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Question ID: 330284 - Error in correction ?

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  • Question ID: 330284 - Error in correction ?

    (Refer to Annexes 033-048, 033-049 and 033-050)
    Given:
    . Take-off mass: 150 000 kg
    . Planned cruise at FL 350
    . Long range MACH
    . Standard Atmosphere (ISA)
    . CG: 37%
    Covering an air distance of 2 000 NM, your trip fuel from take-off to landing will be:
    View Annex View Annex View Annex
    19 660 kg
    20 260 kg
    21 760 kg
    22 360 kg <- quoted as right

    The correction says :

    150 000 kg → 2464 NAM ? 2464 - 2000 = 464 NAM
    464 NAM → 133 250 kg FUEL ? 150 000 - 130 325 = 19 675 kg
    CLIMB CORRECTION ? LR, FL350 ?2100 kg
    DESCENT CORRECTION ?LR, FL350 ? ? WEIGHT OVERHEAD ≈ 130 000 kg ? 600 kg
    TRIP FUEL = 19 675 + 2100 + 600 = 22 375 kg

    As you can see in bold, if I am not making myself any mistake, we should read :
    133 250 kg FUEL ? 150 000 - 133 250 = 16750 kg
    and with the climb and descent corrections TRIP FUEL = 19450

    Nearer answer available : 19 660 kg and not 22 360 kg

  • #2
    Re: Question ID: 330284 - Error in correction ?

    Sorry about this, the error is in the worked answer - the 133 250 kg is INCORRECT ... should be 130 250 kg

    Worked answer should be: the figures on this answer are precise - exact interpolation has been used (ie on a calculator)

    • NAM Question tells us: 2000 NAM

    • TABLE 033-048
    Start Mass 150 000 kg → 2464 NAM
    2464 - 2000 = 464 NAM → 130 324 kg (End Mass)
    FUEL = Start mass – End Mass = 150 000 – 130 324 = 19 676 kg

    • CORRECTIONS:
    Assume PACK FLOW NORMAL, ANTI ICE-OFF (question says nothing)
    CLIMB (ANNEX 033-049) LONG RANGE, FL350, MASS 150 000kg: +2100kg (+6 minutes)
    DESCENT (ANNEX 033-050) LONG RANGE, FL290 and above, 130 324kg: +600kg (+10 minutes)

    FUEL REQUIRED = 19 676 + 2 100 + 600 = 22 376 kg


    INTERPOLATION calculation for 464NAM:
    451 → 130 200 kg
    464 → Interpolate: → 130 200 +[(464-451)/(472-451) x 200] = 130 324 kg
    472 → 130 400 kg


    Worked answer will be corrected - although there may be a little time delay!

    Tom

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    • #3
      Re: Question ID: 330284 - Error in correction ?

      Annexes missing for this question, they only show up in the explanation box after the question has been answered.

      - Lexie

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      • #4
        Re: Question ID: 330284 - Error in correction ?

        Don't know what happened here - have sent update to support.

        Thanks

        Tom

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