Medium large transport pitot static system iced up causing loss of captain's speed rate instruments,...

Attributes
ACN	301406
Time
Date	199504
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : sgf
State Reference	MO
Altitude	msl bound lower : 33000 msl bound upper : 33000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zme
Operator	common carrier : air carrier
Make Model Name	Fokker 100
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	301406
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : critical inflight encounter : weather other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : exited adverse environment other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Engine vibration/pitot static system icing. While IMC at FL330 in navigation/prof a compare speed alert appeared on the lhmfdu. The captain's airspeed, vertical speed indicator and #1 EPR became extremely erratic. The #1 autothrottle, yaw damper, rudder lateral and stabilizer trim faulted. The first officer and standby instruments indicated normal. The PF (first officer) disconnected the autothrottle and matched N1, N2, and turbine gas temperature to provide the required thrust to maintain airspeed. The #2 autoplt was not disconnected. Approximately 5 mins after the #1 pitot static system iced up, a #2 engine vibration alert appeared on the lhmfdu with a noticeable vibration in the airframe. The #2 engine was retarded to idle. No other failure indications were noted. We started a descent and attempted to leave icing conditions. During descent in icing conditions, but at a warmer temperature, captain's flight instruments returned to normal. A decision was made to divert to sgf due to icing conditions associated with a large WX system that made continuation at lower flight level to destination impossible. Below 15000 ft engine vibrations dissipated. All system were turned back on and utilized. A 2-ENG ILS approach to an uneventful landing was made at sgf.

Original NASA ASRS Text

Title: MLG PITOT STATIC SYS ICED UP CAUSING LOSS OF CAPT'S SPD RATE INSTS, 1 ENG ERRATIC EPR INDICATION AND ENG VIBRATION.

Narrative: ENG VIBRATION/PITOT STATIC SYS ICING. WHILE IMC AT FL330 IN NAV/PROF A COMPARE SPD ALERT APPEARED ON THE LHMFDU. THE CAPT'S AIRSPD, VERT SPD INDICATOR AND #1 EPR BECAME EXTREMELY ERRATIC. THE #1 AUTOTHROTTLE, YAW DAMPER, RUDDER LATERAL AND STABILIZER TRIM FAULTED. THE FO AND STANDBY INSTS INDICATED NORMAL. THE PF (FO) DISCONNECTED THE AUTOTHROTTLE AND MATCHED N1, N2, AND TURBINE GAS TEMP TO PROVIDE THE REQUIRED THRUST TO MAINTAIN AIRSPD. THE #2 AUTOPLT WAS NOT DISCONNECTED. APPROX 5 MINS AFTER THE #1 PITOT STATIC SYS ICED UP, A #2 ENG VIBRATION ALERT APPEARED ON THE LHMFDU WITH A NOTICEABLE VIBRATION IN THE AIRFRAME. THE #2 ENG WAS RETARDED TO IDLE. NO OTHER FAILURE INDICATIONS WERE NOTED. WE STARTED A DSCNT AND ATTEMPTED TO LEAVE ICING CONDITIONS. DURING DSCNT IN ICING CONDITIONS, BUT AT A WARMER TEMP, CAPT'S FLT INSTS RETURNED TO NORMAL. A DECISION WAS MADE TO DIVERT TO SGF DUE TO ICING CONDITIONS ASSOCIATED WITH A LARGE WX SYS THAT MADE CONTINUATION AT LOWER FLT LEVEL TO DEST IMPOSSIBLE. BELOW 15000 FT ENG VIBRATIONS DISSIPATED. ALL SYS WERE TURNED BACK ON AND UTILIZED. A 2-ENG ILS APCH TO AN UNEVENTFUL LNDG WAS MADE AT SGF.

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.

Medium large transport pitot static system iced up causing loss of captain's speed rate instruments, 1 engine erratic EPR indication and engine vibration.