dGPS approaches
 

dGPS approaches are more precise since there is a ground station that corrects the GPS signal. Having flown a few GPS approaches in the US I wonder if there's any difference in flying a dGPS approach. The few questions I have on my mind are:

Are the minimums lower? Does the approach plate specify a dGPS approach? Is additional equipment needed in the airplane or can dGPS approaches be flown with GA IFR GPS?

LAAS is required...invented in the USA....works good, lasts a long time.:D
The minimums are lower, equivalent (in some cases) to CAT one ILS, and yes the airborne equipment needs to have the ability to receive the LAAS data.

411A - thank you for your never-ending wisdom. ;) Do you know of any dGPS approaches here in the US? My company has the whole US on Jepp, but so far I have not seen any LAAS dGPS approache plates. I have seen MLS' in Alaska - that's the only particular type of approach I have seen.

:D :D :D :D

7 7 7 7

Believe that Minneapolis has approved dGPS approaches, as they have been under trial by NorthWest (I think) and possibly one other location.
In addition, the Garmin 430/530 will be upgradeable to use LAAS, in the future. So far as I know, no other available GPS receiver for general aviation has this feature.
I have used the King KLN89B for six years now and have found that GPS approaches have been VERY accurate here in the western US. The only time that they have not been available is when scheduled "maintenance" is performed by the DOD, but this is published well in advance and is usually for a four hour period just after midnight, local time, and affects a 400nm circle, generally from White Sands, New Mexico or China Lake, California.

411A - I checked St. Paul (MSP) and the only thing that hints towards a dGPS approach is the note that "RNP 0.3" is required. I have seen this also with the ILS approaches into PHL (forgot the terminology), so I am not really sure, what RNP 0.3 really refers to....

To cut a long story short. None of the approaches plates I have seen, indicate that a dGPS approach.

These charts are issued only to the airline conducting the trial approaches.....and you will find RNP 0.3 required for many Stars and a few SIDS, now known as DP's.

RNP = Required Navigation Performance.

0.3 is the accuracy level, in this case .3 'something'. The 'something' is in nm. , I think.

Not sure but I think there is also a probability attached to it as well eg 95% of the time

Quite correct, Tinstaafl...nautical miles. On most installations, this gives full scale deflection on the HSI (during the required phase of flight using STAR's, DP's etc). And the probability is....RAIM must be available at all times.

I was working for the #5 US airline at the time Honeywell was in the testing phase for dGPS equipment.During that time we installed dual dGPS systems into an MD80 type a/c for flight testing and STC approval.The system that we installed in this a/c was capable of CAT III auto-land.During this test flight period, the only ground stations that were in operation were in EWR (our hub) and in MSP (Honeywell's home). Basically what happened was, the approach was surveyed, and when the a/c came in for landing, a VHF data-link would send the exact location of the touch-down zone to the GNSSU. All this was initiated by the a/p control panel selection of APP. The rest is just electronic magic out of anyones control. Hope that helps !