Originally Posted by
43Inches
I fly for a living using GPS so a lot of hours navigating by it, while its 99.9% foolproof I've had several missed approaches due to no RAIM at the FAF or past it, and several events where the GPS navigation solution became suspect and was confirmed off track. Some of the events were unit related and others satellite or atmospheric related. Ice on the GPS antenna can affect it as well as moisture in the wrong places. It is not regular, but it does happen. This is where installation type really can make a difference. The key being what information is displayed if the navigation unit is operating in a degraded mode, and when will it tell you so. For instance in a TSO unit will not allow operation in approach mode without RAIM, so it will dump flight guidance and make it clear you don't have the required fidelity.
This talk about trusting the unit when low among hills without having RAIM protection shows a lack of understanding of the drawbacks of GPS, like any other navaid.
The iPad as far as I know does not tell you if it has good/bad or no GPS signal.
This is also the issue with creating your own approaches in IMC, without the required programming it will most likely fly in terminal or en-route mode, which means different tolerances, alerting and RAIM requirements.
This talk about trusting the unit when low among hills without having RAIM protection shows a lack of understanding of the drawbacks of GPS, like any other navaid.
I understand the drawbacks of GPS perfectly well, thank you! Suggest you re-read the last sentence in my post! Here it is, as you seemed to have missed it!
[QUOTE
]I am NOT advocating the routine use of handheld GPSs or iPhone/iPad as anything other than backup - but when you have screwed up and your life is on the line, I would not hesitate to take my chances that one could save my skin![/QUOTE]