TTAF and TBO are the two numbers every lender's underwriter checks before an appraisal is even ordered. Below is what they mean, typical TBO intervals for the engine families FLYING Finance sees most often, and what a clean logbook actually looks like versus what raises a flag.
TBO figures are commonly published industry ranges provided for general orientation; confirm exact intervals against your engine's specific maintenance manual and serial number.
TTAF, Total Time Airframe, is the total number of hours the airframe has flown since new, as recorded in the logbooks. TBO, Time Between Overhauls, is the engine manufacturer's recommended interval, in hours (and sometimes calendar years), before a major overhaul. Together, these are the first two numbers an underwriter checks, because they drive both the aircraft's appraised value and how much runway is left before the next major maintenance event.
A logbook doesn't need to show a brand-new engine to get financed; most lenders finance aircraft well past the midpoint of a TBO interval. What actually gets checked is continuity and compliance: no unexplained gaps in the airframe or engine logs, Airworthiness Directives signed off in the maintenance records, and a documented overhaul or top-end history that matches the hours claimed.
TBO intervals are set by the engine manufacturer and vary by model and installation. These are the commonly published ranges for engine families found across the aircraft FLYING Finance typically finances; always confirm the specific TBO for your exact engine model and any service bulletin adjustments.
| Engine family | Typical TBO (hours) | Common installation |
|---|---|---|
| Continental O-200 / O-300 series | 1,800-2,000 | Certified piston singles (Cessna 150/172 early models) |
| Lycoming O-320 / IO-320 / O-360 / IO-360 / IO-390 / O-540 / IO-540 series | Up to 2,600 (extended via SI 1009BF, July 2026; older airframes may still be at the prior 2,000-2,200 base pending compliance) | Certified piston singles and twins (Cessna 172/182, Piper Cherokee/Archer/Saratoga, Beechcraft Bonanza/Baron) |
| Continental/Lycoming turbocharged variants | 1,600-1,800 | High-performance and turbocharged singles/twins |
| Pratt & Whitney Canada PT6A | 3,600-9,000+ (on-condition programs common) | Turboprops (Pilatus PC-12, Daher TBM, King Air) |
| Turbofan (light jet) | On-condition / hot-section inspection intervals | Cirrus Vision Jet, Embraer Phenom, Citation family |
"Tell me the aircraft's hours since new (TTAF) and how it sits relative to its engine's TBO, and I'll tell you what a lender is likely to ask for next."
