Speed & Altitude Constraints (VERT REV)
PremiumintermediateATC wants you at an altitude by a waypoint. The vertical revision page is where that promise gets written into the flight plan.
What this scenario covers
A vertical revision is opened by right-selecting a waypoint on the F-PLN page. It carries the vertical data for that point: altitude constraints, speed constraints, and the wind and step information the FMGS uses to build its profile.
Entering a crossing altitude there does more than annotate the display. The FMGS re-plans the vertical path so that the profile actually meets the constraint, which is what makes managed descent able to fly it.
How it applies in flight ops
Crossing restrictions are the currency of arrival management — "cross ABCDE at or below FL100 at 250 knots" is a normal instruction into any busy terminal area. Typing it into the box means the aeroplane will plan for it rather than the crew flying it by hand and hoping.
It is also a trap worth respecting. A constraint the aircraft cannot make is shown as unable, and crews are expected to notice and tell ATC rather than discover it at the fix. The FMGS will tell you; it will not negotiate for you.
Fly this one with Premium
The MCDU checks every entry as you make it, and tells you when an entry was accepted but wrong.
Step-by-step: Speed & Altitude Constraints (VERT REV)
- Enter a route. Type EGLL/LFPG into the scratchpad and press 1R.
This seeds a route with a discontinuity between EGLL and LFPG — we will put a waypoint in it, clear the gap, then put a constraint on that waypoint.
- Press F-PLN to open the flight plan.
Constraints are entered per waypoint on the flight plan, so we work from the F-PLN page.
- Put a waypoint in the gap so there is something to constrain. Type MID into the scratchpad and press 2L (the discontinuity line) — MID takes the line and the discontinuity moves down below it. Then clear the discontinuity: press CLR, then 3L.
MID (Midhurst VOR) is now an enroute waypoint between EGLL and LFPG. Heathrow's Paris traffic leaves London south via Midhurst, so it is a point on the real route — and the kind of point ATC may give you a crossing altitude for.
- Open the vertical revision for MID. Press 2R — the RIGHT line key next to MID.
On the real A320, a LEFT line-select opens LAT REV (lateral — routing); a RIGHT line-select opens VERT REV (vertical — speed and altitude). This is the page where crossing constraints live.
- Enter a crossing altitude. Type FL100 into the scratchpad and press 1R (ALT CSTR).
ALT CSTR FL100 tells the FMGS to cross MID at FL100. It now feeds the descent/climb profile and the predictions. A constraint shown in magenta is one the FMGS predicts it will meet; an amber one would warn it expects to miss it — which you fix by managing the energy state (speed/speedbrake), not by retyping the altitude.
What to take away
- Right-select a waypoint on F-PLN to open its vertical revision.
- Altitude and speed constraints entered there reshape the computed descent path.
- Managed descent flies constraints; it cannot fly the ones you never entered.
- If the profile says unable, that is a call to ATC, not a number to overwrite.
The rest of Enroute Operations
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📍 EGLL → KJFK⏱ ~5 min📊 5 stepsATC Shortcut: Going Direct
Premiumintermediate"Direct OCK" — five seconds of radio and a chunk of your flight plan gone. On this FMS the keypress is the commitment: there is nothing to confirm and nothing to undo.
📍 EGLL approach — direct routing⏱ ~4 min📊 6 stepsDiversion to Alternate
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📍 HOLD AT LFPG⏱ ~4 min📊 6 steps
Background reading
- GuideWhy VNAV Doesn't Work When You Turn On the Autopilot
VNAV won't engage or won't descend in MSFS 2024? The 6 most common causes on the PMDG 737 and Airbus A320 — and exactly how to fix each one.
- GuideA320 Managed Descent Explained: DES Mode, the Yoyo, and Staying on Profile
How A320 managed descent actually works — DES vs OP DES, push vs pull, the V/DEV yoyo, MORE DRAG, EXPED, and why the aircraft won't descend.
- Guide737 FMC Constraints — 250B/, 10000A, and Every LEGS-Page Format That Actually Works
Every 737 CDU constraint format that works: A and B suffixes, speed/altitude pairs, the trailing slash rule, windows, DELETE, and why entries get rejected.