A Fuel Efficiency Masterclass – Part Two of Three

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In the previous article (A fuel efficiency masterclass – part one), we looked at why fuel efficiency management is important, how to start and organize a fuel efficiency program, including setting a fuel budget, and, from that budget, some ideas on what fuel saving initiatives could be implemented. These are crucial first steps, understanding why it matters and establishing the architecture within which fuel efficiency initiative and processes can effectively operate. In this article, we’re going to look at some further ideas on what to manage in order to manage fuel plus how to discover savings and manage initiatives. Then, in the final part of this masterclass, we’ll consider ‘Choosing the right software for a fuel efficiency program’ and ‘How to ensure that you make the most out of your current software solution’.

COST OF WEIGHT

The next big step in the fuel program is to establish the Cost of Weight. In this we can say that every bit of weight that is put on an aircraft is going to cost fuel to transport to destination: just how much fuel is the big question. In general, across the industry, the number used for a rule-of-thumb calculation is 3% per hour: it used to be 4% per hour but that was considered too severe. How is the 3% per hour arrived at? There are two ways of finding that out (figure 7). One is to use the Breguet Range equation, which is a well-known type of aircraft performance analytics. The other and less accurate but considerably easier way is to use actual data, landing weight versus fuel burn per hour and, if that is done for thousands of flights, one arrives at a plot like the one in figure 7.

Figure 7

The plot reflects, at the lower left, the narrow body aircraft with the fuel burn per flight hour against the actual landing weight, moving upwards to the mid-weight wide bodies and the high-weight wide bodies. Each plot represents a single aircraft with an actual landing weight and an average fuel burn per hour. Using regressive analysis, a standard Excel tool, will give the value at the top of the blue column on the right, 3.02% per hour. So, if an extra tonne of weight (passengers or cargo) is taken on a ten-hour flight, 300kg of that tonne will be burned along the way. In the case of a tonne of extra fuel the number is slightly lower because the remaining amount of extra fuel becomes less as time goes by.

This is a fundamental issue; extra weight on an aircraft costs fuel. The fleet number of 3.02% above can be broken down into a percentage for sub-fleets (see figure 8) which shows different percentages due to design of the aircraft, sector lengths flown, and other factors. If your weight factor is not known, just insert 3% (as is shown in red) while the other figures in that column are based on real data. As an example, an extra kilo of weight on a single A320 during the entire year will cost $108 per year. For the entire airline fleet the number is $12,156 per kilo for the year, for this particular fuel price and route network.

Figure 8

Now we know that if, say, the marketing department wishes to put extra flyers in the aircraft to sell another credit card or something like that, adding 2kg of weight per aircraft on all sectors, all year, the cost would be $24,000-25,000 for the year to carry that material around: that extra cost should come from the marketing budget. This is the kind of information that can be used to make the arguments in a fuel efficiency program when talking to the senior management. You must be able to show these numbers and explain ‘this is what it costs, so please listen’.

DISCOVERING FUEL SAVINGS AND MANAGING INITIATIVES

Among those readers who have a fuel efficiency program in their airline, I wonder how many think that they’re doing everything that is possible and, if not, why not? Sometimes it’s a case of not having enough resources; some airlines don’t have flight data recordings because they’re not allowed to collect such data under Union rules or local rules; sometimes an airline will have a flight operations boss who simply doesn’t allow it because he doesn’t want his department to look bad … there are a variety of reasons. If the fuel efficiency team is high enough in the organization, it’s possible to do something about these excesses, however, a designated ‘fuel guy’ in a performance department or a senior first officer with a fuel efficiency mandate as a side job will have no chance.

How can we discover savings and manage initiatives? I usually break this down into the areas identified in the IATA fuel book of flight operations: flight dispatch, ground operations, commercial, etc. What we try to do is to lower operating costs by using less fuel or, more accurately, produce less wasted fuel. The key areas are lighter aircraft, more efficient aircraft and operating those aircraft more efficiently.

Flight Operations

In Flight Operations when discussing fuel efficiency topics with the management team or with the line staff; when you deliver awareness training sessions to flight crews during their (semi-)annual recurrent training, these are some of the topics that can be discussed:

  • APU operations: always a difficult one because it’s shared between Ground Operations, Technical and Flight Operations.
  • Air Conditioning: how it is used will save fuel cost.
  • Flight Crew procedures and Pilot techniques: a very general consideration for which there is not enough space in this article.
  • Systems Optimization: make sure that all tools and systems are understood and used in the right way; that system or tool limits are understood; that new developments are followed and evaluated if of interest. Lastly, ensure that the aircraft is flown correctly, trimmed, with the automation performing as it should.
  • Briefing and Fuel Efficiency: provide the right statistical information on route and destination for flight crews in pre-flight planning, to help guide discretionary fuel decisions.
  • Fuel Planning and use: a basic requirement of flight dispatch.
  • Flight Technical and Performance: performance degradation factors need to be correct, cost index needs to be correct.

Flight Crew have a large impact on a fuel and operational efficiency program so it’s important to give flight crews the right information and the right tools to do their jobs as best as they can: in-flight optimization, everything.

Discussion items

There are a number of items that will benefit from being the subject of discussions involving flight operations, flight training management and line staff.

  • Engine-out Taxi-Out / Engine-out Taxi-in: I have worked in an airline that did all of this which was great.
  • Optimized take-off flaps: it’s not really a fuel efficiency thing but a combination of lowering costs in general with de-rating: that said, de-rating engines actually costs more in fuel but the engine life increases dramatically, so that’s a lower cost and the cost saved with a properly de-rated take-off is more than the cost of extra fuel burned in a climb.
  • Optimized cruise: there are a few good tools on the market to help optimize climb, but flight crew skill is important as well.
  • Continuous Descent Operations and/or -Approaches (CDO/CDA): this is something to follow and with which readers will be familiar.
  • Low-noise low-drag approaches: a specific type of approach that aims to save fuel and produces less noise.
  • Reduced flap landings and idle reverse on landing: staple fuel saving measures where safe to do so.
  • Pilot technique in general: this is a sensitive subject but has considerable impact.

How many readers are in an airline where all of this is done and discussed? That’s the important thing, that they should be discussed. If flight operations management says that they don’t want to do any of these, ensure that they explain and write down why they are unable to go along with the idea because, at the end of the year, the fuel efficiency manager will be held accountable for why something is not happening. All of the above areas can and should be discussed and implemented where possible and within reason and within the bounds of safety and passenger comfort.

Flight dispatch

This is an area with which I am very familiar. There is a key focus on making the aircraft more efficient and lighter by carrying less fuel and flying them more efficiently, i.e. taking the best route available. Many airlines underestimate this and regard route planning as just the route to be flown; however, route planning in flight dispatch can save millions of dollars. The differences between two routes generated by the flight planning system can be significant, not just in route length, fuel burn, etc., but also in overflight costs and other variable factors. The aim is to find the lowest-cost solution for a given flight.

Data and information

In flight dispatch, we talk about the flight planning system in use and whether it is used properly and/or the relative fit of this system in the operation. We look at other systems and tools in use, Standard Operating Procedures (SOP), planning philosophy, things like always using the third alternate because that’s what management wants; or is balanced planning on the edge the order of the day? Is statistical information for flight planning available? Variable taxi fuels? Runway-specific SIDs/STARs? Then there’s contingency fuel, always a big topic; over the years, the idea of statistical contingency fuel as opposed to a fixed percentage (5% or 3% or…) has grown and those airlines who use statistical contingency fuel find that it contributes enormous savings.

Alternate selection versus arrival planning, minimum contingency fuel when operating to a dubious destination, a lot of factors play a role in deciding on the right fuel planning. For each flight the situation is different; arrival fuels should be planned separately from enroute contingencies. And with arrival fuel requirements expressed in minutes of holding time over destination, there is a metric with which all aircraft types can be compared.

Another important area is the understanding and the application of Cost Index. The most important thing about Cost Index is the time-variable cost and most airlines find it difficult to correctly assess this value. Help is available. The fuel part of the Cost Index formula is easy, it’s simply price per unit. Then there’s understanding Mission Management, most relevant for Movement Control staff who need to decide the amount of fuel to spend on making up (part of) a delay. It’s a very interesting topic and a specialty within any OCC, and somebody should be on top of this in an efficiently run airline.

The final piece here is the Zero Fuel weight (ZFW) process, i.e. the difference between the planned zero fuel weight on the flight plan and the actual zero fuel weight of the aircraft because, if you over-plan, you’ll end up with more fuel on-board than is needed but some of which will be burned to carry its own weight – it’s a waste of that fuel. I have worked with an airline that had no delta between planned ZFW and actual ZFW because they would always re-run the flight plan and top up the fuel after the load sheet was completed. But they only had a few long haul flights per day; it’s not an operation like, say, Ryanair.

Fuel is burned to meet the airline’s business requirements at the lowest overall cost: meaning, if you have to burn more fuel to make up a delay, to avoid a huge missed connection cost at the destination (hotels, re-bookings…) then that extra fuel burned is worth it. Needless to say that the big picture (meeting revised and required arrival times at a balanced cost) must never be compromised by the drive to reduce fuel costs.

Finally, flight documentation (flight plan, briefing package…) must be accurate. Crews must believe it and trust it. If they see that, of the past twenty or fifty flights into that destination, nobody used extra fuel, then that crew may also not take extra fuel. But it has to be true, it has to be trustworthy because if it is found to be wrong, that finding will soon spread across all flight crews and everyone will be taking on extra fuel ‘just to be safe’. Remember that flight crews and flight planners are members of the same team.

External contributors to fuel efficiency

Air Traffic Management (ATM) has a major impact on network operations efficiency, especially when the airline is operating a hub and spoke system, and yet most people say of this, ‘there’s nothing that I can do about it’. But I don’t agree. Local air traffic control should be invited to your annual flight crew barbecue: what I mean is, get them on-site, have controllers talk with your flight crews about the issues from both sides and work out a way of having some CDM (collaborative decision making) to talk about those shared issues and arrive at a more efficient approach and departure to and from your hub.

Are local Air Traffic Management (ATM) / Air Traffic Control (ATC) included in your fuel efficiency program / CDM (Collaborative Decision Making)? Similarly with International ATM/ATC: are you working with them on optimization of slots, and overflight, and enlisting their collaboration with organized initiatives? 50% of arrivals and 50% of departures happen here.

Lastly, meteorology: weather has the potential to impact fuel costs and so is worthy of investment (tools, training).

And, a final thought in this part: Aviation is the only industry that in most countries fully pays for its own infrastructure. It is only fair that this infrastructure (ANSPs, Airports) is as efficient as it can be. Demand participation. Demand optimization.

End of Part 2. Part 3 will follow next week at this website.

About Aircraft Analytics
Aircraft Analytics is building an unrivalled suite of data and analysis modules offering the commercial aviation industry a key reference point for aircraft specifications, performance and operating costs. Our digital tools will act a powerful enabling resource for aircraft performance benchmarking and comparisons, with the subscription-based product offering ranging from regional to wide-body passenger and cargo aircraft, plus a focused ‘Engines’ module. Version one of the ‘Freighters’ launch module will be available shortly.

The author of this article, Sander de Moor, is using his operational performance expertise, alongside data from key industry partners, to build two interactive digital tools:

  • Interactive Payload/Range Tool: Explore how payload, volume, volumetric payload and cargo packing densities vary by selected sector length and airport elevation. View results by individual aircraft or compare variants.
  • Interactive Network Performance Tool: Test and compare aircraft performance on our real-world networks from around the world. Results include: en-route fuel burn, block-times, flight times and available gross and revenue payload.

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