FAA Aviation Mechanic Powerplant (AMP)Reciprocating EnginesEasy
A maintenance shop foreman explains to a new technician that a specific engine's TBO (Time Between Overhaul) is 2,000 hours. Under standard Part 91 operation, what is the significance of this figure?
- AIt is the manufacturer's recommended operating time before overhaul and is not mandatory unless required by the operator's approved program
- BIt is the interval at which an annual inspection must be performed
- CIt is the number of hours before the first 100-hour inspection is due
- DIt is a mandatory life limit; the engine must be overhauled before reaching 2,000 hours
Show answer & explanationAnswer & explanation
Correct answer: A. It is the manufacturer's recommended operating time before overhaul and is not mandatory unless required by the operator's approved program
TBO is a manufacturer recommendation based on typical wear and reliability data. Under Part 91 general operations, it is advisory only; the engine may continue in service past TBO based on condition (on-condition maintenance) unless the operator is under a program (e.g., certain Part 135/121 operations) requiring overhaul at TBO.
Why the other options are wrong
- B. Annual inspections are calendar-based (12 calendar months), unrelated to TBO.
- C. 100-hour inspections apply to aircraft used for hire and are unrelated to TBO.
- D. TBO is not a mandatory life limit for most Part 91 operators.
TBO (Time Between Overhaul)
Manufacturer's recommended number of operating hours (or calendar time) before an engine should be overhauled, based on reliability data.
- Advisory, not regulatory, for Part 91 operators
- Some commercial operations may require overhaul at TBO
- Engines can be operated 'on-condition' past TBO if maintained properly
Memory trick: TBO is a 'suggestion,' not a 'summons'