MBSE for MIL‑HDBK‑516C and the Road to 516D: A Digital‑First Path to Airworthiness

TL;DR: Modern air systems are too complex for a paper‑first approach to airworthiness. Model‑Based Systems Engineering (MBSE) links MIL‑HDBK‑516C criteria directly to the architecture, so evidence collection is built into the model, not a document hunt. Teams move faster, close gaps, and improve traceability from requirement → design → test. With MIL‑HDBK‑516D aiming to embed Digital Engineering, the teams that have airworthiness data in their system model today will be ready tomorrow, with no last‑minute rush.

Why paper‑first breaks down for 516C

A documentation‑centric process struggles with today’s multi‑disciplinary systems:

• Fragmented evidence across Word, PDFs, and spreadsheets creates review churn and rework.

• Late discovery of gaps when verification artifacts don’t align with the current configuration baseline.

• Limited visibility of changes as requirements and design evolve.

MBSE + MIL‑HDBK‑516C: How it works in practice

Model the system and connect airworthiness criteria to the actual architecture:

• Direct criteria linkage: Map 516C criteria to system components, interfaces, and behaviors so compliance context lives where engineering happens.

• Early Safety‑Critical Function (SCF) identification: Surface SCFs during architecture exploration, not after integration, so design decisions reflect safety from the start.

• Hardware–software integration, modeled: Trace SCFs through hardware elements, software components, and their interfaces to expose integration risks early.

• Verification aligned with Section 15 (Computer Systems & Software): Automatically generate verification plans, test cases, and evidence placeholders from the model, ensuring artifacts stay in sync with change.

• Evidence as first‑class data: Attach analyses, test results, and approvals directly to model elements so reviewers can click from a criterion to its live evidence.

What teams gain

• Faster reviews: Evidence is just one click away from the requirement, and there's no scavenger hunt.

• Fewer gaps: Model‑driven traceability highlights missing tests or misaligned methods of compliance.

• End‑to‑end visibility: Clear linkage from requirement → architecture → verification → results.

Looking ahead: What to expect from MIL‑HDBK‑516D

The next release is expected to emphasize Digital Engineering and a more outcome‑based structure, including:

• A clearer, unified organization of criteria.

• Updated, outcome‑based standards that align more naturally with model artifacts.

• Reorganized Methods of Compliance (MoC) to reflect digital flows.

• A digital‑first approach designed to fit MBSE workflows and the system model as the system of record.

Timeline: Public discussions indicate a rollout between late 2025 and early 2026. Teams actively mapping 516C today should begin modeling now to ensure a smooth transition to 516D.

Start now to be ready later

If your airworthiness data is already integrated into your system model, you’ll be prepared for 516D—without a scramble at release time. The work you do now to model 516C becomes an asset, not a sunk cost.

How Dalus helps

Dalus provides an AI‑powered systems engineering platform purpose‑built for complex, safety‑critical programs:

• System Architecture Modeling: Define components, interfaces, and behaviors with a live, editable system graph.

• Requirements Linking & Constraints: Assign criteria to components and evaluate their status automatically (e.g., In Progress, Complete, Failed) as the model evolves.

• Verification Automation: Generate and maintain verification plans and artifacts aligned with Section 15, tied directly to SCFs and system elements.

• Action Nodes & Simulations: Execute Python scripts against live model data to run analyses, produce evidence, and capture outputs as part of the model record.

• Versioning & Traceability: Track changes, impact analysis, and export reviewer‑ready evidence packages.

If you are currently mapping 516C, start modeling now with Dalus to ensure a smooth transition into 516D.

Frequently asked questions (FAQ)

What’s the fastest way to begin transitioning from 516C to 516D?
Start by modeling your current 516C compliance data—requirements, criteria mappings, SCFs, and verification artifacts—directly in the system model. That foundation will carry forward as 516D formalizes digital‑first practices.

Where do Safety‑Critical Functions (SCFs) fit in the model?
Represent SCFs as properties/behaviors linked to the components and interfaces they traverse. Then connect each SCF to its Methods of Compliance and test evidence.

How does MBSE help with Section 15 (Computer Systems & Software)?
Section 15 demands rigorous alignment between software requirements, architecture, and verification. In MBSE, those relationships are explicit and can drive automatic generation of tests, trace matrices, and evidence.

What changes are expected in Methods of Compliance (MoC) under 516D?
Expect clearer, outcome‑oriented MoCs organized to match digital workflows—making it easier to show how each model element satisfies a criterion with linked evidence.

Will we still need documents?
Yes—but documents become outputs of a continuously updated model, not the primary source of truth.