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A DC9-30 in cruise at FL330 diverted due to frozen ailerons caused by water penetrating the aileron spoiler mixers then freezing at altitude.
| Attributes | |
| ACN | 546571 |
| Time | |
| Date | 200205 |
| Day | Mon |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : zzz.artcc |
| State Reference | US |
| Altitude | msl single value : 33000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zzz.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | DC-9 30 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Route In Use | enroute airway : zzzz.airway |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : cfi pilot : commercial pilot : atp pilot : multi engine pilot : instrument |
| Experience | flight time last 90 days : 150 flight time total : 7500 flight time type : 2000 |
| ASRS Report | 546571 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Events | |
| Anomaly | aircraft equipment problem : critical other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : autoplt trim servo indicator other flight crewa other flight crewb |
| Resolutory Action | flight crew : diverted to another airport |
| Consequence | other other |
| Supplementary | |
| Problem Areas | Weather Aircraft |
| Primary Problem | Aircraft |
Narrative:
During cruise flight from ZZZ to bos the captain noticed the aileron servo indicator on the autoplt was at full right deflection. The control yoke was at almost neutral so the captain disengaged the autoplt to troubleshoot the servo problem. At this time he discovered that the ailerons were frozen in place. With moderate force we were able to free up the ailerons but they still had a 'heavy ratchety' feel to them. After talking with our company maintenance on the radio we decided to divert to ZZZ1. The remainder of the flight was uneventful except for the 'heavy' feel of the ailerons. After landing company maintenance found evidence of ice and water on the aileron control cables and mixing assembly. Prior to our departure out of ZZZ, the aircraft sat in heavy rain overnight. The water in the cable area was believed to be the cause of the problem. Callback conversation with reporter revealed the following information: the reporter stated the airplane was parked overnight in ZZZ in a heavy rain storm. The reporter said water entered the overwing emergency exit and flowed down into the main wheel well and pooled on the slant panel covering the aileron-spoiler mixers. The reporter stated the protective slant panel had a defective seal which allowed the water to soak the left and right aileron-spoiler mixers. The reporter said at altitude the water froze and locked up the ailerons. The reporter stated that after clearing the water and ice on the ground the airplane operated normally the remainder of the day.
Original NASA ASRS Text
Title: A DC9-30 IN CRUISE AT FL330 DIVERTED DUE TO FROZEN AILERONS CAUSED BY WATER PENETRATING THE AILERON SPOILER MIXERS THEN FREEZING AT ALTITUDE.
Narrative: DURING CRUISE FLT FROM ZZZ TO BOS THE CAPT NOTICED THE AILERON SERVO INDICATOR ON THE AUTOPLT WAS AT FULL RIGHT DEFLECTION. THE CTL YOKE WAS AT ALMOST NEUTRAL SO THE CAPT DISENGAGED THE AUTOPLT TO TROUBLESHOOT THE SERVO PROB. AT THIS TIME HE DISCOVERED THAT THE AILERONS WERE FROZEN IN PLACE. WITH MODERATE FORCE WE WERE ABLE TO FREE UP THE AILERONS BUT THEY STILL HAD A 'HEAVY RATCHETY' FEEL TO THEM. AFTER TALKING WITH OUR COMPANY MAINT ON THE RADIO WE DECIDED TO DIVERT TO ZZZ1. THE REMAINDER OF THE FLT WAS UNEVENTFUL EXCEPT FOR THE 'HEAVY' FEEL OF THE AILERONS. AFTER LNDG COMPANY MAINT FOUND EVIDENCE OF ICE AND WATER ON THE AILERON CTL CABLES AND MIXING ASSEMBLY. PRIOR TO OUR DEP OUT OF ZZZ, THE ACFT SAT IN HEAVY RAIN OVERNIGHT. THE WATER IN THE CABLE AREA WAS BELIEVED TO BE THE CAUSE OF THE PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE AIRPLANE WAS PARKED OVERNIGHT IN ZZZ IN A HEAVY RAIN STORM. THE RPTR SAID WATER ENTERED THE OVERWING EMER EXIT AND FLOWED DOWN INTO THE MAIN WHEEL WELL AND POOLED ON THE SLANT PANEL COVERING THE AILERON-SPOILER MIXERS. THE RPTR STATED THE PROTECTIVE SLANT PANEL HAD A DEFECTIVE SEAL WHICH ALLOWED THE WATER TO SOAK THE L AND R AILERON-SPOILER MIXERS. THE RPTR SAID AT ALTITUDE THE WATER FROZE AND LOCKED UP THE AILERONS. THE RPTR STATED THAT AFTER CLEARING THE WATER AND ICE ON THE GND THE AIRPLANE OPERATED NORMALLY THE REMAINDER OF THE DAY.
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.