After takeoff, a D328 first officer experienced wild fluctuations on pitot-static instruments. The c...

Attributes
ACN	326726
Time
Date	199601
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : fnt
State Reference	MI
Altitude	agl bound lower : 0 agl bound upper : 100
Environment
Flight Conditions	Marginal
Light	Night
Aircraft 1
Controlling Facilities	tower : fnt
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : initial climbout : takeoff
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : commercial pilot : instrument pilot : atp
Experience	flight time last 90 days : 100 flight time total : 5000 flight time type : 100
ASRS Report	326726
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other flight crewa
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

After takeoff at about 100 ft AGL, first officer (flying) noticed his airspeed indicator to be erratic and drop to 60 KIAS. My airspeed showed 180 KIAS. First officer's altimeter also was erratic. I took the controls and we made a traffic pattern and returned to the field visually. We stayed VMC, landed uneventfully. We didn't declare an emergency. The dornier 328 has an all- glass cockpit. We believe that the air data computer #2 failed due to ice and freezing rain in pitot-static system. Aircraft was parked overnight outside. This was the 1ST flight of the day. We had snow and freezing rain the night before. Maintenance personnel ran up aircraft and applied heat to system and aircraft was ok later. Callback conversation with reporter revealed the following information: flight crew of the D328 had flown and landed in snow conditions the night before. Pitot tubes and static ports were WX proofed after shutdown, but the captain (reporter) believes that the airplane had residual moisture which froze when the aircraft was cold soaked during the night. Reporter states that this happened to be one of the airports where they did not have the aircraft hangared. In the morning, the aircraft had been deiced and passenger boarded. During the first flight of the day checks, the aural stall warning, initially, was stuck on, but then it operated normally. The stuck stall warning made the reporter well aware of the aircraft's frozen condition. Even though the flight crew received an air data computer (air data computer) fail message, the captain states that the problem was strictly related to the pitot-static information that was sent to the air data computer. The air data computer checked normal during ground test before and after this flight. The problem (wildly fluctuating pitot-static instruments) was recognized by the first officer immediately after takeoff and was called to the captain's attention. After return and landing, maintenance ran the aircraft heat on the APU. After the aircraft was thawed and deiced, all checks were normal. The aircraft was cleared for a ferry flight and there were no further problems.

Original NASA ASRS Text

Title: AFTER TKOF, A D328 FO EXPERIENCED WILD FLUCTUATIONS ON PITOT-STATIC INSTS. THE CAPT TOOK THE CTLS AND THE FLT RETURNED AND LANDED.

Narrative: AFTER TKOF AT ABOUT 100 FT AGL, FO (FLYING) NOTICED HIS AIRSPD INDICATOR TO BE ERRATIC AND DROP TO 60 KIAS. MY AIRSPD SHOWED 180 KIAS. FO'S ALTIMETER ALSO WAS ERRATIC. I TOOK THE CTLS AND WE MADE A TFC PATTERN AND RETURNED TO THE FIELD VISUALLY. WE STAYED VMC, LANDED UNEVENTFULLY. WE DIDN'T DECLARE AN EMER. THE DORNIER 328 HAS AN ALL- GLASS COCKPIT. WE BELIEVE THAT THE AIR DATA COMPUTER #2 FAILED DUE TO ICE AND FREEZING RAIN IN PITOT-STATIC SYS. ACFT WAS PARKED OVERNIGHT OUTSIDE. THIS WAS THE 1ST FLT OF THE DAY. WE HAD SNOW AND FREEZING RAIN THE NIGHT BEFORE. MAINT PERSONNEL RAN UP ACFT AND APPLIED HEAT TO SYS AND ACFT WAS OK LATER. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: FLC OF THE D328 HAD FLOWN AND LANDED IN SNOW CONDITIONS THE NIGHT BEFORE. PITOT TUBES AND STATIC PORTS WERE WX PROOFED AFTER SHUTDOWN, BUT THE CAPT (RPTR) BELIEVES THAT THE AIRPLANE HAD RESIDUAL MOISTURE WHICH FROZE WHEN THE ACFT WAS COLD SOAKED DURING THE NIGHT. RPTR STATES THAT THIS HAPPENED TO BE ONE OF THE ARPTS WHERE THEY DID NOT HAVE THE ACFT HANGARED. IN THE MORNING, THE ACFT HAD BEEN DEICED AND PAX BOARDED. DURING THE FIRST FLT OF THE DAY CHKS, THE AURAL STALL WARNING, INITIALLY, WAS STUCK ON, BUT THEN IT OPERATED NORMALLY. THE STUCK STALL WARNING MADE THE RPTR WELL AWARE OF THE ACFT'S FROZEN CONDITION. EVEN THOUGH THE FLC RECEIVED AN ADC (AIR DATA COMPUTER) FAIL MESSAGE, THE CAPT STATES THAT THE PROB WAS STRICTLY RELATED TO THE PITOT-STATIC INFO THAT WAS SENT TO THE ADC. THE ADC CHKED NORMAL DURING GND TEST BEFORE AND AFTER THIS FLT. THE PROB (WILDLY FLUCTUATING PITOT-STATIC INSTS) WAS RECOGNIZED BY THE FO IMMEDIATELY AFTER TKOF AND WAS CALLED TO THE CAPT'S ATTN. AFTER RETURN AND LNDG, MAINT RAN THE ACFT HEAT ON THE APU. AFTER THE ACFT WAS THAWED AND DEICED, ALL CHKS WERE NORMAL. THE ACFT WAS CLRED FOR A FERRY FLT AND THERE WERE NO FURTHER PROBS.

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.

After takeoff, a D328 first officer experienced wild fluctuations on pitot-static instruments. The captain took the controls and the flight returned and landed.