A Problem With NORDOs

Since the incident with Northwest Flight 188 in October, the FAA has been on the hot seat for failing to recognize and take action in a timely manner on flights that lose radio contact with air traffic control (NORDO, an acronym for “no radio”).

In that incident, FAA managers had plenty of time to act but instead failed to follow procedures that would have notified the military of the flight’s NORDO status.

Considering the amount of time the flight went without being in contact with air traffic control, it was a highly suspicious situation.

According the FAA orders, flights that are out of contact with air traffic for more than five minutes are supposed to be considered possibly suspicious (like a hijacking).  Northwest Flight 188 was out of contact for over an hour!

Here’s the exact text from the FAA’s Air Traffic Manual, 7110.65, Section 10-4-4:

e. If radio communications have not been (re)established with the aircraft after five minutes, consider the aircraft’s activity to be possibly suspicious and handle the flight per FAAO JO 7610.4, Chapter 7, Hijacked/Suspicious Aircraft Reporting and Procedures.

In such a case, military fighter aircraft can be dispatched to intercept the suspicious flight, all other options to contact the flight having failed.

In the end “luckily” it turned out to be due to the inattentiveness of the flight crew (and not something nefarious), although FAA procedures are written to err on the side of caution and assume the worst (including hijack situations, especially post 9/11).

The fact that the flight flew for that long and ultimately overflew its destination without communicating with anyone did highlight underlying problems with procedures (or the lack thereof) in the air traffic system.

Flights losing contact with air traffic control for short periods of time isn’t terribly rare.  That’s probably at least part of the reason why in the case of Northwest 188 the FAA managers chose to ignore procedure; they figured the flight would contact someone sooner or later and it would work itself out like it usually does.  Unfortunately it didn’t.

Part of the reason it’s not uncommon for flights to go NORDO for short periods of time is because the process of changing radio frequencies is a completely manual procedure using VHF radio transceivers.

Controllers tell pilots via the radio to contact the next controller and issue a frequency, and the pilots are supposed to read that frequency back.  If the controller doesn’t correct them the pilots can assume they’ve read back the correct frequency, so they then tune in the next frequency on the radio and check in with the next controller who answers them.

It’s a simple process with lots of opportunity for error.  The controller can mistakenly give the wrong frequency to the pilots, the pilots might not comprehend he new frequency, the controller might not realize a pilot has read back the wrong frequency, and a pilot can tune in the wrong frequency on the radio (even if he read the frequency back correctly to start with).

Theoretically if any of those things happens and the pilots try to contact the next controller on the radio and are unsuccessful, they’re supposed to return to their last known good frequency, call on the radio again and try to rectify the problem.

Otherwise, if they call and the controller whose frequency they’ve tuned into doesn’t know who they are because he’s not supposed to be talking to that flight, the controller will either attempt to determine which frequency the aircraft is really supposed to be on, or send him back to his last frequency.

But if for whatever reason those corrections aren’t made, the flight can end up NORDO.

Even though it’s easy enough for an aircraft to become NORDO, that in and of itself isn’t usually a problem, because it’s (usually) easy enough to get the aircraft back on the correct frequency using a variety of different methods.

But in order to use those methods the air traffic controllers must be aware that the flight is NORDO to begin with.  Unfortunately it seems it’s becoming more common for controllers to be ignorant of that fact.

This is at least in part due to procedural and technological changes made within the air traffic system, most significantly the User Request Evaluation Tool (URET), which was deployed nationwide at U.S. Enroute Air Traffic Control Centers in the early 2000’s.

URET replaced the paper flight strips controllers had been using to display flight plan information for each aircraft.  (I won’t even begin to get into how unreliable URET still is, years after it was installed…)

Controllers generally disliked paper flight strips, because managing them was tedious and time consuming.  But there were mandated procedures for using paper strips, including marking them in a certain way when an aircraft initially called, and when the controller told him to contact the next controller.

Properly marked paper flight strips would tell a controller at a glance if an aircraft was on frequency, and was in fact the only method to used for that purpose.

This is a flight strip that has been marked indicating the aircraft has made his initial radio call to the controller (the check mark next to the altitude), and that the controller told him to contact the next controller (the slash on the left side of the strip).

The problem is that once controllers stopped using paper strips the FAA never mandated any procedures with URET to indicate whether an aircraft was on frequency.  Instead they inexplicably left it to controllers to “wing it” and possibly come up with their own methods of ascertaining whether an aircraft is on frequency.

URET eliminated the method controllers had used to tell if an aircraft was on frequency.

Many controllers now don’t use any method to tell if an aircraft made his initial check-on call or is otherwise on his frequency, mostly because they don’t have to.  It’s not required, so it’s easier to not do anything in that regard, instead using the time saved to do other job functions.

FAA management has long been aware of the problem yet has chosen to ignore it.  Those managers that think they’re getting paid the big bucks to make the air traffic system work, are turning a blind eye to this problem, even though they keep briefing controllers on what a big deal NORDO aircraft are.

Another controller blogged about this issue, as well as other shortcomings of URET some time ago:

The very first problem I heard of concerning URET was that controllers would forget to switch airplanes to the next controller after a handoff was completed. Imagine my surprise that this is still a problem. Actually, it is a much bigger problem than is commonly stated. With URET, controllers don’t even know if they are talking to an airplane to start with.


This is basic, fundamental air traffic control. It is unfathomable to me that this system has been installed in a dozen facilities and no one has addressed this issue. No one has found a workable solution (that works in all situations) much less standardized any solution. I remind you of the two NORDO freighters that almost hit over Kansas. The incident that the FAA made the training video about. The chain of events that led up to this event began with a controller simply forgetting to switch an airplane. Knowing whether or not you are in communication with an aircraft is critical.

It’s a known problem the FAA isn’t doing anything about; a problem created because when the FAA designed and deployed new equipment they failed to have a plan as to how to make it work safely and effectively within the air traffic system.

The basics got lost in the technology: controllers got shiny new computer screens but lost the ability to tell whether an aircraft was on frequency.

Last week we were notified that starting this Friday we would have both a NORDO “worksheet” for managers and a new position relief briefing checklist (the list of items controllers go through step by step prior to one controller relieving another from position).  The position relief checklist added “COMMUNICATION STATUS OF EACH AIRCRAFT”.

Of course that’s going to do nothing to solve the problem of controllers not knowing which aircraft are or aren’t on frequency if they’re not using any of the optional methods of indicating that fact.

Either the managers that come up with these new “solutions” really have no idea how to fix the problem or they just really don’t care to fix it.

Regardless, these latest schemes aren’t going to change anything.

Perhaps the FAA expects ERAM to fix the NORDO problem too…

One comment

  1. Tick-tock,tick-tock what DOES that ERAM clock say anymore?

    Another enjoyable posting.

    When in doubt, jusk ask Ssshhh..eryl in Area 2 what list she would use.

    Say Hi to Eddie Baker for me.


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