Loss of Radio Communication (NORDO)

Radio failures are rare but do occur with a certain predictability. If you have never suffered through a NORDO situation, you assuredly will one day, and it is not always an issue of your equipment that creates the problem.

I remember returning to PHNL from an instructional flight a few years ago, when the approach controller handed me off to Tower. As soon as I pressed the frequency toggle switch my headset erupted in a deafening hissing and screeching sound with unrecognizable voice transmissions in the background trying to establish contact. Somewhere, someone had a ‘hot mike’ without knowing it, making communication impossible. What to do?

The first thing that may come to mind is resetting the transponder code to 7600 (for ‘lost communication’). On second thought, this may not be such a good idea. If everyone trying to contact tower switched to 7600, all aircraft-specific information would be lost from the tower radar screen and the controller is likely already aware that there is a wide-spread problem. Go back to Approach frequency? While you may have an audience if you do so, the approach controller is physically removed from the tower control. Departure and Approach controllers are literally ‘kept in the dark’, sitting behind large radar screens in blacked-out rooms and talk to the tower controllers only by phone or intercom. A better approach to this problem is to contact Ground Control on the appropriate frequency. Ground and Tower controllers are practically sitting next to each other. You will likely receive a further clearance from here, or advice to switch to an alternate frequency.

In this particular case, I entered the downwind for the assigned runway (which was the initial clearance limit) and watched for light signals from the tower.  The whole crisis probably lasted less than three minutes and illustrates that the established procedures can work smoothly even at a very busy international airport, as long as everyone knows what is expected of them. I remembered the words of the examiner who signed my private pilot license and who advised me to carry a copy of the light signals and their meaning on my knee board.

NASA’s Aviation Safety Reporting System website reports the statistics and the reasons for COM failures. By far the most common reason for losing communication are mis-set aircraft radios (52%). Pilots either fail to copy or set the correct frequency, an error that can easily be avoided and is often quickly detected but can also lead to a lot of problems. Blocked frequency ranks third in the list of most common COM failures with 15.5%, preceded by aircraft radio problems with 33%. Roughly 10% of all COM losses are attributable to ATC, most of which concern technical failures.

I was on my way back to PHNL from a first-light Coast Guard Auxiliary search mission south-east of Lahaina (Mauia) when it began to dawn on me that there may be a problem with the radio. I had been monitoring the chatter between Kapalua and a number of sight-seeing helicopters to ensure they were aware of our presence and vice versa when I realized I had not heard a sound in the past five minutes or so. I turned up the squelch – silence. I switched to the Molokai ATIS frequency – still, nothing. A scan of all other aircraft systems and a survey of the circuit breakers revealed no widespread problem, just a dead radio. How to get back to Honolulu without a working radio?

The first option that came to mind was to land at Molokai airport and evaluate the situation on the ground. I definitely would not attempt to enter Class B airspace without a working radio. Then it occurred to me that I could link my cell phone to my (BOSE) headset via blue tooth and just call Honolulu Tower on a phone line. Sure enough, they picked up and confirmed a target south of Molokai squawking ‘7600’. They issued a clearance into “Class Bravo’ airspace and asked to be called back in the vicinity of Koko Head VOR, which I did I. I received a further clearance to the downwind of runway 4L and stayed on the phone but at some point the line disconnected and the number appeared busy. From this point forward I never got to speak to anyone again. On downwind to Runway 4L I spotted the green light from the tower. I landed, and again received a ‘green light’. I called the tower again after we shut down the engine to thank everyone for an uneventful and smooth process.

It turned out the radio needed repair. Although I have owned a handheld transmitter for many years it was not in my flight bag that morning and it is uncertain whether the relatively weak transmitter would have even helped me get into Class B airspace. However, it certainly would have helped me to get a landing clearance the ‘regular’ way.

Lessons to be learned?

1. Always have a plan ‘B’.
2. Double-check frequencies you have selected. Keep a log of the last frequency you talked to in case you cannot establish contact with an assigned ATC facility.
3. Always have a plan ‘B’  – and a handheld radio with charged batteries.

Consult the Handbook of Aeronautical Knowledge for standardized procedures on communication failures.


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