The cost index - Fokker

The cost index

2 

Fuel and Environmental Management

Fuel and Environmental Management 

Table of Contents 

1 FOREWORD....................................................................................................................................9 

2 FUEL MANAGEMENT CONCEPTS .............................................................................................11 

2.1 FUEL MANAGEMENT AND SAFETY....................................................................................11 

2.2 CHANGE MANAGEMENT AND AIRLINE CULTURE............................................................11 

2.3 FUEL MANAGEMENT AND THE ENVIRONMENT ...............................................................11 

2.3.1 The Environment .............................................................................................................11 

2.3.2 Emissions ........................................................................................................................11 

2.3.2.1 CO2 and H2O Emissions ..........................................................................................................11 

2.3.2.2 NOX and Other Emissions ........................................................................................................11 

2.3.3 Emission Calculations .....................................................................................................11 

2.3.3.1 Top-Down Approach: Estimates of CO2 and H2O ....................................................................11 

2.3.3.2 Calculation of NOx Emissions ...................................................................................................11 

2.3.3.3 Detailed Approach: Estimates of other Emissions.....................................................................11 

2.3.3.4 Sample Airline Pollution ............................................................................................................11 

2.4 ECONOMIC IMPACT OF EFFICIENT FUEL MANAGEMENT ..............................................11 

2.5 BASIC FACTS REGARDING FUEL CONSUMPTION...........................................................11 

2.6 THE IATA FUEL EFFICIENCY GAP ANALYSIS (FEGA) GREEN TEAMS...........................11 

2.7 AIRLINE BENCHMARKING ...................................................................................................11 

2.8 FUEL MANAGEMENT INFORMATION SYSTEM (FUEL MI)................................................11 

2.8.1 Monitoring the accuracy of the flight planning system ....................................................11 

2.8.2 Tracking of each aircraft fuel burn accurately .................................................................11 

2.8.3 Monitoring Fuel on Board (FOB) and fuel uplift...............................................................11 

2.8.4 Monitor the Fuel over Destination (FOD) ........................................................................11 

2.8.5 Monitor fuel performance of Flight Crews .......................................................................11 

2.8.6 Monitor the planning efficiency of Flight Dispatchers......................................................11 

2.8.7 Monitor Estimated Zero Fuel Weight (EZFW) and payload optimization........................11 

2.8.8 Develop efficient fuel saving procedures and monitor their effectiveness ......................11 

2.8.9 Monitor fuel cost for the various routes ...........................................................................11 

2.8.10 Taxi delays and gate hold including taxi fuel...................................................................12 

2.8.11 Sensitize Managers to Efficient Fuel Usage ...................................................................12 

2.9 HIGH COST OF FULL THRUST TAKEOFF...........................................................................12 

2.10 COST INDEX MANAGEMENT...............................................................................................12 

2.11 DYNAMIC COST INDEX ........................................................................................................12 

2.12 GENERIC AIRLINE ................................................................................................................12 

2.12.1 Generic Airline Fleet........................................................................................................12 

2.12.2 Cost of Weight.................................................................................................................12 

2.13 OVERVIEW OF POTENTIAL FUEL SAVINGS......................................................................12 

2.13.1 Air Traffic Control.............................................................................................................12 

2.13.2 Pilot Technique................................................................................................................12 

2.13.3 Cost Index Flying.............................................................................................................12 

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2.13.4 Accurate Flight Planning .................................................................................................12 

2.13.5 Using Statistics for Fuel Optimization .............................................................................12 

2.13.6 Alternate Selection ..........................................................................................................12 

2.13.7 No Alternate Airport- IFR Operations ..............................................................................12 

2.13.8 Contingency Fuel Calculation..........................................................................................12 

2.13.9 Aircraft Fuel Burn Management ......................................................................................12 

2.13.10 Tankering.........................................................................................................................12 

2.13.11 Zero Fuel Weight Management.......................................................................................12 

2.13.12 Center of Gravity Management .......................................................................................12 

2.13.13 Maintenance....................................................................................................................12 

2.13.14 Other Savings..................................................................................................................12 

2.13.15 Total Potential Savings....................................................................................................12 

2.14 GENERIC AIRLINE SUMMARY OF POTENTIAL SAVINGS ................................................12 

2.15 GENERIC AIRLINE EMISSION REDUCTION POTENTIAL ..................................................................12 

3 FLIGHT DISPATCH.......................................................................................................................12 

3.1 FLIGHT DISPATCHER - PILOT RELATIONSHIP .................................................................12 

3.2 FLIGHT PLANNING................................................................................................................12 

3.2.1 Flight planning considerations.........................................................................................12 

3.2.2 Route selection and planning..........................................................................................13 

3.3 PRINCIPLES OF COST INDEX FLIGHT ...............................................................................13 

3.3.1 Cost Index Calculation Methods......................................................................................13 

3.4 LIMITATIONS OF LEGACY FLIGHT PLANNING SYSTEMS................................................13 

3.5 FLIGHT PLANNING SYSTEM INVESTMENT .......................................................................13 

3.6 EFFICIENT FLIGHT PLANNING............................................................................................13 

3.7 COST INDEX OPTIMIZATION ...............................................................................................13 

3.7.1 Dynamic Cost Index Optimization ...................................................................................13 

3.7.2 Impact of non-Optimized Cost Index Operation ..............................................................13 

3.8 COST INDEX CALCULATIONS .............................................................................................13 

3.8.1 Time Dependent Maintenance Cost................................................................................13 

3.8.2 Crew Cost........................................................................................................................13 

3.8.3 Cost Index Calculations...................................................................................................13 

3.9 COST INDEX FLIGHT............................................................................................................13 

3.10 MISSION MANAGEMENT......................................................................................................13 

3.10.1 The schedule...................................................................................................................13 

3.10.2 On-Time performance .....................................................................................................14 

3.10.3 Managing the mission .....................................................................................................14 

3.11 FLIGHT SCHEDULE IMPACT ON FUEL EFFICIENCY ........................................................14 

3.12 FLIGHT WATCH.....................................................................................................................15 

3.13 FUEL MANAGEMENT INFORMATION .................................................................................15 

3.14 CONTINGENCY FUEL...........................................................................................................15 

3.14.1 FAR Part 121 Regulations Domestic Operations............................................................15 

3.14.2 FAR Part 121 Regulations International Operations.......................................................15 

3.14.2.1 Operations Specification Amendments .....................................................................................15 

3.14.3 Contingency Fuel JAR-OPS............................................................................................15 

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3.15 STATISTICAL EXTRA (COMPANY) FUEL............................................................................15 

3.16 ALTERNATE SELECTION .....................................................................................................15 

3.17 NO ALTERNATE OPERATIONS – IFR..................................................................................15 

3.17.1 Federal Air Regulations (FAR) No Alternate Operations ................................................15 

3.17.1.1 Part 121.619 Alternate Airport for destination IFR Domestic Operations ..................................15 

3.17.1.2 Part 121.619 Alternate Airport for destination IFR Domestic Operations ..................................15 

3.17.1.3 JAR-OPS 1.295 Selection of Aerodromes.................................................................................15 

3.18 RE-DISPATCH OPERATIONS...............................................................................................15 

3.18.1 Re-Dispatch under FAA FAR Regulations ......................................................................15 

3.18.2 JAR-OPS 1.255 Reduced Contingency Fuel Option.......................................................15 

3.19 FUEL BIAS - FLIGHT PLANNING SYSTEM..........................................................................15 

3.20 FUELTANKERING..................................................................................................................15 

3.21 LOAD PLANNING...................................................................................................................15 

3.21.1 Center of Gravity Management .......................................................................................15 

3.21.2 ZFW Planning Variance ..................................................................................................18 

4 FLIGHT OPERATIONS .................................................................................................................18 

4.1 PRE-DEPARTURE PLANNING .............................................................................................18 

4.1.1 Complexity of Flight Planning..........................................................................................19 

4.1.2 Flight Plan Format ...........................................................................................................19 

4.1.3 Graphics and Internet accessibility .................................................................................19 

4.1.4 Communications at Airports ............................................................................................19 

4.1.5 In-Flight Communications................................................................................................19 

4.1.6 Conclusion.......................................................................................................................19 

4.2 FLIGHT CREW AND TACTICAL MISSION MANAGEMENT.................................................19 

4.3 STATISTICAL DISCRETIONARY FUELS..............................................................................19 

4.4 FLIGHT MANAGEMENT SYSTEM PROGRAMMING...........................................................19 

4.5 AUXILIARY POWER UNIT MANAGEMENT..........................................................................19 

4.5.1 Single Pack APU Air Conditioning Optimized Operation ................................................19 

4.6 ENGINE START-UP AND TAXI .............................................................................................19 

4.6.1 Taxi speeds .....................................................................................................................19 

4.6.2 Choice of Departure Runway vs. Taxi times...................................................................19 

4.7 REDUCED THRUST TAKEOFF.............................................................................................20 

4.8 REDUCED TAKEOFF FLAPS................................................................................................20 

4.9 INITIAL CLIMB OUT PROFILE MANAGEMENT ...................................................................20 

4.9.1 Climb-out Considerations ................................................................................................20 

4.10 LATERAL TRACK MANAGEMENT........................................................................................20 

4.11 VERTICAL PROFILE MANAGEMENT IN CRUISE ...............................................................20 

4.12 CRUISE SPEED MANAGEMENT ..........................................................................................20 

4.13 FMS DESCENT PROFILE MANAGEMENT...........................................................................20 

4.14 FMS DESCENT PROFILE .....................................................................................................20 

4.14.1 Energy Management and Trade off ................................................................................20 

4.14.2 Distance, speed and altitude trade off.............................................................................20 

4.14.3 Descent Profile Wind Corrections ...................................................................................21 

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4.14.4 Landing Weight................................................................................................................21 

4.14.5 Engine Anti-Ice ................................................................................................................21 

4.14.6 ATC Restrictions..............................................................................................................21 

4.14.7 Penalties for Early/Late Descent.....................................................................................21 

4.15 PILOT TECHNIQUE AND FUEL EFFICIENCY...................................................................................21 

4.16 DESCENT PROFILE MANAGEMENT FOR NON-FMS AIRCRAFT .....................................21 

4.17 BASIC PRINCIPLES OF THE DECELERATED APPROACH ...............................................21 

4.17.1 FMS Arrivals....................................................................................................................21 

4.17.2 Decelerated Approaches (Low Noise Low Drag)............................................................21 

4.17.3 High Head Winds on Final will result in long final legs....................................................21 

4.18 REDUCED FLAP LANDING...................................................................................................21 

4.19 IDLE ENGINE REVERSE ON LANDING ...............................................................................22 

4.20 ENGINE-OUT TAXI-IN ...........................................................................................................22 

5 AIR TRAFFIC CONTROL..............................................................................................................22 

5.1 OVERVIEW ............................................................................................................................22 

5.1.1 Fuel is burned to carry fuel..............................................................................................22 

5.1.2 Strategic management ....................................................................................................22 

5.1.3 Possible Environment and Fuel Champion Accountabilities...........................................22 

5.2 AT THE GATE ........................................................................................................................22 

5.3 TAXIING AND DEPARTURE .................................................................................................22 

5.4 CLIMB.....................................................................................................................................22 

5.5 CRUISE ..................................................................................................................................22 

5.6 SPEED CONTROL AND HEADING VECTORING ................................................................22 

5.7 DIRECT ROUTING.................................................................................................................22 

5.8 DESCENT...............................................................................................................................22 

5.9 HOLDING ...............................................................................................................................22 

5.10 APPROACH AND LANDING..................................................................................................23 

5.11 WHAT CAN AIR NAVIGATION SERVICE PROVIDERS DO...............................................23 

5.12 WHAT CAN AIR TRAFFIC CONTROLLERS DO.................................................................23 

6 MAINTENANCE AND ENGINEERING (M&E)..............................................................................23 

6.1 GENERAL...............................................................................................................................23 

6.2 FUEL PENALTY CALCULATION...........................................................................................23 

6.3 AIRCRAFT WEIGHTS............................................................................................................23 

6.3.1 Weight & Balance - ATA 8...............................................................................................24 

6.3.2 Fly Away Kits or Flight Spares ........................................................................................24 

6.3.3 Aircraft Refueling - ATA 28..............................................................................................24 

6.4 AERODYNAMIC DETERIORATION ......................................................................................24 

6.4.1 Effect of drag on fuel consumption..................................................................................24 

6.4.2 Aerodynamic critical areas ..............................................................................................25 

6.5 AIRCRAFT PERFORMANCE MONITORING (APM).............................................................27 

6.6 ENGINES................................................................................................................................27 

6.6.1 Engine Water Wash ........................................................................................................27 

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6.6.2 Engine Build Standards...................................................................................................28 

6.6.2.1 Refurbishment of Engines for Fuel Efficiency............................................................................28 

6.6.3 Engine on wing monitoring ..............................................................................................28 

6.6.4 Engine handling while aircraft is in maintenance ............................................................28 

6.6.5 Recommendations ..........................................................................................................28 

6.7 APU.........................................................................................................................................28 

6.7.1 Ground Support Equipment (GSE) .................................................................................28 


6.8 AIRFRAME SYSTEMS...........................................................................................................28 

6.8.1 Environmental Control System - ATA 21 ........................................................................28 

6.8.2 Flight Controls - ATA 27 ..................................................................................................28 

6.8.3 Fuel System (Airframe) - ATA 28 ....................................................................................28 

6.8.4 Instruments - ATA 31 ......................................................................................................28 

6.8.5 Pneumatic System - ATA 36 ...........................................................................................28 

6.8.6 Structure and Doors - ATA 51-57....................................................................................28 

6.8.6.1 Skin roughness..........................................................................................................................29 

6.8.6.2 Gaps and Mismatches...............................................................................................................33 

6.8.6.3 Missing or damaged seals (leakage)........................................................................................36 

6.8.6.4 Mis-rigging and mis-alignment...................................................................................................39 

6.8.6.5 MMEL items and Configuration Deviations ...............................................................................39 


6.9 MAINTENANCE PLANNING ..................................................................................................40 

6.10 MAINTENANCE TRAINING ...................................................................................................40 


6.11 FUEL CONSERVATION DOCUMENTATION........................................................................40 

7 MARKETING AND SALES ...........................................................................................................40 

7.1 GENERAL..................................................................................................................................40 

7.1.1 Cost of Weight.................................................................................................................40 

7.1.1.1 Recommendations ....................................................................................................................40 

7.1.2 Cabin Furnishings and Emergency Equipment - ATA 25 ...............................................40 


7.1.3 Potable Water - ATA 38 ..................................................................................................40 


7.1.4 Aircraft Utilization / Timetable..........................................................................................40 


8 IATA FUEL SERVICES: FUEL STANDARDS & QUALITY.........................................................41 

8.1 COLLABORATION FOR REAL RESULTS ............................................................................41 

8.2 OBJECTIVES OF THE IATA TECHNICAL FUEL GROUP (TFG) .........................................41 

8.3 IATA FUEL QUALITY POOL (IFQP) ......................................................................................41 

8.4 IMPROVING SAFETY AND QUALITY CONTROL ................................................................41 

8.5 COMMON OBJECTIVES .......................................................................................................41 

9 GLOSSARY...................................................................................................................................41 

7


A. THE COST INDEX EXPLAINED .....................................................................................................1 

A.1 MINIMIZING THE COST PER FLIGHT................................................................................................2 

A.2 COST INDEX AND ITS USE BY FMS................................................................................................4 

A.3 SAMPLE CALCULATION OF THE COST INDEX..................................................................................6 

8


1 FOREWORD 

As fuel costs are a significant part of the operating cost of an aircraft, and with the dramatic rise of 

fuel prices over the past decennia, more and more emphasis is being put on fuel conservation by 

airlines. 

With the upcoming introduction of the European Emission Trading Scheme (ETS), aimed at reducing 

the emission of greenhouse gasses, fuel conservation becomes even more important as there is a 

direct relation between CO 2 emission and fuel burn. 

It is not surprising therefore that many airframe manufacturers, airlines and aviation related 

organizations have published many articles, manuals, presentations, etc on the subject of fuel 

conservation. 

Fokker Services shares this intention, however without reinventing the wheel. There are so many 

generic methods to save fuel, independent of aircraft type, that have been described and explained 

by others, that there is no reason to add more of the same. 

Fokker Services considers the IATA "Guidance Material and Best Practices for Fuel and 

Environmental Management" (also known as the IATA Fuelbook) as one of the global standards on 

this subject. 

It is a manual that is regularly updated (the 4 th Edition has just been issued) and it is written especially 

for aircraft operators, which is the audience Fokker Services is focused on as well. 

Furthermore, this manual is being used as a reference by the IATA Green Teams - experts that 

consult with airlines to implement recognized fuel conservation techniques. The experience gained 

during these campaigns will be used to improve the manual on a regular basis. 

This manual already contains many recommendations that are applicable to all types of aircraft, 

including the Fokker aircraft. Many of these recommendations will require some kind of effort to 

implement in the day-to-day operation or maintenance activities of an aircraft operator. It is therefore 

essential to know what the quantitative effect of the implementation of such measures is in terms of 

fuel conservation. In this way an aircraft operator can make the proper trade off between the 

implementation cost and the result in terms of fuel conservation. 

Considering the above, Fokker Services has come to the conclusion that it would be worthwhile for 

Fokker aircraft operators, to have a supplement to the IATA Fuelbook, that specifies the particular 

characteristics of the Fokker aircraft with respect to fuel conservation measures. 

Also additional remarks or different points of view will be provided in this supplement where relevant. 

This supplement has been written for flight planning, maintenance and operations personnel of 

Fokker aircraft operators. It has the same layout as the IATA Fuelbook for easy reference. The 

contents page of this Supplement is identical to the IATA Fuelbook, apart from the page numbering. 

9


Each paragraph is adopted in the body also, even if it does not contain additional information. This 

has been done in anticipation of future updates. These empty paragraphs have been shaded grey in 

this document. 

This Supplement to the IATA Fuelbook will be updated regularly when new experience or knowledge 

is gained. Research is going on all over the world by many organizations to reduce fuel consumption. 

In addition, regulatory changes that affect fuel consumption may become effective in the near future. 

Fokker Services has the intention to gather the results of these developments and to present it in this 

publication through these updates. 

Therefore, any suggestions or comments regarding this publication are more than welcome. 

Please contact us via www.myfokkerfleet.com : “Knowledge - Q&A database – Post new Question” 

on and select “Question Type“ : Technical/ Operational” 

Fokker Services is confident that this document will contribute to the continuous and competitive 

operation of your Fokker aircraft. 

Disclaimer: 

In case of any discrepancy between this article and a Fokker Services issued document such 

as Airplane Flight Manual, Airplane Operating Manual, Aircraft Maintenance Manual, Service 

Letter, All Operators Message, etc, the latter group of documents are leading. 

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2 FUEL MANAGEMENT CONCEPTS 

2.1 FUEL MANAGEMENT AND SAFETY 

2.2 CHANGE MANAGEMENT AND AIRLINE CULTURE 

2.3 FUEL MANAGEMENT AND THE ENVIRONMENT 

2.3.1 The Environment 

2.3.2 Emissions 

2.3.2.1 CO2 and H2O Emissions 

2.3.2.2 NOX and Other Emissions 

Links to the individual Engine Exhaust Emissions Data Sheets for the engines of the Fokker 70 and 

Fokker 100 are given below. For the Fokker 50, no datasheets are available as turboprop engines are 

not included in the database. 

Fokker 70 and Fokker 100 with TAY 620 engines : 

http://www.caa.co.uk/docs/702/1RR020_01102004.pdf 

Fokker 100 with TAY 650 engines : 

http://www.caa.co.uk/docs/702/1RR021_01102004.pdf 

2.3.3 Emission Calculations 

2.3.3.1 Top-Down Approach: Estimates of CO2 and H2O 

2.3.3.2 Calculation of NOx Emissions 

2.3.3.3 Detailed Approach: Estimates of other Emissions 

2.3.3.4 Sample Airline Pollution 

2.4 ECONOMIC IMPACT OF EFFICIENT FUEL MANAGEMENT 

2.5 BASIC FACTS REGARDING FUEL CONSUMPTION 

2.6 THE IATA FUEL EFFICIENCY GAP ANALYSIS (FEGA) GREEN TEAMS 

2.7 AIRLINE BENCHMARKING 

2.8 FUEL MANAGEMENT INFORMATION SYSTEM (FUEL MI) 

2.8.1 Monitoring the accuracy of the flight planning system 

2.8.2 Tracking of each aircraft fuel burn accurately 

2.8.3 Monitoring Fuel on Board (FOB) and fuel uplift 

2.8.4 Monitor the Fuel over Destination (FOD) 

2.8.5 Monitor fuel performance of Flight Crews 

2.8.6 Monitor the planning efficiency of Flight Dispatchers 

2.8.7 Monitor Estimated Zero Fuel Weight (EZFW) and payload optimization 

2.8.8 Develop efficient fuel saving procedures and monitor their effectiveness 

2.8.9 Monitor fuel cost for the various routes 

11


2.8.10 Taxi delays and gate hold including taxi fuel 

2.8.11 Sensitize Managers to Efficient Fuel Usage 

2.9 HIGH COST OF FULL THRUST TAKEOFF 

2.10 COST INDEX MANAGEMENT 

2.11 DYNAMIC COST INDEX 

2.12 GENERIC AIRLINE 

2.12.1 Generic Airline Fleet 

2.12.2 Cost of Weight 

2.13 OVERVIEW OF POTENTIAL FUEL SAVINGS 

2.13.1 Air Traffic Control 

2.13.2 Pilot Technique 

2.13.3 Cost Index Flying 

2.13.4 Accurate Flight Planning 

2.13.5 Using Statistics for Fuel Optimization 

2.13.6 Alternate Selection 

2.13.7 No Alternate Airport- IFR Operations 

2.13.8 Contingency Fuel Calculation 

2.13.9 Aircraft Fuel Burn Management 

2.13.10 Tankering 

2.13.11 Zero Fuel Weight Management 

2.13.12 Center of Gravity Management 

2.13.13 Maintenance 

2.13.14 Other Savings 

2.13.15 Total Potential Savings 

2.14 GENERIC AIRLINE SUMMARY OF POTENTIAL SAVINGS 

2.15 GENERIC AIRLINE EMISSION REDUCTION POTENTIAL 

3 FLIGHT DISPATCH 

3.1 FLIGHT DISPATCHER - PILOT RELATIONSHIP 

3.2 FLIGHT PLANNING 

3.2.1 Flight planning considerations 

For flight planning, performance data is used that is normally provided by the aircraft manufacturer. 

With this performance data, block fuel and block time for a given flight can be calculated. These 

important parameters depend on the climb, cruise and descent speeds, the cruise altitude for a given 

route, ambient conditions, and take-off weight. 

The trip cost of an airplane can be broadly divided into the following elements: 

- fixed costs (typically cost of ownership, landing/nav charges and ground handling) 

- time-related cost (typically maintenance costs, crew costs) 

- fuel-related cost 

12


Flight planning can be used to find the optimum balance between the time and fuel-related cost 

elements to minimize the trip cost. This is done by optimizing the cruise altitude and the climb, cruise 

and descent speeds. This optimization shall be done for the actual wind speeds per flight level as this 

parameter plays an important role in the determination of the optimum vertical flight profile. 

The Cost Index is the parameter that is often used to correlate time and fuel-related cost. A detailed 

explanation of it is given in Appendix A. 

3.2.2 Route selection and planning 

3.3 PRINCIPLES OF COST INDEX FLIGHT 

3.3.1 Cost Index Calculation Methods 

Fokker 70 and Fokker 100 aircraft are equipped with a Flight Management System (FMS) for efficient 

pre-flight and en-route flight planning. The latter is often required as either the en-route weather 

conditions (temperature, wind speeds, etc) deviate from the forecasted values or ATC directs the 

airplane to other flight levels. With the FMS it is possible for the crew to recalculate in-flight the 

optimum vertical profile for three different options; MINIMUM TIME, MINIMUM FUEL and ECONOMY 

(balanced fuel and time related cost). For the latter the Cost Index (CI) parameter is used as an input. 

A detailed explanation of the Cost Index is given in Appendix A. 

3.4 LIMITATIONS OF LEGACY FLIGHT PLANNING SYSTEMS 

3.5 FLIGHT PLANNING SYSTEM INVESTMENT 

3.6 EFFICIENT FLIGHT PLANNING 

The optional Fokker 50 FMS (or better Navigation Management System) does not provide en-route 

vertical profile calculations and fuel predictions. However, guidelines can be prepared in the form of 

tables or graphs for in-flight adjustments by the crew. Also, Electronic Flight Bags can be used to run 

software that determines the optimum profile and speeds. Fokker Services is cooperating with PACE 

GmbH in Germany to develop such software. More information can be found on www.pace.de under 

“product Highlights” “CI OPS”. 

3.7 COST INDEX OPTIMIZATION 

3.7.1 Dynamic Cost Index Optimization 

3.7.2 Impact of non-Optimized Cost Index Operation 

3.8 COST INDEX CALCULATIONS 

3.8.1 Time Dependent Maintenance Cost 

3.8.2 Crew Cost 

3.8.3 Cost Index Calculations 

3.9 COST INDEX FLIGHT 

3.10 MISSION MANAGEMENT 

3.10.1 The schedule 

13


3.10.2 On-Time performance 

3.10.3 Managing the mission 

3.11 FLIGHT SCHEDULE IMPACT ON FUEL EFFICIENCY 

Cruise altitude and cruise speed play an important role in both block time and block fuel. 

By variation of the cruise altitude and speed schedule in flight planning software, the effects of these 

parameters become clear. 

Sophisticated flight planning software has the option to optimize these parameters as a function of the 

Cost Index. 

In the next table examples are given of the effect of flying at a flight level that is 4000 ft below the 

maximum operating altitude. 

Aircraft type 

Speed 

Schedule 

Distance 

[NM] 

Increment in 

block fuel 

[kg] 

Increment in 

block time 

[min] 

Fokker 50 LRC 250 14 1.0 

Max Cruise 250 36 -2.5 


Max Cruise 400 74 -1.0 


Max Cruise 400 68 0.0 

Table 3.11-1 Effect on block fuel and block time when flying 4000 ft below max. operating altitude 

In the table below samples are given to show the effect of flying with max cruise speed instead of 

long-range cruise (LRC) speed. 

Aircraft type 

Cruise 

Flight 

Level 

Distance 

[NM] 

Increment in 

block fuel 

[kg] 

Decrement in 

block time 

[min] 

Fokker 50 250 250 16 4.9 

210 250 38 8.4 


310 400 207 7.0 


310 400 165 6.0 

Table 3.11-2 Effect on block fuel and block time when flying at max cruise instead of long-range 

cruise 

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3.12 FLIGHT WATCH 

3.13 FUEL MANAGEMENT INFORMATION 

3.14 CONTINGENCY FUEL 

3.14.1 FAR Part 121 Regulations Domestic Operations 

3.14.2 FAR Part 121 Regulations International Operations 

3.14.2.1 Operations Specification Amendments 

3.14.3 Contingency Fuel JAR-OPS 

3.15 STATISTICAL EXTRA (COMPANY) FUEL 

In addition to the text in the IATA Fuelbook, it is emphasized that there is an interaction between the 

surplus of statistical and discretionary fuel and the fuel tankering policy. If it is beneficial to carry 

additional fuel because of economic reasons (i.e. the fuel prices at the point of departure are 

favorable), then there is no need for a painstaking process to determine accurate quantities of 

statistical and discretionary fuel. On the other hand, if the flight is to an airfield with lower fuel prices, 

carrying not more than the required fuel becomes even more important. In this case a surplus of fuel 

not only causes additional fuel consumption due to the higher aircraft weight, but also less cheap fuel 

can be tankered at the destination, i.e. after landing you are stuck with the expensive fuel on board 

the airplane! 

3.16 ALTERNATE SELECTION 

3.17 NO ALTERNATE OPERATIONS – IFR 

3.17.1 Federal Air Regulations (FAR) No Alternate Operations 

3.17.1.1 Part 121.619 Alternate Airport for destination IFR Domestic Operations 

3.17.1.2 Part 121.619 Alternate Airport for destination IFR Domestic Operations 

3.17.1.3 JAR-OPS 1.295 Selection of Aerodromes 

3.18 RE-DISPATCH OPERATIONS 

3.18.1 Re-Dispatch under FAA FAR Regulations 

3.18.2 JAR-OPS 1.255 Reduced Contingency Fuel Option 

3.19 FUEL BIAS - FLIGHT PLANNING SYSTEM 

3.20 FUEL TANKERING 

The effect of the weight of the additional fuel carried, is equivalent to that of an increase of the 

Operational Weight which is shown in paragraph 6.3 

3.21 LOAD PLANNING 

3.21.1 Center of Gravity Management 

The longitudinal position of the center of gravity (CG) affects the aerodynamic drag of the aircraft. 

However, the conventional wisdom of a forward CG position resulting in a higher negative tail load 

15


and thus more drag is not always true. For the Fokker 70 and Fokker 100 an aft CG position indeed 

improves fuel economy as shown in the graphs below. These graphs show the fuel saving during 

cruise when the CG position is shifted aft by 10%. These values are applicable over the entire CG 

range. 

It also shows that the fuel savings become more significant at high lift coefficients, i.e. high weight, 

low speed and at the highest flight levels. 

Fokker 100 

Fuel Saving in percentage per 10% aft CG shift 

1.6 

1.4 

1.42 

Ma.65 

Ma.70 

1.2 

Ma.75 

1.0 

0.8 

0.6 

1.00 

0.68 

0.62 

1.00 

0.81 

0.4 

0.2 

0.0 

-0.2 

0.35 

0.24 0.22 

0.21 

0.00 

0.00 

W=36000kg/FL350 W=36000kg/FL250 W=40000kg/FL350 W=40000kg/FL250 

Figure 3-1 Fuel Savings for aft CG shift, Fokker 100 

16




1.4 

1.2 

1.15 

Ma.65 

Ma.70 

1.0 

0.8 

0.90 

0.82 

0.92 

0.84 

Ma.75 

0.6 

0.59 

0.4 

0.2 

0.28 

0.25 

0.22 

0.27 

0.12 

0.32 

0.0 

-0.2 



17


For the Fokker 50 however, a forward CG position gives the best fuel economy, which is illustrated in 

the graph below where additional fuel burn results from an aft CG shift. This contradictory effect is 

caused by the complicated aerodynamic interaction of the propeller wash on the tail plane and the 

position of the engines. 



0.0 


-0.1 

-0.2 

-0.3 

-0.21 

-0.4 

-0.33 

-0.33 

-0.33 

-0.5 

-0.6 

-0.7 

-0.50 

-0.45 

-0.47 

-0.55 

-0.45 

150kEAS 

175 kEAS 

200 kEAS 

-0.55 

-0.47 

-0.68 

-0.8 


Apart from its longitudinal position, the CG lateral position may also be shifted from the centerline due 

to fuel asymmetry and, to a lesser extent, due to asymmetrical passenger seating or cabin 

arrangement. This results in aileron and rudder deflection throughout the flight. 

Although the effect of lateral CG shifts on fuel consumption is very low, it is advised to strive for 

symmetrical fuel distribution. 

3.21.2 ZFW Planning Variance 

4 FLIGHT OPERATIONS 

4.1 PRE-DEPARTURE PLANNING 

18


4.1.1 Complexity of Flight Planning 

4.1.2 Flight Plan Format 

4.1.3 Graphics and Internet accessibility 

4.1.4 Communications at Airports 

4.1.5 In-Flight Communications 

4.1.6 Conclusion 

4.2 FLIGHT CREW AND TACTICAL MISSION MANAGEMENT 

4.3 STATISTICAL DISCRETIONARY FUELS 

4.4 FLIGHT MANAGEMENT SYSTEM PROGRAMMING 

4.5 AUXILIARY POWER UNIT MANAGEMENT 

4.5.1 Single Pack APU Air Conditioning Optimized Operation 

4.6 ENGINE START-UP AND TAXI 

The Fokker 70 and Fokker 100, Airplane Operating Manuals (AOM) give procedures for Single 

Engine Taxiing (AOM 5.14.02 “Delayed Engine Start”). Keep in mind that the engine should be given 

sufficient time to warm-up before the take-off is initiated. (ref. AOM 70/100 5.14.01 “Engine Warm- 

Up”). If these warm-up times are not adhered to, increased engine wear, including a degradation of 

fuel efficiency, will be the result. 

Fuel is saved as it is more efficient to produce a certain amount of thrust with only one engine rather 

than two engines. In addition, at low take-off weights, idle thrust on two engines often exceeds the 

required thrust for taxiing. Single engine taxiing is therefore also beneficial with respect to brake life. 

On average, 25 kg of fuel can be saved when taxiing for 10 minutes with one engine instead of two 

engines. 

There is always a slight risk that difficulties arise during engine start, which is very annoying and time 

consuming if this happens just before the take-off when the aircraft is already lined up to enter the 

runway. 

Under ground icing conditions, delayed engine start is not recommended due to the unavailability of 

engine anti-icing on the inlet of the inoperative engine and also because ice can build up on the fan 

blades causing engine vibrations at engine start. 

For the Fokker 50 Single Engine Taxi is not recommended due to the higher asymmetry and because 

the idle thrust does not exceed the required thrust for taxiing. 

4.6.1 Taxi speeds 

4.6.2 Choice of Departure Runway vs. Taxi times 

19


4.7 REDUCED THRUST TAKEOFF 

For the Fokker 50, the use of reduced take-off thrust has hardly any effect on engine life. This is 

because the day-to-day take-off power (all-engines-operating) is already 10% below the rated take-off 

power. Only after an engine failure in take-off, the power is increased to Maximum Take-Off rating. 

In addition, block fuel will increase as a greater part of the flight is executed at low altitude. 

For the Fokker 70 and Fokker 100, the recommendations of the main IATA document are applicable. 

4.8 REDUCED TAKEOFF FLAPS 

The use of lower flap settings results in improved climb performance, but also in higher take-off 

speeds and longer take-off distances. 

Therefore, the preferred flap setting for a take-off, based on flight safety depends on the criticality of 

available take-off distances and/or required climb performance due to obstacles. A higher flap setting 

may therefore be preferred to increase the safety margin on the take-off distance at the cost of some 

additional fuel. 

4.9 INITIAL CLIMB OUT PROFILE MANAGEMENT 

When taking off away from the intended course, it may sometimes be beneficial to select a low flap 

setting, even though this results in higher initial climb-out speeds. If the turn is to be initiated at a 

certain height, this point is reached earlier and closer to the brake release point than with higher flap 

settings as lower flap settings result in the best climb gradients. 

The Fokker 70 and Fokker 100 have extendable landing lights that normally are left out up to 10,000 

ft. Depending on company policy, operational requirements and weather conditions, this may be 

reduced to a lower flight level. Retracting the landing lights at 5,000 ft in lieu of 10,000 ft would 

typically save 3 kg per take-off. 

4.9.1 Climb-out Considerations 

On Fokker aircraft the ECS bleed selections ECON and NORM are available. If acceptable for 

passenger comfort, ECON is preferred above NORM as this will save fuel. 

For the Fokker 70/100 the fuel savings are approximately 0.5% and for the Fokker 50 this can be as 

high as 0.9% of the block fuel. These figures are valid when the flight conditions are identical for 

ECON and NORM bleed. Under some conditions the rated thrust or power may change when ECS 

bleed is switched from NORM to ECON. 

4.10 LATERAL TRACK MANAGEMENT 

4.11 VERTICAL PROFILE MANAGEMENT IN CRUISE 

4.12 CRUISE SPEED MANAGEMENT 

4.13 FMS DESCENT PROFILE MANAGEMENT 

4.14 FMS DESCENT PROFILE 

4.14.1 Energy Management and Trade off 

4.14.2 Distance, speed and altitude trade off 

20


4.14.3 Descent Profile Wind Corrections 

4.14.4 Landing Weight 

4.14.5 Engine Anti-Ice 

The Fokker 70 and Fokker 100 FMS does not take into account the effects of engine bleed off-takes 

on fuel flow. This may cause only small errors in fuel predictions and flight path optimization. The 

descent idle fuel flow will increase by as much as 5% for the TAY620 engine and 10% for the TAY650 

engine, but as the total descent fuel is only a small part of the trip fuel, the absolute error remains 

small. 

However, if airframe anti-ice is selected during descent, the idle thrust will increase significantly. In 

that case the FMS uses too low idle thrust levels for the calculation of top of descent resulting in late 

descent initiation. In addition, to achieve required rate of descent the use of speed brakes may be 

required. Refer to the Airplane Operating Manuals section 5.08.01 page 2 for applicable procedures. 

Therefore, if during descent the use of airframe anti-icing is anticipated, the descent shall be initiated 

earlier than calculated by FMS. 

For the Fokker 50 the selection of engine anti-ice has no appreciable effect on fuel consumption and 

descent flight path. 

4.14.6 ATC Restrictions 

4.14.7 Penalties for Early/Late Descent 

4.15 PILOT TECHNIQUE AND FUEL EFFICIENCY 

4.16 DESCENT PROFILE MANAGEMENT FOR NON-FMS AIRCRAFT 

4.17 BASIC PRINCIPLES OF THE DECELERATED APPROACH 

4.17.1 FMS Arrivals 

4.17.2 Decelerated Approaches (Low Noise Low Drag) 

4.17.3 High Head Winds on Final will result in long final legs 

4.18 REDUCED FLAP LANDING 

For the Fokker 50 the standard landing flap setting is 25. Only if required by the available landing 

distance, is flap setting 35 being used. Therefore, no fuel savings can be obtained by means of 

reduced flap landings. In addition, flap setting 35 is selected at 300 ft AGL, which means that the 

exposure time to the high drag condition is very limited and hence the additional fuel for flaps 35 is 

only marginal. 

For the Fokker 70 and Fokker 100 however, the standard flap setting for landing is 42 degrees 

favored by the lower landing speeds. Leaving the flaps at 25 degrees throughout the final approach 

from 1300 ft AGL and including the landing if sufficient landing distance is available, reduces the fuel 

consumption by approximately 20-25 kg per landing. Do not use flap 25 if it is anticipated that due to 

21


the increased landing distance the runway will be vacated later such that the fuel to taxi to the ramp 

will increase significantly. 

The Fokker 70 and 100 have extendable landing lights that normally are selected out in the descent 

at 10,000 ft. Depending on company policy, operational requirements, operational and weather 

conditions, this may be reduced to a lower flight level. Extending the landing lights at 5,000 ft in lieu of 

10,000 ft would typically save 2 kg per descent. 

4.19 IDLE ENGINE REVERSE ON LANDING 

On the Fokker 70 and Fokker 100 the use of idle reverse is recommended, refer to Aircraft Operating 

Manual Flight Techniques paragraph 7.06.01. 

For the Fokker 50, ground idle is recommended, which, in most situations is more than sufficient to 

obtain the required deceleration. Use reverse and wheel brakes as required. 

4.20 ENGINE-OUT TAXI-IN 

With the Fokker 70 and Fokker 100, taxi-in fuel can be saved by shutting off one engine as it is more 

efficient to produce a certain amount of thrust with only one engine rather than with two engines. In 

addition, at low landing weights, idle thrust on two engines is often exceeds the required thrust for 

taxiing. Single engine taxiing is therefore also beneficial with respect to brake life. 

After landing and after flaps, liftdumpers and speedbrakes are retracted, one engine may be shut 

down. However, observe one minute at idle for engine cool down. 

On average 25 kg fuel can be saved when taxiing for 10 minutes with one engine instead of two 

engines. 

For the Fokker 50 Single Engine Taxi is not recommended due to the higher asymmetry and because 

the idle thrust does not exceed the required thrust for taxiing. 

5 AIR TRAFFIC CONTROL 

5.1 OVERVIEW 

5.1.1 Fuel is burned to carry fuel 

5.1.2 Strategic management 

5.1.3 Possible Environment and Fuel Champion Accountabilities 

5.2 AT THE GATE 

5.3 TAXIING AND DEPARTURE 

5.4 CLIMB 

5.5 CRUISE 

5.6 SPEED CONTROL AND HEADING VECTORING 

5.7 DIRECT ROUTING 

5.8 DESCENT 

5.9 HOLDING 

22


5.10 APPROACH AND LANDING 

5.11 WHAT CAN AIR NAVIGATION SERVICE PROVIDERS DO 

5.12 WHAT CAN AIR TRAFFIC CONTROLLERS DO 

6 MAINTENANCE AND ENGINEERING (M&E) 

In addition to the standard maintenance documents, you will find a wealth of information on 

maintenance and engineering related subjects on the www.myfokkerfleet.com website. 

Select “Knowledge” and then select one of the following groups for the relevant aircraft type: 

- Service Experience Digest 

- Service Letters 

- Technical Focus Group 

- All Operator Messages (aom) 

- Technical Operational Notices (TON) 

- Technical User Forum 

Many of these documents give “best practices” to keep your aircraft in optimum condition, also with 

respect to fuel consumption. 

6.1 GENERAL 

6.2 FUEL PENALTY CALCULATION 

6.3 AIRCRAFT WEIGHTS 

Block fuel increases with increasing aircraft weight. The aircraft weight is composed of the 

Operational Empty Weight (OEW), the fuel on board and the payload. To save fuel, it is important that 

the OEW is kept as low as possible. 

Apart from the lower fuel consumption, a low OEW has additional advantages, namely: 

- Increase of the maximum payload when limited by the Maximum Zero Fuel Weight (MZFW) 

- Increases of the maximum fuel to be loaded when limited by maximum take-off weight and by that 

either the range is increased or more fuel can be uploaded for fuel tankering purposes. 

In Table 6.3-1, the increase in block fuel and fuel cost is given for an increase of 100kg OEW. An 

average fuel price of € 0.50/kg has been applied, which is equivalent to approximately 0.73 US$/kg 

(Nov.2009) or 2.20 US$ /US Gallon as used in the IATA Fuelbook. 

In this scenario an average number of 2000 flights per aircraft per year is assumed for all Fokker 

aircraft types. The assumed stage length for the Fokker 70 and Fokker 100 is 400 NM and 250 NM 

for the Fokker 50. An average block time of 1.2 hours is assumed for all Fokker aircraft types. 

23


Aircraft type 

Speed 

Schedule 

Cruise 

Flight 

Level 

Increment in 

block fuel 

per flight [kg] 

Increment in 

block fuel 

per flight [%] 

Increment in 

annual fuel cost 

per aircraft [€] 

Fokker 50 LRC 200 1.8 0.30 1,800 

250 2.1 0.36 2,100 

Max Cruise 200 1.0 0.16 1,000 

250 1.5 0.25 1,500 

Fokker70/100 LRC 250 3.8 0.15 3,800 

350 4.5 0.19 4,500 

Max Cruise 250 2.5 0.09 2,500 

350 4.2 0.16 3,500 

Table 6.3-1. Increment in block-fuel for 100 kg additional OEW. 

6.3.1 Weight & Balance - ATA 8 

Fokker aircraft Service Bulletins often have an effect on the weight of the aircraft. It may be 

worthwhile to take this aspect also into account in deciding to install or remove a Service Bulletin. 

One recently developed Service Bulletin is of particular interest, i.e. SBF100-25-110, which 

introduces of DRYLINER TM to reduce the formation of moisture and ice buildup in insulation blankets, 

eliminating significant weight. The details of this SB will be made available soon. 

6.3.2 Fly Away Kits or Flight Spares 

6.3.3 Aircraft Refueling - ATA 28 

6.4 AERODYNAMIC DETERIORATION 

6.4.1 Effect of drag on fuel consumption 

The effect of additional drag on block fuel depends on such parameters like aircraft weight, speed 

schedule, trip length and cruise altitude. 

These parameters have been used to define four representative flight profiles for which the increase 

in block fuel as a result of a drag increment is determined. 

Based on these scenarios, it was concluded that the difference between the scenarios and the 

influence of aircraft weight are both small and that a general rule of thumb regarding the increase in 

block fuel due to a drag increment can be described by: 

∆F [%] = 0.45 * ∆C D for the Fokker 70 and Fokker 100 and 

∆F [%] = 0.20 * ∆C D for the Fokker 50 

24


where ∆F is the relative increase in block fuel and ∆C D is the drag increment in counts. 

In the following sections examples will be given for the Fokker 50, 70 and 100 regarding the effect of 

drag increasing items. 

6.4.2 Aerodynamic critical areas 

In service, wear and tear inevitably leads to deterioration of the aerodynamic characteristics resulting 

in an increase in drag. When drag increases, more engine power or thrust is required, and hence the 

fuel consumption increases too. Reducing the aircraft’s drag whenever possible, is therefore an 

effective way to reduce the fuel consumption. 

The figures below mark the areas for the Fokker 50 and Fokker 70/100, where mismatches and 

surface roughness have the largest impact on the aircraft drag. These critical and semi-critical areas 

are the so-called aerodynamic Class A (light colored areas) and Class B (dark colored areas). 

Especially in these areas, optimal surface quality and smoothness should be strived for. 

25


Figure 6-1: left: Aerodynamic critical areas of the Fokker 70/F100 

right: Aerodynamic critical areas of the Fokker 50 

Important: 

mismatches or roughness on the leading edges of the wing and stabilizer 

should be avoided at all times. This is not only because of the increased drag, 

but because the aircraft’s stall speeds and characteristics will be negatively 

affected. 

26


Aerodynamic smoothness in relation to Boundary Layer Flow: 

The boundary layer thickness of the airflow, together with the local pressure at a certain point 

of the body, determines mainly the area’s sensitivity to drag due to disturbances. 

As the boundary layer thickness of the airflow increases when moving more downstream, 

surface imperfections get more submerged in the boundary layer such that the impact on 

aerodynamic drag is less. On the other hand, surfaces that face the ‘undisturbed’ airflow, like 

the wing leading edges, stabilizer leading edges and the forward section of the fuselage, are 

aerodynamically critical areas where the boundary layer is still thin, and disturbances on the 

aircraft skin have a large impact on drag. 

As described above, the fuel burn penalty caused by drag-inducing items does not only depend on 

the irregularity itself, but also on its location. In the followings sections, items are presented to give 

insight in the various types of aerodynamic deterioration and their effect on the fuel consumption. The 

values presented are mainly based on analysis using aerodynamic principles. The effects are often 

too small to measure during flight-testing. 

The drag increasing items will be discussed in more detail in chapter 6.8.6. 

6.5 AIRCRAFT PERFORMANCE MONITORING (APM) 

6.6 ENGINES 

It is sometimes overlooked that engine ground running also requires fuel. On many occasions 

alternatives are available for ground running. (e.g. Fokker 70/100 P3 Static Leak Test see RR NTO 

88 or in-flight checks during revenue flights). If ground running cannot be avoided, prepare the tests 

carefully such that no time is wasted with running engines. 

6.6.1 Engine Water Wash 

For the Fokker 70 and Fokker 100, engine water washing provides the best means of restoring 

engine efficiency between shop visits. 

Rolls-Royce has issued a (Repeater) Technical Variance 95279R “Alternative Compressor Wash 

procedure”. The on-wing engine wash is performed with EcoPower of which a presentation is 

available through our MyFokkerFleet.com website / Knowledge / Fo70/100 / TFG / TFG23 / 2008-04- 

15-On-Wing-Engine-Water-wash. 

One operator performed several trials with EcoPower to establish the associated fuel burn 

improvement. Preliminary results indicate a reduction of up to 2% fuel burn. Available data however is 

very scattered. Reported experience indicates a typical repeat wash interval of around 500FH. 

However, the optimum engine water wash interval is operator-specific and dependent on the 

operational environment. 

27


For the Fokker 50 no trials have been executed so far. However, provisions are available for the 

Fokker 50 to enable the use of EcoPower. Operators are invited to start a compressor wash trial with 

EcoPower. 

6.6.2 Engine Build Standards 

6.6.2.1 Refurbishment of Engines for Fuel Efficiency 

Fuel efficiency of the Tay engines on the Fokker 70 and Fokker 100 can sometimes be improved with 

Rolls Royce Service Bulletin TAY-72-1603 - “Instructions for a repair to the LP compressor (fan) 

blade leading edge profile” 

6.6.3 Engine on wing monitoring 

6.6.4 Engine handling while aircraft is in maintenance 

6.6.5 Recommendations 

6.7 APU 

The APU on the Fokker 70/100 has an average fuel consumption of: 

Garrett RR type : 87 kg/hr (191 lb/hr) 

Garrett R type : 73 kg/hr (160 lb/hr) 

For those Fokker 50/60 aircraft equipped with an APU an average fuel consumption of 107 kg/hr (236 

lb/hr) is typical. 

6.7.1 Ground Support Equipment (GSE) 


6.8 AIRFRAME SYSTEMS 

6.8.1 Environmental Control System - ATA 21 

6.8.2 Flight Controls - ATA 27 

6.8.3 Fuel System (Airframe) - ATA 28 

6.8.4 Instruments - ATA 31 

6.8.5 Pneumatic System - ATA 36 

6.8.6 Structure and Doors - ATA 51-57 

In this section examples are given of roughness, mismatches, leakages and mis-rigging and their 

effect on fuel consumption. The Structural Repair Manual (SRM) and the Aircraft Maintenance 

Manual (AMM) give maximum values that are based on flight safety (deterioration of flight handling 

and performance). It is emphasized that for fuel conservation reasons more restrictive values are 

recommended. 

28


At all times, the wing leading edges should be kept (aerodynamically) clean, not only from the point of 

increased fuel consumption, but because a contaminated leading edge adversely affects the stall 

speed and stall characteristics of the aircraft, and hence reduces flight safety. 

6.8.6.1 Skin roughness 

In order to minimize the consumption of fuel, the aircraft skin roughness should be minimized as 

much as possible. Roughness may be present in various forms such as damaged paint, non-flush 

rivets, dirt and waviness. 

Paint Peeling and Erosion 

The wings as well as the nose section of the fuselage and stabilizer are typically Class A and B 

aerodynamic areas, where skin roughness has the strongest impact on fuel consumption. The 

following table gives rough estimates of the increase in fuel consumption due to light and heavily 

deteriorated skin paint on the wings and stabilizer, followed by some examples of such paint 

deterioration. 

Paint condition 

Lightly damaged paint 

Fokker 50 Fokker 70/100 

Increase in Block Fuel 

[∆%/m 2 ] 

Increase in Block Fuel 

[∆ %/m 2 ] 

Class A 0.014 0.014 

Class B 0.009 0.009 

Heavily damaged paint 

Class A 0.050 0.050 

Class B 0.014 0.015 

Table 6.8-1: Effect of rough paint on the fuel consumption 

The above values are rough estimates for average cruise conditions. Also, within the defined critical 

areas (Class A and B) the effect may vary. For roughness close to the leading edges of the wings or 

stabilizer, the increase in block fuel may even double because of the high overspeeds and local 

pressures. 

The de-icing boots of the Fokker 50 on the leading edges of the wings may become damaged 

(swelling and ballooning) which is comparable to heavily damaged paint. 

For the Fokker 50, areas that are in the slipstream of the propellers are particularly important. The 

slipstream causes an increase of the dynamic pressure ratio (local over free stream dynamic 

pressure) over the wing, and in some part on the horizontal stabilizer. Since drag is closely related to 

this dynamic pressure ratio, skin roughness in the propeller slipstream has a significant contribution to 

the fuel consumption. The propeller slipstream also affects the outboard side of the left hand nacelle, 

29


and inboard side of the right hand nacelle. The front section of the nacelle is a Class A area, in which 

(distributed) roughness should be minimized as much as possible. 

The propeller leading edges are prone to erosion, especially the de-icing boots. Eroded leading 

edges lead to lower propeller efficiency and hence higher fuel consumption. Therefore the leading 

edges should be inspected regularly for erosion. When operating on unpaved or sandy/dusty 

runways, protection tape may be considered. (See also Fokker 50 Service Experience Digest 61-10) 

NACA inlets, such as the airco inlets, and the engine air intakes are designed as low-drag inlets. 

Roughness in or around the inlet does not only introduce unnecessary drag, but it may also disturb 

the airflow and by that the effectiveness of the inlet is reduced. 

Figure 6-2: Left: Heavily damaged paint on trailing edge of the flap track fairing of a Fokker 70 

Right: Lightly damaged paint on the vertical stabilizer of a Fokker 50 

Dirt 

Dirt adhering to the aircraft skin has only a very small contribution to aircraft drag. It is estimated that 

for an excessively dirty aircraft the fuel consumption rises up to 0.1%. The drag contribution comes 

mainly from the critical aerodynamic areas. Dirt, but also large amounts of dead bugs on the leading 

edges must be avoided as apart from the drag increase, it adversely affects stall speed and stalling 

characteristics. 

Although the drag-rise is small, regular cleaning of the aircraft helps in locating leakages and 

damages on the aircraft. 

30


Dents 

Dents on strongly curved or sharp-edged surfaces such as the leading edges of the wings and 

stabilizer, can have a strong contribution to drag. Dents of 1 mm depth on the wing leading edges of 

the Fokker 70 and Fokker 100 can increase the fuel consumption by as much as 1.5%. When the 

dent is further downstream on the body, the dents gets more submerged in the boundary layer and its 

impact on drag is much smaller or even negligible. 

Large soft dents are interpreted as waviness. Waviness has a drag increase that is proportional to the 

height and length of the wave. 

Protruding, inset and missing fasteners 

Although rivets and screw are relatively small items, their contribution to drag rise when not properly 

installed must not be underestimated, especially fasteners located in the aerodynamically critical 

areas. The following figures show examples of inset fasteners on the boundary layer fence and 

leading edge of the wing fuselage fairing. On the left pictures, it is also shown that the seal shows 

cracks and dents. The cracks and dents increase the aircraft drag, but may also induce improper 

functioning of the seal, i.e. air can leak from one side to the other side of the boundary layer fence. A 

leaking boundary layer fence may affect the stalling characteristics of the aircraft. It is emphasized 

that clean and properly sealed leading edges should be strived for at all times. 

Figure 6-3: Examples of inset fasteners 

The drag of an inset screw as presented in the left picture having soft rounded edges can be at least 

5 times higher than a flush screw. The drag of an inset fastener having sharp and notch edges may 

be more than 20 times higher. The effect of a protruding or inset rivet is demonstrated in the following 

figure. In this figure, the relative drag-rise is shown of a non-flush rivet compared to that of a flush 

rivet. 

31


Figure 6-4: Effect of inset or protruding rivet 

The notched holes in the wing fuselage fairing on the leading edge as shown in the right figure, may 

increase the fuel consumption by 3.3 x 10 -4 % for a single rivet. Having 5 notched holes on leading 

edges of both wing fuselage fairings would hence require 0.0033% additional block fuel. 

Figure 6-5: Example of chipped paint near static ports 

The above figure shows chipped-off paint in front of the static ports. Although only a small increase in 

drag may be expected, more important here is that the airflow is disturbed which can result in an error 

in speed and altitude indication. A lower speed indication of 0.01 Mach, already requires 2.3% 

additional fuel burn in cruising flight. The effect on fuel consumption of an error in altitude indication is 

less, but here flight safety may be reduced especially when operating in RVSM areas. 

32


Waviness 

The fuel burn increase due to waviness is typically due to additional pressure drag. The drag of 

waviness is a function of the ratio of the height squared to length. It has been determined that for the 

Fokker 70 and Fokker 100, a waviness as shown in the following figure, would result in an average 

increase in fuel consumption of approximately 0.5x10 -4 % at non-critical locations. 

Figure 6-6: Waviness; L = 500 mm, h = 5 mm and 1 meter wide 

6.8.6.2 Gaps and Mismatches 

Mismatches may manifest themselves in various ways, not only by external repairs but also for 

example by sealant that protrudes from the filled area. Some of the most common mismatches, and 

their drag contribution are discussed in this section. 

The following figure shows the effect of a step out of the fuselage contour, such as a repair plate or a 

protruding door, etc. It shows that at the forward fuselage section the impact of external deterioration 

is the strongest, and to some extent close to the wings too. In the following figure, the increase in 

block fuel is given in percentage per meter mismatch length. 

Front 

Section 

Wings 

Figure 6-7: Increase in fuel consumption due to repair patch on fuselage (Fokker 70/100) 

33


The figure, which is based on wind tunnel pressure measurements, can be used to illustrate the effect 

of repairs or mismatches on the fuselage surface. It shows that mismatches have a strong impact on 

the front section of the fuselage and close to the wings. 

For example, a main passenger door protruding 3mm, results in a fuel consumption increase of 

approximately 0.05%. 

For the Fokker 50 no wind tunnel pressure measurements are available. However, calculations have 

shown that a main passenger door on the Fokker 50, protruding 3mm, would also result in a fuel rise 

of approximately 0.05%. 

Figure 6-8: Example of NLG door protruding 5 mm out of fuselage skin (Fokker 70), resulting in 

approximately 0.05% increase in fuel consumption 

Figure 6-9: Protruding leading edge seal (h = 1 mm) 

Leading edge mismatches due to protruding sealant, may not only be created during the application 

of the sealant, but also due to aging and the deformation of the wing during operation. At the leading 

34


edges high suction peaks are present and also the boundary layer thickness is still very thin. 

Therefore protruding (or pockmarked) sealant has a strong impact on the fuel consumption, Sealant 

protruding 1 mm over a span of 1 meter, results in a fuel increase of approximately 0.1%. Therefore, 

adhere to the AMM (Restoration of aerodynamic smoothness, subtask 51-14-00-320), regarding 

correct application of sealant. 

Figure 6-10: Correct and incorrect applied sealant 

The engine nacelles (and engine duct/intake) of both Fokker 50 and Fokker 70/100 are critical 

aerodynamic areas. All surface discrepancies here incur considerable drag. As a practical example a 

mismatch of 2 mm on the Fokker 50 cowling was discovered (see Figure 6-11, the mismatch extends 

to both sides of the nacelle). The front part of the engine nacelle is an aerodynamically critical area. 

Conservative calculations showed that the fuel consumption may increase by up to 0.1 % for such a 

misalignment. 

35


Figure 6-11: Mismatch around a Fokker 50 engine air intake having a mismatch of 2 mm 

Repair Patches 

Non-flush repair patches always affect aircraft drag. However, by working the edges, the drag rise 

can be minimized. The next figure demonstrates the importance of rounding the repair patch’s edges. 

It shows that an oblique and a rectangular edge have a drag that are 2.7 times and 10 times higher, 

respectively, compared to that of a rounded edge. A scooping repair patch results in an even higher 

drag. Therefore prevent buckling of the edges of the repair patch. 

Figure 6-12: Drag of steps relative to rounded off edge. 

External repair patches on the leading edges (wings, stabilizer, flaps) must be applied as wrap 

around repairs. By wrapping the patch around the leading edges the drag rise is minimized (only a 

step down at the rear of the patch), and secondly the risk of flow separation is minimized. 

6.8.6.3 Missing or damaged seals (leakage) 

Pressure leakage is an unwanted airflow from, or into, the boundary layer which affects the pressure 

gradient of the boundary layer. A change of the pressure gradient mostly results in a drag rise, 

reduced effectiveness of control surfaces and may even create turbulence. Research in wind tunnels 

has shown that a considerable increment of drag can be caused by all types of leaks, such as 

missing or damaged seals, but also cracks, gaps and holes in the aircraft skin. 

36


Seals can be found at various locations. Examples are: 

- Main passenger door 

- Emergency exit doors 

- Landing gear doors 

- Cargo doors 

- Cockpit windows 

- Stabilizer 

- Engine nacelles 

- Control surfaces (e.g. aileron) 

- Flaps 

- Fairings and radomes 

- Servicing doors 

- Leading edges 

- Wing-fuselage fairing sealant 

- Stubwing seals 

- Boundary Layer Fence 

- Stall Promoter strip 

- Ice protection panels (Fokker 50 fuselage) 

Figure 6-13: Illustration of leakage due to misalignment (left) and missing seal (right) on the shroud 

door 

If the joints between the wings and the fuselage are not completely sealed, high-pressure air from 

below the wings will force its way up through the joints and create turbulence where it emerges on the 

top surface. Not only does this turbulence cause drag but also a reduction in lift by disturbing the 

upper surface airflow. Seals are applied in order to prevent such a pressure leak. 

Special attention must be paid to the Boundary Layer Fence (B.L.F.) (Figure 6-14) at the wing leading 

edges, which are used in conjunction with a stall promoter strip. Leakage of the BLF seal, or stall 

promoter (due to missing adhesives or loose rivets) disturbs the boundary layer and may cause 

undesirable stall behavior. 

37


Joint straps 

Too little sealing may cause leakage of wing anti-icing bleed air to ambient, resulting in a distortion of 

the boundary layer. 

If too much sealing is applied, it will be pressed out of the gaps in flight. The resulting sealing ridges 

will have an unacceptable effect on the stalling characteristics of the wing and they increase fuel 

consumption. 

Figure 6-14:Loose BLF seal 

Cabin air leakage may result from missing and deteriorated seals on passenger doors, windows and 

emergency exits. The estimated increase in block fuel due to cabin seal leakage is approximately 

0.010% per 5 cm of missing seal for aerodynamically semi-critical areas. For less critical areas, 

approximately 0.006% is expected. Leakage may be discovered by the dark traces on the fuselage 

around doors and by inspection of the seals. 

The drag increase for leakage due to missing or damaged sealing, from or to non-pressurized areas, 

is much lower. Other studies indicate that leakage of the wing-body faring, flaps, ailerons, and nose 

gear doors result in a fuel consumption increase of 0.05 %/m 

Figure 6-15: Dark smudges indicating leaking/loose rivets 

38


During a drag cleanup program for the Fokker 50 it was found that unsealed flaps or badly sealed 

flaps increase the fuel consumption with about 0.2 %. Leakage of the main landing gear doors may 

cause up to 0.2 % fuel consumption increase when air is vented through the main landing gear doors 

into the wing. 

6.8.6.4 Mis-rigging and misalignment 

A misalignment of a control surface will have an effect on the pressure distribution around the 

surface’s contour, resulting in additional drag and in a change of the hinge moment. 

For the Fokker 50 this change in hinge moment must be counterbalanced by a trim-tab deflection for 

the ailerons, rudder and elevator, resulting in another drag increment. 

Therefore, the need for trimming of the rudder and ailerons may be an indication of misalignment. 

6.8.6.5 MMEL items and Configuration Deviations 

Drag characteristics based on missing Configuration Deviation List (CDL) items have been 

determined for the Fokker aircraft. The tables below indicate the effect of missing items on the fuel 

consumption. These effects have recently been included in a revision to the CDLs and MMELs. 

Fokker 70 and Fokker 100 

CDL 

Seq. No 

Item Increase in Block Fuel [%] 

52-04 1 Nose wheel door 0.6 

52-04 2 Nose wheel doors 1.2 

52-05 1 Main wheel door 1.1 

52-05 2 Main wheel door 2.2 

52-07 1 Main landing gear strut bay door 0.3 

52-07 2 Main landing gear strut bay doors 0.6 

53-09 1 Speed brake 1.0 

53-09 2 Speed brakes 1.6 

Table 6.8-2: Increase in block fuel due to missing items (Fokker 70/100) 

In the case that landing lights are stuck in the extended position, the following increases of the block 

fuel may be expected: 

39


Fokker 70 and Fokker 100 

MMEL 

ITEM 


33-44-1 Flare-out Light/ Nose Landing Light stuck in ext. pos. 2.6 

33-44-1 

Wing landing light stuck in extended position 

Pre SBF100-33-14 

Post SBF100-33-14 

33-45-1 Taxi light stuck in extended position 2.6 

Table 6.8-3: Increase in block fuel due to landing lights stuck in extended position (Fokker 70/100) 

For the Fokker 50 the fuel consumption increase as a result of missing CDL items is shown below. 

2.6 

2.8 


CDL 

Seq. No 


54-01 1 Rear part of tail cone 0.3 

54-01 Both Rear part of tail cone 0.5 

57-10 Wing Shroud Panel 0.3 

Table 6.8-4: Increase in block fuel due to missing CDL items (Fokker 50) 


6.9 MAINTENANCE PLANNING 

6.10 MAINTENANCE TRAINING 


6.11 FUEL CONSERVATION DOCUMENTATION 

7 MARKETING AND SALES 

7.1 GENERAL 

7.1.1 Cost of Weight 

7.1.1.1 Recommendations 

7.1.2 Cabin Furnishings and Emergency Equipment - ATA 25 


7.1.3 Potable Water - ATA 38 


7.1.4 Aircraft Utilization / Timetable 


40


8 IATA FUEL SERVICES: FUEL STANDARDS & QUALITY 

8.1 COLLABORATION FOR REAL RESULTS 

8.2 OBJECTIVES OF THE IATA TECHNICAL FUEL GROUP (TFG) 

8.3 IATA FUEL QUALITY POOL (IFQP) 

8.4 IMPROVING SAFETY AND QUALITY CONTROL 

8.5 COMMON OBJECTIVES 

9 GLOSSARY 

41

42 

Fuel and Environmental Management

The cost index 

Appendix A 

The Cost Index Explained

Appendix A - The Cost Index Explained 

The Cost Index (CI) as explained below, plays an important role in the determination of the cost 

optimized flight profiles. This appendix provides a brief explanation and a sample calculation of 

the Cost Index. 

A.1 MINIMIZING THE COST PER FLIGHT 

The total cost per flight at a given range can be considered to consist of a fixed cost, cost 

depending on flight time, and fuel cost: 

in which: 

C = total cost per flight 

C 0 = fixed cost 

C T = time related cost 

t = trip time 

C F = fuel cost 

W F = trip fuel 

C = C 0 + C T x t + C F x W F (eq. 1) 

A graphical representation of the total cost C as a function of the speed is shown in the figure 

below. 

2


Cost per 

flight 

Minimum 

cost 

Time 

related 

cost 

Total cost 

Fuel cost 

Max. 

Operating 

Speed 

Speed 

Minimum 

Fuel speed 

Minimum 

Cost speed 

Minimum 

Time speed 

Figure App.A - 1 Cost as a function of speed 

Minimization of the total cost C per flight is independent of C 0 and depends only on the trip time 

dependent cost C T x t and the trip fuel dependent cost C F x W F . 

If the cost per unit of time C T and the cost per unit of fuel C F are known, a trade-off between trip 

fuel and trip time for minimum operating cost may be calculated. Two special cases of the cost 

optimization process are of interest: 

When the trip time dependent costs are ignored or, in other words, the value of C T is set at zero, 

the total cost C expressed in equation 1 is reduced to: 

C = C 0 + C F x W F 

As illustrated in figure App.A-1, a minimum cost flight with C T =0 is achieved at the speed at which 

the trip fuel is minimized. 

When the trip fuel dependent costs are ignored, and thus C F is set at zero, the total cost is 

reduced to: 

C = C 0 + C T x t. 

3


As illustrated in figure App.A-1, a minimum cost flight with C F =0 is achieved when the speed is as 

high as possible. During actual operation of the aircraft, this speed may be limited by either the 

maximum operating speed or the (cruise) thrust of the engines. 

The fixed cost C 0 can be ignored when optimizing the cost per flight. In fact, only the ratio of time 

and fuel dependent cost is of interest. This is illustrated by re-writing equation 1 as follows: 

in which the Cost Index CI = C T /C F . 

C - C 0 = C F x (CI x t + W F ) 

The unit of the Cost Index is normally kg/min and it represents the value of one minute of block 

time expressed in kilograms of fuel. 

By using this conversion of the block time into block fuel, the cost of a flight can be expressed 

entirely in kilograms of fuel. By variation of the flight profile and speed schedule the conditions for 

the lowest cost can now easily be calculated. 

A.2 COST INDEX AND ITS USE BY FMS 

The Flight Management System (FMS) of the Fokker 70 and Fokker 100 provides automatic 

navigation, guidance and in-flight performance optimization. The FMS performance function 

ECON allows the computation of a flight profile that yields the lowest possible cost for a given trip 

by means of the Cost Index. 

The Cost Index allows the Flight Management System to generate cost optimized flight profiles 

independent of the individual values of C T and C F . After activation of the FMS performance 

function ECON, the cost optimization process is started. The optimum cruise speed (Mach) is 

obtained from a table in the FMS. This optimum Mach is a function of altitude, aircraft weight, 

wind speed and cost index, and has been pre-calculated during an off-line study. This study is 

based on the minimization of the so-called cruise cost function λ, representing the cost per unit of 

cruise distance: 

λ = ( CI + FF cruise ) / V G 

in which: 

FF cruise is the total cruise fuel flow 

V G is the airplane ground speed. 

Minimization of this cruise cost function with altitude and airspeed (Mach) as the independent 

variables, results in the minimum cruise cost condition at given values of aircraft weight, wind 

speed and cost index. The influence of the cost index on the optimum cruise speed at a fixed 

altitude and airplane weight is illustrated in Figure App.A-2. 

4


Cruise cost 

function 

λ 

Increasing 

CI 

Locus of 

minimum 

cruise cost 

speed 

. 

Max Cruise 

Speed 

Cruise 

Speed 

Figure App.A - 2 Cruise cost function λ versus cruise speed 

After selection by FMS of the optimum cruise Mach at a given altitude, the corresponding cruise 

cost is calculated. This process is repeated for different altitudes to determine the optimum cruise 

altitude. Once the cruise optimization has been carried out, the climb cost and descent cost are 

minimized by selecting the pre-calculated optimum climb- and descent speed stored in the FMS 

database. Mach during the final part of the climb and the initial part of the descent are set equal 

to the optimum cruise Mach. 

It should be noted that a selection of cost index CI = 0 produces the afore-mentioned minimum 

fuel profile. The same result is achieved when the MIN FUEL strategic mode is selected by the 

pilot via the Control Display Unit (CDU) of the FMS. Representing the other end of the cost index 

range, a high value of the cost index of around 100 kg/min will cause the FMS to generate a 

cruise speed close to M MO , which is also achieved when the MIN TIME strategic mode is 

selected. 

During actual flight operations, the aforementioned optimum (minimum cost) flight profile may be 

subject to certain constraints. For instance, cruise at optimum cruise level is not possible due to 

the difference between the cruise level allowed by Air Traffic Control and the FMS calculated 

optimum cruise level. Short-range flights in which the total distance required to climb to and 

5


descent from the optimum cruise level exceeds the trip distance, may require adjustment of the 

initially calculated optimum cruise altitude. 

A.3 SAMPLE CALCULATION OF THE COST INDEX 

Determination of the cost index value – to be performed by the airline - should be based on a 

careful cost analysis. When designing the flight schedule in an airline's operation, the value 

placed on time is relatively high, because the faster an aircraft flies, the more passenger-miles it 

produces in a working day. Once operating a fixed schedule, a few minutes gained or lost during 

flight, usually cannot be converted into productivity. 

The effect of productivity is therefore excluded from the analysis. The time-related costs are then 

limited to those maintenance tasks which are a function of flight time, and possibly a portion of 

the crew's pay. 

As already explained, the determination of C T requires careful consideration by the airline. 

It is not always obvious which cost elements should be included in C 0 and C T . 

For instance, crew cost may be based on scheduled block time or actual block time. For the latter 

condition it is clear that a gain in actual flying time reduces crew cost for a given trip and shall 

therefore be part of the time-related cost. For the former condition, reducing actual block-time 

does not affect the crew cost and shall therefore be part of the fixed trip cost. 

Another example is maintenance cost. The time related maintenance cost per trip can be reduced 

by decreasing the block time. However, this is usually accomplished by flying faster and thus 

thrust will have to increase. The higher thrust levels may cause increased wear and tear, which 

will have an impact on the overhaul cost of the engines, unless “power-by-the-hour” 

arrangements have been agreed upon with an engine maintenance provider. 

Also, as stated before, the effect of a change in productivity (i.e. an additional flight in a working 

day when sufficient time is gained) is not included. This assumption seems to be reasonable as it 

is usually impossible to schedule another flight on such short notice. However, one can imagine 

that a flight has to be cancelled because the previous flights of the day were flown at low speed to 

save fuel. Also, passengers missing their connection due to late arrival due to fuel saving policies 

may cause huge additional losses far higher than the fuel cost gained. 

6


As an illustration, a sample calculation of C 0 , C T and CI is presented, based on the following 

assumptions: 

number of trips: 2000 per year 

fixed cost: 1,000,000 US$ per year (ownership cost i.e. depreciation, interest, insurance) 

crew cost: 600 US$ per block hour flown (cabin + cockpit) 

maintenance cost: 800 US$ per hour 

direct expenses: 1500 US$ per trip (navigation charges, landing fees, ground handling costs) 

Fixed cost per trip: 

fixed cost per year 

C 0 = ————————————— + direct expenses 

number of trips per year 

1,000,000 

C 0 = ————— + 1500 

2000 

C 0 = 2000 US$ per trip 

Cost per unit of trip time: 

C T = crew cost + maintenance cost per hour 

C T = 600 + 800 = 1400 US$ per hour or 23.3 US$ per minute 

Fuel Cost 

The cost per unit of fuel is assumed to be: 

C F = 2.20 US$ per US gallon or 0.73 US$ per kg. 

Cost Index 

The Cost Index CI is then calculated as 23.3 / 0.73 kg/min = 32 kg/min 

Note that when the crew cost is defined as a fixed value per scheduled block hour instead of per 

flight hour, the value of C T will change from 1400 into 800 US$ per hour and as a consequence 

CI will change from 32 kg/min into 18 kg/min. 

7

8 

Appendix A - The Cost Index Explained

2 

Appendix A - The Cost Index Explained

The cost index - Fokker

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