Squawk Code Changes Options

[kawika]

Is it normal for squawk codes to be changed by pilots. Do ATCs ever ask pilots for them to be changed?

[amazed!]

Sorry for the late reply.

Transponder codes are assigned by ATC. For an IFR flight originating at any airport, the code is given to the crew before departure. After takeoff, the flight is recognized by its code.

Codes are also assigned by ATC to VFR flights IF they enter the system with "flight following" or other functions. Those assigned to VFR flights are more commonly changed sometimes being handed off from sector to sector, assuming the flight goes more than 200 miles or so.

Code changes for IFR flights are less common, but it does happen. It is common for an aircraft to have a code departing Miami, for example, and keep that code all the way to Chicago.

[kawika]

Sorry for the late reply.

Transponder codes are assigned by ATC. For an IFR flight originating at any airport, the code is given to the crew before departure. After takeoff, the flight is recognized by its code.

Codes are also assigned by ATC to VFR flights IF they enter the system with "flight following" or other functions. Those assigned to VFR flights are more commonly changed sometimes being handed off from sector to sector, assuming the flight goes more than 200 miles or so.

Code changes for IFR flights are less common, but it does happen. It is common for an aircraft to have a code departing Miami, for example, and keep that code all the way to Chicago.

The question remains: If ATC did not direct a code change, how was it accomplished? Twice in the case of UA175.

It is unique, as the other three flights turned off the beacon. In the case of UA93 it was turned off and then resumed right before crashing.

[23investigator]

The question remains: If ATC did not direct a code change, how was it accomplished? Twice in the case of UA175.

It is unique, as the other three flights turned off the beacon. In the case of UA93 it was turned off and then resumed right before crashing.
[/quote]

Dear 'kawika'

Do I understand your question correctly.

Is it, if ATC nominate the 'squawk code' numbers, how would they be able to identify that the numbers for a particular aircraft had been changed, if they had not instructed for them to be changed?

In other words do those new 'squawk code' numbers, still realate to the original secondary radar plot details, if they have not been changed by the ATC?

This is not a question, based with any knowledge of how it works, more a question trying to get an understanding of how it does work.

Robert

[kawika]

The question remains: If ATC did not direct a code change, how was it accomplished? Twice in the case of UA175.

It is unique, as the other three flights turned off the beacon. In the case of UA93 it was turned off and then resumed right before crashing.


Dear 'kawika'

Do I understand your question correctly.

Is it, if ATC nominate the 'squawk code' numbers, how would they be able to identify that the numbers for a particular aircraft had been changed, if they had not instructed for them to be changed?

In other words do those new 'squawk code' numbers, still realate to the original secondary radar plot details, if they have not been changed by the ATC?

This is not a question, based with any knowledge of how it works, more a question trying to get an understanding of how it does work.

Robert

I am seeking an explanation of exactly how it does/should work.

I have heard the audio and read the transcripts of the ATC telling UA175 to reset the transponder back to 1470. Clearly they were aware of the change.