Class B · work the take-off data

Which available distance sets the allowed mass?

Start with the aircraft variant, flap, power and surface assumptions. Enter pressure altitude and temperature, interpolate only within the permitted grid, follow the mass and wind correction steps in the stated order, and identify whether the result is ground roll, unfactored distance to the screen, accelerate-go or accelerate-stop distance. The chart’s own instructions decide the sequence.

Read the chart as an algorithm

Start with the aircraft variant, flap, power and surface assumptions. Enter pressure altitude and temperature, interpolate only within the permitted grid, follow the mass and wind correction steps in the stated order, and identify whether the result is ground roll, unfactored distance to the screen, accelerate-go or accelerate-stop distance. The chart’s own instructions decide the sequence.

For normal class-B CAT take-off without declared stopway or clearway, the unfactored AFM take-off distance × 1.25 must fit TORA. With declared stopway and/or clearway, the same unfactored distance must meet all three constraints: distance ≤ TORA, distance × 1.15 ≤ TODA, and distance × 1.30 ≤ ASDA. Thus the defactored chart allowance is min(TORA, TODA/1.15, ASDA/1.30) in that case. Do not substitute the independently determined accelerate-stop distance for the distance term in this particular operational factoring rule.

Then verify the aircraft capability

MEP training manuals may separately give accelerate-go and accelerate-stop data. Those numbers describe different engine-failure outcomes and require the correct mass and configuration; some light twins do not have transport-category balanced-field protection. Use the all-engine and critical-engine-inoperative climb tables for the case actually requested. A negative engine-out gradient must remain negative in the obstacle calculation.

To solve an inverse problem, start from the allowed defactored distance and work back through the chart to mass, then obtain speeds at the actual mass. To find required wind, solve the chart in reverse and check that the actual reported wind supports the answer after regulatory accountability. A numerical wind requirement above the report is a failed check, not permission to assume more wind.

Can the aircraft clear the actual obstacle?

A climb table often gives ROC in ft/min, while an obstacle is described by height and ground distance. Ground gradient (%) = ROC × 60 × 100 /(GS × 6,076.12). If IAS is supplied, first obtain TAS from the atmospheric data or approved conversion, then resolve the wind to get GS.

Convert the rate using the right horizontal speed

A climb table often gives ROC in ft/min, while an obstacle is described by height and ground distance. Ground gradient (%) = ROC × 60 × 100 /(GS × 6,076.12). If IAS is supplied, first obtain TAS from the atmospheric data or approved conversion, then resolve the wind to get GS.

Compare like mass, pressure altitude, temperature, flap, gear and engine status. Use the right gross/net convention from the question. The achieved path height is starting height plus ground gradient × horizontal distance. Subtract obstacle height above that same datum, then compare with the required clearance.

Check more than one point

A terrain profile can become restrictive farther from the runway, after a turn or where a higher temperature reduces performance. A single positive clearance at the nearest obstacle does not prove the complete path. Balked-landing climb data also use a different configuration from take-off climb data. Do not move a number between those charts merely because both have ft/min on the vertical axis.

Can you make the performance decision?

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