Propeller TBO: how often Hartzell, McCauley and MT propellers are overhauled
October 26, 2026 · Chris van Eijk
A propeller's time between overhauls (TBO) is set by its manufacturer as a number of flight hours and a number of calendar months, whichever comes first. For most light aircraft the calendar limit arrives long before the hours do. This guide lists the intervals Hartzell, McCauley and MT-Propeller publish in their own documents, read on 26 October 2026, and works out what that means for an owner, a partnership or a flying club that sets money aside per flight hour.
Short answer: a Hartzell compact two-blade propeller made after April 1997 is overhauled every 2,400 hours or 72 months, whichever comes first (Hartzell Service Letter HC-SL-61-61Y). McCauley's threadless constant-speed propellers, such as the B2D34C214, and most of its fixed-pitch propellers have 2,000 hours or 72 months (McCauley manual MPC26); its older threaded-hub 2A34C66 has 1,200 or 1,500 hours and 60 months (SB137AF). MT-Propeller gives an MTV-12-B on a Lycoming O-360 1,800 hours and 72 months (Service Bulletin No. 1). Governors: Hartzell 2,400 hours with no calendar limit, McCauley 2,000 hours or 60 months, MT 2,400 hours or 72 months. An aircraft flying fewer than 400 hours a year reaches the 72 months first: at 100 hours a year a 2,400-hour propeller is due after 600 hours.
The intervals, from the manufacturers' own documents
Each manufacturer publishes its overhaul periods in one document per product line. The model number stamped on the hub, and for McCauley the change letter after it, decides which row applies. The table shows a selection of the rows that light single-engine aircraft typically run into.
Propeller and governor TBO, by manufacturer
| Propeller | Hours | Months | Source |
|---|---|---|---|
| HartzellCompact two-blade (aluminium hub, piston engine), made after April 1997 | 2,400 | 72 | HC-SL-61-61Y |
| Compact two-blade, made before April 1997, made or overhauled during or after October 1991 | 2,000 | 72 | HC-SL-61-61Y |
| Compact two-blade, made before April 1997, made or overhauled before October 1991 | 2,000 | 60 | HC-SL-61-61Y |
| Governors | 2,400 | none | HC-SL-61-61Y |
| McCauleyThreadless constant-speed, e.g. B2D34C214 and 2A34C203 below change letter C | 2,000 | 72 | MPC26 |
| Fixed-pitch propellers (most models) | 2,000 | 72 | MPC26 |
| Fixed-pitch 1A103/TCM | 1,500 | 72 | MPC26 |
| Governors | 2,000 | 60 | MPC26 |
| Threaded hub 2A34C66, change letter below P | 1,200 | 60 | SB137AF |
| Threaded hub 2A34C66, change letter P or higher | 1,500 | 60 | SB137AF |
| MT-PropellerMTV-12-B on a Lycoming (AE)(I)O-360 | 1,800 | 72 | SB No. 1 |
| MTV-9-B on a Lycoming (AE)(I)O-540 | 2,400 | 72 | SB No. 1 |
| Governors P-4, P-8, P-9 | 2,400 | 72 | SB No. 1 |
Read the full document for your own propeller. Hartzell's rows for its compact series depend on when the propeller was made: two-blade propellers made before April 1997 have 2,000 hours, and 60 instead of 72 months if they were made or overhauled before October 1991. McCauley's threaded-hub 2A34C66 moves from 1,200 to 1,500 hours at change letter P. Agricultural and aerobatic use have shorter intervals in Hartzell's and McCauley's documents. McCauley also lists exceptions for fixed-pitch models: the 1A103/TCM is overhauled every 1,500 hours or 72 months, and a 1A170E/JHA on an aircraft operated as a Part 141 pilot school, or with 2,000 or more cycles per 1,000 flight hours, needs an inspection under Service Bulletin 240 every 1,000 hours or 72 months. Airworthiness directives can require an overhaul or inspection before the TBO; McCauley's manual tells owners to review the applicable FAA airworthiness directives and McCauley service bulletins.
Sensenich is not in the table: its website refused our crawler, and we do not publish a number we could not read at the source.
The calendar limit comes first
Hartzell explains why there is a calendar limit at all: "Corrosion can create hidden defects in critical blade retention components; therefore, a 36, 60, or 72 calendar month limit between overhauls is specified." The clock starts at installation, not at manufacture or overhaul: "Start date for calendar limit is when the propeller is first installed and run on an engine." And a dry hangar does not buy extra time: "Experience has shown that special care, such as keeping an aircraft hangared, is not sufficient to allow extension of the calendar limit."
MT-Propeller allows one adjustment: "When installed in airplanes the calendar time can be extended to coincide with the next annual inspection of the aircraft if the propeller, governor and accumulator are in a proper condition and the limit of hours in service is not yet reached."
For a propeller with 2,400 hours or 72 months, the calendar decides for any aircraft that flies less than 400 hours a year. At 200 hours a year it is due after 1,200 hours, at 100 hours a year after 600, and at 50 hours a year after 300 hours.
Hours until the propeller overhaul, by hours flown a year
- the 72 months come first
- the 2,400 hours come first
| Hours a year | Hours until the overhaul is due | Planning cost per flight hour |
|---|---|---|
| 50 h/yr | due after 300 h | $16.67 |
| 100 h/yr | due after 600 h | $8.33 |
| 200 h/yr | due after 1,200 h | $4.17 |
| 400 h/yr | due after 2,400 h | $2.08 |
What a propeller overhaul costs
We looked for published propeller overhaul prices at about twenty propeller shops and makers in the United States and Europe, and found none for overhauling a metal propeller: the shops we read quote on request. What one governor shop does publish is its governor overhaul rate. West Coast Governor Service writes "$995 is our Standard Overhaul Rate plus any parts (if necessary)" and, for Hartzell governors, "Hartzell Standard Overhaul = $1250".
Our aircraft ownership cost calculator uses a planning figure of $5,000 for a constant-speed propeller overhaul at US prices, with 2,400 hours or 6 years — an assumption, not a published price. With that figure at today's price the reserve is $8.33 per flight hour at 100 hours a year and $16.67 at 50 hours a year, against $2.08 for an aircraft that reaches the full 2,400 hours. The calculator itself shows a little more, because it raises the price to what the overhaul will cost when it falls due. Ask your propeller shop for a quote and put it in the calculator; the effect of the calendar limit stays the same. How the engine and the annual inspection add to that per hour is in aircraft maintenance cost per hour, and the engine overhaul itself in Lycoming engine overhaul cost.
Whose rule is it?
The manufacturers use firm language. McCauley calls its intervals "McCauley's mandatory specified time between overhaul", and its manual states that "operation beyond the specified TBO limits is not permitted." It adds: "All deviations from published TBOs must be approved by your local Regulatory Authority", with a recommendation from McCauley. MT-Propeller writes that deviations "require the approval of the manufacturer". Whether a manufacturer's overhaul period binds a particular aircraft depends on the rules it is operated and maintained under — private, for hire, or under an approved maintenance programme. That is a question for the aircraft's maintenance organisation, not something this guide decides.
Tracking the propeller next to the engine
A propeller has its own hours and its own calendar date, and they rarely line up with the engine's. In Pilot-Next every aircraft can carry maintenance plans with an interval in flight hours, in calendar months or both; each plan shows OK, Due Soon or Overdue against the aircraft's Tacho reading (its Hobbs if it has no Tacho) and today's date, so a propeller at 72 months and a governor at 2,400 hours can be followed as separate plans. See aircraft maintenance tracking.