Wednesday, February 08, 2012

ADS-B Catch-up

Anyone who's not been asleep the last threes years has probably heard that ADS-B (Automatic Dependent Surveillance-Broadcast) is a key component in the FAA strategy known as NextGen. In addition to reducing airport traffic delays and preventing tooth decay in dogs, NextGen will purportedly use ADS-B to replace traditional, expensive, old-fashioned radar used by air traffic control (ATC). I'll pause here to give my readers a chance to stop laughing before I point out the obvious - ADS-B as it currently stands has more security holes than an old pair of work pants. Good old radar is and will remain critical to our national defense, helping to thwart smugglers, terrorists, and other airborne criminals who don't want to be detected. In spite of all the hyperbole, PR whohaa and design problems, ADS-B is nevertheless a cool and appealing concept.

Before getting into the two halves of ADS-B, let me point out that only bureaucrats and propeller-head engineers could come up with a name like Automatic Dependent Surveillance-Broadcast. Don't you like how it just rolls off the tongue? Moving on, there's ADS-B In and ADS-B Out.

ADS-B In is simply the passive reception of traffic data sent from appropriately equipped aircraft and weather information broadcast from local, ground-based stations. ADS-B Out is more complicated (read expensive) for aircraft owners because it involves purchasing and installing new ADS-B transceivers that can transmit and receive GPS-derived position and altitude. The cost of equipping all aircraft with ADS-B is the big hurdle that seems to get glossed over, but such equipment will be mandatory for aircraft that want to use most controlled airspace by January 1, 2020.

In the meantime, there clearly is a void in traffic avoidance technology for light aircraft. Many GA aircraft have equipment that supports the current and useful TIS (Traffic Information System). Unfortunately not all ATC radar sites support TIS and when you're in those areas your TIS equipment will tell you traffic is unavailable. In classic FAA fashion, no sooner had TIS technology become widespread than there was the announcement that TIS would be phased out at some indefinite point in the future (back in 2005, the phase-out was said to be in 2013).

TIS is very useful and has saved my bacon on many occasions. Lately, some local controllers have gotten irritated when instrument pilots practice holding at some airway fixes. One fix in particular has been used by yours truly for holding practice over a decade, but we're now told to practice holds much farther to the East where there is supposedly less traffic. The irony here is that we're often flying TIS-equipped aircraft and in the area we've been asked to avoid we get TIS alerts and visually acquire the traffic, often long before the approach controllers point them out. When we hold further East as requested, we're in an area where ATC's radar does not support TIS, we actually  experience more traffic conflicts, and we have to resolve these with just our eyes. To my mind, some procedures that are implemented in the pursuit of safety actually end up decreasing safety.

GNS 5890 USB Stick ADS-B Receiver

My firsthand experience with ADS-B was nil until the kind folks at Global Navigation Systems (makers of the GNS5870 bluetooth GPS receiver) recently allowed me to test-drive their new GNS 5890 ADS-B Receiver USB-Stick Receiver. This receiver comes with Windows software that allows you to display the position of ADS-B Out equipped aircraft on a map. The software itself is pretty simple and more a proof-of-concept than anything else. This device is small, purportedly the smallest ADS-B receiver made. And GNS has plans to release a Bluetooth ADS-B receiver with weather capability that could be very useful with the iPad, provided iPad EFB software developers introduce support for ADS-B Bluetooth devices. A combination ADS-B/GPS Bluetooth receiver would be an ideal solution. If the hardware and software align, ADS-B on the iPad could become a very useful, cost-effective, and subscription-free alternative to XM weather.

In order for ADS-B traffic capability to become a reality, all aircraft will need to have ADS-B Out capability and that will require an appropriately certified (read expensive) transceiver installed in each aircraft. In short, ADS-B traffic technology just doesn't seem to be something that can be accomplished with a portable device and installing ADS-B transceivers in all GA aircraft will be a huge, expensive, and time-consuming undertaking.

In an imperfect world where safety often seems to take a backseat to cost, ADS-B is a cool and promising technology.  In the meantime, I sure hope that the FAA's proposed phase-out of TIS will be delayed.


JohnOCFII said...

Very interesting! This is the first I've heard of this particular ADS-B receiver.

I was -certain- that Foreflight would be adding ADS-B support as of last summer's EAA Airventure. Sadly, I was wrong. I spoke at length with one of Foreflight's booth people, and they were focused on their XM support.

Now that they have shipped their XM support, I really hope they turn to supporting ADS-B. I made the leap to purchase the Radenna Skyradar ADS-B product in hopes that it would soon be supported by Foreflight. Radenna -does- ship an iOS app to display weather and aircraft, but it would be nice to have the ADS-B data displayed in conjunction with the other data in Foreflight.

John said...

If you currently have TIS, then you have a mode S transponder, such as the GTX330. My eventual path for ADSB Out will be to upgrade my GTX330 to ES. I will wait at least until the GTX330ES supports the current TSO. Once it does, I will consider adding either a portable dual frequency ADSB-In box such as the Skyradar unit or a panel mount with the same capability. The GTX330 can be configured to indicate that I have a dual ADSB-In receiver, so I will receive ground station TISB messages for mode C based non ADSB participating targets. I would initially display these on a portable device that could display traffic and FISB weather. Once the upgrade path becomes clear, I would move towards a panel mount solution. I have a GNS530W which will work with the GTX330ES as a position source, and offers limited TCAD type traffic display capability. The fly in the ointment for me is that now that the GNS530W is discontinued, it is not likely that it will ever support the display of weather. The fly in the ointment for the G1000 users is that it may be some time before it supports ADSB function, In or Out.

John Ewing said...


You make it all sound so simple ... ;-)