Pilot of small aircraft on approach to mke had altimeter problem, excursioned from altitude.

Attributes
ACN	194158
Time
Date	199111
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : mke
State Reference	WI
Altitude	msl bound lower : 2600 msl bound upper : 2800
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mke
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Fixed Gear
Flight Phase	descent : approach descent other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : commercial pilot : instrument pilot : atp pilot : cfi
Experience	flight time last 90 days : 300 flight time total : 1945 flight time type : 250
ASRS Report	194158
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : published procedure other spatial deviation
Independent Detector	other other : unspecified cockpit
Resolutory Action	flight crew : overcame equipment problem flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While being vectored on to ILS 19R at mke, a new altitude indicator installed that morning started to give me conflicting information with my other instruments just outside the OM in IMC conditions. While trying to determine which of the instruments was failing I lost 200 ft of altitude and started off course, this was soon corrected and milwaukee approach never said anything, which the deviation was not very great. As I broke out of the clouds at 1200 ft AGL, the aircraft was back on course and altitude with the ILS approach. Once in VFR conditions I then requested to remain VFR and return back to a local airport where the aircraft is based, and it was easily determined upon entering VFR conditions that the altitude indicator had failed.

Original NASA ASRS Text

Title: PLT OF SMA ON APCH TO MKE HAD ALTIMETER PROBLEM, EXCURSIONED FROM ALT.

Narrative: WHILE BEING VECTORED ON TO ILS 19R AT MKE, A NEW ALT INDICATOR INSTALLED THAT MORNING STARTED TO GIVE ME CONFLICTING INFO WITH MY OTHER INSTS JUST OUTSIDE THE OM IN IMC CONDITIONS. WHILE TRYING TO DETERMINE WHICH OF THE INSTS WAS FAILING I LOST 200 FT OF ALT AND STARTED OFF COURSE, THIS WAS SOON CORRECTED AND MILWAUKEE APCH NEVER SAID ANYTHING, WHICH THE DEV WAS NOT VERY GREAT. AS I BROKE OUT OF THE CLOUDS AT 1200 FT AGL, THE ACFT WAS BACK ON COURSE AND ALT WITH THE ILS APCH. ONCE IN VFR CONDITIONS I THEN REQUESTED TO REMAIN VFR AND RETURN BACK TO A LCL ARPT WHERE THE ACFT IS BASED, AND IT WAS EASILY DETERMINED UPON ENTERING VFR CONDITIONS THAT THE ALT INDICATOR HAD FAILED.

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.