ADS-B – The Good. The Bad. And The Ugly.
ADS-B, or Automatic Dependent Surveillance Broadcast, is a new technology that will allow pilots and controllers to see traffic with more precision than before. Instead of relying on radar technology, ADS-B uses GPS signals from communicating airplanes. Therefore, ADS-B works where radar does not, including remote or mountainous terrain. It can be used to monitor traffic on airport taxiways and runways as a result.
Aircraft equipped with ADS-B receivers will receive ADS-B traffic and subscription FREE weather information in-flight. Weather information includes graphical NEXRAD radar information, as well as METARs, TAFs, etc.
Traffic information is received either directly from other aircraft as they broadcast their ADS-B "Out" messages (Air-to-Air), or from ground stations. Since aircraft may broadcast on either 1090 or 978, a dual channel receiver is needed to reliably receive traffic messages from any ADS-B "Out" aircraft. This is only important if you are ready to see traffic on your screen. See "Bad" below.
ADS-B is all a part of the federal government’s NextGen Air Transportation System for air traffic control. ADS-B is a two part system – one part is called ADS-B “Out”. Planes equipped with ADS-B “Out” transmitters broadcast their identity, position, track, speed, and other data. Air traffic control ground stations and ADS-B “In” equipped aircraft receive this information once every second. These ground stations broadcast information as well. They broadcast traffic information and subscription FREE weather for display in the cockpit.
ADS-B “In” receivers are readily available, relatively in-expensive and can display their data on several different iPad apps. ADS-B “Out” transmitters are more expensive. However, if you fly in controlled airspace, you will need to be equipped with ADS-B “Out” by 2020. Note that “In” is NOT required.
In simple terms for most GA pilots, an ADS-B “In” receiver in the near term is mostly about getting FREE weather information into the cockpit and displaying it on your iPad. You will see why after you read the BAD part. ADS-B "Out" is still too expensive and not well enough defined to be a practical consideration at this point.
During the transition to ADS-B there will be planes flying that are NOT transmitting their information regarding their position with an ADS-B “Out” transmitter but are flying with a transponder. Thus, when you are flying outside the range of a ground station you will not see these targets on your flight display. This means that using an active traffic system such as TCAS, TAS and TCAD will give you the most comprehensive traffic picture available until the year 2020 and beyond 2020 when flying in uncontrolled airspace.
Also during the transition to ADS-B there will be planes flying that are NOT equipped with transponders and no ADS-B “Out” transmitters. These planes will not be seen at all.
The current broadcast from ground stations is a developmental version called Traffic Information Service – Broadcast (TIS-B). TIS-B traffic consists of transponder equipped aircraft being seen by radar and then relayed to your aircraft via the ADS-B data link used in the ADS-B “In” receivers. You need to take note of the following regarding the visibility of targets on a screen of your airplane to others and your view of other planes:
- TIS-B targets may be intermittent when maneuvering or on the ground. Pilots should consider dual (diversity) antenna installation for their ADS-B “Out” solution placing an antenna on both the top and bottom of the airplane.
- TIS-B targets will tend to lag behind the current position and may be positioned anywhere around the aircraft’s position
- TIS-B position updates are approximately 2 to 13 seconds depending upon the radar coverage in the area
- TIS-B system currently only sees transponder equipped aircraft. This means that aircraft that are visible as radar targets to controllers will not be seen by you if they are not equipped with a transponder.
- No transponder equals no TIS-B target
Thus viewing traffic on a device equipped with ADS-B “In” is incomplete and is NOT to be relied upon any time soon.
The broadcast system is incomplete. There are now 400 of about 700 planned stations expected to be up and running by early 2014. Thus, if you are looking to use an ADS-B “In” receiver for weather information, be sure that there is a ground station in the area where you fly.
And The Ugly.
ADS-B is a Federal Government led initiative to make flying safer. There are very specific guidelines that device manufactures must follow for the transmission of ADS-B “Out” – the information that must be sent - and “In” – the information that the government will send back. However, it is left up to the device manufacturers to decide the format and the devices and/or apps they will talk with. This is the UGLY part.
What does this mean? It means that when you make a decision as to which ADS-B “In” receiver you buy you are also at the same time making a decision as to which device and/or app you will be able to see this data on. Said another way, when you choose what app you want to use, you can only select those ADS-B receivers that are known to work with that app.
For example, currently the only ADS-B receiver that works with ForeFlight is the Stratus box which is sold by Sporty’s and is a joint venture of Sporty’s, ForeFlight and Appareo Systems. If you buy the new Garmin GDL 39, it will work with various Garmin devices and Garmin Pilot for the iPad.
Thus, you should first choose what software or device you wish to use and then be sure of which ADS-B receiver will work with it. Changing software or devices in the future may then also necessitate the purchase of a new ADS-B receiver.
As far as we know, only WingX Pro7 by Hilton Software has committed to work with more than one ADS-B receiver with commitments to Dual, Sagetech and others.
I am very excited about ADS-B – both in and out. For now, it is all about weather. Traffic is interesting, but not ready for prime time. Technologies are quickly evolving. Make your decision on an ADS-B receiver based on a short-term desire to view weather in the cockpit. But choose wisely. When you choose an ADS-B "In" receiver, you are also choosing which apps you want to use at the same time.
I will purchase an ADS-B receiver shortly as I would like to have weather on my iPad to help with in-flight navigation and re-planning that result from weather issues. If you don't already have on-board weather information, I feel it to be a must have.
If you do have on-board weather with XM, ADS-B becomes a very nice to have. I already have XM weather on my MFD. However, when I need to look for alternate routes or destinations, it would save a lot of time to already have the weather for those locations readily available. It takes a lot of extra steps and time to enter in possible airports on my route so that XM will display the information, time that I could use flying the airplane.
Additional resources can be found online.
PIREP - Bad Elf GPS Pro
Bad Elf introduced the Bad Elf GPS Pro and I have had a chance now to fly with it now for about eight hours. It is also the first device to have a display screen so that you can see key information such as altitude, speed, satellite locks, etc.
At first I wasn't sure if this device was for me especially since I fly single pilot a lot of the time. However, having flown with it, there is more to this device then meets the eye. Here are some of my observations:
1.You don't have to interpret blinking lights or have to leave a flying app to go to the device's app to see the performance of the unit.
2.Multi-user/device feature works great and is useful even for flying single pilot. In my case, I use my iPhone to back-up my iPad as I have my flying apps and charts on both devices. It is nice to be able to use the GPS signal on both. When I do fly with other pilots, it is nice to be able to share a single device.
3.This unit captures the GPS signal fast. It seemed like seconds and I had a lock.
4.This unit captures the GPS signal in my console. Even before I had a chance to move the device to the windshield I already had a signal lock. I now keep it in my console plugged in and nothing is floating around on the glare screen. This may not be the same in your airplane, so experiment. You may need to have it see the sky to get the initial lock and then be able to move it to the console or elsewhere.
5.There is a data logging function that will record your last 100 hours of flight tracks for later viewing on a map. I have not tried this feature yet. I have heard that this is important to some pilots.
6.It isn't perfect, yet. There are a few minor software glitches being worked out and the folks from Bad Elf are updating the firmware to address them. Their new app will alert you of an update by placing a number over the app's icon. Simply go to the app and you will see a button to perform the update. This is cool because they can release updates without having to go through Apple and the delay that that adds to the process.
Overall, is it worth the extra $50 for this unit over the competition - Dual @ $100 and Garmin @ $129? In my opinion, if you will use the multi-device/user feature or need the data logging feature, then yes. If you want something for a single device only and not use data logging, I would say no.