Narrative:

I was cruising at 9000 ft MSL 25 mi east of milwaukee, IFR. As I was scanning, I noticed the artificial horizon FLIP over and with the autoplt on, the aircraft started to bank. I immediately turned autoplt off and stabilized aircraft using turn and bank instrument, vsi, and magnetic compass. I checked suction gauge and that showed zero. I called milwaukee approach and told them I had a vacuum pump failure and would like to descend down to 6000 ft. (From listening to ATIS, they had reported ceilings at 6500 ft scattered.) the controller cleared me to 6000 ft and asked me to turn to a heading of 240 degrees from 315 degrees. I was flying now to avoid some light rain showers about 10 mi wide. I think he was trying to increase my chances of getting to VFR conditions. I started to descend and turned left into a standard rate turn to new heading 240 degrees. This is when I started getting pitched around from turbulence and clouds, I pulled power back to 15 inches manifold and asked mke to help me out with the heading because the magnetic compass was flopping all over the place, and my descent was getting a little fast. I guess another controller who was a pilot took over my situation. He advised me to forget about heading and level wings and descend to VFR maintain 3000 ft MSL, which I did. I broke out at about 5000 ft MSL went down to 4500 ft MSL and finished flight to fld, VFR. My advice to anyone who ever has this problem is to descend to VFR at present heading if possible and advise ATC of what instruments are out. If you do have to change headings, stop descent and do heading change at standard rate turns. It's very difficult to keep everything under control with half your instruments gone and getting bumped around in clouds.

Related reports:

Google
 

Original NASA ASRS Text

Title: A PIPER ARROW VACUUM PUMP FAILED IN IMC. THE PLT EXPERIENCED FLT ATTITUDE PROBS DURING VECTOR AND DSCNT COMPLIANCE. APCH CTLR INTERVENTION.

Narrative: I WAS CRUISING AT 9000 FT MSL 25 MI E OF MILWAUKEE, IFR. AS I WAS SCANNING, I NOTICED THE ARTIFICIAL HORIZON FLIP OVER AND WITH THE AUTOPLT ON, THE ACFT STARTED TO BANK. I IMMEDIATELY TURNED AUTOPLT OFF AND STABILIZED ACFT USING TURN AND BANK INST, VSI, AND MAGNETIC COMPASS. I CHKED SUCTION GAUGE AND THAT SHOWED ZERO. I CALLED MILWAUKEE APCH AND TOLD THEM I HAD A VACUUM PUMP FAILURE AND WOULD LIKE TO DSND DOWN TO 6000 FT. (FROM LISTENING TO ATIS, THEY HAD RPTED CEILINGS AT 6500 FT SCATTERED.) THE CTLR CLRED ME TO 6000 FT AND ASKED ME TO TURN TO A HDG OF 240 DEGS FROM 315 DEGS. I WAS FLYING NOW TO AVOID SOME LIGHT RAIN SHOWERS ABOUT 10 MI WIDE. I THINK HE WAS TRYING TO INCREASE MY CHANCES OF GETTING TO VFR CONDITIONS. I STARTED TO DSND AND TURNED L INTO A STANDARD RATE TURN TO NEW HDG 240 DEGS. THIS IS WHEN I STARTED GETTING PITCHED AROUND FROM TURB AND CLOUDS, I PULLED PWR BACK TO 15 INCHES MANIFOLD AND ASKED MKE TO HELP ME OUT WITH THE HDG BECAUSE THE MAGNETIC COMPASS WAS FLOPPING ALL OVER THE PLACE, AND MY DSCNT WAS GETTING A LITTLE FAST. I GUESS ANOTHER CTLR WHO WAS A PLT TOOK OVER MY SIT. HE ADVISED ME TO FORGET ABOUT HDG AND LEVEL WINGS AND DSND TO VFR MAINTAIN 3000 FT MSL, WHICH I DID. I BROKE OUT AT ABOUT 5000 FT MSL WENT DOWN TO 4500 FT MSL AND FINISHED FLT TO FLD, VFR. MY ADVICE TO ANYONE WHO EVER HAS THIS PROB IS TO DSND TO VFR AT PRESENT HDG IF POSSIBLE AND ADVISE ATC OF WHAT INSTS ARE OUT. IF YOU DO HAVE TO CHANGE HDGS, STOP DSCNT AND DO HDG CHANGE AT STANDARD RATE TURNS. IT'S VERY DIFFICULT TO KEEP EVERYTHING UNDER CTL WITH HALF YOUR INSTS GONE AND GETTING BUMPED AROUND IN CLOUDS.

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.