What is Alfa, what is MODE?

[TangoAir]

Hi,

Many times ATC says: transponder code Alfa 1234. But if you have mode C you are requested to use it. And finally, in some books I find that the special codes 7500, 7600 and 7700 are expressed as A 7500, A 7600, A7700. Am I wrong or does the “Alfa” means something different than “mode”?

Tango

[Ichabod]

There are two 'Modes' of transponder in use. Mode A simply sends out a four digit code eg: 1234 which will be used to identify a particular aircraft. Generally, every aircraft will be given a specific 4 digit code for the duration of its flight. There are also specific codes, 7500 etc which relate to some form of emergency: any aircraft in a particular emergency will 'squawk' this code to alert ATC.
The second 'Mode' is known as Mode C and provides information on altitude/flight level, which can be very useful. By using mode A ,ATC can see where you are, but by also using mode C ATC can see where you are and also a continuous update of what height you are at.

Hope this helps..... a simplified answer but should give you an idea of what is going on :D

[TangoAir]

Thanks Ichabod !

Tango

[chiglet]

Tango,
In the beginning......There was Alpha for Civilian Tfc 00-77
Bravo for Military Tfc 0000-7777 [4096 separate IDs, also called Selective Identifacation Friend or foe...SIF] Then the "linked altimeter" came into play, so we then got Mode Charlie. So if an ATCO asks you to squawk A1234, and you have a "C" transponder, that's ok:)
we aim to please, it keeps the cleaners happy
ps, there is also a Mode "S" transponder:rolleyes:

[TangoAir]

Hi Chiglet an thanks.

So, if you say AFLA 5600 MODE C, it is civilian + altitud?

Or, if they say Alfa 5600, it's just an old way of speaking, and you still sw to mode C?

Tango

P.S. It's a Test question, for that reason I need the exact meaning...

[chiglet]

Tango
IF you are Mode C equipped and you were asked to squawk A1234, then do so. You have followed the instruction, and [possibly] given altitude info as well :D
we aim to please, it keeps the cleaners happy

[professor yaffle]

er .... tangoair - you list your occupation as a pilot - if this is so surly you ought to know the answer to this

just a thought

prof