The Approach Numbers (PERF APPR)
PremiumintermediateThe approach briefing, in the box: QNH, wind, temperature, VAPP and minima for the ILS onto Heathrow's 27R.
What this scenario covers
PERF APPR is the last of the phase-based performance pages, and it collects everything the FMGS needs to fly and protect the approach: the destination QNH and temperature, the surface wind, the transition altitude, the approach speed VAPP, and the minima - baro or radio, depending on the approach.
VAPP is the one the aircraft cares about most. It is computed from the landing configuration and weight, with a wind additive, and it becomes the managed speed target on final.
How it applies in flight ops
This page is filled during the approach briefing, well before top of descent, because it is the moment the crew agrees what they are going to fly and at what numbers. Doing it late is a workload trap - the descent is the busiest part of a short-haul flight.
Setting the minima has a specific consequence: it drives the automatic callouts and the approach protections. Minima entered as a decision height when the approach is flown to a decision altitude is the kind of quiet mismatch that briefings exist to catch.
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The MCDU checks every entry as you make it, and tells you when an entry was accepted but wrong.
Step-by-step: The Approach Numbers (PERF APPR)
- You're in the descent and ATIS reports QNH 1013, wind 270/10, +15°C. From the PERF page, press NEXT PHASE> until the title shows APPR.
PERF has five phases. Each is filled in at the right moment: TO before pushback, CLB after takeoff, CRZ at top of climb, DES on descent prep, and APPR before the final approach briefing. Setting APPR too early is fine - the FMS uses these values as soon as you arm APPR mode on the FCU. One thing this page does not do is choose the approach. That happens on ARRIVAL, off a lateral revision at the destination, and it is what decides the runway - which is why FINAL here reads dashes rather than ILS: nothing has put an approach in the flight plan. It would have nothing to offer at Heathrow in any case. The trainer's coded procedure data covers US airports and Paris Charles de Gaulle only, so departures, arrivals and approaches exist nowhere else; runways everywhere are real, procedures are not. That is precisely why this exercise drills the numbers.
- Enter the QNH from ATIS. Type 1013 and press 1L.
QNH is the local sea-level pressure at the destination. On the aircraft the field shows amber boxes inside 180 NM, and the entry is used beyond the FMS: the cabin pressure controller works out the cabin's descent from it, so a wrong figure here can bring up a pressurization alert. You also set QNH on the standby altimeter and the FCU baro at transition level - they're separate inputs.
- Enter the surface temperature. Type 15 and press 2L.
The FMS uses the destination temperature to refine its descent profile. It does not change VAPP: the FMS computes VAPP from VLS and the wind (step 6), with no temperature in the formula. ATIS gives you this number directly - never guess or copy yesterday's value.
- Enter the magnetic wind 270/10. Type 270/10 and press 3L.
This is the wind at the threshold, magnetic, in knots - exactly what the tower will give you. The FMS uses it to compute headwind/crosswind components and the VAPP wind correction. With RWY 27 and wind 270, that's a 10-kt direct headwind.
- Set transition altitude to 6000 for London TMA. Type 6000 and press 4L.
Transition altitude is where you switch from QNH to standard 1013 on climb (or back the other way on descent). It varies by country and FIR - the UK is moving towards a unified 18000 ft eventually, but London TMA stays at 6000 ft today. Setting it correctly lets the FMS draw the magenta transition arrow on the ND in the right place.
- Enter VAPP 140 kt. Type 140 and press 5L.
VAPP = VLS + wind correction. The correction is one-third of the tower-reported headwind component, bounded between +5 and +15 kt. With a 10-kt headwind: 1/3 = 3.3, below the +5 minimum so VAPP = VLS + 5. The FMS computes this for you when GW is known, but you can override here. At a representative landing weight near 65 t with FULL flaps, VLS sits around 135 kt and VAPP comes out to 140 kt.
- Enter BARO minima 280 ft (DA for ILS CAT I, RWY 27R). Type 280 and press 2R.
BARO is the altimeter-based decision altitude. EGLL RWY 27R has TDZE ≈ 79 ft, so CAT I DA ≈ 279 ft (we round to 280). It's the altitude at which you must have the runway in sight on a precision approach, otherwise go around. The automatic "MINIMUM" callout comes at this altitude, made by the flight warning computer (not the FMS) from the minimum you enter here. Leave RADIO empty on this approach: it takes a decision height for CAT II or CAT III, and the two fields clear each other, so an entry in 3R would wipe this 280.
What to take away
- PERF APPR carries QNH, temperature, wind, transition altitude, VAPP and minima.
- VAPP comes from landing weight and configuration plus a wind additive.
- Fill it during the briefing, before top of descent - not on the way down.
- The minima you enter drive the callouts; enter the right kind for the approach flown.
- 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 FINAL field reflects whatever approach the flight plan ended up with.
The rest of Descent & Arrival
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PremiumadvancedThe A320 builds its descent backwards from a crossing constraint. Add the fix, hang the constraint on it, then read the profile the FMGS computes.
📍 KORD → KCLE - descent preparation⏱ ~6 min📊 8 stepsManaged Descent Rescue
PremiumadvancedYou are high on the descent profile and the FMGS is not helping. Read the vertical picture off the MCDU, find the real cause (the arrival was never selected, so there are no constraints to descend to), fix it, hang the crossing restriction on the fix, and read what managed DES is actually flying.
📍 KLAX → KLAS - high on profile in the descent⏱ ~8 min📊 10 stepsSelecting the Approach: ILS RWY 27L at Atlanta
PremiumintermediateOn the Airbus you do not type a landing runway. You choose an approach, and the runway comes with it - then the feeder route, then the arrival, in that order.
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PremiumadvancedYou are inbound to San Francisco with the arrival programmed, and ATC changes the landing runway. Re-select the arrival, see what the re-selection does to your flight plan instead of assuming it cleaned up after itself, and put the plan back together so it flies forward from where you are rather than backwards through an arrival you have already left behind.
📍 KLAS → KSFO - ATC changes the landing runway on the arrival⏱ ~9 min📊 10 stepsLondon City Numbers (PERF APPR)
PremiumintermediateA numbers drill for the simulator: PERF APPR for London City runway 09, where the landing distance is 1494 m and the minimum comes off the chart rather than a rule of thumb.
📍 EGLC: PERF APPR numbers for runway 09, simulator exercise⏱ ~6 min📊 7 steps
Background reading
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- GuideFlying an A320 Into London City (EGLC): The Approach It Isn't Allowed to Fly
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