The Approach Numbers (APPROACH REF)

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📍 Route: EGLL — approach numbers for an ILS RWY 27R⏱ ~5 minutes📊 4 steps🎓 Descent & Arrival

APPROACH REF for the ILS onto Heathrow 27R — a narrower page than the Airbus equivalent, and deliberately so.

What this scenario covers

APPROACH REF computes VREF from landing weight and flap setting, and that is very nearly all it does. QNH, minima and the approach mode itself live on the mode control panel and the altimeters, not in the box.

That division is a real design difference from the A320, where PERF APPR gathers QNH, wind, transition altitude, VAPP and minima in one place. On the 737 the approach setup is spread across the flight deck rather than concentrated in the CDU.

How it applies in flight ops

VREF plus a wind additive is the speed flown on final. The additive is a crew computation on the 737 — the page holds a WIND CORR field, resting at +05 kt and accepting up to +20, but it is a number you put there rather than a wind the box measures. That makes the approach briefing the moment it is agreed rather than something the FMC hands you.

The briefing is done before top of descent for the same reason as on any type: the descent and approach are the busiest phase of a short flight, and a page filled late is a page filled badly.

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Step-by-step: The Approach Numbers (APPROACH REF)

  1. Open APPROACH REF from INIT REF INDEX. Press INIT REF (top-left page key), then LSK 5L for APPROACH.

    APPROACH REF is the last CDU page you visit before landing. The FMC needs landing weight, flap setting and (optionally) wind to compute VREF. Real 737 SOPs brief APPROACH REF as part of the approach briefing — usually around top of descent. What this page does not do is choose the approach: that happens on DEP/ARR, on the destination's arrivals page, where the approach, its runway and the arrival are picked. It would have nothing to offer at Heathrow in any case — the trainer's coded procedure data is the FAA's, so departures, arrivals and approaches exist at US airports only, while runways everywhere are real. Which is exactly why this exercise is the numbers.

  2. Enter landing gross weight 55.0 tonnes. Type 55.0 and press 1L.

    Landing weight = takeoff weight minus fuel burned. For our EGLL → LSGG return, after the ~410 nm trip and reserves, the 737 lands around 55 t. The FMC needs this to compute VREF — heavier aircraft = higher stall speed = higher VREF.

  3. Select FLAPS 30 for landing. Press 2R with an empty scratchpad — nothing to type.

    Flap 30 is the 737-800's normal landing flap setting — best balance of approach speed and runway requirement. Flap 40 is for shorter runways and gives a lower VREF; flap 15 is for non-normal landings (overweight, single engine) and gives a much higher VREF. The page shows all three against the weight you entered, and a line select on one copies that flap and speed into FLAP/SPD at 4R. You can also type the pair there yourself — 30/134, or just /134, or 30/.

  4. Set the approach wind correction to 10 kt. Type 10 and press 5R.

    WIND CORR is an additive on top of VREF, and it is the crew's number rather than a wind the box measures — the page has no direction field at all. It rests at +05 kt and takes anything up to +20, and those two values are not arbitrary: with the autothrottle engaged Boeing recommends a command speed of VREF + 5, and with it disengaged, half the steady headwind component plus the gust increment above the steady wind, to a maximum of 20 kt. No correction for a tailwind. With 20 kt of headwind on 27R, half of it is the 10 you have just set.

What to take away

  • APPROACH REF computes VREF from landing weight and flap.
  • QNH and minima are set outside the CDU on the 737.
  • The wind additive to VREF is the crew's number, entered at WIND CORR — the page has no wind direction field.
  • Brief and set up before top of descent, not during it.
  • It holds the numbers, not the approach itself. Selecting the procedure is a different page, and needs the coded procedure data the trainer carries for US airports.

The rest of Descent & Arrival

Background reading

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