Class A · run, rotate, fly

What is included in the take-off distance?

For the normal dry CS-25 case, take-off distance is the greater of the engine-out distance to 35 ft and 115% of the all-engine distance to 35 ft. Take-off run has its separate definition when a clearway is used, including the appropriate midpoint construction between lift-off and the screen point. It is not always identical to ground roll.

The airborne part matters

For the normal dry CS-25 case, take-off distance is the greater of the engine-out distance to 35 ft and 115% of the all-engine distance to 35 ft. Take-off run has its separate definition when a clearway is used, including the appropriate midpoint construction between lift-off and the screen point. It is not always identical to ground roll.

Higher mass increases both required speeds and the time/distance needed to accelerate. Higher pressure altitude and temperature usually reduce thrust and increase TAS at a given IAS. Upslope, tailwind and adverse surfaces lengthen the case. Bleed-air or anti-ice settings can reduce net engine thrust, so a different setting requires the corresponding performance data. Greater flap may help the ground run but worsen climb.

Rotate as demonstrated

Early rotation can add drag before the aircraft can sustain flight. Late rotation consumes runway; a slow rotation rate delays lift-off and screen achievement. Excessive rotation rate or attitude risks tail strike, insufficient VMU margin or poor acceleration. Too little attitude keeps the aircraft on the ground longer; too much can impair climb or margin.

A lower V1 means the assumed failure occurs earlier and more of the continuation is flown with one engine inoperative: accelerate-go distance usually rises. A higher V1 usually reduces go distance but increases stop distance. Under normal class-A CAT take-off rules, the clearway credited in TODA must not exceed half TORA, and the same V1 must serve both the rejected and continued cases. Clearway can relieve the airborne-distance constraint and permit more mass if take-off run, stopping, climb and other checks still fit. It does not help an overrun during a rejected take-off.

What has to happen before the aircraft is stopped?

Accelerate-stop distance includes acceleration to the defined failure/rejection condition, the prescribed recognition and action sequence, transition to deceleration, and the stop. For the CS-25 dry case the specified additional distance equivalent to two seconds at V1 is included. Both all-engine and engine-out rejected cases must be addressed as required.

Acceleration is only the first part

Accelerate-stop distance includes acceleration to the defined failure/rejection condition, the prescribed recognition and action sequence, transition to deceleration, and the stop. For the CS-25 dry case the specified additional distance equivalent to two seconds at V1 is included. Both all-engine and engine-out rejected cases must be addressed as required.

A late first action or a high V1 increases stopping distance. Tailwind raises ground kinetic energy and an adverse slope reduces deceleration. A stopway extends ASDA and can relieve the stop constraint, but cannot change TORA, TODA or engine-out climb. A higher ground speed adds energy proportional to V²; higher mass raises it proportionally.

Devices only help when the data credit them

Wheel brakes absorb energy. Anti-skid controls wheel slip to use available tyre/runway friction; it does not create friction on ice. Ground spoilers reduce residual lift so the wheels carry more load. Reverse thrust can assist deceleration, but certification/operational credit depends on the approved dry/wet case and aircraft data; never invent dry-runway reverse credit.

Autobrake commands a deceleration strategy, subject to available braking. Brake energy limits and hot brakes can bind even if the aircraft stops within ASDA. Brake temperatures may continue rising after the stop because heat reaches the sensor later. High-speed rejection can create tyre, fuse-plug and fire hazards; follow the aircraft’s rejection criteria and post-stop procedures.

Can you make the performance decision?

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