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How to use less fuel and stay safe

There is no shortage of motivation at the airlines to save fuel.

The operators' wish to do their bit for the environment is real, as is the need to control the cost of the compulsory European emissions trading scheme that will be fully operational in 2012. But the most obvious motive for fuel economy is that it is expensive and will almost certainly get more so.

Rather than extracting examples of fuel saving practices from airlines all over the world, this study looks at two specific carriers that have formal fuel saving programmes: Scandinavian Airlines, which has three major hubs in relatively uncluttered Scandinavian airspace, and British Airways, with its main hubs in the "spaghetti junction" terminal airspace around London.

Pilots are being taught "eco-flying" in simulators, but can theory translate into practice? ©Jonathan Player/Rex Features 
BA says measures devised by its carbon efficiency team have already provided considerable benefits and it will continue to search for further improvements. The airline says the programme, its guidelines summed up by its catchphrase "flying smarter, shorter, lighter", delivered 88,375t of CO2 savings during 2009, equivalent to the CO2 produced by burning 28,055t of fuel. The carrier summarises its fuel-saving initiatives as "modifications to our aircraft, weight reductions on board, and new operational practices".

A new project to reduce the emissions from auxiliary power unit use alone, says BA, has the potential to deliver more than 40,000t of carbon savings a year across the airline. The carrier says its engineering team has devised a unique system for accurately monitoring fuel and CO2 emissions from APUs that provides the data necessary to enable BA to develop best practice for APU use.

BA's ongoing emissions reduction plans include working with air navigation service providers to enable flight trajectories to be optimised for fuel efficiency and low noise. Even in the London terminal manoeuvring area's complex airspace, 95% of BA's arrivals use a continuous descent approach profile, says Capt Dean Plumb of BA's carbon efficiency team.

UK air navigation services provider NATS can now provide track distance to run during approaches, he says, to help the crews co-ordinate their descent profile with air traffic control. Tailored arrivals and continuous climbs during departure are now usually available, and Plumb says they can save 18-20% on conventional profiles.

Stepped climbs, once standard on all London terminal manoeuvring area departures, are no longer inevitable, but indirect air traffic control routeings forced by heavy traffic remain the most frequent constraint on the ability to fly efficient trajectories.

Jonathon Counsell, BA's head of environment, says the airline is working with NATS on "perfect flight" trials using the Edinburgh-London Heathrow route. These entail a crew-defined top of descent point for continuous descent approaches. The carrier wants to see airspace redesigned to de-conflict arrival and departure lanes so that aircraft can fly ideal descents or climb profiles without disturbance.

The longer-term, macro-scale objective is to see the Single European Sky develop its capability to deliver "business trajectories" - Europe's description of "perfect flight" profiles.

Refining ground operations at Heathrow and Gatwick, two of Europe's busiest and most space-constrained airports, involves applying improved techniques in many areas. These are being developed not only by BA, but by NATS, the UK Civil Aviation Authority and a number of other UK-based operators that are working together to define a national code of best practice for ground operations. The components of best practice for arrivals have been determined, and those for departures are being finalised.

Meanwhile, the new UK government's withdrawal of plans to approve additional runways at London Stansted and Heathrow will make ground operations efficiencies even more important, not just for fuel saving, but to ensure that the optimum use is made of every scarce resource. Optimising everything from gate occupation - critical at gate-constrained airports - to shortened taxi times and reduced waiting at holding points, depends on the progress of collaborative decision-making, the whole-system network-centric interchange of information. Plumb says it is developing quickly at Heathrow, but has some way to go to reach the standards achieved at Munich airport.

New ground operational practices include minimising the use of auxiliary power units in favour of ground-supplied electricity and air conditioning - preferably from the local electrical grid via the stand, which is more efficient than mobile ground power units. Other initiatives include single-engine taxi-in, and trials on the Boeing 747 fleet with two-engine taxi-out. The latter entails starting all four engines on pushback, then shutting two down for taxi.

SAS recently secured approval to conduct satellite-guided curved approaches to Stockholm Arlanda. The airline says it is the first to obtain clearance to use these required navigation performance (RNP) approaches in regular operations with its Boeing 737s to Runway 01R. Satellite navigation is employed to conduct an S-shaped approach rather than follow the straight-line path that the instrument landing system provides, and this ensures the flightpath avoids noise-sensitive areas, says SAS, which has been working on the curved approaches since 2004.

But the approaches have a fourth dimension: managing flights dictated by required time of arrival, a product of collaborative decision-making data exchange that ensures the aircraft arrives precisely at a time slot when the runway is clear, without having either to hold or to accelerate arrival.

This procedure and others like it are being carried out under a programme called Mint, aiming for minimum CO2 emissions in terminal manoeuvring areas. Mint has the backing of Airbus, the Eurocontrol SESAR air traffic management programme, and airlines.

SAS, which has been working since 2007 to refine new fuel-saving operational techniques, says airlines cannot wait for technological "hard" fixes, so they are having to be inventive with "soft" measures that can deliver results in the near term. Working with Oxford Aviation Academy, Stockholm (OAA Stockholm) - formerly SAS Flight Academy - the airline is working to set global benchmarks for fuel-lean operational practises. The carrier says that fuel savings of 12.5% are possible, using a range of hard and soft techniques, and that a major European operator using them is reporting 4% savings, and a US carrier 5%.

Meanwhile, the academy has worked with SAS to develop a three-day course in pilot skills that are specific to getting the most tonne-kilometres out of every kilogramme of fuel. The airline calls it "eco-piloting". This consists of a day's theory, and two days in a full flight simulator for the type that the pilot flies in line service. The academy's director of training Per de la Motte says the flight training organisation envisages this course fitting in, ideally, at the end of a type rating, and he claims the cost of the course would be recovered in fuel saved within a year.

SAS says the course involves a change in mindset for pilots, and the slaying of some operational sacred cows. For example, putting on power to make up a few minutes on a schedule is almost always counterproductive, says the carrier, but unless they are appraised of the considerations surrounding decisions like that, pilots will continue to do it without questioning the outcome, believing it is the company's top priority. "Chasing schedules to save a couple of minutes is just not worth it," says SAS, which has moved away from in-flight schedule-chasing toward eco-flying.

Awareness of the possibilities of entering actual winds rather than forecast winds is a trick pilots are taught. En-route weather updates can be obtained from meteorological service providers, but actuals can be gleaned from pilots flying at different levels to determine whether a flight level change would be desirable.

Flight International "flew" two identical short sectors in an OAA Stockholm Airbus A320 full flight simulator with the organisation's fuel-saving guru Capt Peter Fogtmann. On the first sector normal operational practices were applied, and on the second numerous "soft" fuel-saving techniques (see Saving fuel the BA way, below). The difference in fuel used was 18.4%.

SAS and OAA Stockholm are validating some of the eco-piloting practices on the line to ensure there are no unforeseen secondary effects and continue to investigate new ideas.

Canada-based flight operations consultancy TFM Aviation embraces all the tactical techniques being practised or tested by BA and SAS, but has also conducted studies of fuel-use data in normal operational practice that throw light on how much opportunity exists for standardisation of best practice.

In plotting the flightplan expected fuel burn against actual fuel burn and the variation in discretionary fuel uplift by pilots or dispatchers, TFM's president Marcel Martineau found a wide range of quantities. He says they cannot all be right, arguing for a more scientific approach to the way individual flights are managed. This inevitably entails improved specialist training for pilots and dispatchers, which chimes with the SAS/Oxford argument.

All the aviation agencies are taking emissions control progressively more seriously, with the European Aviation Safety Agency hosting a "climate change and aviation" seminar in Cologne, Germany in early September. But the airlines, if nothing else, will be glad just to reduce their fuel costs.

All British Airways' departments are looking for measures that will improve fuel efficiency and reduce CO2 emissions. These include:

Cargo Lighter cargo nets

Engineering Boeing 737, time on wing review; Boeing 777, smaller vortex generators; 777 high-speed aileron drop; 777, ram air modulators; whole-fleet weight saving initiatives; long-haul low-friction aircraft coating; Boeing 767 winglets; optimise engine-washing programmes.

Flight operations Reduce fuel carriage; engine-off taxi-out for all aircraft; revise taxi times tactically; reduce long-haul statistical contingency fuel; improve accuracy of zero fuel weight calculation; review alternate airports to optimise fuel carriage; set flight management system cost index zero throughout all Airbus flights; carry out "perfect flight profile" trial; optimise performance advantages available from smart electronic flight bag use.

Ground operations Increase the use of ground power and air conditioning supply so as to decrease auxiliary power unit use on the ground, both at base and at outstations; carry out loading so as to optimise the centre of gravity position; consider options for fuel saving when take-off is delayed; select closest runway for take-off.

Cabin Miniature wine bottles plastic instead of glass; lighter in-flight magazines; lighter cutlery in Club class; lighter serving trolleys.

British Airways has already acted to save fuel and CO2 emimssions. ©British Airways

The Oxford Aviation Academy (Stockholm) Airbus A320 full flight simulator was "flown" twice, with identical weights in identical conditions both times, on the 25min short route from Gothenburg to Copenhagen. This is a short example of the kind of exercise pilots experience on the academy's "eco-piloting" training course.

On the first trip Flight International "flew", the academy's fuel-efficiency guru Capt Peter Fogtmann occupied the right-hand seat. He ensured that procedures used were SAS/A320 standard practices and routeings, with no obviously wasteful practices. Given that fact, the 18.4% fuel saving achieved on the second trip sounds like an impressive improvement.

On the 25min Gothenburg-Copenhagen flight, that translates as a 320kg (705lb) fuel saving.

The differences applied on the second trip included:

  • Reducing the cost index from 30 to seven in the flight management system.
  • Choosing Malmo instead of Gothenburg as the alternate, which allowed carriage of 450kg less fuel.
  • Starting the auxiliary power unit only moments before pushback.
  • Single-engine taxiing (using No 1 engine). The APU was shut down immediately as No 1 had stabilised and been checked.
  • Starting No 2 engine with 3min to go to line up for take-off.
  • Taking off with flap/slat 1 instead of 2, and air conditioning/pressurisation packs selected off.
  • Retarding power levers to the "climb" detent at 800ft (245m) instead of 1,500-3,000ft and initiating acceleration at that point.
  • Request for optimum speed below 10,000ft was simulated accepted by "ATC", and climb continued at the optimum 305kt (565km/h) instead of sticking to the standard 250kt.
  • Requesting direct routeing at every opportunity. In this case the routeing was almost direct, so there were virtually no benefits, but on a route where the opportunities to route direct were available, the percentage fuel saving would have been higher.
  • Inputting forecast or actual winds into the flight management system rather than standard seasonal conditions.
  • Initiating descent at a carefully estimated point beyond the normal top of descent point because a continuous descent approach was confirmed as being available.
  • Selecting flaps as late as possible: flap 1 at glideslope intercept; flap 2 at 2,000ft; gear down just before 1,000ft; flap 3 selected just before 500ft (would be 1,000ft in instrument meteorological conditions); land with flap 3 instead of flap 4.
  • Using idle reverse during the landing run.
  • Shutting down the No 2 engine 3min after touchdown and conducting a single-engined taxi to the aircraft stand.
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