Pre-Flight Fuel Planning (INIT B)

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📍 Route: EGLL → LSGG — pre-flight planning⏱ ~7 minutes📊 7 steps🎓 Performance & Fuel

At the gate with the OFP in hand: seven numbers on INIT B, and the aircraft knows what it weighs and what it is carrying.

What this scenario covers

INIT B is the weights and fuel page. Taxi fuel, zero fuel weight and its centre of gravity, block fuel, route reserve, final reserve and trip wind all go in here, and between them they let the FMGS compute the takeoff weight, the predicted fuel at destination and the margin against reserves.

The page is only reachable before engine start — once the flight is under way it becomes FUEL PRED, its in-flight counterpart. That is a deliberate design: the planning numbers are entered once, and thereafter the aircraft reports against them.

How it applies in flight ops

Every one of these figures comes from paperwork: the loadsheet for ZFW and ZFWCG, the OFP for block fuel and reserves. Entering them is the moment the aircraft's picture of the flight and the dispatcher's picture are reconciled, and a mismatch here is a mismatch that will not surface until it matters.

ZFWCG in particular deserves care: it feeds the trim setting for takeoff. A gross error in centre of gravity is not a fuel-planning inconvenience, it is a takeoff performance problem, which is why it is one of the cross-checked items on every airline's SOP.

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Step-by-step: Pre-Flight Fuel Planning (INIT B)

  1. You're on INIT A. Press the right arrow key (→) to switch to INIT B — the fuel and weight page.

    INIT A is for routing (FROM/TO, CO RTE, CRZ FL). INIT B is for performance — what the aircraft weighs and how much fuel you're carrying. The FMS needs both to compute trip fuel, V-speeds, and time predictions. Most carriers brief INIT B as part of the pre-flight scan.

  2. Enter taxi fuel. Type 0.4 and press 1L.

    Taxi fuel covers engine start, taxi out, and APU during turnaround. The OFP gives this number — it's based on historical taxi times at the airport and the airline's policy. 0.4 t is typical for an A320 at a hub like Heathrow; smaller airports use 0.2–0.3 t.

  3. Enter ZFW/ZFWCG. Type 62.5/27.0 and press 1R.

    Zero Fuel Weight is the aircraft + crew + payload (passengers, baggage, cargo) but no fuel. ZFWCG is the longitudinal centre of gravity at that weight. Both come from the loadsheet that ground ops sends shortly before pushback. Always check the loadsheet against your INIT B entry — a wrong ZFW gives wrong V-speeds.

  4. Enter block fuel. Type 7.2 and press 2R.

    Block fuel is the total uplift = taxi + trip + contingency + alternate + final + any extra. For this short-haul Heathrow → Geneva trip (~466 nm): 0.4 taxi + 3.8 trip + 0.2 contingency (5%) + 1.5 alternate + 1.1 final + 0.2 extra ≈ 7.2 t. The OFP shows the breakdown; you only enter the total here.

  5. Enter route reserve. Type 0.2/5.0 and press 3L.

    Same field as on FUEL PRED — the contingency buffer for unforeseen events. Entering it on INIT B before takeoff lets the FMS show realistic EFOB predictions from the start of the flight, not just after you remember to update it in cruise.

  6. Enter final reserve. Type 1.1/0030 and press 5L.

    The 30-minute holding reserve at 1500 ft above the alternate. ICAO/EASA mandate. For an A320 at light landing weight, ~1.1 t. As with route reserve, setting this pre-flight gives the FMS a hard floor for its EFOB warnings throughout the flight.

  7. Enter the average trip wind. Type HD050 and press 5R.

    Trip wind is the average wind component along your route, taken from the OFP's wind summary. HD050 means 50 kt average headwind. The FMS uses this to refine its trip-fuel prediction and TIME estimate; without it, predictions drift as actual winds differ from forecast. Some operators leave it at HD000 if the route is wind-neutral.

What to take away

  • INIT B carries weights and fuel; FUEL PRED is the same data in flight.
  • ZFW and ZFWCG come off the loadsheet; block fuel and reserves off the OFP.
  • The page computes takeoff weight and destination fuel from your entries — garbage in, confident garbage out.
  • ZFWCG feeds the takeoff trim, which makes it a safety item, not a bookkeeping one.

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