The pilot of a C-421C received two altitude alert warnings while flying the RNAV (GPS) 17 approach t...

Narrative:

There was some confusion about what minimum altitude I should be maintaining during the RNAV (GPS) 17 approach to see. While inbound between asixy and jugal I received a low altitude alert from the tower when I was level at 2;400. The tower then asked whether I was inside asixy. I had crossed asixy at 5;000 so I was well inside before reaching 2;400. Then after jugal I descended following the virtual glide slope provided by my GPS. At some point I received another low altitude warning from the tower saying that the 'MDA' was 1;620. This confused me because the MDA (with the tower operating) is 1;440. The airport came into sight shortly after that and I asked the tower what MDA they were referring to. After a little conversation (the airspace was quiet at the time) the tower referred me to the 1;620 restriction at tomty.on the FAA charts this restriction is fairly obvious; but on the commercially prepared charts that I was using it is a bit off to the side and looks more like a footnote. Since I was following the glide slope after jugal I wasn't focused on the restriction at tomty I actually don't think I was and that it was once again some kind of lag on the radar; but my point is that on the commercially prepared charts it is easy to miss that this is an additional crossing restriction. It was only after the tower pointed it out and I carefully reviewed the chart and the footnotes that I realized that was what the 1;620 on that chart was referring to. This is quite different on the FAA chart.

Original NASA ASRS Text

Title: The pilot of a C-421C received two altitude alert warnings while flying the RNAV (GPS) 17 approach to SEE. Neither warning seemed appropriate to the reporter as the aircraft was in the appropriate vertical and lateral position in each case.

Narrative: There was some confusion about what minimum altitude I should be maintaining during the RNAV (GPS) 17 approach to SEE. While inbound between ASIXY and JUGAL I received a low altitude alert from the Tower when I was level at 2;400. The Tower then asked whether I was inside ASIXY. I had crossed ASIXY at 5;000 so I was well inside before reaching 2;400. Then after JUGAL I descended following the virtual glide slope provided by my GPS. At some point I received another low altitude warning from the Tower saying that the 'MDA' was 1;620. This confused me because the MDA (with the Tower operating) is 1;440. The airport came into sight shortly after that and I asked the Tower what MDA they were referring to. After a little conversation (the airspace was quiet at the time) the Tower referred me to the 1;620 restriction at TOMTY.On the FAA charts this restriction is fairly obvious; but on the commercially prepared charts that I was using it is a bit off to the side and looks more like a footnote. Since I was following the glide slope after JUGAL I wasn't focused on the restriction at TOMTY I actually don't think I was and that it was once again some kind of lag on the radar; but my point is that on the commercially prepared charts it is easy to miss that this is an additional crossing restriction. It was only after the Tower pointed it out and I carefully reviewed the chart and the footnotes that I realized that was what the 1;620 on that chart was referring to. This is quite different on the FAA chart.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	945386
Time
Date	201104
Local Time Of Day	1201-1800
Place
Locale Reference	SEE.Airport
State Reference	CA
Aircraft 1
Make Model Name	Golden Eagle 421
Operating Under FAR Part	Part 91
Flight Phase	Final Approach
Flight Plan	IFR
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Commercial Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 40 Flight Crew Total 1800 Flight Crew Type 500
Events
Anomaly	ATC Issue All Types Deviation - Altitude Crossing Restriction Not Met Deviation - Procedural Published Material / Policy

The pilot of a C-421C received two altitude alert warnings while flying the RNAV (GPS) 17 approach to see. Neither warning seemed appropriate to the reporter as the aircraft was in the appropriate vertical and lateral position in each case.