Why does Astro Link need/have it's own GPS when hour 740'

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HomeHomeDiscussionsDiscussionsiFly Owners Q&AiFly Owners Q&AWhy does Astro Link need/have it's own GPS when hour 740's have them already?Why does Astro Link need/have it's own GPS when hour 740's have them already?
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4/18/2019 11:22 PM
 

From the iFly shop:

".....Meet the Astro Link, an affordable portable device that combines a state-of-the-art aviation grade AHRS technology, dual band ADS-B Receiver, and an internal WAAS GPS for navigation. This USA made device brings peace of mind to every pilot by offering a progressive back-up solution at any time.  The Astro Link is capable of driving Synthetic vision displays and provides navigation information you need to turn your tablet into a real glass panel...."

Is the answer to my question "Astro Link is envisioned as a function and value and navigation added device primarily for iPads (tablets) .... not for those of us with dedicated hardware iFly boxes?"

As someone who flys with a 740 but currently has no ADS-B nor any AHRS, it sounds like a nice package to buy both those missing features at a reasonable price.

Is it suitable for use with 740? If so is there any conflict between the WAAS GPS in the 740 and the one in the Astro Link?

 

Alex

 
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4/22/2019 10:22 AM
 

Hi Alex,

Most ADSB receivers include a GPS.  As they are typically positioned on the glare sheild or attached to a side window, they often have better opportunity for a good lock than the 740b.  And there will be no conflict, the ADSB lock will be used by default, but if that signal is lost it will automatically switch to the internal GPS.

It works equally great with iPads, Androids, or iFly portable units. Regardless of your hardware, it will improve your GPS lock, provide pitch and roll data for your artificial horizon and synthetic vision, and will provide weather and traffic overlays.  

Thanks!
Walter


Walter Boyd
President, Adventure Pilot
 
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8/22/2019 11:40 AM
 
Walter wrote:

.....it will improve your GPS lock, provide pitch and roll data for your artificial horizon and synthetic vision, and will provide weather and traffic overlays.  "

 

.but, but....the iFky already provides synthetic vision.

So which one works in this scenario? How is the Astrolonk's SV acessed?

Which SV works better?

Alex

 
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8/22/2019 4:09 PM
 

Yes, the synthetic vision feature is provided by the iFly software.  But it needs input data from sensors to work.

The best option is to get input data from an AHRS, or Attitude and Heading Reference System.  Many ADSB devices include an AHRS sensor package, and provide the data from those sensors in a standard format that iFly can consume to drive the synthetic vision.  The sensors provide direct data on aircraft roll, pitch, and yaw (RPY), and maybe other data, depending on the AHRS device in question.  (iFly doesn't necessarily use *all* of the data provided by an AHRS, but it definitely uses the RPY info.

If AHRS input data are not available, iFly can use alternate means to drive the synthetic vision.  It will use several consecutive GPS position readings to determine your path through space, then do math on that set of data to derive your pitch, roll, and yaw.  For instance, it will assume you are pitched 0deg if you are flying level, or that your pitch matches your flightpath climb or descent angle if your altitude is changing.  It does similar math to derive roll and yaw.  However, these are simplistic approximations.  For instance, your pitch will be very different at max cruise speed vs. stall speed, but if you are maintaining a constant altitdue, iFly will show you at a 0deg pitch angle for both flight conditions if it's using GPS data.  An AHRS would not be fooled, and would sense your actual pitch angle, so iFly would show you pitched higher up at stall speed than at cruise speed.

Similarly, you could be in a slip, with the aircraft yawed and rolled in a cross-controlled way to maintain a straight-ahead flight path.  If iFly is using GPS, it will show you with 0 roll and 0 yaw, but if it were using AHRS data it would show the correct roll and yaw.

 
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HomeHomeDiscussionsDiscussionsiFly Owners Q&AiFly Owners Q&AWhy does Astro Link need/have it's own GPS when hour 740's have them already?Why does Astro Link need/have it's own GPS when hour 740's have them already?