GA small aircraft altitude deviation overshot during IAP ILS approach.

Attributes
ACN	132405
Time
Date	198912
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dwh
State Reference	TX
Altitude	agl bound lower : 150 agl bound upper : 350
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : iah tracon : bos
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Retractable Gear
Flight Phase	descent : approach landing other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : private
Experience	flight time last 90 days : 56 flight time total : 350 flight time type : 290
ASRS Report	132405
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : published procedure non adherence : clearance other spatial deviation
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Cleared for the approach, on localizer, FAF inbound. Descended to MDA and leveled off. Ceiling ragged with 0 forward visibility, but occasional glimpses of lights or ground. Inadvertently descended below MDA (350' AGL) while fighting turbulence and trying to stay on localizer while going from instruments to outside searching for airport. After catching descent at 150' AGL (300' MSL), climbed back to MDA. Broke into open, spotted the airport. Normal descent from MDA and landing. A major contributing factor was probably fatigue; I'd already logged 9.3 hours of flight during the 11 hours since I started out. The last 2.3 hours had been IMC and the last 1.3 had been at night.

Original NASA ASRS Text

Title: GA SMA ALT DEVIATION OVERSHOT DURING IAP ILS APCH.

Narrative: CLRED FOR THE APCH, ON LOC, FAF INBND. DSNDED TO MDA AND LEVELED OFF. CEILING RAGGED WITH 0 FORWARD VISIBILITY, BUT OCCASIONAL GLIMPSES OF LIGHTS OR GND. INADVERTENTLY DSNDED BELOW MDA (350' AGL) WHILE FIGHTING TURB AND TRYING TO STAY ON LOC WHILE GOING FROM INSTRUMENTS TO OUTSIDE SEARCHING FOR ARPT. AFTER CATCHING DSCNT AT 150' AGL (300' MSL), CLBED BACK TO MDA. BROKE INTO OPEN, SPOTTED THE ARPT. NORMAL DSCNT FROM MDA AND LNDG. A MAJOR CONTRIBUTING FACTOR WAS PROBABLY FATIGUE; I'D ALREADY LOGGED 9.3 HRS OF FLT DURING THE 11 HRS SINCE I STARTED OUT. THE LAST 2.3 HRS HAD BEEN IMC AND THE LAST 1.3 HAD BEEN AT NIGHT.

Data retrieved from NASA's ASRS site as of August 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.