ATC Question

[nickduncs84]

AD APP equipment takes the area QNH below A100 or YPAD QNH or above A100 it uses 1013.2, when you set QNH to the same as everyone else in the similar area, you are all using the same height datum or reference point, and if you are on different settings the information is useless. Between VFR and IFR. In CTR we can use 500ft verticals separation, if your transponder is out by 200 and the other guy is out by 200ft, there is a minimum of 100ft. The 200ft is the maximum tolerance for a mode C transponder, if you have a faulty transponder and also set it incorrectly this can potentially make a greater error.If I get an error greater than 200ft I'm required to instruct the pilot to use mode A only, we prefer the transponder on but outside the 200ft tolerance is bad for many reasons TCAS is just one of them, I will suggest that you get it checked before entering controlled airspace again. We can cancel or refuse a clearance to enter or use CTA if your transponder is out of tolerance.

 

I stand to be corrected, but I think if you have and use a transponder IFR or VFR it is a requirement to have it checked for operation and calibration every two years for private operations and less for commercial operations.

Thanks Patrick this is all very helpful. The aircraft is maintained IFR and has just had an annual. It's also used for IFR flights regularly and spends a lot of time in the Adelaide control zone and other then my two encounters, there haven't been any other issues.... That we know of. Either way probably prudent to get it checked.

 

 

[KRviator]

100NM is about an hour flight in a jab type, allot happens in an hour but more importantly is ALL IFR traffic will be on area.

What is the reference/requirement for IFR aircraft being on Area QNH when Local QNH is available?

[nickduncs84]

What is the reference/requirement for IFR aircraft being on Area QNH when Local QNH is available?

I'm sure it's somewhere, but from a practical perspective any time you're with ATC, which for IFR aircraft is always, you're on whatever QNH they tell you.

 

 

[ayavner]

When I did my coast to coast flight in April I got in the habit each time i would either cross an area boundary OR a FIS/Centre boundary I would make a radio call asking for updated area QNH for the particular spot I was in. Broke up the monotony and it was nice to occasionally hear a voice and confirm my radio was working and could reach someone. I think they seemed happy to help, and there were a few times where the difference was fairly substantial.

 

 

[Yenn]

The controllers are seeing what your transponder is saying. It makes no difference what you set your altimeter to.

 

All aircraft with transponders are required to have them checked, usually every 2 years, but if you have a full check of equipment and plumbing you may be able to make it every 3 years. Look up CASAs AD/RAD/47.

 

 

[Chocolate]

Get the setup checked. Mine was 'plumbed' incorrectly so that when I had doors off it read incorrectly.

 

 

[Patrick Normoyle]

Yen, I beg to differ, it matters greatly what you set your QNH scale to, that's the whole point of have the scale, so everyone in the same area using the same reference point, otherwise someone using one setting compared to a different aircraft using a different setting thinking they are at a certain height when they could be at the same height.

 

Your transponder tell us in ATC what your altimeter is reading.

 

 

[Happyflyer]

Your transponder tell us in ATC what your altimeter is reading.

I think an aircraft altimeter is not connected to the transponder. Most transponders have an inbuilt altimeter always set to 1013.2. They are totally separate to the altimeter the pilot reads. When you set the aircraft altimeter to 1013.2 you can compare the two for accuracy.

 

 

[IanR]

I think an aircraft altimeter is not connected to the transponder. Most transponders have an inbuilt altimeter always set to 1013.2. They are totally separate to the altimeter the pilot reads. When you set the aircraft altimeter to 1013.2 you can compare the two for accuracy.

That is correct - the transponder usually has a separate altitude encoder

 

 

[frank marriott]

That's why they are called a "blind" encoder, 1012.3 regardless of pilot input. Also it prevents a pilot from intentionally transmitting a false altitude.

 

 

[frank marriott]

Optimistic ??

 

 

[rhysmcc]

Patrick, I believe TAAATS makes the conversion from the pilots transponder altimeter to the "displayed" altitude based on what QNH is set in the system, whether that's area or actual would I guess depend what sector/airspace you have.

 

 

[Yenn]

I don't think ATC can see what your altimeter is reading, so its setting is irrelevant. You could fly using QFE and the transponder should still be showing your height according to 1013.2

 

 

[frank marriott]

I don't think ATC can see what your altimeter is reading, so its setting is irrelevant. You could fly using QFE and the transponder should still be showing your height according to 1013.2

Yenn yes the transponder doesn't care what you have on your altimeter. I tried to cover the reason and got "creative" & "optimist " so I'm no longer interested so long as they don't fly in my area - attitude? I make allowances on X country trips and take the radio calls as a rough indication of position only when I hear a RAA callsign - sad but true - reflects on all of us unfortunately.

(I did notice a typo of 1012 instead of 1013 but apparently others know better)

 

 

[shags_j]

I know Taats does correct for QNH.

 

I fairly regularly get IFR or VFR aircraft with wildly different altimeter settings (anywhere up to 600'). The other day we had a low level VFR who's mode C level was FL210. Caused no end of issues.

 

Ask ATC for area QNH if you want (try to wait for a quiet moment though) and please tell us where you are and which direction you are travelling so we know which one to give you. Some sectors are anywhere up to 1200nm which could be any number of different areas or splits.

 

 

[ayavner]

Yenn yes the transponder doesn't care what you have on your altimeter. I tried to cover the reason and got "creative" & "optimist " so I'm no longer interested so long as they don't fly in my area - attitude? I make allowances on X country trips and take the radio calls as a rough indication of position only when I hear a RAA callsign - sad but true - reflects on all of us unfortunately.(I did notice a typo of 1012 instead of 1013 but apparently others know better)

haha i gave the creative as a joke, having a go at whoever put "optimistic". I didn't understand it either. It was funny in my head.

 

 

[Yenn]

ayavner. with all the good gear we have nowadays. GPS, OzRunways, Avplan etc we should be able to give very accurate positions. That is what I consider the best feature of our modern equipment. When it was all map and compass it was too easy to be a few miles out and saying South east is not as accurate as for example 128 deg.

 

 

[facthunter]

If you say bearing 128 from "whatever" @ 10 miles Most won't have a clue. Nev

 

 

[shags_j]

I had a Rex take off the other day and go from balina to sydney with no GPS or FMS. Did it all the old school way. Goes to show that no matter what you are flying you should never lose those skills.

 

 

[facthunter]

I wonder if they all can . Some fly for fun as well and maintain their basics. Nev

 

 

[SDQDI]

I had a Rex take off the other day and go from balina to sydney with no GPS or FMS. Did it all the old school way. Goes to show that no matter what you are flying you should never lose those skills.

But shags even I could do that:yes: Just have to keep the big lake on the left until you see a cool bridge and a funny looking building that looks like upside down bowls:thumb up:

But you are right I was only thinking today how dodgy we get without proper nav practice, although are you SURE that old school way didn't include an iPad?

 

 

[shags_j]

Can't confirm or deny ;)

 

 

[Old Koreelah]

...I was only thinking today how dodgy we get without proper nav practice, although are you SURE that old school way didn't include an iPad?

I flew home last week with the iPad and iPhone turned off. Went back to the paper map. Good practise, not as easy as keeping OzRunway's little aeroplane pointed along the purple line.

 

 

[Ryanm]

100NM is about an hour flight in a jab type, allot happens in an hour but more importantly is ALL IFR traffic will be on area.

No we won't!