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FS9 Flight Level vs. True Altitude Error


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Hello All -

I have been using FS9 for years and stubbornly resist switching to FSX. I have used many different addons at one point or another, most recently the PMDG 747. I have ruled out (hopefully!) any addons as the cause of my trouble.

Lately, and I don't know why this hasn't become a problem at some other point, ATC has been advising me of an altitude deviation while enroute, usually in the 300-400 ft. range. Above 18,000 MSL the altimeter is set to 29.92 and the world of Flight Levels begins - and every time I have been dead on my flight level. However, if you bring up the information at the top (Shift-Z) the true altitude (MSL) is displayed, and that altitude is what ATC thinks I am at, despite the fact that my altimeter is set to 29.92 and I am flying the assigned flight level. Logically, this is only an issue when using real world weather, since when using the "standard" theme the altimeter setting is always 29.92, whether in the flight levels or not. Thus, there would never be any difference between one's true altitude and flight level - because of the standard pressure.

I tested this on my other computer with a stock installation of FS9 and it holds true. So it isn't an addon that is messing it up.

Try this:

Default 737, standard weather - "clear skies" theme in FS9. Press Shift-Z until the true altitude is displayed. Whenever the altimeter setting is the standard pressure, your true altitude will equal your "flight level" because there literally is no difference - flight level is pressure altitude and with the altimeter at 29.92 that is EXACTLY what you are doing - flying pressure altitudes.

Now, change to real world weather. I always do this through the default microsoft interface. Again, using the default 737, climb to FL250. Passing 18,000 MSL set the altimeter from the "local" setting to 29.92 - level off at FL250 and observe the difference between MSL (in red at the top of the screen) and the reading on your altimeter, which is set to 29.92. This is perfectly correct as it should be in the real world - you are now flying pressure altitudes. Now, for illustration purposes of my point, call up ATC and request flight following (obviously we should have been talking to ATC long ago if this one was going to be kosher - but you'll see where I'm going with this in a second). When ATC tells you "radar contact" and gives you your altitude, they'll say something along the lines of "United 123 radar contact 5 North of ABC, FL[xxx]." We are level at FL250, right? They should have read that back. Instead, they think you're at the MSL altitude, your "true" altitude. Thus, they think you are several hundred feet high/low the entire time. Puzzling, huh?

Ideally I'd like to find a way to be able to download real world weather and leave the pressure changes out - so that I'm always at standard pressure, so that the true altitude and the FL always match up so my IFR doesn't continually get cancelled.

Sorry for rambling. Any help would be greatly appreciated. Is there a setting in FSUIPC that can help with this?

Logan DeNelsky

Certified Flight Instructor

Wadsworth, OH

logandenelskycfi@gmail.com

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Lately, and I don't know why this hasn't become a problem at some other point, ATC has been advising me of an altitude deviation while enroute, usually in the 300-400 ft. range. Above 18,000 MSL the altimeter is set to 29.92 and the world of Flight Levels begins - and every time I have been dead on my flight level.

This is all only true in North America, of course. the rest of the world uses various Transition Altitudes when climbing and Transition Levels when descending, ranging from 3000 feet or so to, yes, 18,000 (though not many that high as far as I know)..

Sorry for rambling. Any help would be greatly appreciated. Is there a setting in FSUIPC that can help with this?

No, sorry, there is no way FSUIPC or anything else can come between the built-in faulty ATC and the built in weather system. The solution most folks use for the poor FS ATC is to use thrid party applications, such as Radar Contact (good for IFR) and VoxATC (good for VFR). These also have the benefit of understanding that there's a world outside of North America. ;-)

Regards

Pete

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...or VATSIM, who insist on you using the correct transition altitude, charts and up-to-date navdata, but will actually provide a human being with some common sense as a controller, rather than an utterly illogically programmed ATC system.

I only ever used IVAO briefly. At the time it was dominated by Central Europe and if you wanted to fly anywhere outside of a block surrounding Germany across to Poland, forget it. I'm told it's a lot better now.

Personally, I continue to use the default ATC when flying airliners because I know and can ignore as incorrect its foibles and failings. I, unfortunately, cannot stand the Canned. Robotic. Voices. that are used by ATC generation add-ons (and no voice yet has ever made Microsoft Speech Engine any less annoying to me), so it's either online (where I have neither the time nor the inclination to do all the pre-flight research they demand) or the default ATC. I'll put up with knowing I'm at the right altitude, but being told to climb or descend 300' to where it thinks I should be.

It's the same in FSX, by the way. It was never fixed.

Cheers.

Ian P.

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I, unfortunately, cannot stand the Canned. Robotic. Voices. that are used by ATC generation add-ons (and no voice yet has ever made Microsoft Speech Engine any less annoying to me), so it's either online (where I have neither the time nor the inclination to do all the pre-flight research they demand) or the default ATC.

You've not tried Radar Contact, then, because that uses no synthesised voices. All of them are recorded by a band of volunteers, they are all human.

I also use IYP, which does use speech synthesis, and I agree with you regarding the default speech engine voices and many of the cheaper ones, but the more expensive ones (25-40 UKP each) are very good indeed. I wouldn't spend that much for ATC voices because you need too many different ones, but for IYP acting as a copilot you only need the one. I actually bought two -- a UK male and a UK female, and sometiimes switch.

Regards

Pete

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It was one of the recommended ones for IYP which made me not want to use the speech engine last time. It still sounded like Chris Barrie mimicing Kryten mimicing a Sat Nav to me, I'm afraid.

However I haven't tried Radar Contact recently, no. The last time I looked at it, that used speech synthesis too, but it was a very long time ago, so I'll stand corrected on that one. Thanks!

Cheers,

Ian P.

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It was one of the recommended ones for IYP which made me not want to use the speech engine last time. It still sounded like Chris Barrie mimicing Kryten mimicing a Sat Nav to me, I'm afraid.

I didn't go for any "recommended" ones, at least I don't think it was. I just searched for samples and decided on Daniel from Scansoft, which is very good indeed. The female one is Emily. I only just noticed that the Daniel voice was selected by Apple for its UK iPhone 4S "Siri" application (see

http://www.telegraph...is-silence.html)

I think Robert recommends that folks look at the AT&T voices, which aren't anywhere near as good as the Scansoft ones in my opinion.

However I haven't tried Radar Contact recently, no. The last time I looked at it, that used speech synthesis too, but it was a very long time ago

I've been using Radar Contact ever since it was an Adventure generator for FS95. I don't remember Windows 95 supporting speech synthesis? RC has certainly used recordings as long as i remember. Since it has to keep changing voices for different controllers, as well as those for the pilot (if you opt for auto-read back) I can't imagine it ever working with synthesised voices, it would have been far too expecnsive. I think VoxATC does, and comes with a few cheap ones, but it is a lot more expensive than RC and you do need to buy more voices if you aren't simply doing short VFR hops without venturing through many levels of ATC.

Regards

Pete

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Windows 3.11 supported speech synthesis - but until fairly recently you had to download "Microsoft Speech" to use it, from what I remember.

I certainly remember trying to convince Windows 3.11 to say "Ian" and "Steven", in the office. It never did quite manage it, no matter how creative we got with the spellings!

Anyway. That's a slight aside.

Ian P.

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