Refer to figure CAP 758 Figure 3.44.
Given the following information, what is the maximum permissible take-off mass?
Pressure Altitude: 1500 ft
OAT: ISA
Wind: 10 kt headwind
Distance D4: 2000 m
Climb speed: VY
Landing Gear: Retracted
Refer to figure.
From figure 3.44, the Distance D4 and the Climb gradient can be determined with the helicopter flying with OEI, Climb speed VY and landing gear retracted for a given pressure altitude, temperature, take-off mass and wind conditions.
For this question, for specific pressure altitude, temperature and wind conditions, the maximum permissible take-off mass can be determined for a given minimum climb gradient with the following manner:
- Enter with the Distance D4 2 000 m from the bottom left graph and move vertically up until the reference curve.
- Continue to the right until the 5 kt headwind (50% of 10 kt headwind).
- Move vertically up crossing all the take-off mass lines.
- Enter with the pressure altitude 1 500 ft from the top left graph and move vertically up until OAT +12°C (15ºC - 2ºC x 1 500 ft/1 000).
- Continue horizontally to the right crossing all the take-off mass lines.
- The intersection between the vertical and horizontal lines, which cross all the mass lines in the top right graph, is the maximum permissible take-off mass: 7 600 kg.
NOTE:
According to EASA AIR OPS - CAT.POL.H.105 - General, accountability for wind shall be no more than 50% of any reported steady headwind component of 5 kt or more. But, CAP 758 is under JAR OPS and does not take into account the 50% factor for the reported headwind component.
The correct option according to student's feedback is 7 600 kg, so 50% headwind accountability should be taken.
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