Phase-based Engineering Execution
Phase-based engineering execution describes how execution progresses through implicit phases of readiness, rather than through formal milestones or document states.
In engineering-driven projects, execution does not advance in discrete steps defined by approvals.
It advances when structural conditions for executability are satisfied.
Phases as readiness transitions
Phases in engineering execution represent transitions in executability.
They describe when an assembly or component:
- moves from conceptual feasibility,
- to structural definition,
- to manufacturing readiness.
These phases are not project phases or stage gates.
They are emergent states reflecting whether execution can proceed without structural instability.
A phase is understood here as a readiness condition, not as a project management construct.
Why milestone-based views misrepresent execution
Milestones and gates are administrative instruments.
They confirm that:
- documents exist,
- approvals are granted,
- or plans are accepted.
They do not confirm that:
- dependencies are resolved,
- interfaces are stabilised,
- or execution constraints are structurally satisfied.
As a result, milestone completion often overstates execution readiness.
Milestones confirm intention.
Phases reflect executability.
Readiness emerges incrementally
Execution readiness does not appear at a single point in time.
It emerges incrementally as:
- definition becomes sufficiently complete,
- dependencies converge structurally,
- and constraints are resolved across assemblies.
Phase-based execution therefore describes gradual transitions, not binary states.
Phase overlap and parallel execution
In complex projects, engineering phases overlap.
Different assemblies may simultaneously occupy different readiness phases:
- some stabilising definition,
- others resolving dependencies,
- others approaching manufacturing readiness.
Phase-based engineering execution accommodates this reality by observing readiness locally, rather than enforcing global phase synchronisation.
Relation to BOM-based planning
Phase-based engineering execution builds on BOM-based planning.
While BOM structure defines what must become executable, phases describe how far executability has progressed for each structural element.
Together, structure and phase provide a multidimensional view of execution readiness.
Relation to Product Flow
Product Flow applies the principle of phase-based engineering execution by modelling readiness transitions explicitly across assemblies and components.
The system does not rely on milestone completion.
It observes how execution phases evolve structurally over time.
Phase-based engineering execution is therefore a core principle underlying Product Flow as an Engineering Execution System.
Relation to other execution principles
Phase-based engineering execution connects multiple principles:
- It complements assembly-driven execution by describing readiness at assembly level.
- It depends on BOM-based planning to anchor phase states structurally.
- It enables visibility and risk analysis by revealing phase misalignment and gaps.