# 6.7 Crosscheck Concept

Every critical input must be:

1. Entered by PF
2. Verified by PM

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</div>### Core Rule

**“Garbage in → Garbage out.”**

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</div>### Key Principle

The MCDU is a tool:

- It supports the pilot
- It does not replace decision-making

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</div>### Outcome

A correctly programmed MCDU ensures:

- Accurate navigation
- Efficient flight profile
- Reduced workload