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ATPL Performance study materials
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ATPL Performance (EASA): Climb

ATPL Performance · Work through your exam, one topic at a time.

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Climb

Climb questions test whether you can turn a required obstacle gradient into a gross gradient, then into a rate of climb, and whether you know which segment and configuration apply. The exam distinguishes take-off segments from en-route climb and gross from net flight path.

Segment requirements

For a Class A aeroplane with one engine inoperative, CS-25/FAR 25 gives these gross-gradient minima:

  • First segment: gear down, V2, take-off thrust; at least 0% (twin), 0.3% (three), 0.5% (four).
  • Second segment: gear up, V2, take-off thrust; at least 2.4% (twin), 2.7% (three), 3.0% (four).
  • Final take-off segment: VFTO, at least 1.2% (twin), 1.5% (three), 1.7% (four).
  • En-route: net gradient at least 1.1% (twin), 1.4% (three), 1.6% (four); the corresponding gross values are 2.2%, 2.8% and 3.2%.

The net take-off flight path is the gross path reduced by 0.8% (twin), 0.9% (three) or 1.0% (four). The net en-route path is reduced by 1.1%, 1.4% or 1.6% respectively. Obstacle clearance is assessed on the net path; the usual take-off requirement is 35 ft vertical clearance.

Gradient and rate of climb

Gradient (%) = height gain / horizontal distance × 100. Rate of climb in ft/min is approximately TAS (kt) × gradient (%) × 1.013. Use TAS for the aircraft's climb capability; use ground speed when converting a path over the ground against an obstacle.

Worked example

An obstacle is 500 ft above the 35 ft point and 4 nm away. Required net gradient = 500 / (4 × 6,076) × 100 = 2.06%. For a twin, add the 0.8% net-to-gross increment: required gross gradient = 2.86%. If the AFM gives 3.1% gross at the planned mass and temperature, the margin is 0.24%. At 140 kt TAS, the corresponding rate of climb is 140 × 3.1 × 1.013 ≈ 440 ft/min.

Traps that cost marks

Mixing gross and net; using the second-segment gradient at VFTO; applying the 0.8% increment to en-route climb; forgetting that the first segment is gear-down; and using TAS instead of ground speed for obstacle distance. Temperature and pressure altitude reduce gradient, so a chart valid at one mass cannot be reused unchanged.