By Paul R Salmon FCILT, FSCM
When organisations talk about “rightsizing” fleets to save money, there is often an implicit assumption: fewer assets mean lower support costs. But in reality, this logic can backfire. If each unit is worked harder to meet the same demand, spares consumption can rise dramatically. This counterintuitive phenomenon – “reverse spares logic” – is something every supply chain leader needs to understand.
This article explores why smaller fleets often demand bigger spares strategies, and how organisations in both the defence and commercial sectors can avoid being caught out by this trap.
The Temptation of Smaller Fleets
In both defence and commercial contexts, the pressure to “do more with less” is ever-present. Budget constraints, sustainability goals, and the desire to reduce capital costs drive organisations to reduce fleet sizes.
Examples include:
Airlines cutting aircraft types to optimise operations. Defence forces consolidating vehicle fleets for efficiency. Logistics firms switching to smaller electric delivery van fleets.
On paper, a smaller fleet seems to mean lower costs. But this assumption doesn’t account for utilisation rates and the knock-on effects on maintenance and spares demand.
The Reverse Spares Logic Explained
Here’s the core idea:
Fewer Units → Higher Utilisation per Unit Each asset in the fleet must work harder to maintain the same output. Higher Utilisation → Increased Wear and Tear Greater operational tempo accelerates failure rates for critical components. Increased Failure Rates → More Spares Required To keep assets available, spares demand rises – sometimes exponentially.
Real-World Examples
✈ Commercial Aviation
Low-Cost Carriers (LCCs) often achieve high aircraft utilisation (10+ hours/day). While this drives revenue, it also demands robust spares strategies to support increased engine and component wear.
🛡 Defence Vehicle Fleets
Reducing armoured vehicle numbers can make sense in peacetime. But during high-readiness operations, each vehicle may need to cover more ground – driving up the need for consumables, tyres, and repairable spares.
Why It Happens: The Non-Linear Effect
The relationship between fleet size and spares demand is non-linear because:
Failure rates increase with utilisation (e.g., engine hours, mileage). Maintenance intervals compress, requiring more parts in stock. Supply chains must become more agile to avoid mission failure.
This effect is often underestimated during fleet planning, leading to unbudgeted costs and availability shortfalls.
Mitigating the Risk
To avoid falling into the reverse spares logic trap, organisations should:
✅ Model Utilisation Scenarios
Use support modelling tools to understand how different fleet sizes impact spares demand.
✅ Align Inventory with Failure Patterns
Adjust spares provisioning plans for higher usage rates.
✅ Invest in Predictive Maintenance
Leverage condition monitoring to anticipate spares needs in high-tempo environments.
✅ Balance Fleet Size Against Availability Targets
Recognise that there is a trade-off between fewer assets and higher support costs.
Conclusion: Smaller Fleets, Bigger Support Challenges
In the drive for efficiency, it’s easy to assume that a smaller fleet will save money across the board. But unless utilisation rates and spares demand are carefully modelled, organisations risk eroding those savings – or worse, undermining operational readiness.
The lesson is clear: less equipment doesn’t always mean less support effort.
Supply chain and logistics leaders must challenge assumptions and plan spares strategies that reflect the realities of high-utilisation fleets.
Leave a Reply