getting to grips with fuel economy(39)

6.1 INTRODUCTION

In this brochure it can be seen that there are many ways  of influencing the fuel burn of an aircraft, but most depend on the way that the sector is planned and flown. Maximising the fuel economy requires:
. Good flight planning based on good data.

. Correct aircraft loading (weight and cg).

. An aerodynamically clean aircraft.

. Optimal use of systems (APU, Bleed, Flaps/Slats, Gear, etc).

. Flight Procedures using speeds and altitudes appropriate to the companies economic priorities.

. Use of the FMGS in the managed mode.

. Use of performance factors in flight planning and in the FMGS derived from an ongoing aircraft performance monitoring program.

6.2 GENERAL GUIDELINES

6.2.1 PRE-FLIGHT PROCEDURES

6.2.2 TAKE-OFF AND INITIAL CLIMB

. For most Airbus aircraft, an aft CG position saves fuel.

. Excess weight costs fuel. Minimize zero fuel weight and embarked fuel.

. A good flight planning system will  minimise fuel through correct optimisation.

. An aircraft performance measurement system and good flight planning will give confidence in fuel burn reducing extra reserve.

. Keep A.P.U. running during short turnarounds to reduce A.P.U. start cycles.

. Use ground power, when possible to save both fuel and A.P.U. life.

. Do not start engines until ready to go.

. If considered operationally acceptable, taxi with one engine out. 

. Keep the aircraft in an aerodynamically clean condition.

. Bleeds off fuel improvements normally negated by APU fuel burn

. Lower configurations do save fuel.

. Flex thrust cost fuel but saves engine costs.

. Noise flight paths cost fuel

6.2.3 CLIMB 

6.2.4 CRUISE 

. Climb as close as possible to the optimum climb law.

. Fast Climb speeds use more fuel (except A340)

. The best speed for fuel burn (very low cost index) is slow and has a big time penalty.

. If possible, fly in managed mode at the cost index appropriate to the airlines economic priorities.

. Flying faster than the FMGS economical Mach number costs fuel.

. Try to fly at optimum altitude. Chase the optimum altitude.

. Flying at the cross-over altitude is faster, but costs fuel.

. Step Climb around the optimum altitude (see FCOM).

. Avoid delays in initiating a step climb.

. For short stage lengths, fly at an appropriate altitude (see FCOM).

. Wind variations with altitude can give advantages in flying at lower altitudes.

6.2.5 DESCENT

6.2.6 HOLDING

. Diminishing descent speed can allow significant fuel savings.

. Avoid early descents

. The best combination for fuel burn is clean configuration at green dot speed.

. Manoeuvrability, speed or ATC restrictions may require a hold in configuration 1 at S speed.
　
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