FighterPilot
Topic Author
Posts: 1306
Joined: Sat Jun 25, 2005 2:27 am

Differnent Type Of Transponder Modes?

Thu Feb 07, 2008 4:56 pm

I know theres A and C and several others like 1,2,3,etc. Was there ever a Mode B?

Thanks
Cal  airplane 
*Insert Sound Of GE90 Spooling Up Here*
 
wilco737
Posts: 7279
Joined: Sun Jun 20, 2004 12:21 am

RE: Differnent Type Of Transponder Modes?

Thu Feb 07, 2008 5:14 pm

I just know A, C and S! S is the one good for TCAS...

1, 2, 3? only know the transponder code 0-7! So if you ever get a transponder code with an 8, not possible Big grin

WILCO737 (MD11F)
 airplane 
 
avioniker
Posts: 1099
Joined: Tue Jan 01, 2002 5:38 am

RE: Differnent Type Of Transponder Modes?

Thu Feb 07, 2008 7:52 pm

IFF systems originated in World WII to enable secondary radars to identify U.S. aircraft from enemy aircraft by assigning a unique identifier code to U.S. aircraft transponders. The system is considered a secondary radar system since it operates completely differently and independently of the primary radar system that tracks aircraft skin returns only, although the same CRT display is frequently used for both.

The system was initially intended to distinguish between enemy and friend but has evolved such that the term "IFF" commonly refers to all modes of operation, including civil and foreign aircraft use.

There are four major modes of operation currently in use by military aircraft plus one submode.

Mode 1: A nonsecure low cost method used by ships to track aircraft and other ships
Mode 2: Used by aircraft to make carrier controlled approaches to ships during inclement weather
Mode 3: The standard system also used by commercial aircraft to relay their position to ground controllers throughout the world for air traffic control (ATC)
Mode 4: Secure encrypted IFF (the only true method of determining friend or foe)
Mode "C" is the altitude encoder.

Yes there was (is) a mode B but if you find out what it is we'll have to kill you . . .  Silly

 

[Edited 2008-02-07 11:55:53]

[Edited 2008-02-07 11:57:19]
One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
 
FighterPilot
Topic Author
Posts: 1306
Joined: Sat Jun 25, 2005 2:27 am

RE: Differnent Type Of Transponder Modes?

Thu Feb 07, 2008 9:38 pm

Thanks Phil and Avioniker!

Cal  airplane 
*Insert Sound Of GE90 Spooling Up Here*
 
avioniker
Posts: 1099
Joined: Tue Jan 01, 2002 5:38 am

RE: Differnent Type Of Transponder Modes?

Fri Feb 08, 2008 1:34 am

Just for trivia's sake;
Mode S was so named because it represents a departure from the basic form of operation. (The designers could have just stayed with the system and called it Mode D, E, F, 5, 6, 7, or whatever)
The S stands for selective or selectivity (depending on who you ask) and identifies it as something different from what was.

Rather than waiting for a radar interrogation and responding to it (which would make it a transponder by glossary definition) it selectively interrogates targets or other aircraft sensed by the TCAS antenna/processor as to their altitude and track, vertical and horizontal.

That makes it, technically, an interrogator.
Since convention has it that the responders to the radar interrogation are defined as transponders the name stayed with the box. It does respond to radar station interrogations as well as to the interrogations of other aircraft's Mode S units.

The major difference between a Mode S and a Mode A/C unit is that the A/C units only respond to interrogations from other sources. The Mode S will initiate an interrogation of another aircraft once the TCAS processor identifies one as being in the area. The frequency of the interrogation is increased as the two aircraft grow closer together until the potential for threat is diminished or removed.

Nuff said?
 Smile
One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533

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