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Refer to figure.(For this question use CAP 698 Figure 4.7).
Planned take-off mass is 64000 kg, pressure altitude 4000 ft, OAT +10ºC, V1 151, 155, 161. Runway slope is -1% and tailwind 5 kt. What is the maximum permitted take-off mass?

  • A
    63 400 kg
  • B
    64 000 kg
  • C
    63 700 kg
  • D
    64 900 kg

Refer to figure.
Figure 4.7 enables the determination of the VMBE.

Using Figure 4.7, find the VMBE following the steps below:

  1. Enter with Pressure Altitude 4 000 ft from top left.
  2. Move horizontally until intersecting the OAT +10ºC.
  3. Also check, if the brake release mass 64 000 kg crosses the horizontal line within or outside the shaded area. If it is crossed outside the shaded area of the top left grid or when there is a tail wind or when employing the improved climb technique, always check VMBE. If V1 exceeds VMBE, apply the correction below the graph.
  4. Continue vertically down until intersecting the brake release mass 64000 kg.
  5. Finally, move horizontally to the right and read the VMBE 164 kt.
  6. Since the horizontal line is crossed outside the shaded area and there is a tailwind, then apply the corrections below the graph.
  7. VMBE must be adjusted for slope (-5 kt) and tail wind (-10 kt) giving a new VMBE = 164 kt - 5 kt - 10 kt = 149 kt.
  8. V1 exceeds the new VMBE by 2 kt.
  9. Therefore, the brake release mass 64 000 kg must be decreased by 300 kg for each knot V1 exceeds VMBE and finally, we get: 64 000 - (2 x 300) = 63 400 kg.
NOTE: If V1 exceeds VMBE, apply the correction below the graph, make V1 = VMBE and recalculate the other V speeds for the reduced mass.

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