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Nextgen: Infrastructure progress is accelerating- final decision is not...The aviation world got some excellent- long-awaited and somewhat unexpected news in early December - the kind of news that should quicken the heartbeat of many a technology junky. Later that same month- more news followed related to the same topic- fueling a feeling of actual progress in the often-moribund feeling realm of the nation’s next-generation air-traffic control system.

Dave Higdon   |   1st January 2010
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Dave Higdon Dave Higdon

Dave Higdon writes about aviation from his base in Wichita Kansas. During three decades in...
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Infrastructure progress is accelerating- final decision is not...

The aviation world got some excellent- long-awaited and somewhat unexpected news in early December - the kind of news that should quicken the heartbeat of many a technology junky. Later that same month- more news followed related to the same topic- fueling a feeling of actual progress in the often-moribund feeling realm of the nation’s next-generation air-traffic control system.

These milestones followed an earlier report from an industry group on implementing the switch from the radar-based environment to one based on satellite position information and the underlying technologies. Steaming full speed ahead into the New Year with these bullet points firmly established also portends well for avionics manufacturers and the people involved in updating aircraft systems. After all- equipment mandates come along infrequently and even less frequently apply to the entirety of the aviation fleet – from piston singles to commercial airliners. But the movement forward of Automatic Dependent Surveillance- Broadcast (ADS-B) does all of those things.

Indeed- over the coming couple of years- that movement should continue to the point that paying the costs of equipping early with ADS-B could pay operational dividends in the short term- and provide operators with a cushion against rushing to comply with some future deadline to retain access to the airspace most used by business turbine and commercial aircraft.

For years the organization known as RTCA has been working with players from all levels of aviation to define equipment-performance standards for the hardware needed to enjoy ADS-B. RTCA Special Committee 186 worked steadily- methodically- toward finalizing the Minimum Operational Performance Standards (MOPS) that equipment must meet in a standardized ADS-B supported Air Traffic Control network.

With several internal working groups involved- the committee tackled issues ranging from standards for display of traffic information- on resolving traffic conflicts- and for the standards needed by the two links the FAA wants to use- the so-called 1090-ES (Extended Squitter) hardware as well as the Universal Access Transceiver meant for smaller- non-turbine aircraft.

The committee’s working groups also included one focused on implementation. Those efforts came to fruition on December 4- when the RTCA announced completion of MOPS covering the entirety of the airborne equipment; the ground equipment received its standards some years earlier- allowing the FAA to begin ordering and buying equipment for a ground-based network of some 300 ADS-B stations that will tie together the entire country and relay airborne data to controllers’ screens.

The RTCA reports- long anticipated by the FAA- had barely had time for the ink to dry when they arrived at the agency – which- in turn- issued the Technical Standards Orders (TSOs) for the airborne hardware aircraft will need to work with the NextGen system.

The FAA issued those TSOs to an eager avionics industry that had been awaiting the standards so that companies can complete their own hardware certification efforts.

With these TSOs in effect- the avionics industry now has the roadmap it needs to move ahead with the final design and approval work needed to offer its products to the aircraft owners and operators who will need to install new gear to use NextGen services dependent on ADS-B technologies. It’s a big step forward.

Deploying NextGen depends on the completion of a network of ADS-B ground stations- and the FAA hasn’t been idle here (to say the least). In Southern Florida an initial network of ADS-B ground stations became operational in August of 2008- according to the FAA’s Surveillance and Broadcast Services Office; initial operational capability was achieved the following month allowing controllers in Miami Center to track aircraft already equipped with ADS-B Out technology – the equipment that broadcasts the GPS position of an aircraft as well as its altitude- speed and direction.

The FAA has long operated ADS-B stations and used them for traffic control in Alaska under the Capstone Project- in the Ohio River Valley in conjunction with UPS- and in the Philadelphia area- which poses special issues due to a high level of radio interference sources.

The Ohio River Valley system was declared operational in October. Expected imminently is a declaration of initial operating capability for the largest ADS-B network yet- covering the Gulf of Mexico. IOC is expected for the Gulf imminently.

For as long as aircraft have served oil and natural-gas producing platforms in the nearly 600-000 square miles of the Gulf of Mexico- operations there have struggled to continue anytime the weather goes down.

According to the Helicopter Association International and other sources- a normal day-in-the-life of the Gulf traffic is immense. The Gulf is home to almost 3-800 platforms which daily pump ashore more than 1.5 million barrels of crude oil and almost 8 million cubic feet of natural gas. Some 2-000 helicopters make about 7-500 flights a day moving supplies- equipment- fresh water- food and 10-000 workers needed to keep the platforms working 24 hours a day- 365 days per year.

Working in cooperation with the HAI- the energy industry and equipment suppliers- the FAA has arranged to install a network of ADS-B ground stations on the producers’ platforms- along with Automated Weather Observation System (AWOS) stations and communications relays. A total of 23 ADS-B stations- 35 AWOS sites and a similar number of communications-relay stations have been going in over the past 18 months- with many of the offshore helicopter operators participating by providing lift to technicians and for the hardware they had to install.

Similarly- the producers who operate the platforms have not only provided space for the ground stations- but bandwidth on the underwater communications and computer lines connecting the platforms to shore. These network links will provide the lines between the ADS-B stations and the controllers’ screens at Houston Center- which oversees the Gulf airspace. The potential to improve the efficiency of the Gulf of Mexico energy-company traffic is immense.

Under the old system- operators like to say- you go VFR when the weather is good- IFR when the weather gets bad – and back to VFR when the weather persists. That’s a dangerous approach that typically results in flights being grounded. Under IFR rules- in an environment with no radar coverage beyond about 50 miles- the FAA’s ATC system employed an inefficient way of traffic management.

Under the non-radar system- the Gulf is divided into hundreds of 10-mile-square grids. Aircraft are required to report their position so that the FAA can make sure that only one aircraft at a time is in any given square- as well as assuring no adjoining grid squares have traffic. And- finally- the traffic route needs to have a contiguous line of those 10-mile grids connected one after another between the flight’s point of origin and its final destination.

With the IOC in place- controllers can begin to handle ADS-B equipped helicopters similarly to the way traffic is managed in the radar environment over the Lower 48 states.

But as the FAA and operators gain experience and confidence in the system- the agency and operators anticipate that separation standards common to the on-shore radar environment can be shrunken to as little as five miles from the typical 50 for en trail separation- and as little as three miles in airport traffic areas. Achieving these lower levels of separation will essentially serve to increase capacity.

Additionally- since aircraft equipped with both ADS-B Out and ADS-B In capability can see other ADS-B Out aircraft- pilots will be better equipped to maintain their own separation- even when not under positive control of the FAA’s ATC system. That means benefits on good days- marginal days and bad days- day and night.

Meanwhile- the FAA reports that it is currently at more than 50 ADS-B ground stations installed- with more going on line each month. By the end of 2010- the FAA expects to have the entire nationwide network of 320 ADS-B ground stations installed- connected and functional.

The next significant deadline on the radar scopes of the industry- however- comes in April 2010. That’s when the FAA expects to publish a NextGen implementation final rule for industry comment. And the next milestone is expected in September when the agency makes an in-service decision for the network.

The agency would like to have the system change-over to the NextGen ATC network completed by 2018 and is expected to hold to its deadline of 2020 for users to equip with ADS-B Out- in order to retain access to Class A- Class B and Class C airspace.

For those who may have let their airspace classification knowledge slip- Class A is IFRrequired airspace between 18-000 feet msl and 60-000 feet msl; Class B is over the nation’s busiest airports- with a major airport at the center – think Atlanta- Dallas/Ft. Worth- Chicago O’Hare and other similarly high-traffic areas; Class C is a smaller space over airports down a notch in traffic – like Wichita Mid-Continent- which holds its designation in large part because of the traffic from aircraft factories adjacent to the airport.

Currently- the well-known- widely available Mode A/Mode C transponder meets the FAA’s requirements for access to Class A- Class B and Class C airspace. Come final implementation of NextGen and ADS-B Out will be the key that unlocks access to those airspace designations- as well as for operators who wish to file to fly under IFR rules in Class E airspace- which- in short- is the airspace below Class A- and outside Class B and Class C.

All aircraft must transit at least some Class E to travel any distance- and when the weather goes down- the instrument rules allow any properly equipped and approved aircraft to transit Class E flying under an IFR flight plan.

The FAA is apparently going to stick with its proposed requirement of ADS-B Out hardware only- leaving the decision on whether to equip with ADS-B In to the aircraft owners and operators. Fortunately- equipping with ADS-B Out sets up the aircraft well to also install the receiver that enables it to receive ADS-B signals from other aircraft and from ground stations.

The ADS-B In link offers operators a number of benefits- including weather and traffic links- with traffic visible at distances far outside the capabilities of any current on-board traffic-avoidance gear.

ADS-B In should also allow the aircraft to receive nationwide weather images- text messaging and other services still being debated. And the weather input- now available through a number of subscriptionbased services- will require neither a subscription nor the proprietary receivers these services use.

In the end- equipping for ADS-B In could be a money saver and performance enhancer. But at the moment- it’s the ADS-B Out hardware that will be a must to sustain the kind of access available today with a Mode C transponder. ■

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