CDU Pages Tour
beginnerA tour of the 737 CDU with nothing to type: where each page lives, so that later scenarios can say "go to LEGS" and mean something.
What this scenario covers
The Boeing CDU is organised around a handful of hard keys — INIT REF, RTE, LEGS, DEP/ARR, PERF INIT, PROG, HOLD, N1 LIMIT and MENU — each of which opens a page or a family of pages. Unlike a modern touchscreen, there is no discovery: you either know the key or you do not.
This scenario visits the major pages in sequence. IDENT confirms the database and model, RTE holds the route, PERF INIT the weights and performance, LEGS the waypoint-by-waypoint detail, and MENU is the way out to the other systems that share the box.
How it applies in flight ops
Boeing's layout reflects the order of work: INIT REF and RTE at the gate, LEGS and PROG in the air, DEP/ARR at both ends. Crews build the muscle memory early in type training and it survives fleet changes within the family.
Knowing where things are is also error-defence. When something on the display looks wrong, the fast question is "which page owns this number?" — and on the 737 the answer is nearly always a single page.
Start this scenario
Open the SimTuts 737 CDU trainer and select “CDU Pages Tour” from the scenarios list to walk through it step-by-step on the simulated keypad.
Open trainer →Step-by-step: CDU Pages Tour
- You start on IDENT. Navigate to RTE to see where the flight plan lives.
RTE (Route) is where you enter origin, destination, and the route between them. After IDENT, this is the first page every flight visits. Companies that use saved company routes type the route code here; otherwise you build the route on LEGS.
- Go to the PERF INIT page. PERF INIT holds the performance setup.
PERF INIT (Performance Initialisation) is where you enter cruise altitude, cost index, zero fuel weight, and fuel reserves. The FMC needs all of this before it can compute trip fuel and predictions. Required before takeoff.
- Go to the LEGS page. LEGS shows each waypoint of the route with predictions.
LEGS is the in-flight version of the flight plan — every waypoint with altitude and speed constraints, and predicted ETA / fuel at each one. ATC reroutes are entered here. This is the page you look at most after departure.
- Open the MENU page. MENU is the FMC system index.
MENU is the FMC system page — it lists every subsystem the CDU can talk to (FMC, ACARS, MAINTENANCE). On the ground you use it for the FMC self-test. In flight you rarely need it, but knowing where it lives means you can return to a known state if you get lost in nested pages.
- Return to the IDENT page to complete the tour.
The CDU has more pages than these five — DEP/ARR, HOLD, N1 LIMIT, FIX, PROG — but you can fly a complete flight using just the five you have just toured. Master these first; the others are extensions.
What to take away
- Each major CDU function has its own hard key — there is no menu tree.
- IDENT verifies the navigation database; check its validity dates.
- RTE and PERF INIT are gate work; LEGS and PROG are in-flight work.
- Learn the layout first and every later scenario gets faster.
The rest of Foundations
ROUTE Page Basics
beginnerRTE and PERF INIT — the two pages every 737 flight is built on. Program a JFK to Heathrow route from empty.
📍 KJFK → EGLL⏱ ~3 min📊 8 stepsPOS INIT — Aligning the IRS
PremiumbeginnerBefore the FMC will do anything useful, the inertial reference system has to know where it is. POS INIT is where you tell it.
📍 POS INIT · EGLL⏱ ~3 min📊 4 stepsThe EXEC Light — Boeing's Commit Step
PremiumbeginnerThe single biggest difference between the Boeing CDU and the Airbus MCDU: on the 737, nothing you type takes effect until you press EXEC.
📍 DIRECT LFPG⏱ ~4 min📊 3 stepsREF NAV DATA — Navaid Lookup
PremiumintermediateBefore an approach, real crews verify the navaids they are about to use. REF NAV DATA is where you look them up.
📍 EGLL approach briefing⏱ ~3 min📊 5 steps
Background reading
- GuideThe Boeing 737 CDU / FMC Explained: Every Page
What is the 737 CDU and FMC? A plain-English guide to every Boeing 737 CDU page plus the EXEC/MOD workflow. Practice free in our CDU trainer.
- GuidePMDG 737 FMC Tutorial: Program Your First Flight Plan Step by Step
Program the PMDG 737 FMC from scratch: IDENT, POS INIT, ROUTE, PERF INIT, takeoff speeds, and VNAV setup. Every CDU page explained with the exact inputs.
- GuidePMDG 777-300ER Cold and Dark Startup: Complete Step-by-Step Guide
Battery to takeoff in the PMDG 777-300ER with interactive checklist. FMC setup, GE90 engine start, and the stabiliser trim that prevents tail strikes.