Curiosity about the real-world accuracy of the STEC

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Skydiver79
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Joined: 09 Jul 2012

Curiosity about the real-world accuracy of the STEC

Post Skydiver79 »

Hi all,

Just getting back into flying after a motherboard failure a few years ago. I had had the Cherokee and Comanche back then, but didn't get a chance to fly them much prior to the computer dying.

Anyhow, back up on a new rig, and upgraded from FSX to P3D v5.... the only thing missing is my B-17!

I've been flying a lot with the Comanche, and after some trial and error and manual reading, I figured out the STEC. Brilliant system, easy to use once you figure it out.

I'm curious about how it behaves in-sim vs real world. For example, something that took me a while to wrap my brain around was that the VOR pointer didn't necessarily correspond to a GPS VOR-to-VOR course. It wasn't uncommon for me to use heading mode to align the VOR pointer, and end up being up to 5 miles off the GPS course. It always zeroed in as I get closer to the VOR, but it struck me as backwards from what I was expecting. Likewise, if I set up the next VOR in Nav2 and turn the onmi to match the future heading once I reach the VOR on Nav1, in theory I should make my turn when the omni pointer is centered (right?) and/or the VOR1 pointer temporarily loses signal as I pass overhead. But I often reach the VOR in Nav1 seemingly well before the Omni is centered.

Anyhow, like I said, just curious about how well the implementation stacks up against the real thing.

Thanks,
-Jason
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AKar
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Joined: 26 May 2013

Re: Curiosity about the real-world accuracy of the STEC

Post AKar »

Obviously, the autopilot does not control what the VOR stations transmit, it simply centers the needle. S-TEC or other does not matter.

You can try if updating your simulator navaids makes any difference to the issue. But to some extent, it is normal that the VOR radials are a somewhat offset from their nominal magnetic bearings. This is because the stations (in real life) are calibrated to the magnetic north only every so often, in part to not have to alter the related procedures.

-Esa

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Skydiver79
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Re: Curiosity about the real-world accuracy of the STEC

Post Skydiver79 »

Thanks Esa, that makes sense. Some areas in the US have a pretty significant yearly magnetic drift, so if a station isn't updated in (say) a decade, that can compound to quite a bit of error. Certainly can account for the degree or two difference, which is usually what I'm seeing in the sim. And of course, as you noted, the AP just centers the needle, so it ultimately takes me right to the station, or dead away from it.

I'm not planning on messing with updating the navaids in sim, at least not for the moment.... VOR to VOR happily gets me where I want to go. If I happen to be making a turn where two different radials meet, that works well too, although my intersection from reading the gauges isn't necessarily where the GPS thinks it is. But I'm almost always in Class G or E, so I'm none too worried.

-Jason
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AKar
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Re: Curiosity about the real-world accuracy of the STEC

Post AKar »

Some of my favorite VOR to VOR sim flights are in Alaska. So, long segments and fairly large magnetic variation. Back when I first discovered these navaid updates, they did make a significant improvement on how the VOR radials intersected in the sim versus the charts. I am not sure how up-to-date the P3Dv5 database is. Supposedly they at least included a newer magnetic variation table, though I've updated that as well just to be sure.

The navaid update is easy to do (it has an installer-like thing) and reversible as well. Though annoyingly it ticks off the Win10 threat protection - a known issue.

-Esa

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