Is anyone displaying magnetic heading, either with the app or with a 740? Is it working for you? I have the app on my iPad and I also have a 740b. They won't display magnetic heading when linked to my Stratus, though attitude information comes through fine. When I use my Stratux, heading is displayed but it's incorrect. It does not change with actual aircraft heading, but seems to be always 6 or 7 degrees less than magnetic track, as though the software were just re-applying the magnetic variation to the magnetic track number. The problem is the same on both my iPad and my 740b. I've been in touch with Adventure Pilot about the issue, and they've handed it off to their SW team, but no response yet. Anyone else seeing a similar issue?
I thought about your question when you first posted it but I'm of no help. I don't recall an issue with mine but it's been a few days since I've flown the airplane and I wasn't looking for an issue. I have the iFly 740b & also use an iPhone 12. Traffic & weather come from my uAvionics Echouat with Skyfyx-Ext and displays on both units. Has Adventure Pilot had a software update lately?
There was an update late in 2022 that corrected a problem with the filters for the NRST function. Don’t know whether it did anything else. Their customer service is very responsive but the SW team is very slow with fixes.
Looking at updates the last one was Version 11.1.47 (9/18/2022). An earlier update (Version 11.1.42 - 5/9/2022) has "- Updated Magnetic-North model." I have no idea what that means ...
Where do you think your "magnetic heading" data is coming from? The 740 doesn't have a compass, so it's not going to have a magnetic heading. Tablet compasses can't be used because iFly doesn't know how they're oriented so can't use the date (think tablets mounted in a holder at an angle, etc.) As far as I know, a Stratus doesn't either, but maybe I'm wrong. I think there are very few devices out there that support the magnetic heading instrument (I think the iLevel BOM might). If you don't have one of those devices, then you won't be able to trust that instrument. I don't have such a device, so all the directional data from iFly is track data based on my GPS movement, and it matches the track data from my panel-mounted GPS. I use my compass and my DG for magnetic heading, but iFly has no way to get that data. (I use a Stratux with an AHRS hat, and while there's a magnetometer onboard I don't think its use is supported in the Stratux software. (Ref: https://www.reddit.com/r/stratux/comments/s2q1i1/ahrs_magnetic_heading_possible/)
I don’t think you need a compass. iFly receives AHRS (attitude and heading reference system) data from the Stratus. See https://en.m.wikipedia.org/wiki/Attitude_and_heading_reference_system . “The main difference between an Inertial measurement unit (IMU) and an AHRS is the addition of an on-board processing system in an AHRS, which provides attitude and heading information.” Heading data is derived from a 3-axis MEMS gyro and GPS track data. Magnetic heading, just like magnetic track, can be derived from true heading by adding or subtracting the known magnetic variation for the region. Magnetic heading display is an option in iFly. Why would they have it if they can’t present it? And if they present it, why wouldn’t it be correct?
I never have used an app for heading, but I'll look next time. On another topic, impressed that you have both a Stratux and a Stratus, and a tablet and a 740b.
If I get to fly tonite (xtra sucky forecast), I’ll check. I don’t normally display heading on iFly so this will be something new to do. I have the stratux with me, so maybe I’ll test it if I get some break time at work.
I used the iPad (on a kneeboard) and Stratux when I was renting since they were easy to move to and from different planes. When I bought my Beech it already had a Stratus transponder and ADSB receiver installed. I used my iPad for a while but the display is too dim and it overheated a couple of times, so I bought the 740b and mounted it on the panel. I have the 740b plugged into my audio panel so I can hear alerts in my headset.
"Heading data is derived from a 3-axis MEMS gyro and GPS track data." GPS track data tells you your track, not your magnetic heading. A MEMS gyro also does not have a magnetometer. Thus, you cannot determine magnetic heading from a GPS track and a MEMS gyro. AHRS devices often do have magnetometers. The one on my Stratux does, I know. But I toss my Stratux on the hat shelf in the back of the plane without regard to its orientation with respect to (wrt) the plane, so whatever info coming from that magnetometer is wrt some arbitrary reference frame that is not aligned with my fuselage. In other words, there's no way to take a reading from my Stratux and know which way the plane is pointing. It would need to be fixed in a known orientation wrt to the aircraft structure and calibrated before any magnetic heading info it provided could be useful. (And that says nothing about calibrating the magnetometer for local disturbances, like swinging a whiskey compass.) The attitude info it provides is also a little wonky because I don't precisely align it, but I've played around with it and it could still be somewhat helpful as a gross indicator if my AI completely failed on a dark night. A device like an iLevel BOM, which is rigidly mounted to the wing in a specific orientation, could have a magnetometer that could be used for magnetic heading. (I don't know if it actually does or not, but it's pretty sophisticated so I wouldn't be surprised if it did.) iFly will use magnetic heading data from devices like that if it is available. iFly may also use magnetic heading info from devices that have magnetometers that provide meaningless data, like my Stratux--I dunno. I know there's no way the magnetometer in my Stratux can be providing any useful data, so I've never enabled that instrument.
AHRS provides a heading reference, not a magnetic heading. It doesn't know your magnetic heading any better than a DG does. You need a magnetometer for that.
I wonder if the Stratux could take the true heading and adjust it for known magnetic variance based on its GPS location.
The same question applies: Where will the Stratux get the true heading? Unless it's mounted precisely and calibrated, whatever magnetic-based heading it's providing from an AHRS is going to be inaccurate.
Both Stratus and Stratux can be calibrated once the unit is mounted to the plane. It’s a simple zeroing from the device home page. In fact, if you don’t do this, AHRS is useless as the device doesn’t even know what level is. If the device knows what “nose straight ahead” is (and it does once calibrated) and if it knows the track (and it does from GPS), the difference between the two will be the heading. True or magnetic doesn’t matter; iFly (and other SW like FF) has maps and knows where you are and what the magnetic variation is at that location so either true or magnetic can be displayed.
Okay, if AHRS heading is just a reference, then calculate true track with respect to that reference and true heading will be the negative of that number. Convert to magnetic based on local variation.
I said it provides a heading reference like a DG. The true to magnetic conversion is not the issue. The issue is it needs a reference to show what your heading is in relation to. That is what the magnetometer is for.
The gps would know it is going from this point to that point. Draw a line and that tells it what true direction it is going. And at GPS position XYZ the magnetic variance is X degrees.
I was under the impression that the point of the Stratus/Stratux AHRS module was to provide a back-up attitude source in case of a partial-panel IMC emergency. The G5 direction indicator will only display heading with a magnetometer installed, otherwise it will show GPS track. The AV30 can interface with a magnetometer, but if one is not installed it can function as a heading indicator that must adjusted by the pilot like a conventional unslaved gyroscopic heading indicator. I don't think a portable unit is going to be able to do better.
But...track, or "true direction" as you're calling it, does not equal magnetic heading. So applying the local magnetic variation is as useful as adding inches to centimeters. (At least you're using the same units with degrees, but it's just as meaningless.) Edit: I think we might be confusing what's useful for preflight planning vs. what's useful in flight. You can pull out your chart or favorite EFB, and plot a course to get the heading from point A to point B. You can apply the magnetic variation to get the magnetic heading (or headings, if your flight is long enough for them to change over time). Once you're in flight, you can use your compass to set your DG and fly the magnetic heading(s). And if there's no wind and you keep adjusting your DG for gyro drift, you'll find your destination. But if there are winds, you'll need to account for them and fly a different heading on your DG/compass to reach your destination. Since it's 2023 and everybody has at least one and probably several GPS-driven moving maps, often coupled to an autopilot, in practice we can just tweak the heading on our DG until the GPS Track and its flight plan's "desired track" for the next waypoint align, and then just hold that heading (and adjust it as needed), or else just push a button and let George do the work. But when we're flying in winds and on a DG heading that differs from the GPS desired track, then I don't understand what you think adding magnetic variance to the GPS desired track would be useful for.
Sorry, but I'm a bit confused. Are you just saying that track and heading are different things, which is obvious? (And if there's no wind, they'll be equal.) True and magnetic can be converted back and forth as you like by applying the magnetic variation. I can walk out into my front yard tonight, point at the north star, and say accurately that the direction is 360 degrees true and 6 degrees magnetic since local variation is 6 degrees west.
OK, yeah, I was carrying a couple of thoughts in my mind and they didn't come out right. Yes, with no wind, track and magnetic heading are the same. But since we fly in winds, then in general, what you've got showing on your DG and what you've got showing on your GPS are different. This thread started with questions about why someone's mag north instrument wasn't working on iFly GPS, and I was thinking your post had something to do with that, but now I think it doesn't. Most GPSs already account for magnetic variance (or for some there's a user setting to choose between true north and magnetic north)--that's why we just agreed that track and (no wind) magnetic heading are the same a minute ago. So what is it you're really looking for again that you don't already have?
I'm the OP, and my question was why I can't get magnetic heading to display correctly in iFly. It's an optional instrument available for display. When using my Stratus it remains blank. When using my Stratux, it displays magnetic track minus 6 degrees, not heading. I've pinged the folks at Adventure Pilot about it but do not have an answer yet. They told me their lead SW guy is on vacation, so I'm waiting (im)patiently.
Don't know what you're waiting for. As described above, there is no way for the device to know this information. https://www.iflygps.com/Portals/0/Documentation/iFlyGPS Pilots Guide 11.0.pdf Doesn't describe anywhere a capability to display heading.
Nope, it's not mentioned in the Pilot's Guide, but if you open the app and customize the instrument display you'll see it's one of the options. Why would they have it if there's no way to make it work? And why is it displaying track minus six degrees, rather than remaining blank? Obviously they're calculating something for that display, even if it's wrong. And if it needs initialization in order to function, why isn't there a way to do that?
You have an answer…wait. Why do you think anyone here can give a better answer than the OEM’s software lead?
I was hoping someone here might have already seen the same thing and know a solution, if there is one. But by now I should know better than to tie "hope" and "POA" together....
Out of curiosity I fired up my tablet and turned on IFly and my Stratux. I can get the true and magnetic. True seems believable. What is popping up as magnetic seems random. If you find out what the IFly people think it’s supposed to be doing and how please post up.
Are you looking at track or heading? Do you have a reliable GPS connection? If it doesn't know location, it can't provide the correct variation to convert true to magnetic.
Send an email to customer service at Adventure Pilot. Don't mention me. Maybe if they get several customers with a similar issue it'll get more attention. (Doubtful but worth a try. )
