If you fly a Lycoming-powered aircraft, this is not a drill: the Lycoming connecting rod bushing AD — officially designated AD 2026-04-11 — went into effect on April 8, 2026. Moreover, the FAA estimates this directive covers approximately 45,152 engines on U.S.-registered aircraft. Additionally, this updated AD supersedes the earlier AD 2024-21-02, expanding both the scope of affected engine serial numbers and the list of eligible replacement parts. For GA owner-operators, understanding this directive and taking prompt action isn’t optional. Here is exactly what you need to know.
What Is AD 2026-04-11 and Why Did the FAA Issue It?
The FAA issues airworthiness directives as legally enforceable regulations to correct unsafe conditions in certificated aircraft, engines, propellers, and appliances. Consequently, when the FAA issues an AD, compliance is mandatory — not optional, not suggested. First issued under the predecessor AD 2024-21-02, this directive addresses a serious and documented safety problem with certain Lycoming connecting rod bushings.
Specifically, the FAA acted after receiving multiple reports of connecting rod failures resulting in uncontained engine failures and in-flight shutdowns (IFSDs). In other words, these weren’t minor malfunctions. Furthermore, connecting rod failures can cause catastrophic engine damage where fragments penetrate the engine case. As a result, the risk to aircraft and occupants is severe.
The Connecting Rod Bushing: What It Does and Why It Matters
The connecting rod is one of the most critical components in a reciprocating engine. Essentially, it links each piston to the crankshaft, converting the linear movement of the piston into the rotational force that turns the propeller. The bushing is a small bronze sleeve that fits at the wrist pin end of the connecting rod, providing a wear surface for the piston pin.
However, when that bushing fails — through wear, improper fit, or material defect — the damage cascade is fast and severe. First, the bushing deteriorates and sheds bronze particulates into the engine oil. Then, the connecting rod itself becomes vulnerable to movement and misalignment. Finally, without intervention, a full connecting rod failure can follow, with devastating consequences. That’s exactly why the FAA mandates repetitive inspections under this AD.
Which Lycoming Engines Are Affected?
The scope of AD 2026-04-11 is broad. Moreover, the FAA explicitly expanded the ship date range compared to the earlier AD 2024-21-02. Specifically, parts shipped between January 30, 2009 and September 9, 2021 fall within the affected range. Therefore, many aircraft built or re-engined during that period may be subject to this AD.
The affected Lycoming engine series include:
- O-235, O-290, O-320, and O-340 series
- O-360, IO-360, and AEIO-360 series
- O-435 and O-540 series
- IO-540, AEIO-540, and SO-580 series
- TIO-360, TIO-540, and TEO-540 series
- TIGO-541, TVO-435, TVO-540, and TIVO-540 series
- VO-360, VO-435, and TO-360 series
Furthermore, the AD targets connecting rod bushings with Part Number (P/N) 01K28983 or AEL13923. Additionally, the AD also covers certain connecting rod assemblies: P/N AEL11750, AEL78030, SL78030, SL77450, SL13937, SL19332, SL11750, and SL13422.
Which Aircraft Are Most Commonly Affected?
These engine series power a large portion of the GA fleet. For example, the O-360 and IO-360 series power the Cessna 172S, Piper Warrior III, Piper Cherokee Arrow, and countless Van’s RV homebuilts. Similarly, the O-540 and IO-540 series power aircraft like the Cessna 182, Piper PA-32 Cherokee Six, and Piper Seneca. Additionally, O-320 engines power thousands of older Cessna 172s and Piper Cherokee 140s. Therefore, if you own virtually any single-engine piston aircraft built or re-engined in the last 15 years, there’s a meaningful chance your engine falls within the affected range.
However, part number and ship date determine applicability — not the engine model series alone. Therefore, the definitive way to confirm whether your engine falls under the Lycoming connecting rod bushing AD is to check your engine logbook and cross-reference with the full AD document. Specifically, verify whether your connecting rod bushings match the affected P/Ns and fall within the January 2009 to September 2021 ship date window. When in doubt, consult your A&P or contact Lycoming directly through their Knowledge Base portal.
What the Lycoming Connecting Rod Bushing AD Requires
Understanding the Lycoming connecting rod bushing AD compliance requirements means breaking the directive into three distinct action items: the routine oil inspection, the bushing inspection triggered by bronze findings, and the final bushing replacement. Furthermore, each action has its own timeline and triggering conditions.
Step 1 — The Mandatory Oil Filter and Screen Inspection
First, at the next oil change or within four months of April 8, 2026 — whichever comes first — perform a visual inspection of the engine oil filter, the oil pressure screen, and the oil suction screen. Moreover, repeat this inspection at every subsequent oil change until you complete and document the bushing replacement.
Specifically, you’re looking for bronze metal particulates. Lycoming makes the connecting rod bushing from bronze. Therefore, bronze flakes or particles in the oil system give you the first direct warning that a bushing may be failing. Additionally, if your aircraft is on a 50-hour oil change interval, you’ll run this inspection frequently — which is actually a good thing. Catching the problem early beats allowing it to progress undetected.
Practically speaking, most A&Ps already inspect the oil filter during routine oil service. However, this AD formalizes and mandates that inspection specifically for bronze particulates and adds the requirement to check both the oil pressure and suction screens as well. Consequently, confirm with your shop that each oil service entry clearly documents AD 2026-04-11 compliance by name and designation.
Step 2 — What to Do If You Find Bronze Particulates
Finding bronze in your oil means one thing: ground the aircraft immediately. Specifically, before further flight, inspect all affected connecting rod bushings for damage — deterioration, missing metal, improper fit, movement, and excessive wear. Perform this inspection per Lycoming Mandatory Service Bulletin 630, updated as SB630B.
Furthermore, if any bushing fails the inspection, replace the affected bushing with P/N 01K28983 before further flight. Both the AD and Lycoming Service Instruction SI1575A — which Lycoming revised in February 2026 — specify this as the approved replacement part. Additionally, do not burnish the new bushing after installation. Lycoming specifically warns that burnishing can cause damage. Therefore, make absolutely sure your A&P follows SI1575A exactly as written.
The Lycoming Connecting Rod Bushing AD Compliance Timeline
To summarize the compliance schedule in plain terms:
- Initial inspection deadline: Next oil change OR by August 8, 2026 — whichever comes first
- Recurring inspection: Every oil change thereafter, until you complete and document the bushing replacement
- Bronze particulates found: Ground immediately; bushing inspection and replacement required before next flight
- No bronze found: Continue recurring oil change inspections; document AD compliance in maintenance records every time
- Bushing replacement complete: Recurring oil inspections for this AD are no longer required — document the terminating action clearly
Moreover, if your A&P replaced the connecting rod bushings with P/N 01K28983 before April 8, 2026 and properly documented that work in the logbook, you may already satisfy the terminating action. However, confirm this with your A&P and verify it directly against the AD text before treating your aircraft as fully compliant.
Why Connecting Rod Failures Are a Catastrophic Risk
To understand why the FAA treats this as a mandatory priority, it helps to understand what actually happens when a connecting rod fails in a reciprocating engine. First, the failure is typically sudden and violent. Additionally, because the connecting rod travels at high speed under extreme combustion loads, a failure doesn’t simply stop the engine. Instead, it destroys it from the inside out.
Uncontained Engine Failures — The Real Danger
An uncontained engine failure means fragments from inside the engine penetrate through the engine case and exit the airframe. Consequently, this creates a direct threat to fuel lines, aircraft structure, and the people on board. Furthermore, the failure can damage the crankshaft, causing propeller separation. In-flight shutdowns — even those that stop short of full fragmentation — create immediate emergency situations, particularly during takeoff, initial climb, or low-altitude flight.
Notably, the FAA’s language in AD 2026-04-11 is explicit: failure to address this condition could result in engine failure, an in-flight shutdown, and loss of control of the aircraft. Therefore, this is not a bureaucratic paperwork problem. It is a genuine safety issue with documented real-world failure events behind it. Additionally, connecting rod bushing-related failures have contributed to GA accidents in prior years, which is precisely why the FAA tightened the compliance requirements under this expanded directive.
How AD 2026-04-11 Expands on the Original AD 2024-21-02
The original AD 2024-21-02, issued in November 2024, established the initial framework for the Lycoming connecting rod bushing AD risk. However, since that directive, the FAA gathered additional service data about the failure mode and its scope. Consequently, the 2026 update reflects that expanded understanding in several important ways.
Key Changes Aircraft Owners Need to Know
First, the FAA significantly expanded the ship date range for affected parts. Specifically, the original 2024 AD covered a narrower date window, while AD 2026-04-11 extends coverage to parts shipped through September 9, 2021. Additionally, Lycoming identified more connecting rod assembly part numbers subject to the AD’s requirements. Furthermore, Lycoming revised their Service Instruction — releasing SI1575A in February 2026 — which governs the approved bushing installation procedure the new directive references.
Therefore, even if you went through the compliance process under AD 2024-21-02 and have logbook documentation, review whether your engine falls within the expanded ship date range of the 2026 update. Specifically, some owners whose engines the original AD did not cover may now find themselves subject to AD 2026-04-11 for the first time. When in doubt, cross-reference directly with the full AD text on the FAA’s Dynamic Regulatory System and consult your A&P.
What Will This Cost You?
Let’s be direct: no one wants an unexpected maintenance bill. However, understanding the financial scope upfront helps you plan intelligently and have an informed conversation with your shop.
The Oil Inspection Cost Is Minimal
First, if your A&P already inspects the oil filter during routine oil service — which reputable shops do — the incremental cost of AD compliance is minimal. Specifically, checking the oil pressure and suction screens and logging the inspection typically adds 20 to 30 minutes to your oil change. Consequently, expect an additional $30–$75 at most shops, primarily for documentation and the added screen checks.
Bushing Replacement Costs Are Significant
However, if you find bronze particulates and bushing replacement is necessary, costs escalate considerably. Furthermore, costs vary based on the number of cylinders and your shop’s labor rate. Based on Lycoming service data and industry experience:
- Four-cylinder engines (O-320, O-360, IO-360): Approximately $1,200–$3,500 in labor, plus parts
- Six-cylinder engines (O-540, IO-540, TIO-540): Approximately $2,500–$6,000+ in labor, plus parts
- Eight-cylinder engines (IO-720): Can exceed $7,000–$9,000 in total labor
Additionally, Lycoming’s Service Bulletin 632 historically allocated 12 labor hours for a four-cylinder bushing replacement and 16 labor hours for a six-cylinder engine. Therefore, at current shop rates of $120–$200 per hour, budget accordingly. Moreover, the replacement bushing P/N 01K28983 runs $15–$50 per bushing. Consequently, a four-cylinder engine needs four replacement bushings if all require replacement.
Finally, some owners may have Lycoming warranty coverage depending on when their engine was manufactured, overhauled, or rebuilt. Therefore, contact Lycoming directly if your engine is relatively new before authorizing any paid repair work.
Your Action Plan: Staying Compliant Step by Step
Here is a clear, actionable plan for GA owner-operators to navigate compliance with the Lycoming connecting rod bushing AD efficiently and without last-minute scrambling.
Step 1 — Confirm Whether Your Engine Is Affected
First, pull your engine logbook and identify your engine’s model and serial number. Then, cross-reference with the full AD 2026-04-11 document on the FAA’s Dynamic Regulatory System and the Federal Register. Specifically, check whether your connecting rod bushings match the affected P/Ns (01K28983 or AEL13923) and fall within the ship date range of January 30, 2009 through September 9, 2021. Additionally, if your engine has had an overhaul, the overhaul shop should have documented the connecting rod assembly they installed — check those records as well.
Step 2 — Schedule Your AD-Compliant Oil Change Now
Second, contact your A&P or maintenance shop immediately. Moreover, given that many reputable GA shops are currently booking six to twelve months out due to the worsening A&P mechanic shortage, don’t approach the four-month compliance deadline with no appointment in sight. Therefore, schedule proactively. Furthermore, let your shop know you need AD 2026-04-11 compliance documented during the oil service so they can pull the correct Lycoming service documents in advance.
Step 3 — Demand Proper Logbook Documentation
Third, ensure your A&P makes a thorough logbook entry for each AD-compliant inspection. Specifically, the entry should reference AD 2026-04-11 by designation, confirm that your A&P inspected the oil filter and screens for bronze metal particulates, note the findings clearly, and include the date and tach time. Additionally, this documentation protects you during any subsequent resale and any FAA ramp check. Consequently, vague or missing AD documentation creates problems you don’t want later.
Step 4 — Know the Grounding Trigger
Fourth, and most importantly, understand the bright line: if any bronze particulates turn up during any inspection, ground the aircraft before further flight. Therefore, do not fly the aircraft to a different maintenance facility for the follow-up bushing inspection. Instead, have your A&P perform the SB630B inspection on-site and document the findings thoroughly. Finally, if bushing replacement is necessary, keep the aircraft grounded until your A&P completes the work using the approved parts and installation procedure under Lycoming SI1575A.
Frequently Asked Questions About AD 2026-04-11
Does the Lycoming connecting rod bushing AD apply to my experimental homebuilt aircraft?
Technically, airworthiness directives apply to type-certificated aircraft only. Therefore, if you fly an experimental amateur-built aircraft with a Lycoming engine, you have no legal obligation to comply with AD 2026-04-11. However, the underlying safety logic applies regardless of your aircraft’s certification category. Furthermore, the FAA strongly encourages experimental owners to follow applicable safety directives voluntarily. Consequently, if your experimental has a Lycoming with connecting rod bushings within the affected P/Ns and ship dates, running the AD’s inspections is simply sound airmanship.
How do I know if my engine already has compliant bushings installed?
First, check your engine logbook for any entries referencing Lycoming SB630, SB630B, SI1575, SI1575A, or AD 2024-21-02. Additionally, look specifically for any entry noting connecting rod bushing replacement with P/N 01K28983. Furthermore, if your engine underwent a factory overhaul or new engine delivery after mid-2021, there’s a higher likelihood the factory or overhaul shop already installed compliant bushings. However, always confirm with written documentation rather than assumption. When the logbook is silent, treat your engine as potentially affected until you confirm otherwise.
Will Lycoming cover any replacement costs under warranty?
Lycoming’s warranty coverage depends on your specific situation — when your engine was manufactured, overhauled, or rebuilt and whether you are the original purchaser. Therefore, contact Lycoming directly through their Customer Service line or Knowledge Base portal before authorizing any paid repair work. Additionally, some owners who had their engines overhauled by a Lycoming Authorized Engine Distributor during the affected production period have reported receiving partial labor consideration. However, results vary significantly, so get direct, written confirmation from Lycoming before counting on it.
Sources
- Federal Register — AD 2026-04-11: Airworthiness Directives; Lycoming Engines (March 4, 2026)
- Justia Regulation Tracker — AD 2026-04-11 Lycoming Engines
- Civil Air Patrol — AD 2026-04-11 Lycoming Connecting Rod Bushings
- FAA Dynamic Regulatory System — AD 2026-04-11 Full Text
- Lycoming SB630B — Connecting Rod Bushing Inspection Procedure
- Lycoming SI1575A — New Connecting Rod Bushing Installation Instructions (February 2026)
- Van’s Air Force Forum — Community Discussion: New Lycoming AD for Connecting Rod Assemblies
Staying current on airworthiness directives is one of the most important — and legally required — responsibilities of aircraft ownership. For more coverage of GA maintenance news, regulatory updates, and owner-operator guidance, visit the E3 Aviation Articles page. And for in-depth video content on the topics that matter most to pilots who fly and own their aircraft, subscribe to the E3 Aviation YouTube channel at @E3AviationAssociation.
