Re: Accuracy of GPS in Garmin 430/530

Will wrote:


Hold on, and stop changing topics and talking about new issues. There was
never any debate about FAA mandate. The discussion about whether it is
needed or justified is a separate discussion within the thread. Jim made a
comment that the feature I described would double the cost. I was trying
to respond just to that point. I did so by pointing out:

- It won't take more than a man month to simply code the needed algorithms
(and I doubt it would take that).

If you have an avionics engineering background, you should know that TSO-C129 is not only enabling, it is specific and fairly limiting. The avionics vendors are constrained by the TSO. The TSO serves a purpose, to permit an IFR platfrom for GPS terminal and approach operations within a National Airspace System that has yet to be declared GPS-primary, much less sole source.

I am very familiar with the Garmin 530. I have also owned three Garmin aviation handheld units, the 195, 295, and 296. The handhelds have had progressively sophisticated features that the Garmin 530 does not have because the 530 had to go through a very extensive certification process to be qualified for IFR operations. Not so with the handhelds.

Garmin has millions tied up in both their IFR and VFR programs. They seem to be progressing along quite nicely in providing products appropriate for the operation.

I have my own ways of independendly verifying the accuracy of my 296 by using DME at the appropriate time. That provides a great accuracy check, which is valid for a limited period of time. But, it is hardly approach RAIM. Also, the TSO-C129 sets actually increase accuracy as well as assure a high level of integrity in the final approach segment using approach RAIM.

As I said previously, and you chose to ignore, you seem to be looking for a full press RNP platform, which would not only have redundant alerting and actual navigation performance (ANP) it is not limited to the three levels of sensitivity that TSO C129 constrains; en route, terminal, and approach. (BTW your handheld does not meet those sensitivity requirements, either).

A Boeing 727-NG, which is available is a business jet version, has everything you are looking for, including three IRUs that are constantly updated by GPS and have position blending. Then, in the event of a failue of GPS (typically local jamming) the IRUs will continue to provide very low numbers of RNP accuracy, integrity, and continuity.

I think you might be in over your head a tad and, in the process, digging a hole for yourself for no good reason. ;-)
.

Relevant Pages

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