 22.0 V and falling gives tens of minutes at best, and the second alternator may drop off the bus altogether. The aim is to arrive with the gear down and the lights still burning.
2. Explain why the red floodlight is making the approach plate hard to read, and what lighting technique and EFB settings should be used instead.
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Red light preserves rod-based dark adaptation, but it is the wrong tool for a printed plate: the chart's magenta, red and pale grey symbology reflects red light poorly, so contrast collapses. The fix is a low-intensity white map light, held close to the plate and shielded from the rest of the cockpit, used in short bursts. The small loss of adaptation recovers within a minute or two, whereas an unreadable plate compromises the whole approach.
The EFB at full brightness is worse than the floodlight - a full-white screen in a dark cockpit destroys adaptation for 20–30 minutes, which is consistent with the pilot describing runway lights at 5 nm as 'a blur'. Set night mode and the minimum brightness at which the chart is legible, and keep the screen angled away from the windscreen.
The critical item, though, is the unlit standby attitude indicator. It cannot be used as a reference at all; either it gets a shielded flashlight secured to illuminate it, or the pilot plans a partial-panel approach relying only on the illuminated instruments, and says so on the radio.
3. Should the crew accept the offer of radar vectors for a visual approach? Give the decision and the requests you would make.
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No - not as offered. A visual approach assumes the pilot can see the runway and keep the aircraft lit throughout; both are in doubt, and combining a failing electrical system with visual manoeuvring at night in an unfamiliar area removes the last margin.
Preferred: the instrument approach to the runway in use, flown straight in with no holding, minimum configuration changes and the lowest possible workload, with the pilot stating 'electrical failure, partial panel possible' to obtain priority.
Requests: (a) priority handling and the reason; (b) approach and runway lights at maximum intensity; (c) ARFF on standby; (d) landing light on at about 500 ft only.
Decision point to set now: if the battery falls below the level needed for gear and flaps, or the second alternator drops off the bus, declare and land at the nearest lit aerodrome on the first approach, without a second attempt. Do not hold, and do not accept vectors that lengthen the flight.