DOC references :
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QRH 3.05 & 4.08 to 4.10 (OPS data)
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FCOM 1.22.20 & 30 (Auto Flight)
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FCOM 3.03.15 (SOP’s)
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FCOM 3.05.15 (Cruise)
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FCOM 3.05.20 (In cruise check)
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FCOM 4.05.50 (FMGS Procedure)
04 - INSTRUCTOR’S ACTIONS
Briefing of the following key points.
MAIN
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Maximum flight level.
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Optimum flight level.
SECONDARY
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Long range cruise.
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Atmospheric influence.
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Step climb.
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Insertion of forecast winds in F-PLN page if not done during preflight preparation.
A319/A320/A321 FLIGHT CREW TRAINING MANUAL NORMAL OPERATION BRIEFINGS CRUISE MANAGEMENT 1.02.15 Page 2
REV 21 MAY 98
At the top of climb, and periodically throughout the cruise, conduct a check of the ECAM system pages. Navigation accuracy should be checked regularly and monitored using raw data as required. If FMGS navigation performance is unsatisfactory, use selected guidance and navigate using raw data. See also Briefing Notes - Global Positioning System (if fitted) and FMGS Position Updating.
Selection of cruise altitude and speed will depend on several factors including the overall sector length, cost index and aircraft weight.
Cost index is a number which takes account of fuel costs and aircraft operating costs to allow the FMGS to compute an optimum cruise speed taking into consideration headwind, or tailwind, component. For example, low fuel costs and high operating costs will lead to a high cost index and fast cruise speed. Cost index will also affect climb and descent speeds. In order for the FMGS to enter the cruise phase and the F-PLN page predictions of fuel on arrival (destination and alternate) to be correct, it is necessary to ensure that the cruise altitude entered in the PROG page and the actual cruise altitude are the same. Forecast winds and temperatures should also be entered in the F-PLN at appropriate points along the route so that accurate predictions will be calculated. Additionally any step climbs should be included in the F-PLN.
Should these predictions indicate that the aircraft will arrive below minimum fuel or late, then manipulation of the cost index may allow the target to be achieved. Selection of CI 0 will select maximum range and CI 999 will select minimum time in the FMGS predictions and managed speeds.
If actual cruise altitude is less than that entered in PROG page the FMA will indicate ALT. To enable engagement of ALT CRZ (soft altitude mode) the actual altitude must be entered in the PROG page. Selection of a higher altitude on the FCU than that entered in PROG will automatically update PROG page with a new cruise altitude.
For short sector lengths the most economic cruise altitude is not necessarily the maximum which can be achieved. See FCOM 3.05.15 (In Flight Performance - Cruise) for a graph which enables selection of the best cruise altitude on short sectors.
Optimum altitude (OPT) is the altitude at which the aircraft covers the maximum distance per kilogram of fuel. It is computed from aircraft current GW, CI, deviation from ISA and a minimum of 5 minutes in the cruise. Recommended Maximum (REC MAX) altitude ensures a
0.3 g buffet margin, a minimum rate of climb at MAX CL thrust and level flight at MAX CRZ thrust, limited to FL 390. (FCOM 2.05.20 [Flight Planning - Cruise Level])
In order to fly at maximum range, an aircraft must operate continuously at optimum altitude. This would mean that the aircraft would have to climb continuously in order to remain at optimum altitude (cruise climb). Usually this is not possible so the most fuel efficient way is to step climb to an altitude that is slightly above optimum. As gross weight decreases the optimum altitude will increase and another step climb is required.
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