DejaVu

Deja vu

The following is a narrative from a NASA Aviation Safety Reporting System report, Number ACN 707567. It is from August 2006 (alternatively, one may view the report’s text below with a decoder, by clicking here)...

THIS IS NOT AN ANOMALY OR AN ISOLATED OCCURRENCE. THE FAA ACKNOWLEDGES THAT FACT. THE FAA DOES NOT, HOWEVER, VIEW THIS AS SIGNIFICANT. I DO. OUR PRIMARY RADAR SYS, OR HOST, DOES NOT DISPLAY ALL XPONDER-EQUIPPED (DISCRETE OR NON-DISCRETE CODES) ACFT IN THE AREA OF JBR (JONESBORO, AR), EVEN THOUGH THESE ACFT ARE IN AREAS OF KNOWN RADAR COVERAGE. I WAS WORKING AN IFR ACFT IN THE JBR AREA AT 4000 FT (DISPLAYED ON RADAR), AND THERE WERE VFR ACFT IN THE AREA THAT I WAS NOT DEPICTING ON RADAR. 1 ACFT 3 MI SW OF JBR AT 2500 FT, 1 ACFT 12 MI SW OF JBR AT 4500 FT, AND ANOTHER ACFT 5 MI N OF JBR AT 3500 FT. NONE OF THESE ACFT WERE DEPICTED ON HOST RADAR. HOWEVER, OUR BACKUP SYS, DARC/EBUS, WAS DISPLAYING THESE ACFT ON RADAR, WHICH IS THE ONLY REASON I KNEW THEY WERE THERE. THIS IS A COMMON OCCURRENCE, EVERY DAY, ALL DAY. I'VE EVEN HAD AN ACFT AS HIGH AS 11000 FT THAT WAS NOT DEPICTED ON MY RADAR SCOPE. THIS IS A SAFETY ISSUE. I CANNOT, CONTRARY TO THE STATEMENT BY MGMNT, CONTINUE TO RELY ON THE INTEGRITY OF THE RADAR DISPLAY.

Occasionally one gets a glimpse, from a different perspective, of the way things really are. When that occurs, it can really be eye opening.

I caught such a glimpse back in the mid 80's. It was sometime after a Crown Airways commuter pilot, on his way from Dubois, PA to Pittsburgh, PA, exclaimed on my frequency “Center, DID YOU SEE THAT AIRCRAFT???!!!” The pilot had narrowly missed having a midair collision with a VFR aircraft that was NOT displayed on my scope. (The VFR aircraft, squawking 1200, appeared shortly thereafter, at the commuter’s six o’clock position.)

It made no sense that the other aircraft would’ve been invisible until just after nearly colliding with the Twin Otter I was working.

It was sometime after that incident that we got the capability to individually select our backup computer display at our workstations. That gave me the ability to compare the presentation of my main display, with the display of my backup system called "DARC” (Direct Access Radar Channel). At that time, DARC allowed one to select one and only one radar site at a time, as it simply wasn't sophisticated enough to process radar data from multiple radar sites. Its inability to process radar data from multiple sites in a concurrent fashion, turned out to be very helpful in understanding what was taking place.

I vividly recall how, when I selected QCF (the Clearfield, PA Air Route Surveillance Radar site) on DARC, I was amazed to observe multiple VFR aircraft, squawking 1200 (with altitude information), flying around the Clarion VOR in western Pennsylvania. Yet when I switched back to the display we utilized day in and day out, those low-altitude VFR aircraft were not present for me to see.

That is what lead me to ask a bunch of questions, and dig deep into the maintenance manuals, in an effort to understand what was taking place. That lead me to write my 1988 & 1991 papers. That may seem like ages ago, however....I recently came across the above NASA ASRS report, that shows how the situation really hasn’t changed. The air traffic controller who authored that report apparently took the time to compare the backup DARC display, to the main display, and noticed the same type of situation I observed around Clarion VOR around two decades ago.

If you wish to view the entire NASA report, I recommend that you go to the NASA ASRS web site, select “ASRS Database Online”, and do a search on ACN #707567. Notice how under "Resolutory Action:" it states "None Taken : Anomaly Accepted."

We need to truly process ALL radar data (secondary returns AND "skin paint" primary returns), from ALL radar sites, ALL the time, and not toss valuable radar data into the electronic "bit bucket." Is it possible to accomplish this? Learn more about one man’s vision and work towards such a paradigm shift here.

Sincerely,

Thomas G Lusch

June 6, 2009