Commission Directive (EU) 2015/996Show full title

B8 ACCELERATING CLIMB AND FLAP RETRACTION U.K.

This usually follows the initial climb. As for all flight segments, the start-point altitude h₁ , true airspeed V_T1 , and thrust (F_n /δ)₁ are those from the end of the preceding segment. The end-point calibrated airspeed V_C2 and the average climb rate ROC are user inputs (bank angle ε is a function of speed and radius of turn). As they are interdependent, the end altitude h₂ , end true airspeed V_T2 , end thrust (F_n /δ)₂ and segment track length Δs have to be calculated by iteration; the end altitude h ₂ is guessed initially and then recalculated repeatedly using equations B-16 and B-17 until the difference between successive estimates is less than a specified tolerance, e.g. one foot. A practical initial estimate is h ₂ = h ₁ + 250 feet.

The segment track length (horizontal distance covered) is estimated as:

(B-17)

where

0,95

is a factor to account for effect of 8 kt headwind when climbing at 160 kt

k

is a constant to convert knots to ft/sec = 1,688 ft/s per kt

V_T2

= true airspeed at segment end, kt:

where σ₂ = air density ratio at end altitude h ₂

α_max

= maximum acceleration in level flight (ft/s²)

=

G

= climb gradient

where ROC = climb rate, ft/min

Using this estimate of Δs, the end altitude h ₂′ is then re-estimated using:

h2′ = h 1 + s · G/0,95

(B-18)

As long as the error is outside the specified tolerance, the steps B-17 and B-18 are repeated using the current iteration segment-end values of altitude h ₂, true airspeed V_T2 , corrected net thrust per engine (F_n /δ)₂. When the error is within the tolerance, the iterative cycle is terminated and the acceleration segment is defined by the final segment-end values.

Note: U.K.

If during the iteration process (a_max – G·g) < 0,02 g, the acceleration may be too small to achieve the desired V_C2 in a reasonable distance. In this case, the climb gradient can be limited to G = a_max /g – 0,02, in effect reducing the desired climb rate in order to maintain acceptable acceleration. If G < 0,01 it should be concluded there is not enough thrust to achieve the acceleration and climb rate specified; the calculation should be terminated and the procedure steps revised(1).

The acceleration segment length is corrected for headwind w by using:

(B-19)

Accelerating segment with cutback U.K.

Thrust cutback is inserted into an acceleration segments in the same way as for a constant speed segment; by turning its first part into a transition segment. The cutback thrust level is calculated as for the constant-speed cutback thrust procedure, using equation B-1 only. Note it is not generally possible to accelerate and climb whilst maintaining the minimum engine-out thrust setting. The thrust transition is assigned a 1 000 ft (305 m) ground distance, and the corrected net thrust per engine at the end of 1 000 ft is set equal to the cutback value. The speed at the end of the segment is determined by iteration for a segment length of 1 000 ft. (If the original horizontal distance is less than 2 000 ft, one half of the segment is used for thrust change.) The final thrust on the second sub-segment is also set equal to the cutback thrust. Thus, the second sub-segment is flown at constant thrust.

(1)

In either case the computer model should be programmed to inform the user of the inconsistency.