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TTAF, SMOH, TBO: what aircraft listings mean

MarketPlane.ca ·

Airframe time, time since overhaul, TBO, running 'on condition' and damage history: what each number means, and which of them should stop you buying.

The airframe clock: TTAF

TTAF (Total Time Airframe) is how many hours the aircraft has flown since new. Context is everything: a 1970s trainer showing 8,000+ hours lived a school life; the same type at 3,000 hours was a private machine. Healthier than either extreme is steady use, around 100–200 hours a year. An aircraft that barely flew for years isn't "low time and fresh"; sitting is genuinely hard on engines, seals and cables.

The engine clock: SMOH against TBO

SMOH is hours Since Major Overhaul; TBO is the manufacturer's recommended Time Between Overhauls (commonly 1,800–2,200 hours for piston engines). Read them together: an engine at 400 SMOH with a 2,000 TBO has most of its life ahead; at 1,900 SMOH, you're buying an overhaul, a five-figure bill, and the price should reflect that. This one line explains more of an aircraft's price than anything else in the ad. A very low SMOH deserves its own question: who did the overhaul, and to what standard?

The other clocks: SPOH and friends

SPOH is the propeller's time since overhaul. Smaller money than the engine, but real. You'll also see TTSN (total time since new, for engines or props) and fresh-annual claims. A "fresh annual" is nice, but an annual is a minimum-standard inspection, and it is not equivalent to the pre-purchase inspection done for you.

Equipment shorthand

IFR means equipped and maintained for instrument flight, which is worth real money. VFR means visual flight only. WAAS refers to GPS precision good enough for the best approaches; ADS-B is the position-broadcasting technology increasingly expected in modern panels. Glass panel means screens; steam gauges mean round dials, because the price gap between an old radio stack and a modern IFR panel can exceed the value of the airframe itself, which is why our listings tag avionics individually.

The condition words that matter most

Complete logbooks since new is the phrase that holds value, and missing logs permanently hurt price and raise questions nobody can fully answer. Damage history, properly repaired and documented, is survivable and should simply be priced in; undocumented history is the dealbreaker. Hangared beats tied down outside, especially in Canadian weather. When you read listings on MarketPlane, hover any of these terms. The tooltips give you the short version on the spot.

Red flags, in plain terms

Vague or missing times. Logbook gaps waved away. A fresh annual from a shop nobody can name. "No time to answer questions, lots of interest." None of these mean fraud, but every one of them means slow down and verify. The seller with a great plane wants you to see the logbooks.

Common questions

Is high airframe time (TTAF) bad?

Not automatically. A 10,000-hour airframe that flew steadily and was maintained well can be a better buy than a 2,000-hour plane that sat outside for a decade. Time matters, but history and maintenance matter more.

Can I buy a plane with the engine past TBO?

For private operation in Canada, TBO is a manufacturer recommendation, not an automatic legal limit, and many owners run 'on condition' with good monitoring. But price the aircraft as if the overhaul is due soon, because financially, it is. Lenders and insurers may also take a stricter view than the regulations do.

What does 'on condition' mean?

Operating an engine past its recommended overhaul interval while monitoring its actual health: compressions, oil analysis, metal in the filter, borescope inspections. Reasonable with diligent monitoring, and a red flag when it's just a way to avoid a bill.

What if a listing doesn't mention damage history?

Ask directly, in writing. 'No damage history' is a selling point sellers rarely forget to mention, so silence on the topic is often an answer in itself. Either way, the pre-purchase inspection and logbooks are your verification.

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