FAA Releases ADS-B Avionics NPRM


The Federal Aviation Administration (FAA) has issued a Notice of Proposed Rulemaking to mandate ADS-B equipage by January 1, 2020 on the heels of awarding a national ADS-B contract to ITT Corporation last month to provide ADS-B surveillance uplink (ground-to-air) and downlink (air-to-ground) services and Automatic Dependent Surveillance Rebroadcast (ADS-R), Traffic Information Services – Broadcast (TIS-B), and Flight Information Services-Broadcast (FIS-B) services.  HAI has reviewed the NPRM and provides the following information and analysis of the proposed avionics requirements:

The FAA NPRM only seeks to require ADS-B Out.  The FAA is not proposing to require ADS-B In at this time.  ADS-B Out refers to an equipped aircraft’s broadcasting of aircraft information, and ADS-B In refers to an equipped aircraft’s ability to receive another aircraft’s ADS-B Out information.

The FAA’s schedule for ADS-B Out calls for all ground infrastructure, including the provision of broadcast services, to be in place and available where current surveillance exists by the end of fiscal year 2013.  The FAA believes the schedule will provide reasonably ample time for operators to equip their aircraft for ADS-B Out and meet the proposed compliance data of 2020 in the NPRM.

The FAA has proposed ADS-B Out performance requirements for all aircraft operations in Class A, B, and C airspace areas in the National Airspace System (NAS), and Class E airspace areas at or above 10,000 feet mean sea level (MSL) over the 48 contiguous United States and the District of Columbia.

The NPRM would also require that aircraft meet these performance requirements in the airspace out to 30 nautical miles (NM) from the surface up to 10,000 MSL, around certain identified airports that are among the nation’s busiest.

For the Gulf of Mexico, where over 650 helicopters operate, the NPRM would require that aircraft meet ADS-B Out performance requirements to operate in Class E airspace over the Gulf of Mexico from the coastline of the United States out to 12 nautical miles (NM) at and above 3,000 feet MSL.  The FAA plans to install communications equipment in the Gulf in the 2007/2008 timeframe, weather equipment in the 2008 timeframe, and surveillance equipment in the 2008/2009 timeframe.  The FAA expects initial operational capability of the communications, weather, and surveillance equipment in the 2009/2010 timeframe.

For aircraft flying at or above Flight Level 240, requirements are for ADS-B Out performance capabilities using the 1090 Extended Squitter ((1090ES) broadcast link.  Aircraft flying in the designated airspace below FL 240 would have to use either the 1090ES or Universal Access Transceiver (UAT) broadcast link.

These proposals would affect all U.S. commercial air carrier operations, foreign-flag carriers operating in the designated classes of U.S. airspace, air charter operations, air cargo operations, and a significant portion of the general aviation fleet operating in the NAS.

The implementation of ADS-B requires two datalinks to support the full set of applications:
· UAT is intended to support applications for the general aviation user community that are not needed by air carriers because air carriers have weather radar, fly at high altitudes, and have other aeronautical links.  UAT-equipped general aviation aircraft are not generally equipped with weather and would be flying at low altitudes.
· The 1090ES link is the internationally agreed upon link for ADS-B, and is intended to support applications for air carriers and other high-performance aircraft.  The 1090ES broadcast link does not support applications available from FIS-B, like weather and related flight information.

Operators of air carrier and many private/commercial aircraft are already primarily equipped with Mode S avionics, which are required to function with the Traffic Alert and Collision Avoidance System (TCAS).  Many Mode S transponders can be modified or are designed to provide 1090ES functionality.  Most other general aviation aircraft, typically small aircraft operated in non-commercial service (not required to have TCAS) would likely use the UAT broadcast link for ADS-B Out.  A small number of aircraft are currently equipped with UAT ADS-B In and are capable of receiving TIS-B and FIS-B services.  While the 1090ES link does not support FIS-B, it does support TIS-B.

Under the NPRM, operators may also choose to equip with dual link avionics, i.e. 1090ES and UAT, which would provide the capability to transmit and receive information on both broadcast links at the same time.

Some general aviation aircraft are already equipped with the UAT broadcast link, and most general aviation operators are expected to equip with UAT under the FAA’s NPRM in order to have TIS-B and FIS-B services.

Page 65 of the NPRM contains a chart indicating ADS-B Equipment and Installation Hours Costs.  The FAA has assumed the weight for an ADS-B Out transponder, on a GA aircraft, would be about the same weight as existing transponders, with no additional weight or fuel burn costs.

The FAA is proposing to add an appendix to 14 CFR Part 91 to specify the broadcast message elements necessary for ADS-B Out.  These elements would be broadcast automatically from the aircraft except where pilot entry is necessary:
· The length and width of the aircraft
· An indication of the aircraft’s lateral and longitudinal position.
· An indication of the aircraft’s barometric pressure altitude.
· An indication of the aircraft’s velocity.
· An indication if TCAS or ACAS is installed and operating in a mode that may generate resolution advisory alerts.
· For aircraft with an operable TCAS or ACAS, an indication if a resolution advisory is in progress.
· An indication if ATC services are requested. (Requires flight crew entry)
· An indication of the Mode3/A transponder code specified by ATC (Requires flight crew entry)
· An indication of the aircraft’s call sign that is submitted on the flight plan or the aircraft’s registration number. (Aircraft call sign requires flight crew entry).
· An indication if the flight crew has identified an emergency, and if so, the emergency status being transmitted (Requires flight crew entry)
· An indication of the aircraft’s “IDENT” to ATC.  (Requires flight crew entry)
· An indication of the aircraft’s assigned ICAO24-bit address.
· An indication of the emitter category.
· An indication whether a cockpit display of traffic information is installed and operable.
· An indication of the aircraft’s geometric altitude.

The NPRM also contains considerable discussion on FAA requirements for both a top and bottom antenna.  The FAA is proposing to require that the aircraft be equipped with both a top and bottom antenna to support ADS-B Out applications as well as future air-to-air ADS-B In applications.

For aircraft already equipped with a Mode S transponder which incorporates antenna diversity, no additional antennas would be required for ADS-B Out using 1090ES.  For ADS-B In, additional 1090 MHz receive antennas may be necessary, depending on the additional avionics equipment installed on the aircraft.  It may be possible to share the TCAS 1090 MHZ receiver as long as it can be shown that TCAS performance is not degraded.

For ADS-B installations using UAT, it may be possible to share the aircraft’s existing bottom ATCRBS transponder antenna through the use of an antenna diplexer, thus only requiring installation of a top antenna.

Antennas would also have to transmit their signal at a certain level of power in order to ensure that transmitted signals are received by ground stations and by ADS-B In equipped aircraft and vehicles.

If aircraft are voluntarily equipped with ADS-B In, pilots could see real-time information similar to what ATC views and have access to similar services and applications.  Pilots would have better situational awareness because their flight deck displays would depict all aircraft equipped with ADS-B or transponders.  Pilots may be able to use this information to monitor and maintain safe separation from other aircraft with fewer instructions from ATC.  At night and in poor visual conditions, pilots could also see where they are in relation to the ground using onboard avionics and terrain maps associated with a multi-function display.  The information would be clear and accurate regardless of inclement weather conditions.

Aircraft equipped with ADS-B In capabilities could receive traffic information for other aircraft regardless of whether those aircraft are equipped with a functional ADS-B system.  Aircraft equipped with ADS-B In would also be able to identify other ADS-B equipped aircraft regardless of the broadcast link being used.

The FAA is seeking comments to the ADS-B Avionics NPRM over the next 90 days, and page 2 of the NPRM provides instruction as to where comments may be filed.  Information detailing the specific request for comment begins on page 68 of the NPRM.  HAI encourages all members to carefully review this document.  You may submit comments directly to the FAA or provide a list of your comments to HAI and they will be incorporated within the HAI comment to this NPRM.  Please furnish correspondence to Ann Carroll, HAI Legislative Affairs at ann.carroll@rotor.org.

CLICK HERE to download full 100 page NPRM in PDF format.