The Potomac mid-air collision: the role of ADS-B

Karl D. Stephan

February 14, 2025 3 Reactions

When fully operational, an ADS-B unit in the Black Hawk would have updated air traffic controllers every second with a GPS-determined three-dimensional location data burst. This is vastly superior to what the controllers' radar can tell them on its own. And knowing that the helicopter was high enough to collide with the American Airlines plane would have at least allowed the controllers to alert the pilots to the problem.

That is exactly what happened only a day before, when an air traffic controller warned an Embraer ERJ 175 to abort a landing at a different runway at Reagan National because a nearby helicopter was flying at 300 feet. Although there appeared to be enough altitude difference between the two aircraft, the controller alerted the passenger plane's pilot anyway, who flew around and landed successfully later. Whether the helicopter in this incident was a Black Hawk or something else is not clear from published reports. But near-misses like this can provide warning flags for safety-conscious operators, who can apply lessons learned and prevent major disasters such as the one that happened on 29 January.

Sobering lessons

Late last week, crews successfully recovered all the major pieces of both aircraft involved in the accident, and the hope is that among the rubble is information about whether the helicopter's ADS-B system was working, malfunctioning, or turned off. The signal that ADS-B transmits is readable by anybody, so in an actual emergency flight carrying the President to parts unknown, it's likely that the system might be turned off for security reasons. In peacetime, it's fine to announce your exact location to all and sundry, but in a combat situation, it's the last thing you want to do.

The bottom line on this accident remains to be discovered, as we still don't have critical questions answered, such as the one about the ADS-B system. Speaking statistically, if one decided to stage a mid-air collision, one would have quite a challenge, because the volume of air occupied by a Black Hawk is not that large, and exquisite timing and aiming would be required. Unfortunately, the statistics were not favourable on that deadly evening.

According to a Wikipedia article on the ADS-B, the US somewhat lags behind other countries in requiring adoption of the system by most aircraft. I suspect it is a fairly costly piece of avionics, involving data links to a plane's GPS system and a 1-GHz-range microwave transceiver and antenna. Both aircraft were definitely equipped with ADS-B, but as mentioned above, it has not been determined whether the Black Hawk's unit was operational at the time of the crash.

More generally, this incident provides a good reason to speed up the adoption of ADS-B, which provides faster and more accurate data to air traffic controllers, who need all the help they can get. Another issue unearthed at this early point in the investigation is that the control office in charge of the airspace was understaffed at the time, and one controller was handling situations normally dealt with by two individuals. Whether this understaffing contributed materially to the collision remains to be seen, but the Federal Aviation Administration, which oversees air traffic control operations, is not exactly a poster child for governmental efficiency. Other countries, such as Canada, have transformed their FAA equivalents into private non-profit organisations, paying for them by user fees, and sometimes this makes things run better and cheaper. But that is an argument for another day.

We will keep an eye on the investigation of Flight 5342's crash, and hope that lessons learned will be applied to keep anything like this from happening again.

Is the aviation industry improving safety standards, or are more accidents inevitable with the rise in air traffic?

Karl D. Stephan is a professor of electrical engineering at Texas State University in San Marcos, Texas. His ebook Ethical and Otherwise: Engineering in the Headlines is available in Kindle format and also in theiTunes store. 

This article has been republished, with permission, from his blog Engineering Ethics.  

Image credit: Wikimedia Commons