ISSUED REVISED PAGE NO. REVISION 

MO DAY YEAR MO DAY YEAR 

05 27 60 11 18 09 1 of 4 AU 

©2009 by Lycoming “All Rights Reserved” 

Lycoming Engines, a division of AVCO Corporation, a wholly owned subsidiary of Textron Inc.

652 Oliver Street 

Williamsport, PA. 17701 U.S.A

Tel. 570-323-6181 

Fax. 570-327-7101 

www.lycoming.com 

DATE: November 18, 2009 Service Instruction No. 1009AU 

(Supersedes Service Instruction No. 1009AT) 

 Engineering Aspects are 

FAA (DER) Approved 

SUBJECT: Recommended Time Between Overhaul Periods 

MODELS AFFECTED: All Lycoming Piston Aircraft Engines 

The following chart shows the established time between overhaul (TBO) for Lycoming piston aircraft 

engines. TBO’s can be established on engines that incorporate GENUINE LYCOMING PARTS only, and 

are not applicable if the engine contains parts other than those supplied by Lycoming. Service experience, 

variations in operating conditions, and frequency of operation are some of the factors taken into 

consideration when a TBO is established. Because of variations in the manner in which engines are 

operated and maintained, Lycoming can give no assurance that any individual operator will achieve 

the recommended TBO. 

Continuous service assumes that the aircraft will not be out of service for any extended period of time. 

Refer to latest revision of Service Letter No. L180 if the aircraft is to be out of service for a period of time 

greater than 30 days. 

Engine deterioration in the form of corrosion (rust) and the drying out and hardening of 

composition materials such as gaskets, seals, flexible hoses and fuel pump diaphragms can occur if an 

engine is out of service for an extended period of time. Due to the loss of a protective oil film after an 

extended period of inactivity, abnormal wear on soft metal bearing surfaces can occur during engine 

start. Therefore, all engines that do not accumulate the hourly period of time between overhauls 

specified in this publication are recommended to be overhauled in the twelfth year. 

Engine accessories and propellers may require overhaul prior to engine overhaul. Perform overhaul of these 

components in accordance with the accessory manufacturer’s recommendation. 

The TBO’s in the chart do not apply to engines engaged in crop dusting or other chemical-application 

flying. Overhaul these engines at 1500-hour intervals or at recommended TBO, whichever is lower. 

Reliability and average service life cannot be predicted when an engine has undergone any modification 

not approved by Lycoming. The TBO’s shown in the table are recommendations for engines as 

manufactured, without considering any modifications that may alter the life of the engine. 

SERVICE 

INSTRUCTION
ISSUED REVISED PAGE NO. REVISION 

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RECOMMENDED TIME BETWEEN OVERHAUL PERIODS 

FIXED WING AIRCRAFT 

Engine Models See Note Hours

O-235 Series (except –F, -G, -J) 12 2400

O-235-F, -G, -J 13 2000

O-290-D -------- 2000

O-290-D2 -------- 1500

O-320 Series (except O-320-H) 1,10,11 2000

O-320-H 11 2000

IO-320-A, -E 1,10,11 2000

IO-320-B, -D, -F 4,6,10,11 2000

IO-320-C 2,4,10,11 1800

AIO-320 (160 HP) 6 1600

AEIO-320 Series 6 1600

O-340 Series 1 2000

O-360 Series (except O-360-E, -J2A) 1,4,10,11 2000

O-360-E 4,11 2000

IO-360-L2A 11 2000

IO-360-A, -C, -D, -J (200 HP) 4,5,6,10,11 2000

IO-360-B, -E, -F, -M (180 HP) 1,4,10,11 2000

TO-360-C,-F; TIO-360-C 3,11 1800

TO-360-E (180 HP) 3,4,11 1800

AIO-360 (200 HP) 6 1400

TIO-360-A Series 3,11 1200

AEIO-360 Series (180 HP) 6 1600

AEIO-360 Series (200 HP) 6 1400

IO-390-A 11 2000

O-435; GO-435 -------- 1200

GO, GSO-480; IGSO-480 1 1400

O-540-A, -B, -E4A5 1,10 2000

O-540-E4B5, -E4C5 1,11 2000

O-540-G, -H, -J 10,11 2000

O-540-L3C5D 2,11 2000

IO-540-A, -B (290 HP) 1,10,11 1400

IO-540-C 1,10, 11 2000

IO-540-D 1,10 2000

IO-540-E, -G, -P 1,10,11 1600

IO-540-S, -AA 2,10 1800

IO-540-J, -R 2,10 1800

IO-540-J4A5 10 2000

IO-540-AB1A5, -AC1A5, -AF1A5 11 2000

IO-540-K, -L, -M, -N, -T, -V, -W 10,11 2000

AEIO-540 Series 6 1400

IGO & IGSO-540 Series -------- 1200

TIO-540-V, -W, -AE 3,4,11 2000

TIO-540-C, -AA, -AB, -AF, -AG, -AH, -AJ, -AK 3,4,7,11 2000

TIO-540-A, -F, -J, -N, -R, -S, -U 3,4,11,14 1800

TIO-541-A (320 HP) 3 1300

TIO-541-E (380 HP) 3,9 1600

TIGO-541 (425 HP) 3 1200

IO-580-B1A 11 2000

AEIO-580-B1A 6 1400 
ISSUED REVISED PAGE NO. REVISION 

MO DAY YEAR MO DAY YEAR 

05 27 60 11 18 09 3 of 4 AU S.I. 1009 

RECOMMENDED TIME BETWEEN OVERHAUL PERIODS (CONT.) 

ROTARY WING AIRCRAFT 

Engine Models See Note Hours 

IO-720 Series 11 1800

O-320-A2C, -B2C 11 2000

HO-360-C1A 11 2000

O-360-C2B,-C2D; HO-360 (except –C1A); HIO-360-B -------- 1500

O-360-J2A 11 2000

HIO-360-A, -C, -D, -E, -F Series -------- 1500

HIO-360-G1A 11 2000

VO-360-A Series -------- 600

VO-360-B; IVO-360 -------- 1000

VO-435-A Series -------- 1200

VO-435-B Series -------- 1200

TVO-435 Series 3 1000

O-540-F1B5 11 2000

IO-540-AE1A5 11 2000

VO-540 Series 8 1200

IVO-540 Series -------- 600

TVO, TIVO-540 Series 3,8 1200 

NOTES 

1. Only engines built with 1⁄2 inch dia. exhaust valve stems. Engines of this series with 7/16 inch dia. 

exhaust valves should not exceed 1200 hours between overhauls regardless of the type of operation. 

New and rebuilt engines built with 1⁄2 inch dia. exhaust valve stems are identified, respectively, by serial 

numbers and date in the latest revision of Service Instruction No. 1136. 

2. These engines are designed to incorporate exhaust turbocharging. 

3. Turbochargers may require removal, prior to engine overhaul, for carbon removal and repair. 

4. Engines with reverse rotation have same overhaul times as corresponding normal rotation engines. 

5. 1200 HOURS: Engines that do not have large main bearing dowels should not be operated more than 

1200 hours between overhauls. 

1400 HOURS: Engines that have large main bearing dowels may be operated to 1400 hours between 

overhauls. These include engines with serial numbers L-7100-51A and up, and L-101-67A and up; 

engines which are in compliance with the latest revision of Service Bulletin No. 326; and 

remanufactured engines shipped after January 26, 1970. 

 2000 HOURS: Engines that have large main bearing dowels and redesigned camshafts may be operated 

to 2000 hours between overhauls. These include engines with serial numbers L-9762-51A and up; IO360-C1E6 engines with serial numbers L-9723-51A and up; LIO-360-C1E6 engines with serial numbers 

L-524-67A and up; engines that are in compliance with the latest revision of Service Bulletin No. 326 

and Service Instruction No. 1263. Rebuilt engines shipped after October 1, 1972, may be operated to 

2000 hours between overhauls except those with serial numbers L-2349-51A and L-7852-51A which do 

not have the redesigned camshaft and must not exceed 1400 hours of operating time between overhauls. 
ISSUED REVISED PAGE NO. REVISION 

MO DAY YEAR MO DAY YEAR 

05 27 60 11 18 09 4 of 4 AU S.I. 1009 

6. The reliability and service life of engines can be detrimentally affected if they are repeatedly operated at 

alternating high and low power applications which cause extreme changes in cylinder temperatures. 

Flight maneuvers which cause engine overspeed also contribute to abnormal wear characteristics that 

tend to shorten engine life. These factors must be considered to establish TBO of aerobatic engines; 

therefore it is the responsibility of the operator to determine the percentage of time the engine is used for 

aerobatics and establish his own TBO. The maximum recommended is the time specified in this 

instruction. 

7. TIO-540-C Series engines with serial numbers L-1754-61 and up, TIO-540-C Series engines that were 

rebuilt or overhauled at Lycoming Engines, Williamsport, PA after March 1, 1971, and TIO-540-C 

series engines that have been modified to incorporate large main bearing dowels as described in the 

latest revision of Service Instruction No. 1225 may be operated to 2000 hours. Engines that do not 

incorporate this modification must not exceed 1500 hours between overhauls. 

8. VO, TVO and TIVO-540 engines built with P/N 77450 connecting rods as described in the latest 

revision of Service Bulletin No. 371 may be continued in service to 1200 hours. Engines that do not 

incorporate this new connecting rod are restricted to 1000 hours for VO-540 models and 900 hours for 

TVO and TIVO-540. See latest revision of Service Bulletin No. 371 for improved connecting rod 

assembly. 

9. TIO-541-E series engines with serial numbers L-804-59 and up, rebuilt engines shipped after March 1, 

1976, and all engines that incorporate the improved crankcases and cylinder assemblies described in the 

latest revision to Service Bulletin Nos. 334 and 353 may be operated for 1600 hours before overhaul. 

Engines not in compliance with these requirements are limited to 1200 hours recommended time 

between overhaul. 

10. Some engines in the field have been altered to incorporate an inverted oil system in order to perform 

aerobatic maneuvers. Whenever this modification is done to an engine, the TBO of the engine must be 

determined in the same manner listed for AEIO engines of the same model series. 

11. If an engine is being used in “frequent” type service and accumulates 40 hours or more per month, and 

has been so operated consistently since being placed in service, add 200 hours to TBO time. 

12. To qualify for the 2400 hour TBO, high-compression O-235’s must have the increased strength pistons 

(P/N LW-18729). See latest revision of Service Letter No. L213. 

13. The high-compression O-235-F, -G and -J series do not have the increased-strength pistons (P/N LW18729); therefore, they do not qualify for the 2400 hour TBO. 

14. TIO-540-A series engines with serial numbers L-1880-61 and up, TIO-540-A series engines that were 

rebuilt or overhauled at Lycoming Engines, Williamsport, PA after March 1, 1971, and TIO-540-A 

series engines that have been modified to incorporate large main bearing dowels as described in the 

latest revision of Service Instruction No. 1225 may be operated to 1800 hours. Engines that do not 

incorporate this modification must not exceed 1500 hours between overhauls.