Pitot icing, no airspeed indicator.

Attributes
ACN	100889
Time
Date	198812
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : emt
State Reference	CA
Altitude	msl bound lower : 4500 msl bound upper : 11000
Environment
Flight Conditions	Mixed
Light	Dusk
Aircraft 1
Controlling Facilities	tracon : bur tower : ewr
Operator	common carrier : air taxi
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Retractable Gear
Flight Phase	cruise other descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : cfi pilot : commercial
Experience	flight time last 90 days : 200 flight time total : 2300 flight time type : 50
ASRS Report	100889
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : overcame equipment problem flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

I was flying IFR from bakersfield to el monte when my airspeed indicator failed probably due to icing. Preflight had shown a hot pitot static system and I was flying with the pitot heat on. There was only about an eighth inch of ice on the wings and I was descending down towards VFR conditions. A couple of minutes later I was in moderate turbulence making it hard to read the altitude indicator. ATC asked if I was declaring an emergency. I did and received special handling for a couple of minutes until I was VFR underneath (about 4500). I continued on to el monte VFR. Callback conversation with reporter revealed the following: reporter states after pushing mechanics to check further, learned pitot heat can be partially functioning and give the impression of heat on preflight check. In such a situation heat is not great enough to prevent in severe icing conditions. Reporter knows now to let pitot really heat up during preflight to assure full function. No FAA followup.

Original NASA ASRS Text

Title: PITOT ICING, NO AIRSPEED INDICATOR.

Narrative: I WAS FLYING IFR FROM BAKERSFIELD TO EL MONTE WHEN MY AIRSPEED INDICATOR FAILED PROBABLY DUE TO ICING. PREFLT HAD SHOWN A HOT PITOT STATIC SYSTEM AND I WAS FLYING WITH THE PITOT HEAT ON. THERE WAS ONLY ABOUT AN EIGHTH INCH OF ICE ON THE WINGS AND I WAS DSNDING DOWN TOWARDS VFR CONDITIONS. A COUPLE OF MINUTES LATER I WAS IN MODERATE TURB MAKING IT HARD TO READ THE ALT INDICATOR. ATC ASKED IF I WAS DECLARING AN EMER. I DID AND RECEIVED SPECIAL HANDLING FOR A COUPLE OF MINUTES UNTIL I WAS VFR UNDERNEATH (ABOUT 4500). I CONTINUED ON TO EL MONTE VFR. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: REPORTER STATES AFTER PUSHING MECHANICS TO CHECK FURTHER, LEARNED PITOT HEAT CAN BE PARTIALLY FUNCTIONING AND GIVE THE IMPRESSION OF HEAT ON PREFLT CHECK. IN SUCH A SITUATION HEAT IS NOT GREAT ENOUGH TO PREVENT IN SEVERE ICING CONDITIONS. REPORTER KNOWS NOW TO LET PITOT REALLY HEAT UP DURING PREFLT TO ASSURE FULL FUNCTION. NO FAA FOLLOWUP.

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.