Light single engine aircraft suffers vacuum pump failure in IMC.

Attributes
ACN	127066
Time
Date	198910
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : hou
State Reference	TX
Altitude	msl bound lower : 13000 msl bound upper : 13000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zhu
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Retractable Gear
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private pilot : instrument
Experience	flight time last 90 days : 25 flight time total : 3000 flight time type : 2000
ASRS Report	127066
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	flight crew : declared emergency flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

Problem: on oct/xx/89 I flew my just purchased 1977 small aircraft X from chino, ca to houston, tx. It had a fresh annual and was IFR current. While cruising in building cumulus clouds, turbulence, and rain, my vacuum pump became a little weak, then failed. Observations: #1 - the dg and artificial horizon appeared to be sluggish for about 30 mins before the artificial horizon spun and died while in turbulence. The vacuum gauge indicator varied from the lowest end of the green range to just below the green range. #2 - it took a second or two to determine if I had lost a vacuum pump while flying in turbulence because of the jostling of the aircraft in zero visibility. #3 - the autoplt automatically disengaged. Comments: #1 - I have never heard of that weak period before failure I thought it possibly was a dirty filter or pinched line. If a needle ever drops just out of, then goes back into that safe green ranges, does that indicate a pending failure? Would it be possible to develop a pre-failure sensor, possibly a temperature sensor on the vacuum pump? My equipment failure was due to a sheared vacuum pump shaft. I am sure it must have gotten hotter than normal before failure.

Original NASA ASRS Text

Title: LIGHT SINGLE ENGINE ACFT SUFFERS VACUUM PUMP FAILURE IN IMC.

Narrative: PROBLEM: ON OCT/XX/89 I FLEW MY JUST PURCHASED 1977 SMA X FROM CHINO, CA TO HOUSTON, TX. IT HAD A FRESH ANNUAL AND WAS IFR CURRENT. WHILE CRUISING IN BUILDING CUMULUS CLOUDS, TURBULENCE, AND RAIN, MY VACUUM PUMP BECAME A LITTLE WEAK, THEN FAILED. OBSERVATIONS: #1 - THE DG AND ARTIFICIAL HORIZON APPEARED TO BE SLUGGISH FOR ABOUT 30 MINS BEFORE THE ARTIFICIAL HORIZON SPUN AND DIED WHILE IN TURBULENCE. THE VACUUM GAUGE INDICATOR VARIED FROM THE LOWEST END OF THE GREEN RANGE TO JUST BELOW THE GREEN RANGE. #2 - IT TOOK A SECOND OR TWO TO DETERMINE IF I HAD LOST A VACUUM PUMP WHILE FLYING IN TURBULENCE BECAUSE OF THE JOSTLING OF THE ACFT IN ZERO VISIBILITY. #3 - THE AUTOPLT AUTOMATICALLY DISENGAGED. COMMENTS: #1 - I HAVE NEVER HEARD OF THAT WEAK PERIOD BEFORE FAILURE I THOUGHT IT POSSIBLY WAS A DIRTY FILTER OR PINCHED LINE. IF A NEEDLE EVER DROPS JUST OUT OF, THEN GOES BACK INTO THAT SAFE GREEN RANGES, DOES THAT INDICATE A PENDING FAILURE? WOULD IT BE POSSIBLE TO DEVELOP A PRE-FAILURE SENSOR, POSSIBLY A TEMPERATURE SENSOR ON THE VACUUM PUMP? MY EQUIPMENT FAILURE WAS DUE TO A SHEARED VACUUM PUMP SHAFT. I AM SURE IT MUST HAVE GOTTEN HOTTER THAN NORMAL BEFORE FAILURE.

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.