The pre-buy inspection checklist

A mismatch is not necessarily fraud — LLCs, estates and recent sales all produce them — but every one needs an explanation before money moves. The FAA registry is free and public.

US registrations expire and must be renewed. An expired registration grounds the aeroplane, and people genuinely miss it.

It stays with the aircraft for life and is displayed in the cabin. A missing one is a replacement application and a delay.

A lien follows the aeroplane, not the seller. Buying one means buying someone else’s debt, and it is the single cheapest catastrophic risk to remove.

Incomplete logs cost twenty per cent of value or more, and sometimes far more. This is a price question and an airworthiness question at the same time.

Old aeroplanes have messy histories. What matters is whether a gap can be explained and whether the aircraft was returned to service properly afterwards.

An aeroplane that sat for four years has its own set of problems — seals, corrosion, cam and lifter spalling — regardless of what the hour meter says.

A 337 means significant work was done. Read each one. An alteration with no 337 behind it is an unapproved modification and an airworthiness problem you inherit.

Avionics come and go over decades and the list often does not follow. A mismatch means the weight and balance is wrong too.

An aeroplane weighed in 1978 with forty years of avionics added since has an empty weight that is fiction — and useful load is the number that decides whether it does your mission.

Not "the seller says it is all done." A current signed list, verified item by item against the entries. An AD that cannot be economically complied with is a walk-away.

Ask the question directly and in writing. Then look for the repair paperwork yourself. Undisclosed damage found at the pre-buy tells you about the seller as much as the aeroplane.

An imported aircraft needs a proper US airworthiness certificate and the conformity behind it. Gaps here are expensive and slow to fix.

A differential compression number means nothing without the calibration reading from the same gauge on the same day. Ask for both, and for the previous annual’s numbers to compare against.

This is the test that finds what compression misses. An exhaust valve burning unevenly shows a distinctive pattern long before the compression drops, and it is a cylinder off within fifty hours.

Fine grey fuzz is normal. Flakes, shiny slivers or bronze are not. Bronze means bearing material, which means the engine, not a cylinder.

One sample is a data point. Four are a trajectory, and the trajectory is the information. A seller who has been sampling all along will have them.

A prop strike requires an engine teardown inspection. A strike in the history with no teardown entry is a crankshaft you cannot trust and a bill you will eventually pay.

Case cracks mean a split-case repair or a replacement case. They are also easy to see if someone looks.

Pulled studs are a cylinder off at best and a case repair at worst.

This is the carbon monoxide item. Cabin heat on most singles is drawn over the muffler, so an exhaust leak inside the shroud puts CO in the cabin. People have died from this. Treat it as a life-safety item, not a maintenance one.

Poor baffling is the usual reason for high cylinder head temperatures, and high CHTs are the usual reason cylinders do not make TBO.

Cracked mounts are a weld and a re-hang. Collapsed rubber shows up as unusual vibration that gets blamed on the propeller.

Rubber has a calendar life whether it has been flown or not. A full set is not ruinous but it is a real number, and it is almost always due on an older aeroplane.

Most magnetos want a 500-hour internal inspection. Two mags due at once is a predictable four-figure item that belongs in the negotiation.

A dry vacuum pump is a wear item with no warning before it fails. If the aircraft still depends on one for attitude, its age matters to your safety as well as your wallet.

Turbo systems add a whole category of expensive parts, and coking from poor shutdown discipline is invisible until it is not.

Factory new, factory rebuilt, factory overhaul and field overhaul are four different things with four different values, and adverts use the terms interchangeably. Read the entry, not the advert.

Out of track means a bent blade or a damaged hub. Dynamic balancing is cheap and makes almost any aeroplane nicer to fly.

Every dressing removes metal. A blade that has been dressed repeatedly may be at or near its minimum dimensions, at which point it is scrap rather than a repair.

On a constant-speed hub this is an overhaul, not a wipe-down.

Most manufacturers publish a calendar limit as well as an hourly one, and low-time aeroplanes routinely blow through the calendar without anyone noticing.

Some hubs are life-limited outright. An unairworthy hub on an otherwise good aeroplane is a five-figure surprise.

Corrosion in primary structure is the classic walk-away. It is not always repairable at any sensible cost, and a type specialist knows exactly which stations to open on this model.

Water and spilled electrolyte collect at the low points. The battery box in particular eats structure quietly for years.

An aeroplane that lived on a salt-air ramp or hauled fertiliser is a different corrosion proposition from one that lived in a dry hangar in Kansas. The registry tells you where it has been based.

Worn hinges are cheap; a loose balance weight is a flutter risk, which is the kind of finding that does not get negotiated.

Frayed cables at the pulleys are a common find on aeroplanes that sat, and rigging that is out explains a lot of "it always flew left wing low."

A gear swing on jacks is the only way to find a tired actuator, a misrigged squat switch or a gear that will not lock. Do not skip it to save an hour.

Individually minor, collectively a four-figure line, and entirely negotiable if it is written down.

Worn rails are the subject of long-standing airworthiness directives on several common types, because a seat sliding back on rotation has killed people.

Webbing degrades with sunlight and age. If the aeroplane has no shoulder harnesses at all, price fitting them and then fit them.

A windscreen is not a small item on most types, and a crack that has not been stop-drilled will grow.

A door that does not latch cleanly is a distraction on every flight and a certificate issue if it opens.

Bladders have a service life and replacing them is a wing-off job on some types. Blue staining on the underside of a wing is fuel, and fuel is never cheap to chase.

Worn cap seals let rain into the tanks, which is how water gets in the fuel, which is how engines stop.

A selector that does not detent positively, on an aeroplane where the pilot must change tanks in flight, is an accident waiting for a distraction.

The same item as the exhaust check, from the cabin side. Ask for the CO test explicitly. Fit a detector on day one whatever the answer.

The battery is cheap. The corrosion under a leaking box is not.

Fifty-year-old insulation, home-made splices and abandoned wiring from removed equipment. Expensive, invisible, and the thing an avionics shop finds after you own it.

Required every 24 calendar months for IFR. An expired check is a small bill and a grounded aeroplane for IFR until it is done.

A 121.5 ELT is no longer monitored by satellite. Battery dates are a routine miss.

If attitude information still depends on a dry pump with unknown hours, that is a single point of failure in cloud.

Boots, panels and pumps are expensive, and an aircraft advertised as known-ice capable with unserviceable equipment is not.

Installed, approved and documented are three different things. An unapproved installation is an airworthiness problem regardless of how well it works.

The FAA will send a free public performance report for a tail number. It says whether the equipment actually meets the rule in flight — which a placard on the panel does not.

Non-WAAS means no LPV approaches. And find out who holds the subscription — it does not transfer automatically and it is not cheap.

Autopilots are routinely sold as working on the basis that they engage on the ground. Fly heading, nav, altitude hold, altitude preselect and a coupled approach. Repairs on older units can exceed the value of the whole panel.

A weak transmitter or a corroded antenna base is cheap to find now and infuriating to chase later.

The tidiness back there is a fair proxy for how the whole aeroplane has been treated.

A digital engine monitor with saved data is a gift — an honest history of how the engine has been operated, and very hard to fake.

Set a published power setting at a published altitude and compare. Ten knots down on the handbook is a rigging problem, a tired engine, or an advert that was optimistic.

Watch the cylinder head temperatures in the climb especially. A hot cylinder in the climb is the one that will not make TBO.

Static RPM below spec on a fixed-pitch aeroplane means the engine, the propeller or the rigging, and it is measurable rather than a matter of opinion.

A persistent wing-low or heavy rudder is rigging, and rigging is hours of labour nobody budgets for.

The stall tells you about rigging and whether the stall warning works. The gear cycle in flight tells you what the swing on jacks could not.

You will never again be as alert to this aeroplane’s oddities as you are on the first flight. Write them down in the air.