POS INIT — Aligning the IRS

beginner
📍 Route: POS INIT · EGLL⏱ ~3 minutes📊 4 steps

Before the FMC will work, the inertial reference system (IRS) must be aligned with a known position. Learn where POS INIT lives, how to enter the reference airport, and how to set the IRS position to start alignment.

Start this scenario

Open the SimTuts 737 CDU trainer and select “POS INIT — Aligning the IRS” from the scenarios list to walk through it step-by-step on the simulated keypad.

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What you'll do

  1. Open the INIT REF index. Press the INIT REF key.
  2. Open POS INIT. Press 2L (<POS INIT).
  3. Enter the reference airport. Type EGLL and press 2L (REF AIRPORT).
  4. Set the IRS position to start alignment. Press 5R (SET IRS POS).

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