Wed 27 June 2012 – A collaboration involving the UK aviation industry with support from the UK Department for Transport (DfT) has resulted in the launch of a new code of practice that is intended to reduce the environmental impacts from ground operations and departing aircraft at UK airports. The code addresses aircraft operations at the terminal and on the taxiways, as well as air traffic operations on departure, and aims for substantial reductions in noise and carbon and NOx emissions. Four key initiatives form the core of the code: using terminal or ground based sources of electrical power for aircraft on the stand rather than an aircraft’s auxiliary power unit (APU), taxiing without using all an aircraft’s engines, aircraft taking off on continuous climbs and the introduction of Airport Collaborative Decision Making (A-CDM) at all main UK airports to streamline decision-making between airport partners.
A high proportion of stands at Heathrow are equipped with Pre-Conditioned Air units (photo: BAA)
The new code complements the Noise from Arriving Aircraft Code of Practice that was introduced in 2004 and updated in 2006. The UK government considered in the latter half of the 1990s to set noise limits on arriving aircraft but instead chose to establish an industry code of practice to address the issue. The arrivals code focused largely on rolling out the implementation of Continuous Descent Approaches at the larger UK airports.
“Even as the work on the arrivals code was being completed it became obvious to everyone in the aviation industry that there was more opportunity for us to reduce the impacts of aviation on the environment across a broader range of operational activities,” said Captain Dean Plumb of British Airways, who chaired the working group that drew up the new code, at an event in London yesterday to announce its launch.
The Departures & Ground Operations Code of Practice has taken nearly five years to develop since the establishment of the working group in 2007 initially by British Airways, BAA Heathrow, BAA Stansted, NATS and Virgin Atlantic Airways, and later joined by Manchester Airports Group, Gatwick Airport, ERCD, DfT and UK aerospace industry body ADS. The UK Civil Aviation Authority, the industry’s regulator, provided technical support on behalf of the DfT, primarily on noise issues.
The development of the new code proved more difficult than the arrivals code, said Plumb, because of the comparative lack of available relevant technical background information and also because of the environmental trade-offs that need to be considered for departing aircraft.
“The departures and ground operations code primarily pulls together best practice from around the industry and to develop it in a UK context,” he said.
The voluntary code is a technical document primarily written for flight planners, pilots, ground handling agents, air traffic controllers and airport operators but may also include advice relevant to regulators and other groups. Although not developed with a specific aircraft or airport in mind, the greatest benefits are likely to be achieved by larger aircraft at busy airports. However, says the working group, the reductions in noise, fuel burn and associated emissions will be of significance for all airports and operators regardless of aircraft type or airport and associated facilities.
The first of the four operational practices included in the code is the use of airport ground power rather than aircraft APUs. It recommends that operators and ground handling agents follow a ground power hierarchy of using, where available, airport terminal-based Fixed Electrical Ground Power (FEGP) and Pre-Conditioned Air (PCA) systems first, then mobile ground-based Ground Power Units (GPUs) and air conditioning trucks, followed only then by APU use.
Significant emissions savings may be possible as APUs are noisier and can burn up to six times more fuel than a GPU, which in turn burns more fuel than a terminal-based FEGP. APU fuel burn for a typical small aircraft type is in the region of 90 to 110 kg/hr and for a large aircraft ranges from 240 to 300 kg/hr. Similarly, NOx emissions range from 0.452 to 2.892 kg/hr depending on the size of aircraft.
However, the code’s working group recognises there are challenges in persuading all airlines to comply with the recommendation as APUs are seen as reliable and trusted sources of ground power and provide crews with a sense of autonomy, since an interruption of ground power can cause loss of pre-flight preparation and programming, resulting in a possible delayed departure. APUs can also help mitigate cabin temperatures that may reach 30-40 degrees C for a Boeing 747 on an average day.
At London Heathrow, all but two temporary stands now have FEGP and 56 stands are equipped with 73 PCA units, which is expected to rise to 93 stands with 113 PCA units by 2014/15. One major UK airline achieved a 20% reduction in measured APU run-time in 2011 compared to 2010.
The second initiative is to recommend aircraft operators use less than all engines when taxiing-in from the runway to the airport terminal as long as safety and procedural concerns can be met. Shutting down an engine during taxi-in operations need to be planned in advance and accomplished as early as possible during the taxi to obtain the maximum reduction of fuel burn and environmental benefit. Reductions of 20-40% of the ground level fuel burn and CO2, and 10-30% of ground emitted NOx emissions may be realised, dependent on aircraft type and operator technique.
However, these reductions have been shown to be less than simply reducing the rate of production by the ratio of the number of engines not operating. The importance of incorporating the effects of APU operation, which is often required when following this technique, is important in establishing the actual benefits, says the advice to operators.
Reduced engine taxiing-in by the code’s working group airlines have resulted in short-haul fleets achieving single-engine shut-downs in around 70% of flights, rising to 80% for four-engine, long-haul flights. However, for larger twin-engined aircraft, such as the Boeing 777, the percentage falls to 30% because of the extra workload of the remaining engine and the greater risk of jet blast.
Two working group airlines have reported adopting reduced engine taxiing-out but the achievement rate is just 10% because of extra factors such as the heavier weight of the aircraft and the engine warm time required.
The third recommendation is that Air Navigation Service Providers (ANSPs) identify opportunities to increase the uptake of Continuous Climb Operations (CCOs), which enable aircraft to reach final efficient cruising altitude sooner.
In the short term, this means raising awareness of the benefits and opportunities to make procedural or tactical changes to enable more CCOs where airspace and traffic conditions allow. For the mid to long term, achieving more CCOs will require structural changes to airspace and further investment in ATC and aircraft technology, says the working group. The UK airspace, they say, is a complex system that needs to take account of safety separation requirements and the interaction of different flows of traffic including over-flights and arriving and departing aircraft at multiple airports.
However, the benefits of CCOs, depending on aircraft types and operator techniques, can amount to climb fuel and emissions reductions of around 5% for an Airbus A320 to 8% for a Boeing 747-400. Initial analysis of a variety of CCO scenarios suggests an overall neutral effect on noise or, at best, a potentially small beneficial effect. This is dependent on the difference between the CCO and the previous practice as well as local population distribution.
The fourth and final recommendation of the Code of Practice is that Airport Collaboration Decision Making (A-CDM) should be introduced at all major UK airports. A-CDM involves all airport partners, including aircraft operators, handling agents, the ANSP and the airport operator, efficiently working together to provide accurate and timely live operational data, such as the expected arrival and departure times of aircraft.
Benefits include improved taxi times and reduced emissions by alleviating congestion and waiting times on the airfield, for example by ensuring stands are allocated to aircraft no later than 20 minutes before arrival.
Experience from European airports and analysis at UK airports indicate that significant savings in aircraft taxi times and consequent fuel and emissions reductions are possible. According to the working group, one large UK airport estimates the benefits amount to an average two-minute reduction of taxi time on each departure and 30 seconds on each arrival. UK ANSP NATS calculated that the total fuel saved annually by a two-minute reduction in average departure taxi time at a large UK airport (measured over 227,000 departures) amounted to around 9,000 tonnes, representing some 30,000 tonnes of CO2.
A-CDM is not just a collection of software tools, said BA’s Plumb, but a fundamental operational change programme in which partners work with targets rather than estimates.
A-CDM is currently being implemented at Heathrow, Gatwick and Manchester. This week, the body representing ANSPs worldwide, CANSO, and ACI, which represents airports, announced they would work together to promote the global implementation of A-CDM. The two trade associations aim to develop an Airport/ANSP A-CDM implementation best practices guide and promote global standards, as well as encourage the creation of pilot project teams.
“The aviation industry has consistently delivered improvements to limit the impact of its operations on the environment,” said Plumb. “This is another example of the UK taking the lead in innovating new solutions and our aspiration is to create a universal code of practice. The biggest benefits will be at the bigger airports but reductions in noise, fuel burn and associated emissions will be of significance for all airports and operators.”
The UK cross-industry environmental initiative Sustainable Aviation will now take over implementation of the Departures & Ground Operations Code and will report progress in line with the group’s next report in the spring of 2013.
Commenting on the launch of the code, Matt Gorman, Chair of Sustainable Aviation and Sustainability Director at BAA, said: “This shows what can be achieved by the industry working collaboratively to bring about cleaner, quieter, smarter aviation both now and in the future.”
Gorman said the code would be built into the work of Sustainable Aviation’s Operational Improvements Group. After the progress report, the intention is to launch a further collaborative effort to consolidate both the Arrivals and Departures codes of practice and address any new opportunities.
The full Departures & Ground Operations Code of Practice will be published shortly by the Department for Transport.
Department for Transport - Aviation
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