Introduction

The performance database for a modern jet aircraft is invariably contained in the operating company’s flight planning computer set-up and the aircraft’s Flight Management System (FMS). The company Operation’s computers will produce flight plans for optimum routes and cruise modes, according to the instructions given.

•Best direct track non-airways.

•Best direct airways track.

•Best North Atlantic track.

•Least fuel or time track.

•Extended Range Operations (EROPS) and Non-normal Operations, such as gear down flight.

Crews use the FMS data base for in-flight fuel monitoring, and replanning of the aircraft’s performance when necessary, in order to obtain prompt accurate information and to reduce the need to refer to the relevant Operations Manual.

However, Part Flight Crew Licensing, Flight Planning & Monitoring (Aeroplanes), requires the student to be familiar with the reference material in the CAP 697 MRJT , which is based upon extracts from the Boeing 737-400 Operations Manual, and to answer related examination questions.

NB. In the Flight Planning exam you will be issued with a workbook instead of the CAP 697 in which will be the necessary pages for your particular exam.

Aeroplane Data and Constants

The aeroplane is a monoplane with twin turbojet engines and a retractable undercarriage.

From the foregoing data note the following:

•Maximum Take-off Mass (MTOM) is the maximum permissible total aeroplane mass at the start of the take-off run.

•Maximum Landing Mass (MLM) is the maximum total permissible landing mass upon landing under normal circumstances.

•Maximum Zero Fuel Mass (MZFM) is the maximum permissible mass of the aeroplane with no usable fuel.

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Planning Flight Simplified (MRJT) Transport Jet Range Medium 6

•Dry Operating Mass (DOM) is the total mass of the aeroplane ready for a specific type of operation, excluding all usable fuel and traffic load. This mass includes:

•crew and their baggage.

•catering and removable passenger service equipment.

•potable water and lavatory chemicals.

•food and beverages.

•Traffic Load is the total mass of passengers, baggage and cargo, including any non-revenue

load.

•The amount of fuel allowed for running the Auxiliary Power Unit (APU), starting the engines, “push-back” and taxi to the take-off point is:

Maximum Ramp Mass (MRM) - Maximum Take-off Mass (MTOM) 63 060 - 62 800 = 260 kg

Taxi fuel is roughly 11 kg/min. The APU burns 115 kg/h

•The maximum traffic load is:

MZFM - DOM

51 300 - 34 270 = 17 030 kg

Optimum Cruise Altitude

(Refer to CAP 697 Figure 4.1)

The optimum pressure altitude for best fuel mileage is presented for .78 Mach cruise, and Long Range Cruise (LRC) or .74 Mach. LRC is recommended for minimum trip fuel as it gives 99% of the maximum fuel mileage in zero wind. When cruising within 2000 ft of the optimum altitude LRC approximates to a .74 Mach cruise.

If the aircraft is flown above or below the optimum altitude for LRC or .78 Mach Table 4.1 tabulates the fuel penalty incurred as a % correction.

Example 1

Enter the Optimum Cruise Altitude table with the Cruise Mass (Weight) 56 800 kg, move vertically up to the selected cruise profile, LRC/.74 Mach or .78 Mach, and move horizontally to read the optimum cruise pressure altitude.

...............................?

...............................?

NB. There are two axis on Fig 4.1 used for the Weight - Brake Release Weight (Take-off Weight) or Cruise Weight. Be sure to get the right one!

Example 2

Cruise weight 62 000 kg. Calculate the optimum pressure altitude for a .74 Mach cruise and the fuel and mileage penalty if the aircraft is cleared to fly 4000 ft below.

..............................?

(Answers page 80)

Short Distance Cruise Altitude

(Refer CAP 697 Figure 4.2)

The cruise distance for sectors of 235 NM or less is limited by those required for the climb and descent. The Short Distance Cruise Pressure Altitude table shows the maximum pressure altitude at which it is possible to cruise for at least a minute.

NB. The only interpolation for ISA is done between +10°C and +20°C

Example 3:

Enter with the trip distance, 175 NM, and move to the temperature line, ISA +20°C; move horizontally to the Reference Line and follow the trade lines to intercept the vertical at the Brake Release Weight, 52 000 kg; move horizontally to read the optimum cruise pressure altitude:

..............................?

Example 4:

Sector distance 150 NM, temperature at MSL take-off of 30°C and brake release weight 42 500 kg. Calculate the maximum short distance cruise pressure altitude.

...............................?

(Answers page 80)

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Planning Flight Simplified (MRJT) Transport Jet Range Medium 6

Simplified Flight Planning - Introduction

(Refer to CAP 697 Figures 4.3.1a to 4.4)

Simplified Flight Planning graphs are provided in the CAP 697 MRJT1 for:

One ALTERNATE PLANNING - LRC: 0 - 500 NM

One HOLDING FUEL PLANNING

The LRC, 0.74 Mach, 0.78 Mach and 300 KIAS Cruise graphs have the same presentation.

The Simplified Flight Planning charts determine trip fuel and time from brake release to touchdown. APU usage, taxi, in-flight flaps down manoeuvring (other than straight in approach), Cost Index Adjustments and reserve fuel should be added to the trip fuel from these charts to obtain the total fuel required. Additional fuel for holding is obtained from the Holding Fuel Planning table. (CAP 697 Figure 4.4)

Simplified Flight Planning - Method

Example 5

LRC trip distance 1000 NM; cruise at FL290 with 50 kt headwind, ISA -10°C. Estimated landing weight 40 000 kg. Calculate the fuel required and flight time.

Enter with the trip distance and go vertically to the reference line. Follow the flow lines and correct for 50 kt headwind.

Move vertically from this point to the first 29 intersection of the Pressure Altitude lines. Move horizontally across to the Landing Weight reference line and follow the flow lines to correct for Landing Weight.

Go back to the original vertical line and at the 29 intersection on the upper Pressure Altitude intersections move horizontally to the Trip Time reference line; follow the flow lines to ISA -10°C.

If the given wind component exceeds that on a chart, convert the trip distance to nautical ground miles (NGM) to nautical air miles (NAM) and ignore the head and tail flow lines:

Simplified Flight Planning - Additional Allowances

Cost Index Adjustment

The LRC Simplified Flight Planning charts are based upon climb, cruise and descent speeds which produce an approximate minimum trip fuel. If the flight is planned to operate with the Flight Management System (FMS) in the economy (ECON) mode adjustments to the trip fuel and time are necessary to account for the different flight profile; the table above itemizes these adjustments.

Ground Operations

Fuel may be saved by minimizing APU operation. The average APU fuel flow for normal operations is 115 kg/h (250 lb/h).

The taxi fuel allowance is 11 kg/min (25 lb/min).

Cruise - Air Conditioning (AC) Packs and Engine/Wing Anti-ice

• AC packs at high flow:

Altitude Selection

The best fuel consumption for mileage at a given cruise profile is achieved at the optimum altitude. The fuel penalty for operations off the optimum altitudes is given by CAP 697 Table 4.1 of section 4 page 1.

Descent

The Simplified Flight Planning charts assume a descent at 0.74 Mach/250 KIAS and a straight in approach.

For every additional minute of flaps down operation add 75 kg of fuel. For Engine Anti-ice during the descent add 50 kg.

Holding Fuel (EU-OPS Final Reserve Fuel is extracted from this table)

The holding fuel is extracted from the HOLDING FUEL PLANNING table (Refer to CAP 697 Figure 4.4). The chart is based upon a racetrack pattern at the minimum drag airspeed, with a minimum of 210 KIAS. Interpolation for weight and pressure altitude is required.

Example: An aircraft holding at a pressure altitude of 1500 ft with a weight, at the start of a 30 minute hold, of 54 000 kg has a planned fuel flow of 2520 k/h. The expected fuel burn in the 30 minute hold is thus:

2520 ÷ 2 = 1260 kg. The aircraft weight at the end of the hold is 54 000 - 1260 = 52 740 kg.

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