# Decision: RotatingMachine Hydraulic Efficiency Correction and Prediction Confidence

- Date: 2026-02-24
- Scope: `nodes/rotatingMachine/src/specificClass.js`, rotatingMachine integration tests

## Context
Hydraulic efficiency calculation in `rotatingMachine` was dimensionally inconsistent and could over/under-report efficiency KPIs.  
At the same time, prediction drift tooling (`nrmse`) existed but was not actively connected to rotatingMachine output confidence.

## Options Considered
1. Keep existing formula and only tune thresholds.
2. Replace formula with standard hydraulic power/efficiency equations and expose prediction confidence from live pressure source + drift.

## Decision
Adopt option 2.

- Hydraulic power now follows standard engineering relation:
  - `P_h = Q * Δp` (equivalent to `ρ g Q H`)
  - `η_h = P_h / P_in`
- RotatingMachine now computes flow drift via `nrmse` from measured vs predicted flow windows.
- RotatingMachine now exposes prediction confidence fields in output:
  - `predictionQuality`
  - `predictionConfidence`
  - `predictionPressureSource`
  - `predictionFlags`

## Consequences
- Efficiency KPIs become physically interpretable and traceable to pressure/flow/power inputs.
- Prediction trust is now observable by downstream control/dashboard layers.
- Output schema is expanded with new prediction confidence fields.

## Rollback / Migration Notes
- Rollback path: revert `specificClass.js` hydraulic block and prediction-health integration.
- No mandatory migration required for existing flows unless they choose to consume new prediction confidence fields.