Winter Maintenance:

The ground might be thawing, but your engine’s internal plumbing hasn't received the memo yet. The AAIB reports that they are seeing a spike in "breather-ice" incidents. When you fly in cold, damp UK air, water vapour (a natural byproduct of combustion) leaks past the piston rings and mixes with oil mist. In a warm engine, this exits via the breather tube. However, if that tube is chilled by the slipstream, the moisture condenses and forms a thick, yellowish emulsion -aviation's infamous "mayonnaise."

​The danger isn't just a rough-running engine; it’s a total oil system failure. If that breather tube is blocked by a frozen plug of this emulsion, the "blow-by" pressure inside the crankcase has nowhere to go. While many pilots fear a popped front crankshaft seal, the reality is often less dramatic but just as terminal: the pressure frequently forces the oil dipstick out of its tube or, in some models, causes an oil cooler to rupture.

Once that pressure relief is gone, your oil is pumped out of the engine in minutes, often coating the windscreen and leading to a catastrophic loss of pressure. Before you pull the prop today, use a torch to inspect the breather exit.

If you see any sign of congealed emulsion, clear it completely. It’s a five-minute check that keeps you from becoming a forced-landing statistic.