On 12 September at 19:30 Air New Zealand flight NZ8 left Auckland airport for San Francisco just like it does every Friday evening. But this service was different.
The Boeing 777 pushed back from the gate on time and arrived on the other side of the Pacific at its gate at San Francisco airport at 12:40, 5min ahead of schedule. But it is what happened throughout the flight - from gate to gate - which makes the 10,610km (5,735nm) flight unusual and allowed it to save 4,540 litres (1,200USgal) of fuel and 11t of carbon dioxide compared with a "normal" Auckland-San Francisco flight.
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© Boeing |
The flight, dubbed the "perfect flight", was the first part of the Asia and South Pacific Initiative to Reduce Emissions (Aspire). The Aspire agreement was signed by Airservices Australia, Airways New Zealand and the US Federal Aviation Administration in February in a move designed to accelerate the development of air traffic control procedures that will reduce aviation's environmental footprint.
Flight NZ8 was the first of three demonstration flights planned so far under Aspire. The flights are designed to measure the impact of optimum flight conduct on reducing carbon emissions. The flight operated under optimum air traffic management flight planning conditions, using concepts and technologies to maximise efficiency throughout all phases of the flight, says Mark Goodall, manager of oceanic services at Airways NZ. All normal operational restraints, which lead to delays, increased fuel use and increased emissions, were removed. This included air traffic congestion control vectoring, air traffic fixed route structure, procedures, flow restrictions and airline restraints.
The Aspire 1 flight was as "fuel-optimised" and as environmentally friendly as technology allows in all phases, says Airways NZ.
The first phase involved pre-flight, taxiing and take-off. Unlike a normal flight, on the ground at Auckland Aspire 1 used air conditioning and electrical power supplied from the airport aerobridge, with the aircraft auxiliary power unit started only 15min before departure. Minimising the use of the APU is a significant opportunity to reduce emissions, with a 777's APU typically consuming 227 litres of fuel an hour, says Airways NZ.
Aspire 1 also made use of the "just in time" fuelling concept that was implemented by ANZ on its widebody aircraft in Auckland in February 2007 and rolled out to other airports over the following 12 months, says Goodall. It involves the fuel tanker loading 2,000kg less fuel than the initial estimate and remaining connected to the aircraft until the captain is able to "fine tune" the fuel load requirement 20min before departure. The final amount of fuel is carefully loaded to minimise an "over-fuel", with final calculations confirming the correct fuel loading 5min before departure.
AIRCRAFT HOLDING MINIMISED
Aircraft engine start was managed to minimise aircraft holding before take-off, while aircraft taxi speed was also managed to ensure the aircraft arrived at the take-off clearance point without having to slow down or speed up, to minimise fuel burn. Unlike a normal flight, where aircraft pushback and taxiing are often delayed due to other surface movements, Aspire 1 received priority clearance from ATC for taxiing and departure.
ATC provided the flight with the optimum engine start-up time following pushback to achieve an unimpeded taxi to the departure point. Although from a fuel conservation perspective it is more efficient to taxi a twin-engine aircraft on one engine, Aspire 1 used both due to the aircraft weight, says Airways NZ.
Considerable environmental improvements on the airport surface can be realised by minimising aircraft ground run time, says Airways NZ. "Optimal runway usage planning will increasingly play a more significant role in reducing aircraft emissions as promising new technologies that use collaborative surface operations in maximising airport throughput become available. For the moment, more efficient surface operations for even just a few flights during busy hours can provide significant delay reductions, as well as emissions reduction benefits," the service provider adds.
Estimated fuel savings for Aspire 1 on the ground, in addition to the APU savings, included a 644 litres reduction in fuel load through use of the just-in-time fuelling concept, with a fuel burn saving of 257 litres achieved by not having to carry the extra fuel.
Phase two was departure and climb, with Aspire 1 provided a priority departure route and unimpeded climb through to cruise altitude, allowing it to reach its optimum cruise altitude as quickly and efficiently as possible. After take-off engine power was reduced and retraction of the flaps started at 1,000ft (300m), further contributing to fuel conservation.
The sooner an aircraft is able to track on to its optimised route, the fewer emissions produced. Airways NZ says it has developed departure routes from Auckland that take full advantage of the flight's preferred track direction and altitude climb, allowing it to start its preferred route right from the moment of take-off. The Aspire 1 departure used the minimum track miles and a climb with the only restrictions being those that ensured it met local noise restrictions. Maximum climb power was used for the climb rather than the more traditional derate climb power. The latter improves engine life and maintenance costs, but increases the amount of fuel consumed.
In the en route cruise phase the aircraft operated at optimum altitude for its weight and engine configuration. This is the portion of the flight where most emissions are produced and where most of the industry's focus to date has been concentrated to implement operating techniques that minimise fuel consumption.
"Air navigation service providers can have a significant impact on the emissions optimisation of a flight by allowing the aircraft to fly as close to its optimum flight profile as possible in terms of route and altitude, and by making changes to the profile as often and as quickly as possible to allow it to maintain its optimum flight profile," says Airways NZ.
Like most other aircraft flying in New Zealand and US oceanic airspace today, Aspire 1 benefited from user preferred routes (UPR) which take into consideration forecast winds and the weight and engine configuration of the aircraft. UPRs, as opposed to flying the best fixed track route, provide the greatest improvement in terms of fuel consumption and emissions, says Goodall. The flight also made use of dynamic airborne reroute procedure, with the route adjusted a couple of times based on updated wind and weather information.
Aircraft flying between New Zealand and the USA also benefit from the "most efficient reduced aircraft separation standard available globally" - 30nm longitudinally and laterally.
The fourth phase of the flight - descent and approach - is often the biggest challenge facing an ANSP, says Airways NZ. The need to manage arrival and departure capacity often overshadows the goal of providing environmentally friendly and efficient descent profiles, it adds.
TAILORED ARRIVAL
Aspire 1's descent and approach involved a tailored arrival, which is an emissions-optimised continuous descent arrival. CDA allows an aircraft to fly a continuous descent path to an airport rather than the traditional step-downs. Descent is initialised from a high altitude at low engine power until a stabilisation point before touchdown, resulting in fuel savings, reduced emissions and noise beyond the airport. Tailored arrival takes CDA further by creating the most beneficial flightpath available based on aircraft performance, air traffic, airspace, meteorological, obstacle clearance and environmental constraints. Air New Zealand has been part of a tailored arrival trial at San Francisco since late 2007.
Surface movements at San Francisco were manually optimised to ensure the most efficient and environmentally beneficial operation possible, with Aspire 1 receiving priority taxi clearance directly to the gate. Electrical power and air conditioning was provided from the aerobridge, which has been available from the airport for a number of years.
Fuel and emissions savings were slightly better than predicted, says Airways NZ.
The second "perfect flight", involving a Qantas Airbus A380 operating between Los Angeles and Melbourne, was due to be conducted on 22 October. The third flight in the series is planned for 14 November, with a United Airlines Boeing 747-400 flight between Sydney and San Francisco.
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© Qantas |
The flights will use similar technologies and processes as used on the ANZ flight, although there will be differences, says Airservices. The Qantas flight will involve a larger aircraft and travel in the opposite direction, so wind and weather will be coming towards the aircraft rather than going in the same direction.
"The other difference is the work we will be doing with the aircraft in tailored arrivals," says Airservices. "The aircraft will be providing us with data on a regular basis as it crosses the Pacific, similar to that of the first flight. But we'll be checking the accuracy of the data and then we will be able to provide wind and other conditions information, enabling the flight management system to calculate the best vertical path for descent. In turn, this should allow the crew to fly their controlled descent approach without using the speedbrake or throttle," it adds.
The Aspire partners are also developing a fuel and emission reduction metrics model, which will be used to establish the reductions already made through the implementation of reduced separation standards, such as the 30nm oceanic en route and 1,000ft reduced vertical separation, optimised arrivals and UPRs, says Airways NZ. The model will also be used to determine the fuel and emission impact of new procedures and separations and will form part of the business case for their introduction, the service provider adds.
Aspire is unlikely to stop there, with the three original partners keen to attract new members. The long-term aim is to co-ordinate the Asia-Pacific region's ATM environmental efforts and eventually for the group to provide some sort of global leadership. Air navigation service providers in the northern Pacific area, including Japan, are expressing interest in the programme and they would be a welcome addition in 2009-10, says Airservices. Talks have also taken place with Tahiti and Fiji.
Airservices adds: "The three demonstration flights will set the priorities for Aspire and will inform the strategic plan. They will also help build the case for ongoing improvement of ATM and aviation in the Asia-Pacific."
UNITED READIES FOR ASPIRE FLIGHT
United Airlines will round out a series of "fuel-optimised" flights for the Asia and South Pacific Initiative to Reduce Emissions (Aspire) on 14 November using a Boeing 747-400 between Sydney and San Francisco.
The United flight follows an Air New Zealand Boeing 777 flight from Auckland to San Francisco on 12 September and a Qantas Airbus A380 operation from Los Angeles to Melbourne on 22 October.
Data collected during United's flight will be used by stakeholders, including the US Federal Aviation Administration, to help develop industry best practices for reducing fuel consumption and environmental impact, United says.
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"We're pleased to participate," the carrier adds, noting that the flight also demonstrates how important technology is to improving efficiency of the national aviation system and performance.
As done by ANZ during the first Aspire flight, United will use a tailored arrival at San Francisco International airport. Both Star alliance members have been participating in a tailored arrival trial at the California airport.
Electronic communications between the FAA and the flightcrew will provide the crew with the most efficient cruising altitude, United says, adding that by using tailored arrival alone, the flight is expected to save up to 180kg (400lb) of fuel.
While United prepares for its Aspire flight, other carriers have considered operating fuel-optimised flights. The FAA has held discussions with its Asian counterparts and Asian flag carriers about participating, FAA Air Traffic Organisation senior vice-president operations Rick Day says. There is a lot of interest, but details need to be fleshed out, he says, but declines to identify what countries or carriers might test fuel-optimised flights.
The 777 ANZ flight proved what an optimal flight looked like and the long-term goal is for such flights to become routine rather than planned events, Day says. "The way to advance this is to repeat this with other airlines," he adds.
While other carriers evaluate participation, the FAA will comb through data collected to determine what can be improved upon to consistently provide a high level of service, Day says, adding that the FAA is developing tools to share with other airline operations centres to identify the most advantageous taxi time and optimise that flight segment.
Airports involved seem supportive of fuel-optimised flights. San Francisco International did not have to do anything other than make sure a gate was available, it says. "We don't want to prepare anything. We want to make this a seamless operation for any flight," it adds.
TRANSATLANTIC CO-OPERATION SAVES FUEL
Aspire's sister partnership established between the US Federal Aviation Administration and European Commission is aimed similarly at reducing carbon dioxide emissions on transatlantic flights through co-operation on air traffic management measures is gaining in vital experience.
The focus of the Atlantic Interoperability Initiative to Reduce Emissions (AIRE) has always been on interaction between the USA's Next Generation Air Transportation System and the European Union's Single European Sky (SESAR) initiative.
Jim McDaniel, FAA programme manager for the AIRE initiative, says progress on the initiative, launched in June 2007, has seen the agency establish several domains, including flight demonstration, surface movement studies (limited to arrivals for now) and oceanic route optimisation.
In July, the FAA signed three further airlines to take part in the fuel and time-saving oceanic trajectory-based operations pilot programme for flights over the Atlantic starting in September.
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© Simon Wilson/AirTeamImages.com |
Those tests followed a successful demonstration of the concept in May with Mallorca-based Air Europa on eight trips departing from Madrid and landing in Caracas, Havana or Santo Domingo using an Airbus A340.
Using web chat tools available through the FAA's advanced technologies and oceanic procedures (ATOP), Air Europa air operations managers in Madrid were allowed to communicate at 1,110km (600nm) intervals with air traffic controllers handling flights at the New York oceanic centre to request time or fuel saving deviations.
If controllers approved the request, the managers sent the options to flightcrews via ACARS datalink. Pilots would then send their approval or comments back to the operations centre, which would then contact controllers again via web chat, says Paul Fontaine, FAA air traffic organisation manager for advance technology development.
In one case, Fontaine says airline controllers had requested a deviation due to 200kt (370km/h) headwinds caused by an upper air disturbance. Although the approved deviation resulted in a longer distance, the airline saved fuel by battling weaker head wind.
Fontaine says Air Europa saved 1,025kg (2,257lb) of fuel and produced 3,040kg less carbon dioxide emissions as a result of seven successful flights using the web-enabled communication. Testing on one flight was disrupted due to problems in the airline operations centre.
McDaniel says the demonstration flights, which featured continuous descent approaches, were all heading towards the Caribbean and South American destinations, but were following the same trajectory as flights bound for North America.
The FAA also worked on optimising continuous descent approaches at Atlanta and Miami and conducted tailored arrivals - pre-planned trajectory from the top of descent - on more than 300 flights bound for San Francisco.
Tailored arrivals were also demonstrated in September at Miami - two flights a day for three days from Europe - on American Airlines Flight 57 and Air France Flight 90 from Paris Charles de Gaulle airport, all arriving between 14:00 and 16:00 local time.
The trials served principally to expand the scope of the programme and gather data that will be used in part to derive a business case for such operations.
McDaniel says that flight data on three Air France flights was auto-loaded into flight computers, with clearance approved by air traffic controllers. He says all three were able to perform complete tailored arrivals. Three American Airlines flight demonstration saw one tailored arrival completed, although the remaining two had to be abandoned because of conflicting arrivals downwind.
The FAA is now looking at 600 airports in the USA and prioritising them for development of continuous descent approaches. "To really make them most effective we would conduct an airspace redesign for the airport. We'll go through them and identify issues, things that do go well and things that don't," says McDaniel.
Tackling the problem posed by the most congested North American airspace around New York may seem a long way off, although McDaniel says the agency's steady pace of optimisation work will enable them to "walk before we run". In 2009-10 McDaniel says the FAA wants to build on current work to a point where it can conduct some oceanic and terminal trials as well as optimise surface movements.
The FAA will also need to team with its SESAR partners. Paul Fontaine says that by the end of 2010 AIRE should be in a position to conduct gate-to-gate trials, but will need its European partners to be in place. "We should know who has been selected by the end of October as the SESAR Joint Undertaking let a call for tender, so we would expect an announcement in November."
McDaniel says there is still plenty of work. "Even over here, it's primarily a co-ordination exercise between the various domains - air traffic control facilities, developing optimisation concepts, determining who is going to play/pay etc. For the moment we are seeing a wide variety of co-operation between the FAA and the regional folks, keeping them apprised through weekly meetings. Communication between all stakeholders is proving vital in this initiative."
Source: Flight International
