Small aircraft pilot on approach uses GPS for distance but has it set on VOR instead of airport. Believing he has a false GS he descends. He is given a low alert by the controller. A go around follows with second approach correct.

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Attributes
ACN	390497
Time
Date	199801
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : sac
State Reference	CA
Altitude	msl bound lower : 1000 msl bound upper : 1400
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mcc tower : sac artcc : zau
Operator	general aviation : corporate
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : cfi pilot : atp
Experience	flight time last 90 days : 36 flight time total : 2600 flight time type : 187
ASRS Report	390497
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	non adherence : published procedure non adherence : clearance other anomaly other
Independent Detector	atc equipment other atc equipment : unspecified
Resolutory Action	flight crew : returned to intended course or assigned course other other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I used the GPS for distance information when it was set for the VOR instead of the airport. Thinking that I was too high and having a 'false' GS I descended under the minimum altitude. Being 1.5-2 mi from the VOR but thinking it's the airport I descended down to 1000 ft. I was supposed to stay at 1400 ft until reaching the VOR. ATC advised of low altitude. I made a go around and changed the GPS for the airport instead. And I used the DME for distance information which I should have done in the first place. The second approach went without any problems. Callback conversation with reporter revealed the following information: reporter states that he felt very embarrassed when he realized his error. He just knew things were not right on the first approach and had to review his procedures to discover the problem. He is very pleased with GPS use and feels it is very helpful for navigation and very precise. It had malfunctioned twice when there was heavy rain and static along with turbulence. The card was removed, cleaned and replaced in-flight then worked ok. The aircraft is in for an annual currently and he has requested a check of the GPS.

Original NASA ASRS Text

Title: SMA PLT ON APCH USES GPS FOR DISTANCE BUT HAS IT SET ON VOR INSTEAD OF ARPT. BELIEVING HE HAS A FALSE GS HE DSNDS. HE IS GIVEN A LOW ALERT BY THE CTLR. A GAR FOLLOWS WITH SECOND APCH CORRECT.

Narrative: I USED THE GPS FOR DISTANCE INFO WHEN IT WAS SET FOR THE VOR INSTEAD OF THE ARPT. THINKING THAT I WAS TOO HIGH AND HAVING A 'FALSE' GS I DSNDED UNDER THE MINIMUM ALT. BEING 1.5-2 MI FROM THE VOR BUT THINKING IT'S THE ARPT I DSNDED DOWN TO 1000 FT. I WAS SUPPOSED TO STAY AT 1400 FT UNTIL REACHING THE VOR. ATC ADVISED OF LOW ALT. I MADE A GAR AND CHANGED THE GPS FOR THE ARPT INSTEAD. AND I USED THE DME FOR DISTANCE INFO WHICH I SHOULD HAVE DONE IN THE FIRST PLACE. THE SECOND APCH WENT WITHOUT ANY PROBS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT HE FELT VERY EMBARRASSED WHEN HE REALIZED HIS ERROR. HE JUST KNEW THINGS WERE NOT RIGHT ON THE FIRST APCH AND HAD TO REVIEW HIS PROCS TO DISCOVER THE PROB. HE IS VERY PLEASED WITH GPS USE AND FEELS IT IS VERY HELPFUL FOR NAV AND VERY PRECISE. IT HAD MALFUNCTIONED TWICE WHEN THERE WAS HVY RAIN AND STATIC ALONG WITH TURB. THE CARD WAS REMOVED, CLEANED AND REPLACED INFLT THEN WORKED OK. THE ACFT IS IN FOR AN ANNUAL CURRENTLY AND HE HAS REQUESTED A CHK OF THE GPS.

Data retrieved from NASA's ASRS site as of July 2007 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.