Jet engines are complex machines that require immaculate servicing and periodic maintenance. Depending on the scope of work, jet engines may spend a few months in the maintenance hangar, costing several million dollars to the airline.
While an operational failure or an in-flight incident may trigger a shop visit, routine maintenance checks are mandatory at regular intervals. This article highlights some of the common reasons for an engine shop visit, typical downtimes, and the cost of maintenance.
Jet engines are prone to having extreme temperatures both on the inside and outside of the engine. Varying operating conditions result in extensive wear on various parts of the engine. The core of the engine, also known as the hot section, is subjected to high operating temperatures. As such, the parts within the hot section are most susceptive to wear.
Hot Section Refurbishment (HSR)
The HSR shop visit is when an engine is removed from the wing due to the life-limited parts (LLPs) approaching their cyclic limits. Another reason for the HSR visit is when the overall condition of the hot section is close to exceeding the airworthiness limits defined in the Aircraft Maintenance Manual (AMM).
In most cases, the entire hot section is disassembled to piece parts, and a maximum level of inspection and repair (where necessary) is performed. After the HSR visit, the engine is capable of achieving its full-time on wing. An HSR visit may require the engine to spend anywhere between 60 and 120 days in the shop. Depending on the size and condition of the engine, the HSR visit costs between $3 million and $12 million.
Special project visit
Engines that come in the maintenance shop due to specific reasons, such as foreign object debris (FOD) damage, including bird strikes, or oil or hydraulic fluid leaks are maintained under the special project category. MRO focuses on repairing the special damage while minimizing disassembly and inspection of the remainder of the engine.
The on-wing health of the engine must be satisfactory to qualify the engine for the special project visit. Such visits are quick and take between 3 and 12 weeks in the shop. The cost of such visits, while significantly varies based on the extent of work, maybe in the range of $500,000 and $2.5 million.
Miscellaneous repair visit
The engine may be removed from the wing for miscellaneous repair, particularly when disassembly of one or more modules is required. This requirement can be driven by a higher-than-normal EGT margin or other hardware conditions. The time and cost of such visits are determined on a case-to-case basis and contracted between the parties.
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Other visits
Other factors including a complete teardown of the engine, end-of-lease restoration, or planned retirement may also bring the engine for a shop visit. Such engines spend a relatively shorter time in the shop due to the limited scope of work. For example, a planned retirement engine may only go through the disassembly process for salvaging critical parts.
What are your thoughts on various work scopes and costs of engine maintenance? Tell us in the comments section.