Pilot of a C210 descended below the GS outside of the outer marker causing an altitude alert from ap...

Attributes
ACN	424505
Time
Date	199901
Day	Thu
Local Time Of Day	1201 To 1800
Place
State Reference	IA
Altitude	msl bound lower : 2300 msl bound upper : 2600
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : yum
Operator	general aviation : personal
Make Model Name	Cessna 210 Centurion / Turbo Centurion 210C, 210D
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : cfi pilot : commercial
Experience	flight time last 90 days : 80 flight time total : 1500 flight time type : 500
ASRS Report	424505
Person 2
Affiliation	government : faa
Function	controller : approach
Events
Anomaly	inflight encounter : weather other anomaly other other spatial deviation
Independent Detector	other controllera
Resolutory Action	other
Consequence	Other
Supplementary
Air Traffic Incident	Pilot Deviation

Narrative:

My destination became impossible due to snow, so I requested vectors to my alternate, which was near minimums (unforecast). I was vectored onto the localizer and for some reason, misread the GS indicator and thought I was inside the OM when I was still outside. I started to descend and was 300 ft below GS at the marker when ATC called 'low altitude alert,' at which time I corrected and landed uneventfully. The combination of disappointment on not being able to make my destination, plus ATC's request to keep 'best forward speed to the marker' overloaded me. I should have went 'missed' and refocused. Although I am instrument current and proficient, I was not mentally prepared to fly an approach at that moment, a critical requirement. Flying any instrument approach requires a great deal of concentration and mental self-discipline -- especially when transitioning from cruise flight.

Original NASA ASRS Text

Title: PLT OF A C210 DSNDED BELOW THE GS OUTSIDE OF THE OUTER MARKER CAUSING AN ALT ALERT FROM APCH CTLR. PLT THEN RECOGNIZED HIS EARLY DSCNT AND CLBED BACK TO THE OM ALT COMPLETING THE ILS APCH SUCCESSFULLY.

Narrative: MY DEST BECAME IMPOSSIBLE DUE TO SNOW, SO I REQUESTED VECTORS TO MY ALTERNATE, WHICH WAS NEAR MINIMUMS (UNFORECAST). I WAS VECTORED ONTO THE LOC AND FOR SOME REASON, MISREAD THE GS INDICATOR AND THOUGHT I WAS INSIDE THE OM WHEN I WAS STILL OUTSIDE. I STARTED TO DSND AND WAS 300 FT BELOW GS AT THE MARKER WHEN ATC CALLED 'LOW ALT ALERT,' AT WHICH TIME I CORRECTED AND LANDED UNEVENTFULLY. THE COMBINATION OF DISAPPOINTMENT ON NOT BEING ABLE TO MAKE MY DEST, PLUS ATC'S REQUEST TO KEEP 'BEST FORWARD SPD TO THE MARKER' OVERLOADED ME. I SHOULD HAVE WENT 'MISSED' AND REFOCUSED. ALTHOUGH I AM INST CURRENT AND PROFICIENT, I WAS NOT MENTALLY PREPARED TO FLY AN APCH AT THAT MOMENT, A CRITICAL REQUIREMENT. FLYING ANY INST APCH REQUIRES A GREAT DEAL OF CONCENTRATION AND MENTAL SELF-DISCIPLINE -- ESPECIALLY WHEN TRANSITIONING FROM CRUISE FLT.

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.

Pilot of a C210 descended below the GS outside of the outer marker causing an altitude alert from approach controller. Pilot then recognized his early descent and climbed back to the OM altitude completing the ILS approach successfully.