Commission Directive (EU) 2015/996Dangos y teitl llawn

B5 TAKEOFF GROUND ROLL U.K.

Take-off thrust accelerates the aeroplane along the runway until lift-off. Calibrated airspeed is then assumed to be constant throughout the initial part of the climbout. Landing gear, if retractable, is assumed to be retracted shortly after lift-off.

For the purpose of this document, the actual takeoff ground-roll is approximated by an equivalent take-off distance (into a default headwind of 8 kt), s_TO8 , defined as shown in Figure B-1, as the distance along the runway from brake release to the point where a straight line extension of the initial landing-gear-retracted climb flight path intersects the runway.

Figure B-1

Equivalent takeoff distance

On a level runway, the equivalent takeoff ground-roll distance s_TO8 in feet is determined from

(B-9)

where

B₈

is a coefficient appropriate to a specific aeroplane/flap-deflection combination for the ISA reference conditions, including the 8-knot headwind, ft/lbf

W

is the aeroplane gross weight at brake release, lbf

N

is the number of engines supplying thrust.

Note: U.K.

Since equation B-9 accounts for variation of thrust with airspeed and runway elevation, for a given aeroplane the coefficient B₈ depends only on flap deflection.

For headwind other than the default 8 kt, the takeoff ground-roll distance is corrected by using:

(B-10)

where

S_TOw

is the ground-roll distance corrected for headwind w, ft

V_C

(in this equation) is the calibrated speed at takeoff rotation, kt

w

is the headwind, kt

The takeoff ground-roll distance is also corrected for runway gradient as follows:

(B-11)

where

S_TOG

is the ground-roll distance (ft) corrected for headwind and runway gradient,

a

is the average acceleration along the runway, equal to , ft/s²

G_R

is the runway gradient; positive when taking-off uphill