TRANSPONDER - STBY or AUTO?

H

HHAS

New Member
Dear Controllers,


I am in need of some clarification as far as ATC is concerned.

The Chief Pilot of our carrier has devised a SOP policy that requires the following:

Because of the routes we fly, various radar controls will issue us new squawk code and changes enroute.

The SOP requires us to first put the transponder on STANDBY before entering the code then back to AUTO upon entry of the new squawk code.
My question is from a controller's operational standpoint, is it neccessary to put the transponder on STANDBY or can the NEW squawk code while the transponder is transmitting
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For a controller's system does it make a difference
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PLEASE ADVISE
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Thanks in advance.
 
I think it has more to do with the transponders memory in case of power failure. In some models, if you put the new code in with it in ALT and then have power failure to the unit, it will reset to the last saved code.
 
I dunno... if an A/C needs a code the wrong code splits time with the speed in the data block. I know nothing about transponders... as long as you get the code in that should be fine.
 
Well, here's my take on this. The AIM in my opinion says not to squawk STBY during code changes. It does not say that directly, but by implication.

4-1-19. Transponder Operation

3. Civil and military transponders should be adjusted to the "on" or normal operating position as late as practicable prior to takeoff and to "off" or "standby" as soon as practicable after completing landing roll, unless the change to "standby" has been accomplished previously at the request of ATC. IN ALL CASES, WHILE IN CONTROLLED AIRSPACE EACH PILOT OPERATING AN AIRCRAFT EQUIPPED WITH AN OPERABLE ATC TRANSPONDER MAINTAINED IN ACCORDANCE WITH 14 CFR SECTION 91.413 SHALL OPERATE THE TRANSPONDER, INCLUDING MODE C IF INSTALLED, ON THE APPROPRIATE CODE OR AS ASSIGNED BY ATC. IN CLASS G AIRSPACE, THE TRANSPONDER SHOULD BE OPERATING WHILE AIRBORNE UNLESS OTHERWISE REQUESTED BY ATC.

and,

e. Code Changes

​
1. When making routine code changes, pilots should avoid inadvertent selection of Codes 7500, 7600 or 7700 thereby causing momentary false alarms at automated ground facilities. For example, when switching from Code 2700 to Code 7200, switch first to 2200 then to 7200, NOT to 7700 and then 7200. This procedure applies to nondiscrete Code 7500 and all discrete codes in the 7600 and 7700 series (i.e., 7600-7677, 7700-7777) which will trigger special indicators in automated facilities. Only nondiscrete Code 7500 will be decoded as the hijack code.

In saying to avoid inadvertent selection of certain codes and using the examples they give, it implies you're to remain "on" during code changes.

One more important fact worth mentioning. Even though you might only be in STBY for a few seconds, ATC would lose radar contact with you during that period (perhaps not a big problem, I don't know), but more importantly, you would render TCAS inoperative during this time.

gary
​
 
ghogue said:
4-1-19. Transponder Operation

3. Civil and military transponders should be adjusted to the "on" or normal operating position as late as practicable prior to takeoff and to "off" or "standby" as soon as practicable after completing landing roll, unless the change to "standby" has been accomplished previously at the request of ATC.
Click to expand...

Unless of course you're flying out of ATL or the other handful of other airports which require your transponder to be on while taxing on the airport.
 
At every company I've worked for we kept our transponders on ALT at all times unless asked to do otherwise. I can't imagine why you boss would ask you do that unless the manufacturer has deemed it neccesary.
 
Sounds like your Chief Pilot is from the "olden days" before solid state radios. Back then, you went to STBY to lift the points off the radio crystals so you wouldn't damage them. Solid state avionics changed all that...in the 60's.
 
Cptnchia said:
Unless of course you're flying out of ATL or the other handful of other airports which require your transponder to be on while taxing on the airport.
Click to expand...
Yeah. I wasn't going to go there since the OP was about changing codes in flight.
 
It's always amusing to watch a pilot with the old dial transponder spin the numbers in. If they're really slow, you can watch the numbers change on the scope.
 
Today I had a controler tell me "check transponder, you appear to be squaking standby." For the record we weren't; but I thought you couldn't see us when we were on standby.
 
Thanks for the quick reply folks.

Perhaps some clarification is due.

We operate the B767/200-300 and the transponder utilizes a NUMBER PAD entry sytem which is similiar to a phone and upon receipt of sqwauk code we punch in the S code, it's NOT a DIAL switch that would inadvertently transmit a distress or emergency signal as we are toggling thru the various numbers etc.
 
PilotChip said:
Everybody just squawk low then we wouldn't have this problem...

:sarcasm: :laff:
Click to expand...

The transponder in our LJ55 has STBY/ALT/LOW. What the heck does LOW do? I mistakenly set it to LOW (its the top switch position; ALT is in the middle) one flight and didn't get any indication that it caused a problem.
 
HHAS said:
Thanks for the quick reply folks.

Perhaps some clarification is due.

We operate the B767/200-300 and the transponder utilizes a NUMBER PAD entry sytem which is similiar to a phone and upon receipt of sqwauk code we punch in the S code, it's NOT a DIAL switch that would inadvertently transmit a distress or emergency signal as we are toggling thru the various numbers etc.
Click to expand...

From your original post I assumed you were flying older equipment, I had no idea you were operating B767's. I'm sure you do not want to say what company this is but from what I understand there is no reason to squawk standby, depending on how fast you go to the new code your radar track could go into coast # ... meaning no flight plan tracking.

I don't understand why the chief pilot wants standby squawked for a code change ???
 
If your chief pilot is like our CP, he's probably like Velo said - he probably "grew up" with this procedure and just never saw fit to change once the necessity to do so became obsolete.
 
Towerboss said:
Yes we can tell when you are squawking stndby.
Click to expand...

Interesting...I thought STDBY was just the "warm-up" position and
no replies to interrogations were being made. So maybe you can tell
when we are in STDBY because you only get a primary echo? yes/no?
 
HHAS said:
Because of the routes we fly, various radar controls will issue us new squawk code and changes enroute.

The SOP requires us to first put the transponder on STANDBY before entering the code then back to AUTO upon entry of the new squawk code.
My question is from a controller's operational standpoint, is it neccessary to put the transponder on STANDBY or can the NEW squawk code while the transponder is transmitting
Click to expand...

Just going from memory, but I'd guess that SOP has more to do with the transponder than ATC.

I think one of the contributory factors in the GOL/Legacy crash in Brazil last year was that the Legacy's XPDR was in STBY. The SOP may be an attempt to encourage monitoring of the transponder and prevent repeated squawk changes from being interpreted as an RMP fault, potentially causing at least one brand of transponder to go into standby mode.
 
w5cdt said:
Interesting...I thought STDBY was just the "warm-up" position and
no replies to interrogations were being made. So maybe you can tell
when we are in STDBY because you only get a primary echo? yes/no?
Click to expand...



Yes we still get a primary.

TB :cool:
 
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