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In the event of lost comms, GA pilots are generally expected to circle over the airport looking for light gun signals from the tower. What about big commercials jets? Are they also expected to circle over the airport until they see green light from the tower?

One of my flight instructors once told me, in real lost comms situations, don't circle over the airport and just take a traffic pattern and land, because the tower is already aware of your situation and they will clear traffic for you accordingly, if you were squawking 7600. I was not sure at the time he was right on this, but maybe that's the case for big commercial jets.

So what does the tower expect from the pilots of Boeing or Airbus in lost communications? Do they expect you to circle over them looking for light signals or just go ahead land expecting to get the signals on the pattern?

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    $\begingroup$ In Europe you just follow the fighter jets which are dispatched for... every... single... loss... of... coms... incident $\endgroup$ – TomMcW Jul 25 '17 at 18:17
  • $\begingroup$ When it comes to loss of communications on approach, I've definitely seen specific instructions for loss of communication on several STAR charts. Presumably once you start to squawk 7600 and ATC can see you're following the charted lost comms procedure, they know what to expect and can keep other traffic out the way. For example, VHHH BETTY2A says "LOST COMMS: Comply with descent requirements and STAR to maintain FL130 to LIMES, join LIMES holding and descend to 4500, then carry out the appropriate ILS approach procedure." $\endgroup$ – jbg Feb 6 at 15:05
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In the US, for VFR, the answer to both of your questions (when and where) is when you are established on downwind. You may not be able to see the light signal if you circle above. I don't think it matters what size the aircraft is. In IFR operations, you may not even be able to see the tower, and as 757toga points out there are different rules.

This actually happened to me years ago at a tower controlled airport in California (although I was in a small aircraft). Radio stopped working. Not sure if it was transmitting so I continued to transmit my intentions just in case the transmitter was functional. I squawked 7600. I observed the traffic pattern and entered downwind at a 45. Sure enough, a few seconds later, solid green light from inside of the tower was seen. I rocked my wings to acknowledge the light signal, then controller put down the light gun. It was faint, but visible in the daylight, but if you weren't looking right at it, you wouldn't see it. (Most glass at towers is pretty thick and at an angle so I suspect it absorbs, diffuses, and/or refracts some of the light guns intensity). I never talked to the tower about it, but its possible they were shooting the light at me before I entered the downwind, but its possible I couldn't see it until I was at traffic pattern altitude and established on the downwind leg. Also, keep in mind that it is a light gun with a narrow beam, they have to hold it up and aim through a scope like a rifle at the cockpit, so you need to acknowledge you received the signal so they can put it down. Some small airports only have one controller, so s/he can't really look out for other traffic while holding the light gun up at you.

enter image description here

Had uneventful landing, and got light signal on the ground to taxi to parking. It worked just like it was supposed to.

See AIM section "4−3−13 Traffic Control Light Signals" for additional information.

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  • $\begingroup$ Cool. I always wondered if they ever actually used those $\endgroup$ – TomMcW Jul 25 '17 at 18:19
  • $\begingroup$ I imagine its very rare, since so many aircraft nowadays have two radios. Back then my aircraft only had one radio. $\endgroup$ – Devil07 Jul 25 '17 at 19:31
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    $\begingroup$ Instead of light guns... laser pointers! :D $\endgroup$ – TomMcW Jul 25 '17 at 19:39
  • $\begingroup$ To add a tower controller's perspective: the light gun was probably hard to see because a lot of them don't work very well. One place I worked had a gun so dim you couldn't see it from the building next door. A lot are working on old, weak batteries and less effective light sources than the LEDs we're becoming used to in other lighting applications. Good answer. $\endgroup$ – Aluminum Showers Jun 30 at 2:34
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Your question seems primarily to ask what an air carrier aircraft without radio communication ability (sometimes known as NORDO) should do once it arrives at the airport.

First, a bit of background. FAR 91.185 covers how aircraft operating under IFR (IMC and VMC) should respond if they become NORDO. This applies to both General Aviation and Air Carrier aircraft. Further it covers the expected pilot actions for the following:

  1. What the pilot should do if in VMC conditions (the rule uses the term "VFR conditions" instead of VMC [visual meteorological conditions]).
  2. What the pilot should do if in IMC conditions (the rule uses the term "IFR conditions" instead of IMC [Instrument meteorological conditions]) pertaining to:

    a. Route;

    b. Altitude;

    c. Leaving the clearance limit and beginning the approach.

Second, for NORDO aircraft operating under VFR the route, altitude, etc. to get to an airport is left to the discretion of the pilot.

Now, once either a VFR or IFR aircraft arrives at an airport what should the pilot do and what should he/she expect from ATC?

FAR 91.125 specifies ATC (Control Tower) light gun signals and their meaning. These light gun signals represent appropriate clearance and instruction from ATC and are responded to by the pilot based on the signal's meaning. (e.g., cleared to land, do not land, etc.)

Importantly, the Aeronautical Information Manual AIM, para. 6-4-2 instructs pilots to set their aircraft's transponder to code 7600, whether or not the pilot is operating under VFR or IFR.

As can be seen from reading the information above, there is not a regulatory distinction between a General Aviation aircraft and an Air Carrier Aircraft (GA/AC) with respect to NORDO operations.

However, practically speaking the actions of the pilot and of ATC may be quite different between GA and AC aircraft depending on the circumstances.

For example, even if a GA aircraft filed a VFR flight plan, if the pilot was not communicating with ATC prior to becoming NORDO, operating into a busy tower controlled pattern could be hazardous. The tower controller may never even see that an aircraft is circling near the pattern waiting for a light gun signal to land.

An option for a NORDO GA aircraft (operating under VFR) might be landing at an uncontrolled airport without interacting with ATC.

With respect to a NORDO AC aircraft operating under IFR, the handling by ATC, in my opinion, would likely be quite different. Since the AC aircraft is operating on a IFR clearance issued by ATC where the destination and estimated time of arrival are clearly known, ATC's awareness of the aircraft is probably not in question. Also, since the NORDO AC aircraft has been squawking code 7600, and most areas in the U.S., for example, are covered by radar, there is little mystery as to when the aircraft will need to be sent a light gun signal (hopefully showing a clearance to land) from the tower.

Finally, there is no doubt that many who read my answer above can envision a variety of circumstances under which my points could fail or not be sufficient response to the question. However, regulations and procedures can only anticipate a limited number of operational circumstances. Often, in real time, the pilot and ATC must consider the best course of action based on their knowledge of existing rules and procedures, and an understanding of the practical limitations of safely operating in a very complex environment.

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