Next Gen, When?

A CritiqueBy

James R. Spensley

Neighborhood Noise

Air Traffic Control and Airspace Design Impacts Noise Exposure

Neighborhood Noise

Air Traffic Control and Airspace Design Impacts Noise Exposure

Altitude is Important: Noise dissipates and sound intensity is attenuated by height.Altitude is Important: Noise dissipates and sound intensity is attenuated by height.

Neighborhood Noise

Air Traffic Control and Airspace Design Impact Noise Exposure

Altitude is Important: Noise dissipates and sound intensity is attenuated by height.Altitude is Important: Noise dissipates and sound intensity is attenuated by height.

Height is a dynamic air traffic control variable closely related tosafety, with responsibility shared by procedure, controller, pilot,weather, aircraft capabilities and runway configuration.

Height is a dynamic air traffic control variable closely related tosafety, with responsibility shared by procedure, controller, pilot,weather, aircraft capabilities and runway configuration.

On to Next Gen

Airport and cockpit security got all the FAA budget attention after 9/11/2001.

In 2005 around the country, air travel peaked. More so at hubslike MSP, where many multiple-stopflights were replaced by direct flights.

U.S. ATC Now

En Route Centers (TRACON)• 21 radar sites “guide

aircraft flying at high altitudes through large sections of airspace.”

• “Data from these radars” is communicated to FAA controllers digitally.

• Controllers use data display consoles to identify and track aircraft.

Airport Towers • “At (airport) control

facilities, controllers guide aircraft (at low altitudes) within about 40 miles of an airport.”

• Most busy airports have towers, but approach and descent control is often “remote”.

• Towers “guide aircraft “ to, from, and on airports.

Phased ArrayTRACON

TRACON

Airport Radar

To Aircraft: SYNCH, TIME.From: ID, TIMEr, SYNCH

TRANSCEIVER

Tower displays tracks as taggedIcons relative to the airport

ATC Tower radartracks flights nearthe airport.

Console

FAA COMMENTS:

FAA: “Most air traffic controllers today do their jobs without ever seeing the aircraft they guide.”

FAA: “The ATC System Command Center plans air traffic for the entire country.”

The History of “Tracks”

• Flight dynamics are such that one can predict future positions, headings, and velocities from position histories with high reliability.

1.WWII radars: reflections.2.1950’s doppler (wig-wag tags)3.1960’s UHF/VHF IFF response4.1970’s Automated IFF (encrypted)5.Radar transceivers (embedded tags).

Marion Blakey’s Dream

• As air traffic increased after 9/11 flights were more often sharing corridors and using major hubs. The 1970-era radar/transceiver systems could not keep up.

• FAA R&D budgets requests were cut -- a lot -- and Congress limited FAA R&D programs by failure to pass re-authorizations.

• Administrator Blakey’s 2007 response:

Let’s start over!

Aircraft GPS computes position Exchange with

Next Gen Radar

Airport Radar

Tower displays tracks as taggedIcons relative to the airport

ATC Tower radartracks flights nearthe airport.

Console

Next Gen Concept

The Politicized Motive

• GPS and other area navigation systems allowed aircraft to “cut the corners” of routes center to center.

• These “shorter routes” were advertised as better fuel consumption and lower emissions• Flight plans and available radar surveillance by

FAA allowed en route separations to be maintained using RNAV routes.

Two Big Issues

Technology “Challenges”

• There are 6 to 8 FAA computer and Operating System platforms.

• Controller console displays are more complicated at airports.

• The cockpit display(s) are not yet designed, much less tested.

Schedule and Funding

• Next Gen projects are currently for en route centers.

• Airport tower displays were not scheduled before 2018, and the 2012 FAA budget request stretches this out.

• The last of the Next Gen improvements assumes all challenges are met in a timely way.

GPS: Minimum of 3 SatellitesLatitude, Longitude Accuracy

• Distance to the center of each satellite’s orbit projects a large ellipsoid on the earth surface.

Altitude Accuracy

• Neither the earth nor the satellite orbit being a plane, the vertical error is an order of magnitude greater (a function of the distance to the center of the earth.)

20 M

30 MNot to scale

Position “History” is more useful and accurate.

From past position data, including uncertainty, a new position, direction, and speed can be “predicted.“

The “GPS” track can be converted to range and azimuth and displayed on associated ATC consoles.

Does GPS “certainty” support thereduced safe separations advertised for NEXT GEN?

IT DEPENDS (on more than a few variables and interpretations), but the analysis is vague and varied.

1. ATC is not collision avoidance. Separations should be based on routine responses, not emergencies.

2. Safe ATC separations depend entirely on closing speed, not accuracy, although the alarm sensitivity (time to collision) is no better than the worst possible position errors.

3. Next Gen’s automated ATC messages are not yet response tested; what will pilots be watching?

4. How many tracks can be displayed on a cockpit display, and what is the best perspective?

Does GPS “certainty” support NEXT GEN reduced safe separations at airports?

• Probably not. • At airports, an airspace management system

is the ATC basis, with intervals more important than separations as the controlled variable.

• The focus is on communications: controller direction and pilot response

Shannon’s Equation

I = –p log2 (p)• Information equals minus the inverse uncertainty

times the log, base 2, of the probability.

The increase in accuracy needed to alarm separations of 2,500 feet compared to en route separations of 25 miles (132,000 feet):

10 bits/dimensionOr 4 bytes.

Airline & Flight Deck Expectations

1. Cockpit displays will “extend” the visual field.2. Closing rates will be limited and “lanes”

widened.3. The Next Gen system will reduce cockpit display

clutter and lessen communications for a given flight and situation.

4. Projected tracks can be re-computed for each cockpit; course and speed corrections displayed, simulating extended vision.

5. Finally, routine place-keeping can be automated.

FAA Safety Manual

“Changes … create increased safety risk as the changes interact or interface with existing procedures, systems, or operations.”

Their example: Such as “reducing separation minima.”

How much is too much?

Cockpit displays will have limitations depending on locations (those of GPS) and Next Gen complexity.

Relative speed and lateral position demands are Increased by area traffic: Four aircraft per sector means 15 pairs. Eight aircraft per sector means 50 pairs.

Hands-On Instrument Approaches?

What criteria is used to reduce the tracks displayed in the cockpit?

Any criteria will increase automated communications from Next Gen centers.

If there are more aircraft en route per hour, more airports are needed.

Track updates for 150 aircraft in flight is an en route design goal. The communications rate is the same for whatever separation is alarmed. Greater use of a given airspace depends on precision, not bandwidth.

The airspace at an airport is smaller and control is based on one less degree of freedom and more restraints.

QUESTIONS?

Next Gen topics were:Concepts and technology examples.

Technical feasibility.

Technical difficulty and scheduled level-of-effort.

Funding and Management.