What is the NOx Technical File, and why must the engine's components match it?

flowchart LR
  A["Pre-certification survey"] --> B["Technical File approved: components, settings, allowable ranges"]
  B --> C["EIAPP issued to the engine"]
  C --> D["In service: parameter check at survey, or direct measurement with data within the last 30 days"]
  D --> E{"Components and settings match the File?"}
  E -->|Yes| F["EIAPP valid for the life of the engine"]
  E -->|No| G["EIAPP invalidated: re-verify and re-certify"]

• What it is (NOx TC §2.3.4): every engine over 130 kW carries a Technical File, prepared by the maker and approved at pre-certification: the identity card of its NOx configuration.
• Contents (§2.4.1): the components, settings and operating values that influence NOx (injection, timing, turbocharger, charge-air cooler, combustion chamber, Pmax), their allowable adjustments and alternatives, rated speed and power, and the on-board verification procedures.
• Matching (§6.2.2.1): the parameter check verifies the components fitted and the settings against the File and the EIAPP; spares must be File-approved; settings within the allowable range.
• Alternative (§2.4.5): direct NOx measurement per 6.4, spot checks or continuous monitoring, data within the last 30 days, records on board.
• Mismatch: a non-approved component or an out-of-range setting means the engine is no longer the certified engine: EIAPP invalidated, re-certification.
• As Chief Engineer: fit only File-approved parts, keep timing and settings in range, log every NOx-critical change in the Record Book of Engine Parameters.