Operational measures

Reducing fuel consumption through operational measures

Brief overview

• Fuel costs and CO2 costs are a major factor for aviation companies. Cost pressure means that aircraft are becoming ever more economical and great efforts are made to use fuel as efficiently as possible through operational measures.
• The most important operational measures are weight reductions, optimised weight distribution in the aircraft, reduction in cruising speed, optimised climb and descent and more direct routes, optimised consideration of wind conditions and avoidance of holding patterns.
  

Fuel costs money. This is a key factor in an airline’s profitability, with fuel accounting for up to 40% of operating costs. The efficiency of air passenger and freight transport is determined and enhanced by market mechanisms. There are also additional regulatory market measures such as the Carbon Offsetting and Reduction Scheme for International Aviation CORSIA and – in the near future – the requirement to blend sustainable aviation fuels with kerosene. The focus here is on ever more effi-cient aircraft and operations.

CORSIA - Carbon Offsetting and Reduction Scheme for International Aviation

Increasing efficiency in flight operations involves a number of factors:

• Weight reductions

  Basic cabin equipment is made lighter, e.g. lighter aircraft seats or lighter freight containers. Fuel calculation is refined to ensure that the aircraft does not carry a single excess tonne of fuel, other than its reserve fuel. On long-haul flights, every avoidable tonne reduces fuel consumption disproportionately.
  

• Weight distribution

  Freight weights are optimally distributed. Larger aircraft pump fuel back and forth between the tanks on the main wings and the tail fin during flight in order to keep the aircraft in a flight attitude that minimises drag when cruising, without having to adjust the control surfaces. This is also done when passengers or crew move back and forth in the aircraft.
  

• Cruising speed

  Even if an aircraft can reach high speeds at high altitudes with relatively little propulsion power thanks to low air density, the laws of physics still apply. Specifically, this means that a small increase in the normal cruising speed requires a lot of additional power. Whether it is a plane in the air, a car on the motorway or a train on a high-speed rail line, 10% more speed requires 30% more propulsion power. So increasing speed to make up time is inefficient in terms of fuel and energy consumption. Conversely, even a small reduction in cruising speed can save an airline a significant amount of fuel. The cruising speed is therefore reduced slightly and an acceptable balance is sought between passenger requirements (journey time, arrival time) and fuel consumption.
  

• Direct flight routes and fuel-optimised climb and descent

  European airspace is highly fragmented. In addition, political factors such as the war in Ukraine are lengthening flight routes. The Single European Sky project aims to optimise the use of Europe’s airspace.
  Climbs and descents harbour further potential. For example, passenger jets can cover the last 200km of their route with the engines idling, without the need to repeatedly generate thrust. In an optimum approach, a jet descends to its destination like a glider.
  

• Avoiding holding patterns

  Previously, aircraft on long-haul flights landing at Zurich sometimes had to fly holding pat-terns if they arrived at too close intervals or before the airport opened at 6am. That is no longer the case thanks to iStream, an initiative by the airline SWISS, the air navigation ser-vice provider Skyguide and the airport operator Flughafen Zürich AG. Now, a time slot is re-served for each flight in the wave of early-morning arrivals at Zurich Airport. From then on, a minute-by-minute calculation is performed, factoring in the economical cruising speed, the weather and the route. The departure time for these flights is then adjusted accordingly. If there is a strong tailwind on flights from North America to Switzerland, take-off is delayed so that the flight does not arrive in Zurich before 6am and can keep to its landing slot. This op-timised procedure has cut the number of holding patterns at Zurich by 96% and shortened the approach routes by around 30%, thereby reducing kerosene consumption and CO2 emis-sions. iStream is now being rolled out to other airlines and European airports.
  

• Adapting routes to wind conditions

  Weather forecasts have become very accurate, especially those for high-altitude winds. Modern flight management systems allow these winds to be better exploited.