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I just read the NTSB press release of Northwest Airlines Flight 188 that flew more than one hour without making any radio contact. I imagine there may be many causes for losing radio contact with the ground (distraction, electrical failure,...) and I found a video (in French) saying that one way to solve the situation is to send a fighter to have a closer view of the situation and possibly assist the pilots.

I wonder if the situation of losing contact with an airplane is frequent? I imagine it happens between one and ten times per month over a region as big as the USA, but that is just a guess.

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    $\begingroup$ I rephrased your question slightly because it looks like you're asking about lost communications rather than aircraft that are deliberately flying without radios. "NORDO" could be taken to mean both of those things. $\endgroup$ – Pondlife Sep 25 '14 at 14:55
  • $\begingroup$ OK, I thought "communication loss" and "NORDO" were synonyms $\endgroup$ – Manu H Sep 25 '14 at 15:29
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    $\begingroup$ In some places radio coverage is just poor at lower altitudes too. I've lost comm on the ATC specified frequency after getting a descent still 15 minutes out from my approach. In this case I looked up the other frequencies in the area and was able to re-establish contact on an alternate. $\endgroup$ – Brian Knoblauch Sep 25 '14 at 15:43
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According to this FAA paper, Table 3, ASRS reports were analyzed for 16 months between 1978 and 1979. This included 553 incidents where the recipient was not monitoring, which seems to be the closest category to loss of communications. This equates to a little more than 1 incident a day. Note that this only includes incidents that were reported, and air traffic has increased since then.

This report contains info from ICAO in in Europe. The focus is on the security issues from unresponsive aircraft. In just the northern region, there were 230 flights over just 6 months in the beginning of 2004. This number inclues airlines, business jets, and military transports. This frequency is a little higher than the previous report, but is more recent and probably includes less flights.

Other reports like this one don't include a time frame for the reports analyzed, but look at other factors involved. For example, pilots with fewer hours and GA pilots are more likely to be involved in such an incident. The average duration of these incidents was 7.6 minutes.

This page also has some good information about this type of incident, including a list of some of the many possible reasons for lost communications and excerpts from some of the reports.

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  • $\begingroup$ An average ot just 7.6 mins sounds like user error, e.g. dialing in the wrong frequency or being distracted. That happens all the time, and I'd bet most cases aren't even reported. Any data on permanent loss of comms, e.g. equipment failure? $\endgroup$ – StephenS Dec 14 '18 at 19:28
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I think it happens all the time actually. Most of the time its likely not reported. When I did my first solo cross country in a 152, my radio button went out while using VFR flight following. Perhaps they did report it, but they likely just thought it was a new pilot not knowing what he was doing. It was really distracting for myself at the time as a pilot in training. I could hear them talking about me and it took a while to understand that they were not hearing my responses. As a pilot, you are supposed to squawk 7600 to let them know you lost your radio. At the time though, I couldn't remember if it was 7500 or 7600. I knew one of them was for the radio and the other was for a highjacking, and I wasn't needing a fighter jet for my broken radio.

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I think losing contact for an hour is unusual, but not being in contact with ATC for a few minutes is pretty common. On a cross the US flight you might hear 5-6 incidents. Most of these seem to occur as planes are handed off from different sectors that use different frequencies. It not uncommon for the pilot to tune in the incorrect frequency.

Also, as aircraft descend into fields with obstacles (ex. mountains) it is not unusual to lose contact. As you fly along you sometime hear ATC attempting to contact a plane and get no reply. If you have just heard that call sign you might volunteer to give the aircraft a call and then act as a relay. For example, you are over some place and hear ATC: "KingAir 123 contact center on 123.55" KA123: no response. ATC: "KingAir 123 contact center on 123.55" KA123: no response. ATC: "KingAir 123 over someplace contact center on 123.55" You: "Center, N12345, we are over someplace, would like us to try to contact KA 123?" ATC Center: "N12345, affirmative, contact KingAir 123 and ask them contact center on 123.55" You: "KingAir 123, N12345, center would like you to contact them on 123.55" KA123: "Contact Center 123.55, thanks N12345"

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    $\begingroup$ it's also possible you don't hear a reply because the plane is on the other side of the antenna and out of your range but inside ATC's range $\endgroup$ – ratchet freak Sep 26 '14 at 7:47
  • $\begingroup$ In that case, @ratchetfreak, it would be like being in the same room with someone on a phone conversation - you'd hear 1/2 of it and know that communication was happening, just not the whole conversation. $\endgroup$ – FreeMan Oct 19 '15 at 19:19
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A supervisor at the local ATC facility (medium sized TRACON/Tower) said they have loss of radio several times a month. Sometimes the plane "lost" the frequency, and showed up elsewhere. Sometimes they had an equipment failure. On nice weekends, they have more, and those are written off as VFR pilot error situations.

While we were talking, I asked how many 7600 squawks they got per month, and he said somewhere between 0 and 2. More common during the summer when more people are flying, and during the hard part of winter when there are just more equipment failures.

Not a big study, but just one ATC supervisor's opinion and observation.

As for looking at 1970 and 1980 data, the whole business of radios, and how well they work has changed quite a bit in 20 years. I can remember radios being out as much as 1/3 of the time (well one or the other most of the time) back in the 70's. Today it rarely happens. For one thing, the radios today don't have the large ganged switches that the older radios had. And the avionics guys say that today's transponders are more stable, and last longer as well.

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