Night Offshore Transfer with a Rising Load and a Fading Battery
You are the PIC of a single-engine, single-pilot IFR-certified light helicopter on a night offshore transfer to a platform 42 NM from the coast. Before departure the operator's load sheet gives an all-up weight of 1,420 kg against a maximum of 1,450 kg and a CG 40 mm aft of the forward limit, inside the envelope. Fuel on board is 380 kg; planned trip fuel is 250 kg, alternate 40 kg, and the final reserve required by the flight plan is 45 kg. During the approach the platform reports the deck is pitching, and the marshaller asks you to remain airborne for 12 minutes because a previous arrival is still being secured. Ambient temperature is above standard and the helicopter is hovering out of ground effect at 1,000 ft pressure altitude. About eight minutes into the hold, the main battery caution illuminates and the generator-off warning follows. The standby attitude indicator is on its own battery, and the operator's minimum equipment list permits continued flight to a suitable landing site.
1. Evaluate the fuel and weight situation at the moment you are asked to hold, and decide whether the 12-minute hold is acceptable.
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Compute the fuel margin first. Fuel available for the hold is the fuel on board minus trip fuel, alternate fuel and final reserve: 380 − 250 − 40 − 45 = 45 kg. At a typical cruise burn of roughly 120 kg/h that is about 22 minutes of holding, so 12 minutes is arithmetically possible but leaves only about 10 minutes of contingency, and the hold is not at cruise power - hovering out of ground effect burns far more. Recompute at the hover burn: even a modest 180 kg/h hover burn consumes about 36 kg in 12 minutes, leaving roughly 9 kg. That is inside the final reserve. The weight is also against you: at 1,420 kg you are 30 kg below maximum, and hover performance at 1,000 ft pressure altitude in ISA+ conditions is already marginal. The correct decision is to decline the hold and either divert to the alternate or request an immediate landing slot, because the combination of high hover fuel flow, high density altitude and a near-maximum weight erodes both the fuel reserve and the power margin simultaneously. Do not rely on the arithmetic margin alone; the reserve exists to protect against the unexpected, and here the unexpected has already occurred.
2. The generator has failed and you are on battery. Explain how this changes your diversion decision and what you must protect.
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On battery alone the electrical endurance, not the fuel, becomes the binding limit. The battery must carry the essential bus: at least one attitude reference, one radio, the intercom, the engine and fuel indications and the lighting needed for a night approach. The standby attitude indicator has its own battery, which buys time, but the main battery is being drained by everything else. You should therefore treat the situation as a time-limited diversion: shed all non-essential loads (cabin lighting, unnecessary avionics, pitot heat if conditions allow), declare the condition to ATC, and select the nearest suitable landing site rather than the planned alternate if the planned alternate is farther. Confirm the battery endurance figure from the flight manual rather than guessing. The decision rule is that you must land with electrical power remaining for the approach and landing, not merely arrive with the battery flat. Because the platform is not ready and the deck is pitching, a coastal diversion to a lit helipad with a straight-in approach is preferable to a demanding deck landing with degraded instruments.
3. State the sequence of actions and communications you would take in the next two minutes.
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First, fly the aircraft: maintain the hold or begin the diversion, and confirm the generator-off warning against the ammeter and the battery caution. Second, reduce electrical load to the essential bus. Third, transmit a concise urgency call to the platform and to ATC: callsign, position, altitude, nature of the problem (generator failure, on battery), intentions (diverting to the named coastal site), and fuel and persons on board. Fourth, request priority and, if the situation warrants, declare an urgency condition so that emergency services are alerted. Fifth, brief the approach: because night and degraded electrical state raise workload, use a stabilised approach profile with a defined decision point, and be prepared to go around early rather than late. Sixth, after landing, record the times and the nature of the defect for the maintenance organisation. The judgement being tested is that the electrical failure, not the deck delay, now drives the plan, and that communication is part of the solution rather than an afterthought.