AN ACR MD80 FLC HAD THE ACFT DEPART ITS ASSIGNED ALT THEN WHEN THEY ATTEMPTED TO CLB; IT SUDDENLY PITCHED UP AND OVERSHOT THE ALT. THEY SUSPECT TAIL ICING.
Synopsis
AN ACR MD80 FLC HAD THE ACFT DEPART ITS ASSIGNED ALT THEN WHEN THEY ATTEMPTED TO CLB; IT SUDDENLY PITCHED UP AND OVERSHOT THE ALT. THEY SUSPECT TAIL ICING.
Narrative
ON ARR INTO ORD DURING MODERATE ICING THE ACFT LEFT ALT HOLD AT 300 KTS AND STARTED AN UNCOMMANDED 500-700 FPM DSCNT. I NOTICED AT 10900 FT AND SELECTED 700 FT PITCH UP ON THE VSI. THE ACFT WAS SLOW TO RESPOND AT FIRST; BUT THEN PITCHED UP INTO A 3000 FPM CLB. THE CAPT HAD SELECTED TAIL DEICE AT APPROX THE SAME TIME I SELECTED 700 FT UP ON THE VSI. THE AUTOPLT WAS DISCONNECTED AND I RETURNED THE ACFT BACK DOWN TO 11000 FT; 300-400 FT DEV; CONSIDERABLE FORWARD PRESSURE WAS REQUIRED TO LEVEL THE ACFT; YET IT APPEARED TO BE IN TRIM ONCE LEVEL. SUSPECT ICING ON TAIL EVEN THOUGH WE HAD CYCLED IT AT LEAST 3 TIMES. NO COMMENT FROM APCH. SUPPLEMENTAL INFO FROM ACN 391292: FO PUSHED FORWARD THE SAME TIME I DID AND THE ACFT CLBED TO APPROX 11350 FT BEFORE WE STARTED A DSCNT TO 11000 FT AND LEVELED OFF. APCH DID NOT SAY ANYTHING IF THEY NOTICED. SUSPECT ICING ON TAIL. ADDITION TO PREVIOUS RPT TITLED THE SAME. WE HAD BEEN SELECTING TAIL DEICE EVERY 10 MINS PRIOR TO THE INCIDENT DUE TO THE MODERATE ICING.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.