Engine on condition
Most aircraft engines have a manufacturer-specified Time Between Overhaul (TBO), typically expressed in both flight hours and calendar years. Once these limits are reached, the engine is generally required to undergo a full overhaul.
However, if an owner chooses to continue operating the engine safely beyond these limits, it enters an “On-Condition” (O/C) status. In this situation, the airworthiness of the engine is determined by its physical condition during frequent, specialized inspections rather than by fixed time limits.
Managing an On-Condition engine requires strict adherence to the 6-month inspection cycle and utilization hours.
Regulations and Requirements
Since 2009, EASA has implemented specific limitations on O/C maintenance for piston engines. In response, the Dutch authorities published Maintenance Directive MD-NL2010-001, which outlines the mandatory requirements for operating engines beyond their TBO.
Applicability: This applies to all PH-registered aircraft with an EASA or ICAO Standard Certificate of Airworthiness (CofA) operating an engine past its TBO.
Mandatory Requirements for the Owner/Operator
To remain compliant and ensure the renewal of your Airworthiness Certificate, the following operational requirements must be met:
Oil Analysis: At least 6 consistent oil analyses must be performed before the engine reaches its TBO.
Monthly Utilization: A minimum of 1 continuous flight hour per month.
Bi-Annual Utilization: A minimum of 15 flight hours every 6 months.
Periodic Inspections: A specialized O/C engine inspection must be performed every 6 months.
Our Approved O/C Maintenance Programs
Vliegwerk Holland has developed comprehensive, government-approved O/C maintenance programs for nearly all Lycoming and Continental (TCM) engines. Our programs are designed for easy integration into your current Aircraft Maintenance Program (AMP).
What is covered? Our programs are thorough, covering not only the core engine but also:
Fuel and Fuel-Injection systems
Magnetos
Starters and Alternators/Generators (separate O/C programs are available for non-standard installations).
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