Kevin's Korner - GPS Back up to your Back up!

Q: What is the difference between everyday GPS and Aviation GPS?
A: Global Positioning System is your basic driving day to day GPS.
These are a network of orbiting satellites that send precise details of their position in space back to earth.
Aviation GPS or WAAS signal bounces back with help from these same satellites.
The Wide Area Augmentation System or WAAS, (is a much more precise GPS system for Aviation) it is an air navigation aid developed by the Federal Aviation Administration to augment the Global Positioning System (GPS), with the goal of improving its accuracy, integrity, and availability.
With each satellite, we know the speed it takes to get from that satellite to the ground with WAAS it now needs to be determined how long it takes to get to the tower to the plane to the plane next to them and to the ground. This is done by multiple ground reference stations positioned across the U.S. that monitor GPS satellite data. Two master stations, located on either coast, collect data from the reference stations and create a GPS correction message.
Because there are two types of GPS’s. There is the standard GPS unit like we have in our cars, or our cell phones. and then there is WAAS.
Example: Do you care if you are a couple 100 yards off from your destination in your car?

Sure, but you can still figure out where you are and where you are going from there.
With air planes, they need to be much more precise.
At least with in ten feet. 9.843 to be more exact…
(less than 3 meters from exact location trying to reach)
With an airplane GPS navigation receiver, a pilot can quickly and accurately determine his or her location relative to the ground.
Pilots are recommended to have at least two antena sourced GPSs. That way, they can more accurately know their position. (A Back up to your Back up)
Q:  So that’s why pilots have more than two in their aircraft?
A: Yes, two or more are recommended... in my opinion they should be required. But it only takes one to navigate an airplane. But I cannot stress enough how important it is to have a back up to your back up on almost every piece of equipment in your plane.
Not only that, sometimes you have these all-in-one units that include a comm. (communication) system. So, if your all-in-one goes down then you lose your comm. and GPS.
Even if you have an all-in-one unit you should always have a back up to your back.
If I’m going to pick up an accurate signal, I’m going to need at least three satellites.
One signal is slightly different than the other two.
These are combined and I can see exactly where I am at in flight.
(Location, Longitude, and Latitude, Height above the ground, feet and directions)
Q: As a professional A&P mechanic you recommend that pilots not only have several installed GPS’s in their install panel but should also have separate back up GPS?
A: Yes. not only that you will need a separate GPS Antenna.
(Two installed GPS systems with a hand held is a minimum) But if I have four or five I can pick up.. than I know I can be very productive.
Q: Is a 296 Garmin hand held unit just as good?
A:   It can be used as an AID not as a source. I still recommend have two GPS Sources installed in your panel.

WAAS GPS transponder has its own GPS System.   Sometimes you can tap into a WAAS source to navigate with your other GPS /Navigation systems.
Avidyne & Aspen brands have some of their own GPS WAAS source units.
Questions you need to ask yourself about your Aviation GPS:
If your GPS fails, what kind of back up do you have?
Does it have a source? (Do you have more than one?
Are one of these main GPS systems your main source? Does it have a backup?
Example: Avidyne IFD540 and an Avidyne IFD440 as your back up.
When’s the last time you had an IFR done on your plane?
It’s recommended to have these done every two years. (Just like an oil change. You don’t want to be stuck flying blind in the sky!)
Pilots, just like drivers are becoming too dependent on their GPS to drive for them and forget how to fly or function in a situation where it may not be available.
(you could lose a wi-fi WAAS connection due to storm, loose wire, bad panel connection. It could be anything. And you never know when it may happen)
Just like if I get lost in my car, I better know some land marks or know how to read a map! Or I’m lost. It’s even more dangerous in flight. No one wants to fly blind. I also recommended a simple hand held Transceiver Radio so at least when you get close to a tower you can communicate with them to land (if all else fails)
Final Thoughts:
GPS is good, it’s reliable, it’s accurate, it gives you a lot of good information. But satellite failure can happen.
Safety First. Get a Back up to your Back up!

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