WAAS - iFly General Discussions

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WAAS

9/28/2012 1:10 PM

Shane

Joined: 4/21/2010

Posts: 1709

Re: WAAS

Tim,

WAAS is a hot topic here in the office and on the forums. It is definitely a feature on our Wishlist and we take all our feature on the list serious. I think most of our iFly Owners will agree... "our track record is evidence that we do business the right way". I'll leave my personal position on WAAS under the hood. This has produce some very interesting discussion for sure.

On the WAAS front, I was thinking along the same line. Basically detecting an external antenna to drive an option to enable WAAS. However if an external antenna is not connected, basically bypass the WAAS coding altogether. This would allow for those looking for the "perceived benefit" of WAAS, and for those not desiring WAAS it would not present any performance draw.

As for your Power User status, That was weird! I know your Power User icon was there.

Shane Woodson
Vice President | Adventure Pilot LLC.

9/28/2012 3:17 PM

Chas

Joined: 9/8/2010

Posts: 116

Re: WAAS

Having waas would add to the accuracy of altitude reported on the ifly so if a weather front is passing and the barometric pressure rises or falls rapidly and asos or awos isnt avsilable it can signal significant weather changes are on the way . Guys who fly out of uncontrolled fields always set field elevation and when pressure changes occur they have no way of noting that .

My ifly is within 100 feet without waas having better accuracy would be a bonus .

10/1/2012 12:22 PM

SP

Joined: 12/6/2010

Posts: 69

Re: WAAS

I'll advocate for optional WAAS using a different argument: Need for additional position accuracy in iFly Streets. I recently drove a 3000 mile trip using Streets and found that often it could not tell whether I was on a highway or the parallel service road.

Steve

10/2/2012 1:29 PM

ComputerDoc

Joined: 4/1/2012

Posts: 269

Re: WAAS

You wrote --

"using any handheld GPS to perform a percision approach is simply not a good idea, and I really don't want folks to use an iFly for that purpose"

The counter argument is that although we never expect and certainly shouldn't put ourselves in situations where we try to do a precision approach with a handheld GPS, there's always that emergency, what if, scenario where it comes down I'd rather know within 5 or 10 feet (WAAS) than within 30 or 50 feet.

Which brings up a related question and concern (and possibly yet another argument against trying a precision landing with an ifly even with WAAS enabled):

As far as I can tell iFly in locating "the airport" seems to be locating some particular point on the airport grounds. It appears to me when I'm taxiing that perhaps iFly is centering on the FBO? Can you correct, confirm, or educate me on that? If so, with WAAS or no WAAS if I was trying to use it guide me down on the numbers with, say, only 100 foot visibility it could be leading me down on top of the FBO..

My point being that under low or marginal visibility conditions I can't even depend on it to locate the numbers on the runway I want to touch down on within 30 feet or even within 500 feet , as it seems it would be flying me in to touch down right on top of the FBO which can easily be located 500 feet or more from every available runway end? Not so?

Another "con" argument might be "aren't there areas where there is no WAAS coverage?"

Alex

t

10/2/2012 1:47 PM

Cobra

Joined: 4/20/2011

Posts: 2602

Re: WAAS

During my IFR training, my CFII and I shot a GPS practice approach to landing while monitoring the needles, with the intention of demonstrating that it's accurate enough to put you on the runway in 0/0 conditions in an emergency.

It can do that because the needle is very sensitive. It's not an angular displacement measurement like a localizer, it's a positional offset, but at the threshold full-scale deflection is only .3nm. Keep the needle centered, and you'll land on the pavement.

The iFly doesn't have anything like that, and (for liability reasons) I doubt AP will ever add that. Youve got the magenta line, and you can zoom in on an approach plate, but...really? You really want to believe that your portable GPS is going to put you on the numbers in 0/0 conditions?

That's a lousy reason for advocating for WAAS to be enabled. As it is, the unit can get you to the airport. If you can find a safe way down through the clouds (or ATC can keep you vectored safely), you can circle as required to land whether you've got WAAS or not.

As for areas that don't have WAAS coverage, I don't think that's an issue: click here.

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