Narrative:

After installation of new transponder, overhauled T&B and altimeter (with built-in encoder) and bi-annual static system certification, I test flew aircraft on 11/mon/89 from ads to/from 10E. Altimeter read 30.12 on ground for 643 ads elevation, but ATIS said 30.03. In air at 1850', ads reported encoder said 1700'. Told electronics tech after flight, who said altimeter was right on setting when installed. Flew plane home that evening, no problem. Took off from tko on 11/thu/89 on runway 17. Climbed to 3000'. Saw altimeter stuck at 2100' with 800 FPM rate of climb after entering solid 1400' overcast. Then told controller altimeter just overhauled, now stuck, and asked his encoder reading. Was about 2900', I think. I told departure that I wanted descent on west heading to break back into 1400' overcast VFR and return to tki. He said to turn to 350 degrees and down to 2000'. I said 'ok, 350 degrees, descending 500 FPM, and altimeter totally useless.' broke out at 1400', 2 mi west of radio tower. Flight to ads electronics shop on 11/sun/89 had altimeter at field setting (tki=580'). Was 29.30' and stayed stuck at 580', even though ads tower said en route that encoder reported 2500'. Lessons: 1) pay attention to all symptoms, not just those that are foremost on your mind. In this case, I had replaced a marginal transponder. 2) the redundancy in a twin (engines, alternators, etc) is incomplete if you don't have 2 altimeters. In 45 yrs of flying (10 military), I never saw a stuck altimeter.

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Original NASA ASRS Text

Title: GA SMA PLT DISCOVERED A STUCK ALTIMETER WHILE ON IFR DEP IN IMC. RECEIVED DESCENT VECTORS UNTIL CLEAR OF OVERCAST.

Narrative: AFTER INSTALLATION OF NEW XPONDER, OVERHAULED T&B AND ALTIMETER (WITH BUILT-IN ENCODER) AND BI-ANNUAL STATIC SYS CERTIFICATION, I TEST FLEW ACFT ON 11/MON/89 FROM ADS TO/FROM 10E. ALTIMETER READ 30.12 ON GND FOR 643 ADS ELEVATION, BUT ATIS SAID 30.03. IN AIR AT 1850', ADS RPTED ENCODER SAID 1700'. TOLD ELECTRONICS TECH AFTER FLT, WHO SAID ALTIMETER WAS RIGHT ON SETTING WHEN INSTALLED. FLEW PLANE HOME THAT EVENING, NO PROB. TOOK OFF FROM TKO ON 11/THU/89 ON RWY 17. CLBED TO 3000'. SAW ALTIMETER STUCK AT 2100' WITH 800 FPM RATE OF CLB AFTER ENTERING SOLID 1400' OVCST. THEN TOLD CTLR ALTIMETER JUST OVERHAULED, NOW STUCK, AND ASKED HIS ENCODER READING. WAS ABOUT 2900', I THINK. I TOLD DEP THAT I WANTED DSCNT ON W HDG TO BREAK BACK INTO 1400' OVCST VFR AND RETURN TO TKI. HE SAID TO TURN TO 350 DEGS AND DOWN TO 2000'. I SAID 'OK, 350 DEGS, DSNDING 500 FPM, AND ALTIMETER TOTALLY USELESS.' BROKE OUT AT 1400', 2 MI W OF RADIO TWR. FLT TO ADS ELECTRONICS SHOP ON 11/SUN/89 HAD ALTIMETER AT FIELD SETTING (TKI=580'). WAS 29.30' AND STAYED STUCK AT 580', EVEN THOUGH ADS TWR SAID ENRTE THAT ENCODER RPTED 2500'. LESSONS: 1) PAY ATTN TO ALL SYMPTOMS, NOT JUST THOSE THAT ARE FOREMOST ON YOUR MIND. IN THIS CASE, I HAD REPLACED A MARGINAL XPONDER. 2) THE REDUNDANCY IN A TWIN (ENGS, ALTERNATORS, ETC) IS INCOMPLETE IF YOU DON'T HAVE 2 ALTIMETERS. IN 45 YRS OF FLYING (10 MIL), I NEVER SAW A STUCK ALTIMETER.

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.