Climb beyond the screen

Why can a long runway still leave you too heavy?

Climb-limited take-off mass is the mass that still meets the required certified climb gradient at the actual pressure altitude, temperature, thrust setting and configuration. In the take-off second segment, with gear retracted and the critical engine inoperative, the CS-25 minimum gross gradients are 2.4%, 2.7% and 3.0% for two, three and four engines.

A runway cannot manufacture climb thrust

Climb-limited take-off mass is the mass that still meets the required certified climb gradient at the actual pressure altitude, temperature, thrust setting and configuration. In the take-off second segment, with gear retracted and the critical engine inoperative, the CS-25 minimum gross gradients are 2.4%, 2.7% and 3.0% for two, three and four engines.

First-segment gear-extended requirements differ: a twin needs a positive gradient, while three/four engines use 0.3/0.5%. Final take-off climb at maximum continuous thrust uses 1.2/1.5/1.7%. These values are certification conditions; actual obstacle assessment still uses the net path. Do not substitute a 2.4% gross certification minimum for 2.4% net obstacle performance.

Understand the temperature kink

A flat-rated engine can maintain a limited rated thrust up to a corner temperature at a given altitude; above it the engine reaches a thermal limit and available thrust falls. Even on the flat-rated side, climb performance can change with density, drag and speed. A flat-rated thrust line is not proof of constant permitted mass.

Gear, excess flap, anti-ice/bleed use and adverse atmospheric conditions reduce the surplus. Read the correct side of the chart’s flat-rating boundary, interpolate as instructed, and compare the climb-limited mass with field and structural limits. Extra pavement only helps when one of the field constraints is the governing limit.

Can the net flight path clear the entire departure?

A conventional four-segment teaching model starts at the screen: first segment is gear retraction; second is gear-up climb at take-off flap and scheduled V2; third is acceleration/configuration change; final is clean climb at the scheduled speed and maximum continuous thrust. Actual procedures, acceleration height and the extent of each segment come from the aircraft data.

Build the segments

A conventional four-segment teaching model starts at the screen: first segment is gear retraction; second is gear-up climb at take-off flap and scheduled V2; third is acceleration/configuration change; final is clean climb at the scheduled speed and maximum continuous thrust. Actual procedures, acceleration height and the extent of each segment come from the aircraft data.

The certified take-off flight path extends to the specified endpoint, normally at least 1,500 ft above the take-off surface with the transition completed. The net path is derived by the 0.8/0.9/1.0 percentage-point reductions for two/three/four engines. Acceleration uses energy that could have become height, so it can flatten the path. Retraction later reduces drag; it does not instantly restore height already spent.

Account for turns and terrain

Normal class-A CAT net take-off paths need at least 35 ft vertical clearance or the required lateral clearance from accountable obstacles. The base domain is 90 m + 0.125D, with the half-span + 60 m option for span below 60 m and the applicable navigation/turn caps. With track changes ≤15°, caps are 300 m with required accuracy or 600 m otherwise; for larger changes, 600/900 m apply.

Normally no bank is assumed before half-span height and at least 50 ft; up to 400 ft use at most 15°, above 400 ft ordinarily at most 25°, subject to specific approvals. Turns above 15° need at least 50 ft vertical obstacle clearance and the prescribed climb penalties. Load factor increases stall speed approximately with √n; bank and extra speed both consume performance margin. The first and second segment cannot be treated as straight-flight performance while drawing a steep turn.

Can you make the performance decision?

Four original questions. Work from the stated conditions and review the reasoning.