Large Commercial Aircraft Down

[BinaryMode]

In my opinion, I think the ball was dropped from multiple fronts and common sense may have went right out the window. Like Bruce Hornsby once sung, and Home Depot used for advertisement circa 2006, "there's gonna be some changes made."

And there are changes being made.

In the wake of a deadly midair collision near Ronald Reagan National Airport that killed 67 people, the U.S. Army has revised key aviation procedures, including how it uses the aircraft-tracking system known as ADSB (Automatic Dependent Surveillance–Broadcast), and significantly scaled back helicopter flights over the Washington, D.C., area.

Army Adjusts Helicopter Safety and Tracker Protocols After Fatal D.C. Crash - Common Defense

In the wake of a deadly midair collision near Ronald Reagan National Airport that killed 67 people, the U.S. Army has revised key aviation procedures, including how it uses the aircraft-tracking system known as ADSB (Automatic Dependent Surveillance–Broadcast), and significantly scaled back...

www.commondef.com

According to the website ADS-B Exchange, the helicopter WAS using Mode-S. Otherwise there would have not been any location awareness using MLAT via the website. As you can see in the video of the ADS-B Exchange tracker map I attached in this thread somewhere.

 

[maus92]

Having a Mode S transponder ≠ ADS-B, and aircraft do not use MLAT. In other words, nothing particularly revelatory.

 

[BinaryMode]

Mode-S is what allows people that feed into ADS-B Exchange and the likes to allow us to view an aircraft's location. You need a minimum of four receivers on the ground feeding to ADS-B Exchange to allow for multilateration, i.e. MLAT.

The article questions what kind of mode they were using - I stated here that they were in FACT using Mode-S.

Mode- S does NOT contain GPS data in the data, but MLAT fills in that gap. If it's Mode-C or whatever, MLAT will not work.

I'm referring to this bit from the article:

Although the crash involving an Army Black Hawk helicopter and an American Airlines passenger jet remains under investigation, officials have zeroed in on the lack of ADSB-out data from the helicopter as a potential factor.

-snip-

The Black Hawk’s transponder was functioning and actively transmitting in three modes — A, C, and S — providing controllers with the aircraft’s identity, altitude, and location.

“There was no question where that aircraft was,” Braman stated. “There was no point during the flight where the jet and the airport control tower could not see the Black Hawk.”

 

[maus92]

A Mode S transponder encodes a unique identifier so individual aircraft can be identified by ground based surveillance radar during its interrogation cycle (~ every 5 secs). A Mode S ES capable transponder also encodes GPS position data which can be used for ADS-B Out equipage requirements (broadcasts position data every second). A legitimate question is what mode was it using when the incident occurred. The military uses Modes 1 - 5, with Mode 3 being being more or less equivalent to civilian Modes A/C. Mode 5 is more or less equivalent to a Mode S ES transponder configured for ADS-B Out (although it can be encrypted). It seems that the helicopter was using Mode 5 based on what you've written. The sad point is that while ADS-B Out is mandated for most aircraft, ADS-B In (the ability to display nearby aircraft in the cockpit) is NOT. Also, not all air traffic facilities directly utilize ADS-B data, thus are relying on radar data based on 5-second sweeps to provide separation services. Finally, MLAT is not used at DCA as SSR AFAIK. I *think* sites like ADS-B Exchange use a form of MLAT technology using hobbyist ground receivers - certainly not certified stations.

 

[BinaryMode]

Yeah, the MLAT is coming from ADS-B Exchange participates. Nothing more, nothing less. Not FAA ground stations or anything like that.

IF The mode-S squawk output carried GPS data it would be ADS-B.... Or at least show up as ADS-B on ADS-B Exchange's website. The lack of GPS date means MLAT has to be used to effectively track the aircraft position via a minimum of four ADS-B Exchange participates who feed into the ADS-B Exchange server.

So, in a nutshell the helicopter was NOT outputting location awareness data via GPS... And this is done quite often from my observation of military aircraft. In my opinion this should NOT be the case in civilian airspace. Over military owned land designated as restricted airspace would be a different story.

It's another case of just because you can doesn't mean you should. Which is right up there in the encrypted public safety Comms arena... But I digress.