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Is there a special protocol for a situation where the on-board radio communication equipment suddenly breaks down? Would the pilot be able to land on a busy towered airfield or would they be forced to look for a small landing strip in the middle of nowhere?

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This question has more and more detailed answers than the one it is proposed to be a duplicate of. It would be silly, IMO, to close this one, rather than the other one, even though the other one was posted earlier. – David Richerby Oct 19 '15 at 20:49
up vote 29 down vote accepted

It is important to remember that it is often difficult to diagnose radio malfunction during flight. Therefore it is hard to know whether you have a malfunctioning transmitter, a malfunctioning receiver, or perhaps both. You also have the point-of-failure that is the headset you are using. For this reason it is quite usual to carry a spare headset and the first piece of diagnostics is to swap headsets. Many General aviation aircraft also have a handheld microphone and speakers integrated into the radio stack.

Once you've ascertained that its the actual transmitter and/or receiver that has failed it is common to set the transponder to 7600. For landing, the relevant detail for the procedure to follow is contained within Chapter 4, Section 2-13 of the AIM:

Receiver Inoperative

  • Remain outside class D airspace until the direction of air traffic can be ascertained
  • Notify the tower your type, position, altitude, intention to land and request you are controlled with light signals
  • At 3 -5 miles, advise the tower of your position and join the traffic pattern
  • Watch the tower for light signals
  • Continue to advise of position (downwind, turning base, etc)

Transmitter inoperative

  • Remain outside class D airspace until the direction of air traffic can be ascertained
  • Monitor the primary local control frequency as depicted on sectional charts for landing or traffic info.
  • Look out for light signals that may be directed to your aircraft
  • During hours of daylight, acknowledge tower transmissions or light signals by rocking your wings
  • At night, acknowledge by blinking landing of navigation lights

Transmitter & Receiver inoperative

  • Remain outside class D airspace until the direction of air traffic can be ascertained
  • Maintain visual contact with the tower and acknowledge light signals as above.

The light signals used for an aircraft in flight are as followssource:

Steady green - Cleared to land
Flashing green - Cleared to approach airport, or return to land
Steady red - Continue circling, give way to other aircraft
Flashing red - Airport unsafe, do not land
Alternating red and green - Exercise extreme caution

They can be seen in this video.

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Now, how is the light from the light gun visible on a bright day? Aren't the window panes of ATC towers tinted? Do light guns use lasers? (but that would cause a lot more problems than it would solve I guess) :d – shortstheory May 9 '14 at 14:17
@shortstheory - I suspect they use high intensity bulbs. Historically, sodium bulbs probably - more recently I suspect they may have gone to LED. Short answer - I don't know! – Jamiec May 9 '14 at 14:19
Oh well, I guess I'll just post it as a question then...but thanks anyway! – shortstheory May 9 '14 at 14:20
@shortstheory I have seen a light gun in action, they're quite visible even in bright daylight. – falstro May 9 '14 at 15:17
@shortstheory A lot of the time, the controllers just walk outside the cab onto the catwalk that (usually) runs around the outside of the control tower. :) – egid May 9 '14 at 16:19

First thing you do when the radio breaks down is to start squawking 7600 (the code for radio malfunction) on your transponder.

Then when you approach the airport they will attempt to contact you first through radio (to see if you can still hear them) and you use alternate means of replying (sending IDENT on transponder, rocking your wings,...).

If you can't hear them they will use a light gun to convey messages.

enter image description here

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Nice answer. Please add that pilot should also continue to transmit on radio, even when it has failed. It could be that the radio would transmits some messages. – Farhan May 9 '14 at 13:07
... or that its their receiver/headset not working, and that they're transmitting just fine. – Jamiec May 9 '14 at 13:17
How does is the light gun used to transmit messages? Does it just send pulses of light (a la morse code)? I'm withholding a +1 till I get an explanation XD – shortstheory May 9 '14 at 14:13
@shortstheory - you might like to check my answer ;) – Jamiec May 9 '14 at 14:13
note that it is often legal to fly VFR even without a radio, so you don't have to squawk 7600 – falstro May 9 '14 at 15:25

Ratchet Freak has a good answer. In addition, please pull out your cellphone and try calling the tower. Somewhere in the bottom of my flight bag I have a small book with telephone numbers at towers. If you don't have that, call Lock-Mart Flight Service at 1-800-wx-brief tell him you need the tower number.

Also remember that there is no requirement for a radio in an airplane. NORDO (No Radio) aircraft are perfectly legal although in practice, they operate mostly out of non-towered fields. Operating out of a towered airport is still possible, but it requires prior coordination with the tower. Note please that flight in the SFRA around Washington DC does require a radio, and I have seen no procedures to allow for NORDO aircraft in this area.

If your radio stops working, one option is to fly to a non-towered field and do what the NORDO planes do: Overfly the field at a safe altitude, note wind direction from the wind sock or tetrahedron, note other traffic in the area, and fit yourself into the traffic pattern... and land.

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Ever tried using a cellphone in a GA cockpit? I'll stick with the light signals! – Jamiec May 9 '14 at 14:12
@Jamiec it works quite well actually, depending on the aircraft of course. It might be illegal though. – falstro May 9 '14 at 15:23
@Jamiec You can get headsets with bluetooth connectivity for your phone now (heaven help us when someone taxis into the fuel farm because they were yakking away...) - Headset or not though, you should try to use all available means of communication at your disposal, and that includes a cell phone if you have one - maybe the person on the other end can understand you & at least relay your situation. Worst case scenario the phone will be unusable, but at least you tried. – voretaq7 May 9 '14 at 16:00
Yeah, from what I gather, using a cell phone in the plane is still illegal (FCC if VFR, FAA & FCC if IFR). Would I use a cell in an emergency, sure, if I thought it would help. Is losing radios an emergency? Typically no (although I can imagine circumstances where it might be)... – Brian Knoblauch May 31 '14 at 13:48
@BrianKnoblauch Yes using a cellphone in a plane is illegal. Does anyone reading this have knowledge of anyone being arrested or fined for doing so, in an emergency situation (or even one where safety is enhanced by using the cellphone as in this example)? I believe it is de jure illegal and de facto legal. – Skip Miller May 31 '14 at 23:02

I was a Junior Technician, later Corporal, Air Wireless Fitter in the R.A.F. in 1952-4, servicing Gloster Meteors' radios at a Flying Training School, and the signal then was for the pilot to waggle the aircraft's wings as he approached, or flew by, on his way to land, to show he could not contact the Control Tower. Then we had to fix it.

I was made a Corporal so that I could sign off our work on the aircraft out on the airfield, usually just tuning up to a new crystal to suit the frequencies of a distant Station. I got the promotion so the Sergeant could stay in the nice warm office: I didn't mind -- I was "/Paid" extra, nice for a "National Service Only" erk.

Happy days

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If your radio was broken during a flight, you could use a light or come up with a sign of help that a helicopter or other airplanes can see so that they can contact the radio people and rescue them to safety.

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Welcome to Aviation.SE. There is already a defined signal if your radio equipment becomes unserviceable: Set your squawk to 7600 and wait for light signals from the Tower. In case you are IFR, there is defined procedures to be flown under lost comms situations. – SentryRaven Jul 8 '15 at 6:05

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