Why Inventory Strategy Matters Just As Much As Repair Skills for Simulator Reliability
- Daniel de Vries
- Dec 26, 2025
- 8 min read
Simulators (in all their various flavours) are the backbone of modern aviation training. They provide the immersive, highly realistic environment where pilots build the skills necessary for safety and proficiency. To keep these high value assets running, operators continue to invest heavily in technicians, engineers and maintenance schedules.
However, within this framework of support lies a challenge that is often overlooked until it causes a crisis - the complex task of managing the procurement and inventory Strategy of flight simulator spare parts.
Maintenance usually keeps a simulator compliant and operational, but if there is a problem with the availability of parts; it all goes out the window. This aspect of operations is fundamental to reliability and directly impacts training fidelity, safety, and your bottom line.
The Interconnected Sub-Systems of a Simulator
To understand why inventory management can be such a challenge, we first need to look at the architecture of the machines in question. A flight simulator is not a single homogenous device per se; it is a system of interconnected sub-systems, all of which must perform exactly as designed or else risk underperformance, or even negative training.
Some sub-systems include:
Simulated Cockpit: Replicates the actual aircraft controls, instruments, and switches.
Motion System: Provides the physical sensation of flight (acceleration, turbulence).
Visual System: Generates and displays the external world, terrain, and weather.
Compute System: The "brain" that drives the simulation and manages data exchange.
Instructor Operator Station: Allows instructors to control scenarios and monitor performance.
A malfunction or intermittent operation in just one component within any of these sub-systems can render the entire device unfit for training (i.e. downtime). Because simulators are in constant use (often operating close to 24/7) the wear and tear is substantial. The frequency of failures naturally increases with accumulated operational time, creating a constant, demand for replacement parts that isn't always 'top of mind'.
Sourcing and Procurement Difficulties
While the need for spare parts is obvious to even the most inexperienced operator, getting them becomes increasingly difficult over time. Supply chains are facing a perfect storm of challenges that can leave expensive simulators grounded for significant periods of time.
Diminishing Manufacturing Sources (DMSMS)
A major hurdle is Diminishing Manufacturing Sources and Material Shortages (DMSMS). This occurs when Original Equipment Manufacturers (OEMs) and other vendors stop producing specific parts.
Simulators often have operational lifecycles of 15-20 years, but the electronic components inside them may have a lifecycle of only 3-5 years (if you're lucky). This mismatch creates rapid obsolescence - one of the biggest issues faced by simulator operators over time. It is particularly troublesome for older simulator models, where critical components are no longer available through normal channels - or sometimes, at all.
Supply Chain Complexity
Adding to the difficulty is the nature of the parts themselves. Many simulator components are aviation specific, military specification, or otherwise highly specialised. They often have no local suppliers in some parts of the world, requiring importation (increasing cost and lead time). This adds layers of complexity:
Reduced Supplier Base: The number of reliable suppliers is decreasing, limiting options.
Lead Times: Administrative procedures, customs, and shipping can cause significant delays.
Obsolescence: You may find that a reliable supplier has exited the market just when you need a critical replacement.
The Consequences of an Empty Shelf
What happens when you cannot source a part in time? The consequences cascade through the entire training program, leading to:
1. Degraded Reliability
If you cannot get the part, you cannot do the maintenance. This inability to conduct necessary repairs leads to a cumulative decrease in simulator reliability. A device that frequently faults cannot provide the consistent training environment required for regulatory compliance.
2. Training Disruption
This is the most visible impact. Pilot training outcomes are directly affected, leading to delayed qualifications and proficiency checks. In a tight pilot market, delaying a cohort because a simulator is offline is a massive operational failure.
3. Financial and Regulatory Penalties
Beyond the immediate loss of revenue, unaddressed faults can cause more severe issues within the system, increasing long-term repair costs. In extreme cases, falling short on compliance due to missing parts can lead to the suspension of the device’s qualification by the regulator.
System Dynamics
How do we solve this? Well ideally, we use data to drive decisions. Using System Dynamics (SD) modelling, we can view maintenance not just as a list of tasks, but as a set of interconnected variables; operations, part substitution, and inventory strategies.
Simulations derived from these models have revealed a critical insight for training centres:
The effect of backup supply on reliability is stronger than the effect of operating time.
We often assume that running a simulator for more hours is the main driver of failure. However, the data suggests that while usage causes wear, the availability of parts to address that wear has a much bigger impact on overall reliability. How?
Increased Backup Supply ensures timely maintenance and sustains long-term reliability.
Decreased Backup Supply prevents timely maintenance, leading to an increase in downtime.
Strategies for Effective Inventory Strategy Management
Given the stakes, a passive buy it when it breaks approach and replenish when you can, is not viable. You need a systematic strategy.
Spare Parts Assessment
The first step is a rigorous audit. Analyse your complete spare parts list against your current operations. Which parts are critical? Which are at risk of obsolescence? This proactive assessment helps you identify shortages early, allowing you to source "at-risk" parts before they become a crisis. This isn't a 'one and done' kind of task either, it's a continuous and ongoing requirement to stay on top of changes in near realtime.
Robust Spare Parts Policies
Developing a strong spare parts holding and management policy is essential. The benefits include:
Immediate Readiness: If done well, parts are available the moment they are needed, preventing downtime.
Reduced Admin: You decrease the scramble of emergency procurement, shipping, and any customs clearances required.
Cost Avoidance: You avoid the premium costs associated with rushing parts from overseas and other more expensive suppliers.
Fighting Obsolescence
To reduce the risk of obsolescence, you must be active. This means systematically analysing suppliers to detect who might be leaving the market at the very least. It may require finding suitable substitutes, preparing alternative manufacturing processes, or working with independent partners to engineer custom solutions for obsolete components.
Integration with Maintenance Planning
Finally, effective parts management must be integrated into your broader simulator maintenance planning.
Training slots are often booked months in advance. Maintenance windows are tight. If you have the right part available at the right time, maintenance can be performed efficiently within those windows.
Looking ahead, we are seeing the rise of AI-driven predictive maintenance. These technologies could help us predict when a part might fail and schedule its own replacement. But even with AI, human expertise remains critical to ensure the high levels of availability that this industry demands.
Summing Up
Managing inventory and strategic sourcing is one of the most significant factors to consider when attempting to impact your simulator's reliability. From the motion system to the IOS, every sub-system matters. By moving from a reactive approach to a proactive strategy, managing the challenge of supply chains and obsolescence, you reduce the risks of your training centre becoming non-compliant; leading to be more efficient, and remain ready for the next batch of pilots coming through for training.
FAQs
What advantage does just in case inventory management have over just-in-time inventory management?
In general manufacturing, Just-in-Time (JIT) is praised for reducing storage costs. However, in the aviation training industry, Just-in-Case (JIC) is often the superior strategy for critical systems.
The primary advantage of JIC is operational resilience.
Immediate Recovery: As noted in the blog, System Dynamics modelling shows that backup supply availability has a stronger impact on reliability than operating hours. When a critical part fails, a JIC approach means the replacement is already on the shelf, reducing downtime from days (or weeks) to mere hours (or minutes).
Insulation from Supply Chain Shocks: JIT relies on a perfect supply chain. Aviation supply chains are rarely perfect; they are plagued by customs delays, DMSMS (obsolescence), and long lead times. JIC acts as an insurance policy against these external disruptions.
Cost of Downtime vs. Cost of Holding: The cost of storing a spare circuit board is negligible compared to the revenue loss of cancelling a week of Type Rating training because that board failed and the replacement is stuck in transit.
Why is it important to maintain accurate records in inventory systems?
Accurate record-keeping is the most important data input process to ensure you can extract meaningful insights from your inventory data; it is also a regulatory and operational necessity.
Predictive Maintenance: You can't manage what you don't measure. Accurate historical data on part usage allows you to identify failure trends. If you know a specific power supply tends to fail every 18 months, you can stock it in month 17.
Regulatory Compliance (ESL): As we move toward the FSTD Capability Signature (FCS), maintaining the integrity of your Equipment Specification List (ESL) is vital. You must be able to prove to the regulator that the replacement part installed won't impact the fidelity level required by your device's qualification.
Wasted Expenditure: Inaccurate records lead to "phantom inventory" (thinking you have a part when you don't) or redundant purchasing (buying a part you already have hidden on a shelf); adding either cost or risk to your operations.
How do you manage obsolescence in your simulator?
Managing obsolescence and DMSMS (Diminishing Manufacturing Sources and Material Shortages), requires a proactive and ongoing approach.
Audit and Identify: Regularly audit your Bill of Materials (BOM) against current market availability. Identify "high-risk" components; usually aging electronics or proprietary vendor parts.
Lifetime Buys: When a supplier issues a "Last Time Buy" notice, calculate the remaining life of your simulator and buy enough stock to last until the device is retired.
Engineering Alternatives: Do not rely solely on the original manufacturer. Work with independent maintenance partners to find modern equivalents or Form-Fit-Function (FFF) replacements that meet the technical requirements without needing the original supplier.
Cannibalisation Strategy: In some cases for legacy fleets, secure a decommissioned simulator of the same type to harvest parts; though this is mostly a temporary fix, and not a long-term solution (unless you're only looking to operate for a limited extra time).
How do you optimise your spares holdings for both cost and risk?
You cannot afford to stock everything, so you must find the "Goldilocks" zone. This is done through criticality analysis.
Categorise Your Parts:
Category A (Training Stoppers): If this fails, the simulator stops. (e.g., Visual System Projector, Host Computer, Motion Actuator). Strategy: Must have on-site (Just-in-Case). High stock level.
Category B (Degraded but Operational): If this fails, training can continue with restrictions. (e.g., A specific bulb, a non-essential panel light). Strategy: Low stock level or fast-ship agreement with a supplier.
Category C (Cosmetic/Non-Essential): (e.g., Upholstery, trim). Strategy: Order on demand (Just-in-Time).
Use Data (MTBF): Look at the Mean Time Between Failures. If a "Category A" part has a high failure rate, your stock holding should be higher. If it fails once every 10 years, one spare is likely enough. A hot tip for simulator operators though: MTBF data supplied by vendors is often inaccurate in the environments that simulators operate within - so don't take them as gospel.
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