Okay, so they thought that the transponder was accidentally turned off by the pilot. My question here is, why would there be any reason to turn off the transponder at all? Why would there be a switch to turn it off? Wouldn't you always want it on? After all, the transponder tells you where you are in the air and alerts other airplanes of your presence.
Maybe a pilot can explain this.
Good question. How about if it was malfuncting giving out incorrect data? That could be pretty dangerous causing false collision alerts and planes taking evasive action.
shareNot only that, you need to cut power to it for maintenance purposes at the very least, to pull it out during overhauls, etc. Also, if the aircraft is parked overnight, it must be shut down so as to not drain the battery, etc. Once the aircraft has landed as is taxiing to the gate, systems can be shut down until the next flight.
shareHello. I am a Canadian licensed private pilot and might be able to provide some insight on this issue. As said previously, you have to shut off the transponder when you shut down electrics on the aircraft. However that is not the main reason.
A typical, what is referred to as "Mode C" transponder, doesn't have a simple 'on' or 'off' switch. It can have 'off' 'standby' 'on' 'alt' and 'test' positions. After engine start, you typically turn the transponder to 'stby' to let the unit 'warm up'. The xponder is then generally set to 'ALT' (for altitude reporting) during the pre-takeoff checklist or when taking the runway. This is the main reason for not having a transponder run all the time. At airports, especially busy ones, there can be a lot of traffic not only in the air but also on the ground. The screens of air traffic controllers can be crowed enough when they are full of aircraft spaced miles apart in the sky let alone just feet apart on the ground. When the xponder is set to 'off' or 'stby' the controller doesn't see a "tag" which displays information about the aircraft. Tags can fill up the controller's screen. An approach controller, for example, doesn't want nor need to know what 15 planes waiting for take-off are doing, he's only concerned with planes already in the air and doesn't want to be bombarded with information he doesn't need. That's why the xponder is set to report only when the aircraft is about to become airborne. Xponders are a bit more complex and there are other reasons and functions, but that's a main one.
Simply put, it is to help prevent overcrowding of a controller's scope.
Excellent question, hope that helps.
And I thank you for your response.
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