Heathrow Operational Freedoms trials, the A380 and impact of its vortex on smaller planes following it
The A380, being such a massive plane, and classed as a “Super” by weight – above the next category of “Heavy” creates a greater vortex behind it. Therefore there have to be significant separation distances between A380s and planes following them, especially smaller planes. In the Heathrow Operational Freedoms trials, one of the changes they are looking at involves landing Airbus A380 on the designated departures runway (this means that those living under the approach flight paths are having planes overhead during the part of the day that should be their “quiet” time). The A380 is the biggest aircraft that operates at the airport. Due to the vortex it produces, aircraft behind it have to allow a greater distance when coming into land. The knock-on effect is that the arrivals programme can be delayed allowing for the A380 to come in before smaller aircraft can then make their approach to land. The airport is testing what difference it would make to the arrival schedule by allowing the aircraft to land on the departure runway. Heathrow hopes to use more larger planes, to deal with ever more passengers. This A380 effect could be a problem.
Wikipedia page on A380:
A380 – Takeoff and landing separation
In 2005, the ICAO recommended that provisional separation criteria for the A380 on takeoff and landing be substantially greater than for the 747 because preliminary flight test data suggested a stronger wake turbulence.
These criteria were in effect while the ICAO’s wake vortex steering group, with representatives from the JAA, Eurocontrol, the FAA, and Airbus, refined its 3-year study of the issue with additional flight testing. In September 2006, the working group presented its first conclusions to the ICAO.
In November 2006, the ICAO issued new interim recommendations. Replacing a blanket 10 nautical miles (19 km) separation for aircraft trailing an A380 during approach, the new distances were 6 nmi (11 km), 8 nmi (15 km) and 10 nmi (19 km) respectively for non-A380 “Heavy”, “Medium”, and “Light” ICAO aircraft categories.
These compared with the 4 nmi (7.4 km), 5 nmi (9.3 km) and 6 nmi (11 km) spacing applicable to other “Heavy” aircraft. Another A380 following an A380 should maintain a separation of 4 nmi (7.4 km). On departure behind an A380, non-A380 “Heavy” aircraft are required to wait two minutes, and “Medium”/”Light” aircraft three minutes for time based operations.
The ICAO also recommends that pilots append the term “Super” to the aircraft’s callsign when initiating communication with air traffic control, in order to distinguish the A380 from “Heavy” aircraft.
In August 2008, the ICAO issued revised approach separations of 4 nmi (7.4 km) for Super (another A380), 6 nmi (11 km) for Heavy, 7 nmi (13 km) for medium/small, and 8 nmi (15 km) for light. In November 2008, an incident on a parallel runway during crosswinds made the Australian authorities change procedures for those conditions.
BAA’s Operational Freedoms website:
Operational Freedom 4 – Proactive tests
During Phase 2 we will trial a number of proactive tests used as part of Phase 1 to further explore the passenger, environmental and operational impacts. These proactive tests are:
- Landing Airbus A380 on the designated departures runway; The A380 is the biggest aircraft that operates at the airport. Due to the vortex it produces, aircraft behind it have to allow a greater distance when coming into land. The knock-on effect is that the arrivals programme can be delayed allowing for the A380 to come in before smaller aircraft can then make their approach to land. The airport is testing what difference it would make to the arrival schedule by allowing the aircraft to land on the departure runway.
- Landing small aircraft on the designated departures runway; Smaller aircraft are affected by the vortex produced by larger aircraft and therefore more spacing is needed between them. Heathrow is interested in testing whether the landing flow of aircraft can be improved, whilst reducing the number of aircraft held in the stack, by taking the smaller aircraft out of the current arrival flow and landing them on the designated departure runway.
- Use of the southern runway for Terminal 4 arrivals; Terminal 4 is situated south of the southern runway and therefore permitting arriving aircraft to operate from the southern runway, will result in a shorter taxi route for the aircraft. This will have the added benefit of reducing ground noise and emissions and avoiding crossing the southern runway and so reducing disruption.
When will these procedures be used and how often?
During Phase 2, these tests will be limited to three defined periods, the dates of which are
- 16 July – 15 August 2012
- 1 October – 31 October 2012
- 1 March – 31 March 2013
What benefits are expected from using this procedure?
- The use of proactive tests may reduce the amount of taxiing times and therefore lead to a reduction in ground emissions.
- The use of this procedure may improve punctuality for airlines and passengers.
What are the expected impacts for local residents?
- By implementing this Operational Freedom we anticipate there will be more flights landing out of alternation.
- The scope to use this will be limited by arrival and departure demand.
Phase 1 of the trial also included a number of proactive tests using the same
measures described above but specifically involving:
• landing Airbus A380 flights on the runway closest to their destination stand;
• landing small aircraft on the designated departure runway;
• use of the southern runway for Terminal 4 (T4) arrivals and departures.
These proactive tests were restricted to two four week periods during Phase 1 of the
trial – between 28 November 2011 and 25 December 2011 inclusive, and between 16
January 2012 and 12 February 2012 inclusive.
220.127.116.11 Proactive tests
The following conclusions can be drawn from the use of the proactive tests in Phase
• landing T4 aircraft on the southern runway has further improved taxi-in times on
top of the improvement already observed during the non-proactive part of the
• it appears that where significant de-alternation of A380s occurs stack-holding is
1.6 Lessons for Phase 2
There has been some valuable learning from the first phase which will be
incorporated into Phase 2 of the trial and will be used to assess future progress with
the development of Operational Freedoms:
• The proactive tests have demonstrated that removing the A380 from the arrival
stream of aircraft has been useful in improving delay. However, two conclusions
have emerged, one that the sample size is small in relation to the other data
gathered and the other that the real benefit in terms of arrival delay is not to
remove the A380 from the arrival stream per se but to de alternate the following
aircraft. This is because the impact of growing A380 traffic is to increase the
distances required between the A380 and the following aircraft.
In the proactive case, there were likely to be multiple linkages between the freedoms
applied and the performance area and KPIs:
• landing T4 arrivals on the southern runway will likely impact all three performance
• landing A380s on the departures runway will likely impact on stack holding, both
for the A380s and for those aircraft following behind
• landing small and light aircraft on the departures runway will also likely impact on
stack holding for those aircraft and those following immediately behind.
7.10 A380 arrivals
A second dimension of the proactive tests concerns A380 operations where proactive
• A380s to be landed on the runway most convenient for their destination terminal.
The hypothesis associated with this freedom was that A380 taxi-in time would be
reduced during the period that proactive tests were active compared to the other
periods of the trial
• A380s to be landed on the designated departures runway. The hypothesis
associated with this proactive test was that stack holding would be reduced when
significant A380 de-alternation took place compared to other periods.
BAA OPERATIONAL FREEDOMS TRIAL AT HEATHROW
INTERIM REPORT BY THE CIVIL AVIATION AUTHORITY FOR THE MINISTER OF STATE
The future of flying
29 October 2012
Image: Heathrow Airport Credit: John Wood on flickr
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Meanwhile, the focus of Professor Duncan McFarlane’s research is what happens on the ground. Working with Alan Thorne and other colleagues at the Department of Engineering’s Institute for Manufacturing (IfM), the team is involved in trials conducted by BAA at Heathrow Airport on measures to increase punctuality, reduce delays and strengthen resilience at the UK’s hub airport. The trials are centred on making the best use of the airport’s two runways, which are in heavy demand.
In the first phase of the Operational Freedoms trial Heathrow explored how its runways and airspace can be better used to recover quickly following airport disruption, such as that caused by bad weather. One strategy was to use both runways for either arrivals or for departures, instead of one for each. Initial results indicated improvements in punctuality, reduced emissions and fewer planes having to taxi across runways. A second phase is now ongoing until March 2013 to carry out a more-detailed analysis.
“The Civil Aviation Authority is overseeing the tests. Our role has been to independently audit the trial and ensure its objectives are met,” explained Professor McFarlane. “We measure everything to do with the impact of changes on the performance of the airport, from how long the aircraft are in overhead ‘circulation stacks’, to take-off delays, to emissions and noise, and then we generate what we think are appropriate recommendations.”
A further study has also just started, this time examining the order of aircraft landing on runways. “A big aircraft creates a huge air turbulence behind it and small aircraft have to wait proportionally longer before landing,” said McFarlane. “Flexible use of runways could mean landing larger aircraft on one and smaller on another, or ordering planes in overhead circulation stacks into optimal landing sequences. Using runways effectively could go a long way towards helping airport operations recover quickly and efficiently from unwanted variability.”