Changing Transponder Codes In-Flight

[SB4200]

When changing transponder codes on a transponder such as this what is the preferred method?

This Article states

Pilots are instructed not to place the transponder in "standby mode" while changing the codes as it causes the loss of target information on the ATC radar screen, but instead to carefully change codes to avoid inadvertently selecting an emergency code

I have always selected standby, input the new code then selected ALT (unless it's a newer style transponder which doesn't squawk the code until all digits have been inputted).

What is the preferred method in OZ?

[apollo85]

i agree

i have always been taught the same as you champ:

turn transponder to sby then changes the code and switch it back to alt.

makes sens you i guess you give then 3 diff codes as you start changing digits!!!

actually recalling thats what is in bob tait and trev thom books too

[chimbu warrior]

When I started operating into the US it was pointed out to me (with appropriate text in Jeppesen ATC) that it is a requirement not to select standby in US airspace. Reasons are apparently [*]loss of TCAS target info[*]an invitation to itchy trigger fingers in USAF fighters (post 9/11)
Seems like a good reason to me.

[Blockla]

With our unique TAAATS system cycling "live" through codes could trigger the activation of various flight plans. Whilst it is imperative that the emergency codes are avoided going from 1200 to 1237 (poor example but you get the point) for example, there is a possibility of activating 9 flight plans in TAAATS on codes 1210, 1220, 1230, 1231, 1232, 1233, 1234, 1235, 1236 etc. or similar combinations there of.

With our auto coupling and flight "corridor" matching it should be less of a problem; however certainly not outside the realms of possibility that whilst transitioning from one code to another that another flight-plan is moved from announced to active; based on autocoupling; rudimentary route segment and code match.

I certainly would suggest that you are less likely to cause problems by switching to STBY changing codes (how long does it take?) then back to Mode C - ALT. etc.

Doc search:

AIP ENR 1.6-10 8.1.9 Pilots must select the transponder to STANDBY before effecting an SSR code change and returning the transponder to ON/ALT.

Note: This action is required to prevent possible loss of displayed aircraft position/label information and possible misidentification of aircraft in automated Australian ATC systems due to temporary selection (while effecting the change) of a code already in use.

[Islander Jock]

I take anything on Wikepedia with a grain of salt. I've even made my own amendments to entries on some of their topics. It's more of a bulleting board than an authoritative document.

Blockla has given us the definitive answer to what applies on Oz.

As for being a target for itchy triggered fighters, does anyone really think that a 10 - 15 second loss of Txp paint would have a squadron of F18s leaping into the air?

[J430]

My transponder allows a code to be entered and not transmitted, then hot swapped at the push of a button, so you have an active code and a standby one.

Solves that issue!

J