Flight Levels

Doesn’t the media and internet just love a mid-air drama….or was it? In truth, the facts will only emerge once the incident has been fully investigated, but that has never stood in the way of mainstream media sensationalising an aviation story.

‘Despite all of this planning and forethought, situations can still occur en route.’

Simply put, a ‘fuel Mayday’ is a required action by the crew when its fuel on board is insufficient to meet the minimum amount that is legally required to be remaining on landing. The AIP Enroute section expresses the requirement for “…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 fixed fuel reserve and as a result of this predicted fuel state, the aircraft requires immediate assistance.”

It is not that the flight has already run out of fuel. It is about offering adequate warning to air traffic control and other aircraft in the surrounding airspace that priority in the landing sequence is required, not requested.

Still, it is not an ambiguous, understated, “We’re getting a bit low on gas here…” Such phrases have been used in the past on occasions and have left air traffic control in the dark as to the severity of the situation. For fans of the show “Air Crash Investigations”, you may recall the loss of Avianca Flight 52, a Boeing 707 flying from Bogota to New York, via Medellin. It crashed due to fuel exhaustion, and poor communication of the aircraft’s fuel state was pivotal. By transmitting “Mayday Mayday Mayday FUEL”, it is clear and concise and understood by all concerned, including other aircraft in the nearby airspace. Furthermore, using the term “FUEL” as part of the emergency declaration conveys clearly the nature of the emergency to ATC.

When a fuel Mayday is declared, the ground support services have an action plan which they activate to prepare for a range of possible scenarios. From the aircraft being unable to taxi to the gate, to potentially not being able to make the airport at all. The first responders practise these scenarios on training days to validate their processes, from entry to the aircraft to triage and distribution of patients at nearby hospitals.

As with all aspects of aviation, we prepare for the worst but endeavour to manage the situation towards a far less dramatic outcome. Passengers are briefed prior to every departure on the safety features of an aircraft and crews review engine failure scenarios before take-off as a safeguard. However, the moment “Mayday” hits the general public’s eardrums and eyeballs via the ever-enthusiastic media, the prospect of rational reporting is doubtful.

This is not to say that a fuel Mayday is routine – it is not – it is a distress message. Airlines and their crews go through numerous process to mitigate against risk and fuel management is at the forefront of those strategies. The carriage of fuel needs to be considered in terms of safety, aircraft performance and commercial aspects. Even then, the final fuel order is often subject to further interpretation and increased to cover unforeseen eventualities that that may take place, based upon experience and local knowledge.

Despite all of this planning and forethought, situations can still occur en route. Unforecast winds, conflicting traffic ‘trapping’ an aircraft at a lower and more fuel-thirsty level, aircraft system faults or significant diversions around weather are just a handful of possible causes. In most cases, there are still airports available for aircraft to divert into if a fuel issue is becoming critical – but not always. Occasionally an unforecast weather phenomena can occur at the planned destination with minimal notice.

Well before a fuel Mayday is declared, crews will be very aware of any additional destination holding fuel that may become required after their departure and they will also request any expected delay if their fuel state is surfacing as a potential issue. As a prelude to a fuel Mayday, the pilot-in-command can declare “minimum fuel” if any change to the existing clearance will result in a landing with less than the planned fixed reserve of fuel. It is not an emergency situation but advises ATC that an emergency situation is possible if any further delays occur. Unlike the Mayday, a minimum fuel declaration does not provide any priority handling by ATC, however it will ensure that other ATC units are aware of the aircraft’s fuel state when handing them onto another frequency.

That the recent fuel Mayday attracted so much media attention is testament to the fact that it is a relatively rare event. It would have been refreshing if a deeper explanation of the terminology had been a part of the reporting, although that may be asking too much.

A fuel Mayday is a distress message, but as with most aspects of aviation there is a process in place leading up to this declaration that is relatively unseen. However, when a situation becomes critical, there is no room for subtlety or ambiguity and the cold hard words of a Mayday call are necessary for all parties to fully understand the gravity of the situation. For those of us in aviation, it is a critical part of our vocabulary, for others it would seem to be a passing headline.