All time error noted when warning horn sounded and airspeed indicator became erratic. Pilot deduced ...

Attributes
ACN	199019
Time
Date	199201
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : eno
State Reference	DE
Altitude	msl bound lower : 6000 msl bound upper : 8000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : dov
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 : instrument pilot : commercial
Experience	flight time last 90 days : 49 flight time total : 4090 flight time type : 1796
ASRS Report	199019
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude inflight encounter other
Independent Detector	other other : unspecified cockpit
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

WX VFR with a brief climb through snow flurries to the assigned altitude of 6000. Conditions 10 NM north of eno were VFR and cavu. Just before arriving over eno, a warning horn began sounding and continued to sound... I assumed it was the gear warning horn. It was perplexing because I had not retarded the throttle. In scanning the panel, I noticed my airspeed indicator showed a much higher speed than was possible. This led me to believe I had a static air problem. I engaged the alternate static air source and immediately the altitude jumped to 8000 and the warning horn stopped sounding. I immediately contacted dover approach and advised them that I had a static air problem and that after engaging the alternate static air source, my altimeter suddenly read 8000. Dover approach confirmed at this time that they also read my altitude at 8000. I announced that I would descend to 6000 with dover's approval and did so. Contributing factors: tuesday night was a howler in the wilmington-philadelphia area with high and gusty winds and rain. Wednesday morning was bright and very cold with a brisk southwest wind. The climb to 6000 brought me into very cold air...10 degrees centigrade. I imagine that some water must have gotten into the static system and froze in the very cold air. In the preflight inspection I drained the 2 static system drains but no water was released...this was not surprising since it was very cold and never in the past had any water been released on draining the static system.

Original NASA ASRS Text

Title: ALL TIME ERROR NOTED WHEN WARNING HORN SOUNDED AND AIRSPD INDICATOR BECAME ERRATIC. PLT DEDUCED STATIC LINE PROBLEM. SWITCHED TO ALTERNATE STATIC. INSTS BACK TO NORMAL. RECOVERED 6000 CRUISE ALT.

Narrative: WX VFR WITH A BRIEF CLB THROUGH SNOW FLURRIES TO THE ASSIGNED ALT OF 6000. CONDITIONS 10 NM N OF ENO WERE VFR AND CAVU. JUST BEFORE ARRIVING OVER ENO, A WARNING HORN BEGAN SOUNDING AND CONTINUED TO SOUND... I ASSUMED IT WAS THE GEAR WARNING HORN. IT WAS PERPLEXING BECAUSE I HAD NOT RETARDED THE THROTTLE. IN SCANNING THE PANEL, I NOTICED MY AIRSPD INDICATOR SHOWED A MUCH HIGHER SPD THAN WAS POSSIBLE. THIS LED ME TO BELIEVE I HAD A STATIC AIR PROBLEM. I ENGAGED THE ALTERNATE STATIC AIR SOURCE AND IMMEDIATELY THE ALT JUMPED TO 8000 AND THE WARNING HORN STOPPED SOUNDING. I IMMEDIATELY CONTACTED DOVER APCH AND ADVISED THEM THAT I HAD A STATIC AIR PROBLEM AND THAT AFTER ENGAGING THE ALTERNATE STATIC AIR SOURCE, MY ALTIMETER SUDDENLY READ 8000. DOVER APCH CONFIRMED AT THIS TIME THAT THEY ALSO READ MY ALT AT 8000. I ANNOUNCED THAT I WOULD DSND TO 6000 WITH DOVER'S APPROVAL AND DID SO. CONTRIBUTING FACTORS: TUESDAY NIGHT WAS A HOWLER IN THE WILMINGTON-PHILADELPHIA AREA WITH HIGH AND GUSTY WINDS AND RAIN. WEDNESDAY MORNING WAS BRIGHT AND VERY COLD WITH A BRISK SW WIND. THE CLB TO 6000 BROUGHT ME INTO VERY COLD AIR...10 DEGS CENTIGRADE. I IMAGINE THAT SOME WATER MUST HAVE GOTTEN INTO THE STATIC SYS AND FROZE IN THE VERY COLD AIR. IN THE PREFLT INSPECTION I DRAINED THE 2 STATIC SYS DRAINS BUT NO WATER WAS RELEASED...THIS WAS NOT SURPRISING SINCE IT WAS VERY COLD AND NEVER IN THE PAST HAD ANY WATER BEEN RELEASED ON DRAINING THE STATIC SYS.

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.

All time error noted when warning horn sounded and airspeed indicator became erratic. Pilot deduced static line problem. Switched to alternate static. Instruments back to normal. Recovered 6000 cruise altitude.