There is an old adage in aviation that there is no such thing as an aircraft, just a collection of parts which happened to be joined together at a particular time with the ability to fly from one place to another.

There are hundreds of thousands of parts in an aircraft and it’s arguable that the highest concentration of those can be found in the whole powerplant system – engines, dressing and nacelle. Ensuring that every one of those parts is in an airworthy condition is vital, so keeping spares at hand is necessary at all times.

The problem with holding a stick of parts is that it ties up capital, which given the competitiveness of the airline industry is not ideal. So there is a constant effort to reduce the number of spare parts in stores and to exercise tighter management of spares in the supply chain.

Of course, there has to be a capital outlay for the initial provisioning required when inducting an engine into the fleet, but the task then is to maintain an appropriate level of spares throughout the operational life of the engine without overstocking and having money ostensibly sat on the shelf. There are a number of ways to minimize this scenario.

The first, as noted, is to ensure that the source for any spare component is part of a well-run supply chain. The result would be to have enough stock to handle replacing engine parts with either new parts (the majority of which would be consumables) or repaired and refurbished parts (rotables).

That, however, may not keep costs down enough. For even a medium-sized operator, further reductions in the costs of spares are required, which is where the pooling of parts becomes a useful strategy.

One way this can be done is for a number of airlines requiring similar parts to purchase their spares together in order to benefit from economies of scale. While many may find this unusual, while the marketing teams of airline compete vigorously, those involved in maintaining the safety of flight operations often exchange helpful information.

Pooling among carriers may reduce purchase prices, but for rotable parts, the costs of their repair and overhaul also have to be considered. This is when a pool of parts held and handled by a third party becomes an option. The third party will take in a part from an airline, send a replacement (new or refurbished) from its own pool and, at the same time, arrange for the airline’s part to go to an authorized repair and overhaul facility. Once repaired, that part will go back into the third party’s pool.

The whole premise is to guarantee component availability from a single partner resulting in predictable costs for the airline. A potential obstacle to this is when an engine is leased. Lessors almost always want to ensure that parts from the pool which replace an OEM original are also OEM originals, albeit potentially repaired and/or overhauled. As parts supplier Locatory has noted, “Lessors are naturally wary of their aircraft coming back in substandard condition. Therefore, terms like ‘no pooled parts’ aboard an aircraft are often motivated by the potential risk to the residual asset value of that aircraft.”

Logic then, has led to OEMs themselves setting up parts pools as part of their now wide range of aftermarket services. Not only would the parts be original equipment, but any maintenance on them would come with the OEM’s stamp of approval.

For customers of GE Aviation and CFM, one of the services within the TRUEngine program is the place to look for parts pooling. TrueChoice Material is the plan that offers high-quality OEM new and used parts. Moreover, as the company notes, “advanced repairs and technology upgrades for airlines and MROs is in our DNA”.

Clearly, an OEM has an advantage by having designed and manufactured a component, which is heightened when a part is mission critical, as many engine parts are. Hence GE’s claim that it is in the best position to understand “how each part within a complex engine system interacts with the others”. And the outcome is improved time-on-wing and a reduction in disruptive events.

Pratt & Whitney offers a similar service through the EngineWise Materials section of its overarching EngineWise program. Again, the service provides the new or surplus material approved by the OEM and also offers fully managed programs including the repair and overhaul of parts.

Within Rolls-Royce’s TotalCare core services, an Engine Logistics Management module covers this area, with the optional Spare Engine Services offering “planned and emergency spare engine leasing, either via dedicated spare engines or via access to shared engine pools”.

Thus, throughout the lifecycle of an engine, no part needs to be out of place when the time comes for it to be one of that collection of parts joined together and ready to fly.