Navigate with GPS

[tacvbo]

Hey you guys,

my father and I had a discussion the other day. We were talking about navigation and GPS systems when I stated that nowadays it is possible to navigate with GPS. My father replied that this would be possible but is currently not allowed by the LBA (the German FAA). All aircraft operating RNAV are getting their data via the inertial reference system and the GPS system is only a backup but still not available for RNAV. So far so good.

What I cannot understand is that there are charts that officially publish GPS approaches, like this one http://155.178.201.160/d-tpp/1506/00256R9L.PDF
As I understand that, the use of GPS is allowed for RNAV navigation. Is that correct?
I also see a lot of smaller aircraft like Socata TB850, Cessna Caravan, etc. using the GPS to display and follow their flightplan.

Please help me out on this topic.

[5LY]

Modern transport jets navigate using FMC position info. The FMC looks at IRS pos., radio pos. (by auto tuning VOR's and DME's) and GPS pos. and derives it's pos. by comparing all info and choosing what it perceives to be the most accurate. This is almost always GPS pos. IRS's drift, VOR's and DME's aren't always in range.

[aterpster]

tacybo:

my father and I had a discussion the other day. We were talking about navigation and GPS systems when I stated that nowadays it is possible to navigate with GPS. My father replied that this would be possible but is currently not allowed by the LBA (the German FAA). All aircraft operating RNAV are getting their data via the inertial reference system and the GPS system is only a backup but still not available for RNAV...

Ask him for an authoritative reference to support his position.

[aterpster]

5LY:

Modern transport jets navigate using FMC position info. The FMC looks at IRS pos., radio pos. (by auto tuning VOR's and DME's) and GPS pos. and derives it's pos. by comparing all info and choosing what it perceives to be the most accurate. This is almost always GPS pos. IRS's drift, VOR's and DME's aren't always in range.

That isn't the case with some of the smaller aircraft he included in his question. They may have only a flux-gate compass and a Garmin panel navigator.

[cessnapete]

tacvbo
Incorrect, many modern aircraft now fly RNav and all IFR with just GPS. Inertial nav is not required and is not fitted. Even flying in Germany!

[sgenie]

In New Zealand, for example, GPS is not allowed as a sole mean navigation system but is allowed as a primary mean navigation system - maybe Germany has the same limit?

[AerocatS2A]

True, but primary means is, for practical purposes, the same as sole means except that you have a VOR tuned up and displayed somewhere in the cockpit for the pilot to disregard, or perhaps you have an FMS that tunes a VOR and disregards it in preference to the highly accurate GPS position. In other words, to all practical purposes, you are using GPS to navigate and the OPs father is wrong.

[172_driver]

And unless you are a big airliner you are likely not equipped with inertial nav system. So something else would have to suffice.

[aterpster]

Or, a higher end biz jet.