Landing · from 50 feet to a stop

Which landing distance are you comparing with LDA?

Normal CS-25 demonstrated landing distance runs from 50 ft above the landing surface to a complete stop using the specified approach, configuration and technique. VSR0 is the reference stall speed in landing configuration; VREF is the reference landing speed and must meet its applicable stall/control floor. For a common CS-25 jet case the stall term is 1.23 VSR0; VMCL protects minimum control during approach and landing under the specified OEI conditions. The AFM schedule remains the source for actual VREF.

Start with the demonstrated case

Normal CS-25 demonstrated landing distance runs from 50 ft above the landing surface to a complete stop using the specified approach, configuration and technique. VSR0 is the reference stall speed in landing configuration; VREF is the reference landing speed and must meet its applicable stall/control floor. For a common CS-25 jet case the stall term is 1.23 VSR0; VMCL protects minimum control during approach and landing under the specified OEI conditions. The AFM schedule remains the source for actual VREF.

LDA is the declared landing distance available in the intended direction. Do not add clearway, stopway or a displaced-threshold area merely because pavement is visible. The applicable declared landing length and start point govern.

Keep dispatch and arrival assessments separate

Normal class-A CAT dry dispatch requires the demonstrated distance to fit within 60% of LDA for turbojets and 70% for turboprops. Required dry LDA is therefore AFM distance/0.60 or /0.70. Special approvals such as CAT.POL.A.255 change the conditions and are not the default rule. Assess the required runway selections and forecast conditions under CAT.POL.A.230.

Normal wet dispatch uses the applicable CAT.POL.A.235 case; where specific approved wet dispatch data are absent, the usual increase is 15% over the required dry distance. Approved alternatives and contaminated-runway data must be used according to their conditions. At time of arrival, CAT.OP.MPA.303 requires the applicable assessment using actual expected conditions, normally with a 15% margin over the assessed landing distance. This is a separate gate: a valid dispatch calculation does not guarantee a valid arrival.

Why can a small speed excess cost so much runway?

At a given indicated VREF, high density altitude means higher TAS; a tailwind further raises touchdown ground speed. Higher mass and ground speed raise kinetic energy, with speed squared. Downhill slope adds a gravity component opposing deceleration; wet or contaminated conditions can reduce usable friction. Field-length-limited landing mass can therefore fall even with an unchanged structural limit.

The energy arrives before braking begins

At a given indicated VREF, high density altitude means higher TAS; a tailwind further raises touchdown ground speed. Higher mass and ground speed raise kinetic energy, with speed squared. Downhill slope adds a gravity component opposing deceleration; wet or contaminated conditions can reduce usable friction. Field-length-limited landing mass can therefore fall even with an unchanged structural limit.

Arriving high or fast extends the airborne portion before braking. Avoid treating a stopping-device improvement as a remedy for a late touchdown. The published landing data assume a defined screen crossing, flare, touchdown and deceleration sequence.

Know what each device does

Ground spoilers dump lift and load the tyres. Anti-skid seeks useful wheel slip within the available friction. Autobrake targets a deceleration or pressure strategy and can be limited by the surface and installed capability. Reverse provides a separate decelerating force with specific approved credit and restrictions. A failed device needs its own performance penalty; it is not enough to plan to press harder.

Hydroplaning can sharply reduce wheel braking and directional control; dynamic, viscous and reverted-rubber mechanisms need different awareness. Use the current runway report, approved braking technique, crosswind limits and actual-condition landing data. If required margin cannot be met, choose a valid alternative or go around according to the applicable procedure.

Why can brakes get hotter after the aircraft stops?

During deceleration kinetic energy is dissipated into brakes, tyres, air and other sinks. The brake assembly can absorb a large part of it. Heat takes time to move from the discs to sensors and nearby components, so the temperature indication can rise after the aircraft is parked. A low immediate indication does not prove the brakes have reached their final peak.

The displayed peak can be delayed

During deceleration kinetic energy is dissipated into brakes, tyres, air and other sinks. The brake assembly can absorb a large part of it. Heat takes time to move from the discs to sensors and nearby components, so the temperature indication can rise after the aircraft is parked. A low immediate indication does not prove the brakes have reached their final peak.

A quick turnaround limit protects the next take-off and its potential rejected-take-off energy case, as well as tyre, fuse-plug and fire limits. Cooling depends on initial temperature, absorbed energy, ambient conditions, brake fans and the manufacturer’s cooling data. The fan-on indication and its limitations must be interpreted using the aircraft procedure.

Use a cooling chart as a condition, not a timer guess

Enter the specified mass/speed or brake-energy condition, initial state and cooling assumptions. Read the required time or temperature threshold for the next operation. Taxi braking after landing can add energy and reset the assumptions. Following a high-energy rejection, inspection or emergency procedures may apply before any next departure; waiting a guessed number of minutes is not a release.

Can you make the performance decision?

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