American 44 faulty radios causes abort

[Hollis]

Not a happy situation for THAT crew.
Nor for the pax either I would guess!

[Jayhawk]

here are the flight details

[Check Airman]

Thanks for the great clip!

Didn't hear anything about an abort in the clip. Does anyone know the science or tech stuff behind the carrier he's talking about? I presume he means a carrier wave?

[Greg01]

He aborted the flight...

Greg

[Pearson]

Didn't hear anything about an abort in the clip. Does anyone know the science or tech stuff behind the carrier he's talking about? I presume he means a carrier wave?

Just means he's keying up his mic, or rather the mic is sending a signal since it wasn't intentional. As you know must know about aviation radios only one person can talk at a time or it goes all crazy.

[Hollis]

Two transmitters keyed at the same time on the same frequency is known as being 'stepped on'.
A carrier wave is a continuous electromagnetic signal that the transmitter puts out at a certain resonant frequency when the tuned circuit is activated, and is then modulated in amplitude by a microphone or similar input. As in AM (amplitude modulated) radio. FM works differently, being Frequency Modulated. CW means continuous wave, where the carrier is clicked on and off, such as in sending Morse Code signals, etc.
I suspect his problem was the relay that kicks on the transmitter when he keys the mic. Probably a broken retract spring, allowing the relay to stay in the 'hot' position. Only a guess.

[Check Airman]

So is "carrier" simply the scientific term for stuck mic?

[athaker]

Nope -  "carrier" actually is a physics term.  When you need to transmit some sort of signal via airwave, you're on a certain frequency, which is how fast the wave "wiggles".  But if its a constant frequency, how can you transmit information, which is constantly changing (like voices)?  Thats done by "modulating" (changing) the carrier wave.   

The most simple way to think about it is take a wave whose peaks are always spread equally apart, no matter what.  Equally spaced wiggles.  Then, take one peak and make it bigger.  Take the peak after that and make it even bigger.  Then, make the next one smaller, the next one smaller, smaller, bigger, bigger and so on, going higher and lower as you move along the peaks.

The spacing is still the same, but now if you draw a curve connecting those peaks and remove the original wave, you'll have drawn a new wave.  That small, always wiggling wave is the carrier, and the wave riding from peak to peak is the modulation.

Thats how AM radio stations can transmit different frequency sounds on a single frequency/ carrier channel.

The carrier itself carries no information unless its modulated, and just steps on other carrier waves that do have information (like other planes).  So he doesn't necessarily have an open mic, just an open carrier signal...it sounds like static only.

hope that made sense...i'm an engineering student...

[r12055p]

I thought that they had changed the radio system after Tenerife so that radio transmissions couldn't get stepped on.

[cessna157]

I thought that they had changed the radio system after Tenerife so that radio transmissions couldn't get stepped on.

No, aviation radios still use the same original early-1900s tech with AM radios.

[anand]

Note that Aviation radios also use AM modulation and not FM , used in conventional Land mobile radios.
With AM, when two carriers are present (two trying to talk at the same time), they add up and one can hear
a conversation taking place, although garbled. If it was FM, it will completely wipe out.