Study Minimum Fuel

Study Minimum Fuel

53RD ANNUAL CONFERENCE, Gran Canaria, Spain, 5-9 May 2014

WP No. 90

Study Minimum Fuel

Presented by TOC

Summary

Proper fuel management is responsibility of the airlines and pilots but ATM is also involved. Correct flow management may be as important as good weather information to prevent an emergency situation fuel situation. Air Traffic Controllers have also to be aware of recent changes in ICAO rules clarifying that “minimum fuel” is not an emergency state, but that additional delay could lead to an emergency and that in order to receive priority “Mayday Fuel” must be declared.

Introduction

1.1 While fuel management is not the role of the air traffic controller, the consequences of different fuel management strategies may have an effect on the air traffic environment. For this reason, controllers should be aware of changes in this area.

1.2 Fuel management is a problem with two different aspects: the pre-flight fuel determination and in-flight fuel management, related to the need to proceed to an alternate airport or to declare an emergency due to low fuel.

1.3 There are clear rules related to fuel management. Nonetheless these rules are subject to revision as demonstrated by Amendment 36 to ICAO Annex 6.

1.4 Competition between airlines has led to aggressive practices that can potentially stretch the legal margin to its very limit and leading to serious safety issues related to lack of fuel.

Discussion

2.1  It seems at first sight that a plane should carry as much fuel as possible so to ensure that flight time can be extended as long as needed.

2.2  Unfortunately fuel burn is directly linked to the weight of the aircraft i.e. the heavier the aircraft, the higher the consumption of fuel. A plane carrying more fuel than necessary uses even more fuel due to the weight of the extra fuel. This consumption is undesirable for economic and environmental reasons.

2.3  The dilemma is evident. An aircraft must carry enough fuel to perform its flight as planned plus an extra amount in case unforeseen situations arise but this extra amount should not go beyond what can be considered reasonable. As “reasonable” is not precise enough, authorities have developed rules to calculate a proper amount of fuel.

2.4  Incidents due to lack of fuel may happen due to the aircraft being fueled with less fuel than necessary or due to unexpected events like strong headwinds during flight which make the plane burn more fuel than expected. It is possible to find examples of the first case but they are very unusual. The second case is more common, especially in relation to adverse weather conditions.


2.5  ICAO regulation

2.5.1  Prior to the Amendment 36 in November 2012, ICAO Annex 6 Part I required planes to load sufficient fuel to fly to their destination plus an amount to perform a missed approach and proceed to an alternate airport or to hold for a specified amount of time with some variations in the quantity of fuel depending on the type of aircraft (piston- engine or turbine-engine). There were no provisions about when it was necessary to declare an emergency due to low fuel state.

2.5.2  After Amendment 36, Annex 6 explains in great detail pre-flight fuel calculation including 7 different amounts such as fuel needed for taxi, flight according to the flight plan and fuel for unforeseen circumstances such as deviations from the flight plan or the need to proceed to an alternate aerodrome. The term defined as final reserve fuel is of particular interest for the purpose of this paper because it determines when a pilot must declare an emergency. It is an amount of fuel that should never be consumed and defined as follows:

ICAO Annex 6 Part I

4.3.6.3 (…)

e) Final reserve fuel, which shall be the amount of fuel calculated using the estimated mass on arrival at the destination alternate aerodrome, or the destination aerodrome when no destination alternate aerodrome is required:

1) for a reciprocating engine aeroplane, the amount of fuel required to fly for 45 minutes, under speed and altitude conditions specified by the State of the Operator; or

2) for a turbine-engined aeroplane, the amount of fuel required to fly for 30 minutes at holding speed at 450 m (1 500 ft) above aerodrome elevation in standard conditions;

2.5.3 Amendment 36 of Annex 6 details when the pilot must declare a fuel emergency and also makes a distinction of minimum fuel, which indicates that additional delay may result in a state of emergency.

4.3.7.2.2 The pilot-in-command shall advise ATC of a minimum fuel state by declaring MINIMUM FUEL when, having committed to land at a specific aerodrome, the pilot calculates that any change to the existing clearance to that aerodrome may result in landing with less than the planned final reserve fuel.

Note 1.— The declaration of MINIMUM FUEL informs ATC that all planned aerodrome options have been reduced to a specific aerodrome of intended landing and any change to the existing clearance may result in landing with less than the planned final reserve fuel. This is not an emergency situation but an indication that an emergency situation is possible should any additional delay occur.

Note 2.— Guidance on declaring minimum fuel is contained in the Flight Planning and Fuel Management Manual (Doc 9976).

4.3.7.2.3 The pilot-in-command shall declare a situation of fuel emergency by broadcasting MAYDAY MAYDAY MAYDAY FUEL, when the calculated usable fuel predicted to be available upon landing at the nearest aerodrome where a safe landing can be made is less than the planned final reserve fuel.

Note 1.— The planned final reserve fuel refers to the value calculated in 4.3.6.3 e) 1) or 2) and is the minimum amount of fuel required upon landing at any aerodrome.

2.5.4  It must be noted that Minimum Fuel is not to be considered as an emergency situation. This means that aircraft affected by such condition should not expect any priority. Doc 4444 (PANS-ATM) does not list Minimum Fuel as a reason to give priority in approach or landing to an aircraft. The reasons for priority are listed in paragraphs 6.5.6.1.1 (approach sequence) and 7.7.3.3 (landing):

Priority shall be given to:

a) an aircraft which anticipates being compelled to land because of factors affecting the safe operation of the aircraft (engine failure, shortage of fuel, etc.) (…)

The situation so described corresponds to an emergency, however Minimum Fuel is not an emergency situation as stated in Annex 6 and also in Doc 4444 paragraph 15.5.4.1. (see 2.5.5 below). To avoid any ambiguity the ATM Procedures Development Sub-Group (APDSG) of EUROCONTROL has proposed to change the wording in the above sentence replacing shortage of fuel with fuel emergency.

2.5.5  The expected behaviour from Air Traffic Control in a Minimum Fuel situation is described as follows:

ICAO Doc 4444 PANS-ATM

15.5.4.1 When a pilot reports a state of minimum fuel, the controller shall inform the pilot as soon as practicable of any anticipated delays or that no delays are expected.

Note.- The declaration of MINIMUM FUEL informs ATC that all planned aerodrome options have been reduced to a specific aerodrome of intended landing, and any change to the existing clearance may result in landing with less than planned final reserve fuel. This is not an emergency situation but an indication that an emergency situation is possible should any additional delay occur.


2.6  FAA

2.6.1  The FAA has a simpler approach than ICAO for pre-flight fuel calculation. Unlike ICAO the FAA has not issued any rule explicitly defining Minimum Fuel, Emergency Fuel and Reserve Fuel. Nonetheless such concepts are mentioned in the InFO (Information for Operators) 08004:

  • Minimum Fuel indicates that an aircraft’s fuel supply has reached a state where, upon reaching the destination, it can accept little or no delay. This is not an emergency situation but merely indicates an emergency situation is possible should any undue delay occur.
  • Fuel Emergency is the point at which, in the judgment of the pilot-in-command, it is necessary to proceed directly to the airport of intended landing due to low fuel. Declaration of a fuel emergency is an explicit statement that priority handling by ATC is both required and expected.

2.6.2  The FAA does not use regulatory definition issued as to when, specifically, a pilot must declare minimum fuel or a fuel emergency, leaving it to the Operations Manuals of air carriers. Typical guidance is:

  • Pilots declare minimum fuel when in their judgment any additional delay will cause to burn part of the reserve fuel.
  • Pilots declare fuel emergency when in their judgment it is necessary to proceed directly to the airport at which landing is intended.

2.7  European Union

2.7.1  The rules related to pre-flight fuel calculation and in-flight fuel management are included in the Commission Regulation 859/2008 and 965/2012. They are very similar to the ICAO ones but being less restrictive. A final reserve fuel is defined:

OPS 1.255 Fuel Policy

(…) Final reserve fuel — Fuel to fly for an additional period of 45 minutes (piston engines) or 30 minutes (turbine engines);

About the proper time to declare fuel emergency the Commission Regulation 859/2008 and 965/2012 state:

OPS 1.375 In-flight fuel management

(…) 3. The commander shall declare an emergency when the calculated usable fuel on landing, at the nearest adequate aerodrome where a safe landing can be performed, is less than final reserve fuel.


2.8 IFALPA

2.8.1  In a Briefing Leaflet dated 10 October 2012. IFALPA summarized Amendment 36 to ICAO Annex 6 in a 3-step approach (being a very clear summary, the IFALPA leaflet is included as an annex to this paper).

  • Step 1: Request delay information (from ATC) when required.
  • Step 2: Declare MINIMUM FUEL when committed to land at a specific aerodrome and any change in the existing clearance may result in a landing with less than planned final reserve fuel.
  • Step 3: Declare a fuel emergency when the calculated fuel on landing at the nearest suitable aerodrome where a safe landing can be made will be less than the planned final reserve fuel.

2.8.2  This approach summarizes perfectly the provisions concerning Minimum Fuel and Emergency Fuel. As it includes the request of delay information the provisions regarding ATC in a situation of Minimum Fuel are also covered.


2.9 Operational scenarios

The operational scenarios below describe the importance of three aspects that involve Air Traffic Management and can be decisive in cases of minimum fuel or fuel emergency:

  • accurate information on weather forecasts,
  • correct use of Flow Management measures and
  • foresight considering alternate aerodromes.

2.9.1 Case 1: The importance of accurate weather forecast

On 18th of June 2013 two B737s from Qantas and Virgin Australia diverted to Mildura due to fog at their original destination (Adelaide). While the weather report presented Mildura as suitable, the planes found low ceiling conditions. The first plane landed below weather minima with conditions rapidly deteriorating. The second one performed a go-around but due to lack of fuel, the flight was committed to land on the next approach. The plane finally landed below weather minima with an amount of fuel well below the required final reserve. At present an interim report has been issued by the Australian Transport Safety Board, being the final report anticipated for release to the public by June 2014.

2.9.2  Case 2: The importance of proper ATFM measures

On the 26th of July 2012, thunderstorms at Madrid Barajas Airport made up to 17 aircraft divert to their alternate airports. Four of these 17 planes (three Ryanair B737 and one LAN Chile A340) declared fuel emergency while diverting to Valencia. All planes landed safely. The media attention of the incidents raised concerns in the public, leading the Spanish Minister of Transport to express her disposition to change the aviation rules to avoid similar situations.

The mass diversions situation suggests a lack of safety measures from ATFM. Unfortunately these incidents did not deserve a specific report but were included as part of another one about an isolated fuel incident that happened two years earlier. As a consequence the report does not even include the weather information and forecast for Madrid the day of the incidents, and fails to explain the link between weather information, ATFM regulations and fuel emergencies.

2.9.3  Case 3: The importance of foresight considering alternate aerodromes

A situation of mass diversions as the one described above can be aggravated if the planes have the same alternate airport. On April 20th, 2011, another situation involving severe thunderstorms took place in the Madrid area with multiple planes deviating to Valencia, the alternate airport for most of the flights. But this airport had already reached its maximum capacity because of the Spanish Football Cup final in Valencia. The situation evolved into a general improvisation exercise with multiple coordinations to find suitable aerodromes for the diverting planes.

Conclusions

3.1  ICAO and EU rules define a final reserve of fuel that must be protected. If calculation shows that upon landing the plane will carry less fuel than the reserve amount, an emergency must be declared. A similar concept exists, though not explicitly defined, in the FAA regulations.

3.2  The phraseology “Minimum Fuel” has been redefined to state that any subsequent delay can lead to a Fuel Emergency. Minimum Fuel is not a situation of Emergency but an indication that an emergency situation is possible should any additional delay occur.

3.3  Not being an emergency situation, Minimum Fuel is not a reason to give priority to an aircraft. If a pilot reports a state of Minimum Fuel, the controller must inform the pilot as soon as practicable of any anticipated delays or that no delays are expected.

3.4  Incidents linked to lack of fuel often arise during delay conditions (usually due to weather) at the destination aerodrome. These incidents can especially be troublesome if coincident with poor ATFM management, incorrect weather forecast or any incident or congestion at a designated alternate aerodrome.

Recommendations

It is recommended that;

4.1. This paper is accepted as information material.

References

ICAO: Annex 6 Operation of aircraft.

ICAO: Doc 4444 ATM/501 PANS-ATM.

ICAO: Doc 9976 Flight Planning and Fuel Management Manual.

European Commission Regulation 859/2008.

European Commission Regulation 965/2012.

FAA: InFO 08004.

EUROCONTROL ATM Procedures Development Sub-Group (APDSG) WP62.05 NTSB: Aircraft Accident Report.

NTSB/AAR-91/04.

CIAIAC: Report IN-010/2010.

ATSB: Aviation Occurrence Investigation AO-2013-100. Preliminary Report.

IFALPA: Briefing Leaflet; ICAO changes for minimum and emergency fuel. 10 October 2010 (Included as Annex).

Annex 1 – IFALPA Briefing Leaflet

Note: This IFALPA leaflet mentioned in 2.8.1 is very good summary of the provisions concerning minimum and emergency fuel. The following is its full text.

ICAO changes for minimum and emergency fuel

Background

The term MINIMUM FUEL has had different connotations globally. In addition, there has been no standard phraseology to be used when it has been determined that an aircraft will infringe upon its final fuel reserves before landing. ICAO has issued amendments to both ICAO Annex 6 Part I and the Procedures for Air Navigation Services – Air Traffic Management (PANS-ATM) (Doc4444) and these will take effect from 15 November 2012.
In summary, there are amendments to the definitions of declaring MINIMUM FUEL and procedures for protecting final fuel reserve. This briefing leaflet sets out those procedures but the reader should note that the full amendment to the ICAO Annex 6, Doc 4444 and the ICAO Doc 9976 Flight Planning and Fuel Management Manual (FPFMM), including example scenarios, can be found at the following links:

  • Adoption of Amendment 36 to Annex 6 Part 1 12 10
  • Procedures for Air Navigations Services Air Traffic Management
  • Flight Planning and Fuel Management Manual

Amendment 36 to ICAO Annex 6 Part I

Chapter 4

4.3.7 In-flight fuel management

4.3.7.1 An operator shall establish policies and procedures, approved by the State of the Operator, to ensure that in-flight fuel checks and fuel management are performed.

4.3.7.2 The pilot-in-command shall continually ensure that the amount of usable fuel remaining on board is not less than the fuel required to proceed to an aerodrome where a safe landing can be made with the planned final reserve fuel remaining upon landing.

4.3.7.2.1 The pilot-in-command shall request delay information from ATC when unanticipated circumstances may result in landing at the destination aerodrome with less than the final reserve fuel plus any fuel required to proceed to an alternate aero- drome or the fuel required to operate to an isolated aerodrome.

4.3.7.2.2 The pilot-in-command shall advise ATC of a minimum fuel state by declaring MINIMUM FUEL when, having committed to land at a specific aerodrome, the pilot calculates that any change to the existing clearance to that aerodrome may result in landing with less than planned final reserve fuel.

Note 1.— The declaration of MINIMUM FUEL informs ATC that all planned aerodrome options have been reduced to a specific aerodrome of intended landing and any change to the existing clearance may result in landing with less than planned final reserve fuel. This is not an emergency situation but an indication that an emergency situation is possible should any ad- ditional delay occur.

Note 2.— Guidance on declaring minimum fuel is contained in the Fuel Planning Manual (Doc 9976).

It should be noted that Pilots should not expect any form of priority handling as a result of a “MINIMUM FUEL” decla- ration. ATC will, however, advise the flight crew of any additional expected delays as well as coordinate when transferring control of the aeroplane to ensure other ATC units are aware of the flight’s fuel state.

4.3.7.2.3 The pilot-in-command shall declare a situation of fuel emergency by broadcasting MAYDAY, MAYDAY, MAYDAY, FUEL, when the calculated usable fuel predicted to be available upon landing at the nearest aerodrome where a safe landing can be made is less than the planned final reserve fuel.

Note 1.— The planned final reserve fuel refers to the value calculated in 4.3.6.3 e) 1) or 2) and is the minimum amount of fuel required upon landing at any aerodrome.

Note 2.— The words “MAYDAY FUEL” describe the nature of the distress conditions as required in Annex 10, Volume II, 5.3.2.1, b) 3.

Note 3.— Guidance on procedures for in-flight fuel management are contained in the Fuel Planning Manual (Doc 9976).


Amendment 4 to ICAO PANS ATM (Doc 4444)

The changes in PANS ATM complement those of Annex 6 Part I by providing the appropriate phraseology to be used in a Minimum or Emergency Fuel situation.

Explanation

These changes can basically be broken down into a 3 step approach whereby the flight crew notifies ATC of the progression of their fuel state when it has been determined by the crew that they are nearing a critical fuel situation. It is important to note that a common element in every scenario is that each time MINIMUM FUEL is declared, the PIC has already committed to land at a specific aerodrome and is concerned that a landing may occur with less than final reserve fuel in the tanks. It is equally important to note that, although the coor- dinated escalation process (with ATC) related to the protection of final reserve typically occurs in 3 steps, each situation is different, and may be resolved at any stage in the process. The 3 steps in the escalation process are:

Step 1: Request delay information when required (in accordance with 4.3.7.2.1):
Seek information from ATC concerning any expected delays.

Step 2: Declare MINIMUM FUEL when committed to land at a specific aerodrome and any change in the existing clearance may result in a landing with less than planned final reserve fuel (in accordance with 4.3.7.2.2):
Declare “Minimum Fuel” which should represent the last lines of defense in a multilayered strategy designed to ensure the protection of final reserve fuel and safe flight completion. Practically speaking, the PIC should declare “MINIMUM FUEL” when, based on the current ATC clearance, the anticipated amount of fuel remaining upon landing at the aerodrome to which the aeroplane is committed is approaching the planned Final Reserve fuel quantity. This declaration is intended to convey to the applicable air traffic controller that so long as the current clearance is not modified, the flight should be able to proceed as cleared without compromising the PIC’s responsibility to protect final reserve fuel.

Step 3: Declare a fuel emergency when the calculated fuel on landing at the nearest suitable aerodrome, where a safe landing can be made, will be less than the planned final reserve fuel (in accordance with 4.3.7.2.3):
Declare Fuel Emergency using “MAYDAY, MAYDAY, MAYDAY, FUEL”. The last in a series of procedural steps to ensure the safe completion of a flight is the declaration of an emergency. Conformance with Annex 6, Part I, 4.3.7.2.3 requires the PIC to declare a situation of emergency by broadcasting MAYDAY, MAYDAY, MAYDAY, FUEL when the calculated usable fuel to be available upon landing at the nearest suitable aerodrome where a safe landing can be made will be less than the planned final reserve fuel. This declaration provides the clearest and most urgent expression of an emergency situation brought about by insufficient usable fuel remaining to protect the planned final reserve. It communicates that immediate action must be taken by the PIC and the air traffic control authority to ensure that the aeroplane can land as soon as possible. The “MAYDAY” declaration is used when all opportunities to protect final reserve fuel have been exploited and in the judgment of the PIC,
the flight will now land with less than final reserve fuel remaining in the tanks. The word FUEL is used as part of the declaration simply to convey the nature of the emergency to ATC. It is also important to note an emergency declaration not only opens all options for pilots (e.g. available closed runways, military fields, etc.) but it also allows ATC added flexibility in handling an aeroplane.

 

©2012 The International Federation of Air Line Pilots’ Associations

IFALPA provides this data for information only, in all cases pilots should follow their company’s guidance and procedures. In the interests of flight safety, reproduction of this Bulletin in whole or in part is encouraged. It may not be offered for sale or used commercially. All reprints must credit IFALPA.

Last Update: September 30, 2020  

May 5, 2020   1230   Jean-Francois Lepage    2014    

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