Here is a summary of Geremy’s presentation to our Association on September 22.
ADS-B stands for Automatic Dependent Surveillance Broadcast and it is part of FAA’s NexGen revamping of the air traffic control system. It provides better information to the air traffic control system and pilots. The FAA mandate for ADS-B Out in Class B and C airspace is December 31, 2019 at midnight.
For example, a typical transponder, when it is interrogated by radar, says “Here I am. Here is my altitude, here’s my squawk code.”
An ADS-B Out system will automatically send out “Here I am, here is my latitude and longitude”, every second. By that the ATC system can calculate your speed and direction. It also tells the system what kind of plane you have, which tells it your performance capabilities and size. Some think ADS-B is the entry way to user fees.
There are two main data sets in ADS-B world. ADS-B Out makes you legal. ADS-B In makes you safe.
It broadcasts on two frequencies, 978 megahertz known as UAT (Universal Access Transceiver) and 1090 megahertz known as ES (Extended Squitter). ES is what you need if you are flying above 18,000 feet and/or out of the U.S.
UAT is only good in the US below 18,000 feet, and you will still need your existing transponder. The rule of thumb is that if you don’t need a transponder for the flying you currently do, you won’t need ADS-B post-2020 either. But if you ever want to sell your plane, you will probably need ADS-B.
ADS-B In provides two services, FIS-B and TIS-B. Your ADS-B In receiver doesn’t have to be permanently installed in the aircraft (such as the Stratus), and isn’t required for the 2020 mandate.
FIS-B stands for Flight Information Services Broadcast. It includes textual weather (METAR and TAF), winds aloft, NEXRAD weather radar, TFRs, AIRMETs, SIGMETs, and PIREPs, all of which can be displayed on your device (iPad, GPS, multifunction display, etc., depending on your equipment). The FIS-B data is continuously being broadcast by ADS-B towers, which are laid out in a ground-based network. There are about 600 of them around the country (usually installed on cell phone towers) with more being added to improve coverage. The closest tower to FNL is near Johnstown.
TIS-B stands for Traffic Information Services. This is not broadcast to all traffic. It is a custom report that only responds to an ADS-B out trigger. A nearby ADS-B tower responds with all known traffic in your “hockey puck”, a chunk of airspace centered on your aircraft that is about 3,500′ tall (1,750′ below you and 1,750′ above you) and 30nm in diameter (aircraft within 15nm of you).
If you are not ADS-B Out equipped, your ADS-B In receiver can see this hockey puck data as well, but unless you are co-located with the aircraft that is generating the data (and I hope you aren’t), you can be missing out on a substantial amount of information. For example, if you are 15nm east of an ADS-B Out aircraft, your receiver will see traffic to your west but not to your east.
ADS-B In receivers also receive direct air-to-air traffic information — UAT if they receive that band and ES if they receive that band. Many receivers these days are dual-band. So you can see ADS-B Out equipped traffic that is outside your hockey puck.
The more congested the area is, and the more aircraft there are with ADS-B Out, you’re probably always in someone’s hockey puck. The farther east you go from here, away from the metropolitan area, you won’t benefit much from TIS-B if you don’t have ADS-B Out. But you will still get the FIS-B weather.
ADS-B ground stations are one of three types: low (local information), medium (regional information), and high (national information). They are laid out in a honeycomb pattern:
The theory is that the higher you are (and thus the more towers you can receive), the more likely you have a more capable, faster cruising aircraft that benefits from longer range data.
All the weather is at least ten minutes old by the time it is broadcast, and usually closer to twenty minutes. So if you are using Foreflight or something to try to fly around weather, please don’t. Weather can move quickly. Use the weather for big-picture weather trends, not to sneak through a hole between cells.
XM weather works better than ADS-B, but ADS-B is free. It’s all about the granularity.
ADS-B out will be required in 2020 where Mode C transponders are required today. In order to be compliant you will need a WAAS GPS source for your ADS-B Out device. Some devices come with built-in WAAS GPS (at a higher cost). ADS-B Out must be panel mounted and permanent due to the fact of the information about your plane.
If you choose to use UAT for ADS-B out, you are going to retain your existing transponder, and the UAT device must synchronize to it. Various methods are used by different vendors, from a “head” device on your panel where you enter or verify your squawk code, to devices that clamp to your transponder’s coax, to antennas mounted near your transponder antenna.
At the moment the ES installs are leading the UAT installs by about 3 or 4 to 1. Because of the piggy back nature, remote mounting, and old tired transponders that have to be replaced with new ones, installation costs for UAT are usually substantially more than the cost of an ES solution.
Previously in order to have a TSO piece of equipment, a manufacturer had to prove that it works on one particular aircraft (generating an STC) and then provide data to add other aircraft to the list (generating an AML). So, for example, you could install an Appareo ADS-B Transponder on a Cessna 182 but not on a Cessna 210. In May, FAA came out with a memo with updated information stating that you don’t need an AML for a transponder, particularly an ADS-B transponder upgrade. So now there is a little paperwork that needs to be done by your installer, but any certified ADS-B device can be installed on any aircraft.