TO: FAA Approved Propeller Repair Stations, Aircraft Manufacturers and Owners

SUBJECT: Revised Time Between Overhaul (TBO) Specifications

MODELS AFFECTED: All Propellers, Governors, and Accumulators

SERVICE MANUALS AFFECTED: 701115, 710930, 720415, 730720, 761001, 780401, 780630, 790901, 810301, 810915, 860201, 880415, 890119, MPC1100-[X], CMM1100-[X]

Service Bulletin 137R replaces Service Bulletin 137Q dated June 21, 1999. This update provides TBO information for new propeller models and updates some older TBO requirements. All previously published data concerning time between overhaul for McCauley products is superseded. Vertical lines in margin indicate changes.

The following pages show McCauley's mandatory specified time between overhaul for propellers, governors, and accumulators. Specifications are based on hours of operation but, in addition, a calendar limit is specified for all. The flight time or calendar limit is applicable, whichever occurs first. The starting point for the calendar limit is the date of first installation on an engine (not from date of manufacture or overhaul).

All deviations from published TBOs must be approved by your local Regulatory Authority with a recommendation from McCauley.

If the propeller is in storage in excess of two years prior to its first use, additional inspections are required, see page 2. Once installed on an aircraft the propeller calendar limit is not interrupted by subsequent removal and/or storage.

Propeller and governor overhaul should, as much as practical, coincide with engine overhaul. For example, in a case where propeller TBO is 1500 hours and engine TBO is 1400 hours, the propeller should be overhauled at the same time as the engine. This is appropriate as long as neither TBO limit is exceeded.

TBO specifications are based on normal aircraft with normal and continuous usage. Flight time and calendar limit must not be the only factors considered in determining when a propeller needs to be overhauled. Factors such as operating conditions or environment often demand that a propeller be overhauled prior to TBO. Even though a propeller may be operating normally and have a good external appearance when the TBO flight time or calendar limit is reached, operation beyond the specified TBO limits is not permitted.

CAUTION:
Please review applicable FAA Airworthiness
Directives or McCauley Service Bulletins.
These may require compliance prior to TBO.

Long Term Storage of Controllable Pitch Propellers
The following is applicable to new and overhauled propellers prior to entering service (engine installation). Storage time is determined from date of manufacture or overhaul:

1. Storage must be in a clean and dry environment, preferably in the original shipping carton and above ground level, to minimize exposure to dirt and moisture.
2. If storage period exceeds two (2) years before entering service, perform the following inspection:
   1. For all propeller models, inspect externally for damage and corrosion. Inspection may be accomplished by an A & P mechanic or international equivalent. Make logbook entry of compliance with Service Bulletin 137[X].
   2. For non-oil-filled propeller models, remove propeller cylinder, inspect for internal corrosion and signs of deterioration, and repair as necessary. This must be accomplished only by an FAA approved propeller repair station in accordance with the appropriate propeller service manual. Make logbook entry of compliance with Service Bulletin 137[X]
3. For all propeller models, if storage period exceeds five (5) years before entering service, perform the following inspection and parts replacement:
   1. Disassemble as necessary to replace all rubber seals and lubricants. Total disassembly (such as removing ferrules from blades) is not required unless evidence of corrosion warrants further disassembly. This must be accomplished only by an FAA approved propeller repair station in accordance with the appropriate propeller service manual. Make logbook entry of compliance with Service Bulletin 137[X]
   2. Inspect parts for damage and corrosion, repair/replace parts as necessary. Work must be accomplished only by an FAA-approved propeller repair station or international equivalent in accordance with the appropriate propeller service manual. Make logbook entry of compliance with Service Bulletin 137[X].

Long Term Storage of Governors
The following is applicable to new and overhauled governors prior to entering service (engine installation). Storage time is determined from date of manufacture or overhaul:

1. Storage must be in a clean and dry environment, preferably in the original shipping carton and above ground level, to minimize exposure to dirt and moisture.
2. If storage period exceeds two (2) years before entering service, perform the following inspection:
   1. Inspect externally for damage and corrosion.
   2. Test run the governor on a governor test bench to verify correct operation and check for leakage. This must be accomplished only by an FAA approved propeller repair station or international equivalent in accordance with the governor service manual.
3. If storage period exceeds five (5) years before entering service, perform the following inspection and parts replacement:
   1. Disassemble as necessary to replace all rubber seals and gaskets. Total disassembly (such as disassembling the flyweight assembly) is not required unless evidence of corrosion warrants further disassembly.
   2. Inspect parts for damage and corrosion, repair/replace parts as necessary. Critical inspection areas are I.D. of drive gear, O.D. of the pilot spool, and "toes" of flyweight. Work must be accomplished only by an FAA approved propeller repair station or international equivalent in accordance with the governor service manual.
   3. Test run the governor on a governor test bench to verify correct operation and check for leakage. This must be accomplished only by an FAA approved propeller repair station in accordance with the governor service manual.

Table I. Propeller Models

APPROVAL: FAA approval has been obtained on technical data in this publication that affects product type design.

TO OBTAIN SATISFACTORY RESULTS, PROCEDURES SPECIFIED IN THIS SERVICE INFORMATION MUST BE ACCOMPLISHED IN ACCORDANCE WITH ACCEPTED METHODS AND PREVAILING GOVERNMENT REGULATIONS. MCCAULEY PROPELLER SYSTEMS CANNOT BE RESPONSIBLE FOR THE QUALITY OF THE WORK PERFORMED IN ACCOMPLISHING THIS SERVICE INFORMATION.

McCauley Propeller Systems | P.O. Box 5053 | 3535 McCauley Drive | Vandalia, Ohio 45377-5053 | USA
800-621-PROP (7767) | Telephone (937) 890-5246 | Telefax (937) 890-6001