Some basic aviation questions.......

**positiveg** · 09-13-2003, 09:09 AM

What is a transponder for?
Why does atc tell me to change it?
What is a sqawk?
Why do airports say for example: Altimeter 1992?
What is the climb and descent vertical speed for a 767-300?

Well guys, for now this is it. I have always flown on fs but never really studied these things and I would like to start taking the fs lessons. But what are these things I see everytime but I never know what it means?

**RiddlePilot** · 09-13-2003, 11:28 AM

When a radar sweeps around, the signal bounces off all aircraft and sends a "blip" back to the controller's scope. When this sweep hits your aircraft, the transponder sends an extra signal back to the controller, and he sees the code that you have selected on your transponder. When you call him for services (flight following, to land at a Class B or C airport, etc), he will ask you to put a specific code in your transponder. This way he can distinguish you from other aircraft on his scope. This is known as squawking a code. When they say altimeter 29.92 (inches of mercury, or in Europe and most other places, the equivalent would be 1013.2 hectopascals. They say "QNH 1013.2"), this is the barometric pressure of the airport. It changes all of the time based on high and low pressure weather systems, fronts, and storms. Its basically so that all aircraft's altimters are reading the same thing, to prevent any conflicts. Sometimes though, aircraft's altimters are calibrated incorrectly, and can cause some problems. Also, the altimter is likely linked to the transponder, and sends your altitude readout to the controller. This is known as a Mode C transponder. If you ever get around to VATSIM, and you hear a controller say "Squawk Mode C", it means he's not receiving that altitude information because the pilot forgot to turn on that function on his transponder.

**positiveg** · 09-13-2003, 11:48 AM

WoW! Thank you very much. I learned a lot, it would be nice to have a space on the forum where we could discuss thse things and teach each other what something is. Thank you very much!:)

**RiddlePilot** · 09-13-2003, 11:53 AM

I forgot to mention about the altimeter, you have to manually input the current pressure into the altimter, this can be done by turning the knob on the bottom left of the instrument. There is a little moving card inside a window on the right side of the instrument inbetween the 2 and 3 (on the 172/182 panel) that has 29.x or 30.x and then 4 dashed lines between each numeral. Each of these dashed lines represents .02 inches of mercury. So if the controller says "Altimeter 30.12", you would turn the dial until it reaches the dash right below 30.1. In the sim, you can press "B" and it will do it for you. Load up some real weather and give it a shot and you'll quickly see what I'm talking about.

**scotland_rules** · 09-13-2003, 01:20 PM

I'd love to answer those questions for you, but RiddlePilot did a great job himself! lol.

**lnuss** · 09-13-2003, 02:58 PM

it would be nice to have a space on the forum where we could discuss thse things
That space is right here on the Outer Marker. Almost anything aviation-related is allowed here, and there are plenty of us around to answer such questions.