Engine roughness over the Mozambique Channel
You are ferrying a Piper PA-28-181 (Lycoming O-360) from Maputo to Inhambane, 20 NM offshore over the Mozambique Channel at 4,500 ft, in smooth air, with the coast about 15 NM to your left. Fuel is 40 gal usable, you have been airborne 1.2 hours at 10 gal/h. Suddenly the engine runs rough, the EGT on one cylinder drops, and the oil pressure gauge begins to fluctuate. The engine is still producing power but noticeably less. There is no land within gliding distance; the nearest coast is 15 NM away, which at a 9:1 glide ratio from 4,500 ft is roughly 7 NM of glide - not enough.
1. Diagnose the likely cause and explain what the instrument indications tell you.
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Diagnosis. A single-cylinder EGT drop with roughness indicates that cylinder is no longer producing power - likely ignition (fouled plug, failed magneto lead) or fuel distribution (blocked injector/nozzle, induction leak) or a mechanical fault (sticking valve, failing lifter). The fluctuating oil pressure is the more serious sign: it points to oil system distress (pump, relief valve, or a developing internal failure) rather than a simple ignition problem.
Instruments. EGT drop = that cylinder is cold, i.e. not firing. Roughness = the engine is running on fewer than four cylinders. Fluctuating oil pressure = the engine may be heading toward seizure or loss of lubrication. The combination is not a nuisance; it is a potential total power loss.
Implication. You are 20 NM offshore with no glide to land. The priority is to preserve the engine and get to a position where a forced landing is survivable.
2. Given the position offshore, state your immediate actions and your decision logic for continuing versus turning back.
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Immediate actions.
- Maintain aircraft control - pitch for best glide if power fails, but for now hold altitude or a shallow climb only if the engine allows; do not trade height for speed unnecessarily.
- Turn toward the coast now, not later. A 15 NM track to the coast at 110 kt takes about 8 minutes; every minute spent deliberating is a minute further from a survivable landing site.
- Troubleshoot briefly: check fuel selector on a tank with fuel, mixture rich enough, carb heat (if fitted) - but time-box this to about 30 seconds.
- Declare an emergency to ATC on the appropriate frequency: "Mayday, Mayday, Mayday", position, altitude, nature of problem, intentions, souls on board.
- Prepare the cabin and brief a ditching/forced landing: life jackets, doors, radio call, emergency locator.
Decision logic. Continue only if the engine holds power and the coast is reachable with margin. If oil pressure continues to fall or the engine loses further power, treat it as a total failure and commit to the nearest landfall or a controlled ditching. Turning back to Maputo (20 NM) is worse than the coast (15 NM) - go to the nearer survivable option.