We have all heard about Tailored Arrivals. But what are Initial Tailored Arrivals? The following article from the FAA explains it for us.
An Initial Tailored Arrival (ITA) is a pre-negotiated arrival path through airspace of multiple air traffic control (ATC) facilities. The ITA limits vectoring and minimizes the time the aircraft spends maintaining level flight during its descent. The concept has matured during four years of demonstrations, and we will make the transition to normal operations in 2011.
The pilot initiates an ITA with a request to ATC while the aircraft still is in its cruise phase. If an ITA is available, the controller sends the pilot a clearance that includes a descent profile with speed and altitude restrictions, as applicable. The clearance is sent as data, which limits ITAs at present to aircraft equipped with the Future Air Navigation System (FANS) for communications over oceans. The pilot loads the clearance directly into the aircraft’s flight management system, which controls the descent.
ITAs differ from other types of Optimized Profile Descents (OPDs) in that they are assigned by controllers to specific approaches and tailored to the characteristics of a limited number of FANS-equipped aircraft types – 747s, 777s, A330s, A340s and A380s. They begin at the top of the descent and, when completed, control the aircraft all the way down to the runway. By contrast, other types of OPDs, such as Area Navigation arrival procedures, are published for all users and must serve a wide variety of aircraft types.
Controllers monitor ITAs throughout the aircraft’s descent. Traffic conflicts, unfavorable weather or other factors often cause them to discontinue an ITA while it is in progress, converting it to a conventional arrival. Data show that even partial ITAs are beneficial to operators and the environment. A key feature of an ITA is that the aircraft descends from its cruise altitude more continuously, with a minimal requirement to maintain level flight. If an aircraft needn’t maintain level flight, its engines can be set at or near idle. This saves fuel and reduces emissions of carbon dioxide and other harmful gases.
We have conducted ITA flight demonstrations at San Francisco, Los Angeles and Miami, all in conjunction with our international green-aviation initiatives, the Asia and Pacific Initiative to Reduce Emissions and the Atlantic Interoperability Initiative to Reduce Emissions. In fall 2010, we completed a rough-order-of-magnitude life cycle business case estimate using data from 11,476 arrivals at San Francisco of 747-400 and 777-200 aircraft between December 2007 and September 2010.
We estimated that the 747s saved an average of 176 gallons of fuel per arrival in ITAs and 78 gallons per flight in partial ITAs, compared with conventional approaches. For 777s, the corresponding savings were 99 gallons in full ITAs and 43 gallons in partial ITAs.
To assess the business case, we estimated the costs of establishing ITAs and operating them through 2030 at 10 airports – the current three, plus Anchorage, Alaska; Honolulu; Orlando, Fla.; Portland, Ore.; San Juan, Puerto Rico; Seattle-Tacoma, Wash.; and Travis Air Force Base in California. Most Atlantic Coast airports are not near-term candidates because the ITA clearance would have to be given in Canadian airspace.
We also estimated benefits over the 20-year period, based entirely on fuel savings. We did not try to put a value on the reduction in carbon dioxide emissions or noise.
We found very high benefit-to-cost ratios – 44:1, 33:1 and 22:1, depending on whether growth in Data Communications avionics equipage over 2010 levels is high, moderate or zero. In each case the payback year is 2012. The benefit-to-cost ratios are unusually high because the main driver of benefits is avionics – FANS and an advanced flight management system – and airlines already have incurred the cost of each. The remaining costs are very low relative to benefits.
When ITAs are fully operational, they still will be limited to aircraft with FANS. Also, ATC facilities still will need the Advanced Technologies and Oceanic Procedures system, which is the only automated platform that can send the ITA data messages. But all airlines with FANS-equipped aircraft, not just the airlines involved in the demonstration programs, will be able to use the procedure. And we will make it available at other international gateway airports.
(Source:FAA)
After reading this article I still wonder if there is any difference with a Tailored Arrival, or is it that ITA is going to be it’s final standard definition (wording)?
One thing that I still haven’t understood is WHO calculates the descent profile on the ground (taking into account the a/c type) “with speed and altitude restrictions, as applicable” or is this data (tactical set of windows and limitations) inserted in the FMS, which then calculates its Optimal Performance Descent (paraphrasing another definition).
I am guessing there is a WHO, as OPDs are static.
Yes indeed, there is indeed a WHO and this is the appropriate funcionality built into the system of the air traffic control unit concerned. If it is possible to issue an ITA for the flight concerned, its details are calculated by the system and a clearance is defined and uplinked to the aircraft. This is then loaded into the FMS which will control the descent.
ITAs are one of the so called ground oriented solutions. New concepts tend to rely more on the capabilities of advanced FMSs as well as the trajectories calculated by airline systems.