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 (a) Takeoff, approach and go around speeds The takeoff reference speeds (F, S or VFTO) are computed from the TOGW value if one exists. If there is no TOGW value, these speeds are not computed. Before transition to approach, the approach reference speeds (VLS, VAPP, VFTO, S and F) are computed from the gross weight value predicted at the destination, if a destination is defined, or from the current gross weight value, if a destination is not defined. At transition to approach phase, the speeds are computed from the current gross weight value and are frozen. Wind at destination is taken into account for VAPP computation. VLS is computed according to the selected landing configuration. Before transition to go around, the go around reference speeds (F, S and VFTO) are equal to the corresponding approach speeds. After transition to go around the speeds are computed using the current gross weight value. They are displayed on the corresponding PERF pages. (Ref. Fig. 004) On the PERF TAKEOFF page, additional speeds may be entered by the pilot. These speeds are taken into account for prediction and guidance ; they are the decision speed (V1), the rotation speed (VR) and the reference speed for initial climb (V2). V1 and V2 are displayed on the PFD speed scale. On the PERF APPROACH page, WIND and LDG CONF fields must be entered for accurate estimation of VAPP and VLS.

 F, S and VFTO Display on PERF Pages
 Figure 004

 

 (b)
 Optimum speeds All speeds defined in this paragraph are computed within the speed envelope. The lower limit is the maximum between the minimum selectable speed (VLS) and the green dot speed (VFTO). The upper limit is the maximum performance speed, which is the smallest of:

 -VMAX = maximum selectable speed (0.2 g buffet margin)
 -VMO-10 kts or MMO-0.02
 -VMX CRZ = maximum speed held in level flight with max cruise
 thrust. Climb, cruise and descent Optimum speeds are optimized (within above speed envelope) according to:
 -
the aircraft weight (GW) and center of gravity (CG)

 -
the cost index (CI)

 -
the cruise flight level (CRZ FL)

 -
the wind and temperature models.
 If there is no gross weight value defined, the optimum speed is
 not computed. If there is no cost index or cruise flight level
 selected, the speeds default to VFTO.
 Climb optimum speed is a CAS/MACH pair which is frozen at
 transition to CLIMB phase. It is updated if cost index, cruise
 flight level or meteorological data are modified during climb.
 Cruise optimum speed is optimized along the cruise, and is
 updated in real-time according to the actual flight conditions.
 In level flight, it is a MACH above FL 250, else it is a CAS.
 Step speed is a CAS/MACH pair : the CAS is computed with the
 lower CRZ FL, the MACH with the higher CRZ FL.
 Descent optimum speed is a MACH/CAS pair which is frozen at
 transition to DESCENT phase. Prior to descent, it can be
 superseded by pilot entry.
 GO AROUND optimum speed is VFTO.

 

 (c)
 ECON speeds (Ref. Fig. 005) The ECON speeds are the optimum speeds described above, limited to the applicable speed constraints and limits at actual or predicted aircraft position. The ECON speed corresponding to the nearest point for each flight phase is displayed on related PERF page below the ECON prompt. For the descent, the ECON prompt is replaced by AUTO SPEED if the optimum descent speed has been superseded by the pilot entry.

 Time constraint option:

 ECON Speed/Mach Display on PERF Pages
 Figure 005

 

 When a time constraint has been entered in the flight plan, the ECON speeds are adjusted between the origin or current aircraft position and the time constraint waypoint, within applicable constraints/limits and aircraft speed enveloppe, to attempt meeting the time constraint.
 (d)
 EXPEDITE speeds Expedite climb speed is the maximum speed between the maneuver speed (VMAN = F, S or VFTO according to present configuration) and VLS. Expedite descent speed is the minimum speed between VMAX (which takes into account VFE of the current configuration and VLE when the landing gear is extended), VMO-10 and MMO-00.2.

 (e)
 Holding pattern speeds
 The holding speeds are defined as the minimum of:

 

 -ICAO limitations
 -Max endurance speed
 -Nav data base holding pattern speed constraint (if one exists)
 -Any flight plan speed constraints or limits that apply to the holding pattern.
 -The predicted speed at the entry fix, if the holding pattern is
 in approach, beyond the DECEL point. They are displayed on the FLIGHT PLAN A page. (Ref. Fig. 006) Before the holding fix is overflown, the Max Endurance speed is computed assuming a clean configuration. During the holding leg, the Max Endurance speed is calculated using the current aircraft configuration.
　
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