Narrative:

My colleague, mr X, and I decided we would share an incident that occurred during an small aircraft flight in the hope that this experience might shed light on your investigation of small aircraft in-flight breakups. Prior to last summer, we both plted a corporate owned 1984 aircraft for a new jersey based company. The chief executive officer, a relatively low time VFR rated pilot at the time of the incident, usually flew in the cockpit with one of us in order to obtain instrument training. Since I was not on board during the flight in question, I am sure I will miss some of the details. However, the story related to me this evening by mr X is as follows: the ceo was manually flying the airplane during cruise flight in icing conditions. The instructor, mr X, noticed that the flying pilot was repeatedly adjusting the trim upwards to keep the airplane from descending. However, the more the pilot adjusted the pitch trim upwards, the greater the descent tendency became. The PF, wholly unaccustomed to flight in icing conditions and perhaps denying the gravity of the situation, said nothing, but appeared concerned. Finally, the instrument forced the yoke, freeing the elevator. With the pitch trim by now set almost full up, the airplane violently pitched upwards, with a resultant marked g-load increase. I am no engineer. But, it occurs to us that if the elevator froze up during climb, then applying down pitch trim during the transition to cruise might have an opp effect. That is, as the pilot applied down trim, the airplane would tend to climb. With a nose down pitch trim setting, once sufficient elevator pressure was applied to break the ice, the airplane would violently nose down, perhaps imposing a severe negative g-force on the airframe, with catastrophic results. That, at least, is our theory. Callback conversation with reporter revealed the following information. Reporter stats one of the pilot passengers spoke with mfr regarding this situation. When reporter went to training school for this aircraft he was told to watch for freezing in the tail assembly. States the crew was hand flying the aircraft at time of incident which helped them realize the lack of movement of the yoke. If one was on autoplt he would not notice this.

Google
 

Original NASA ASRS Text

Title: SMA HAS ELEVATOR FREEZE DURING CRUISE UPON FORCING RELEASE OF YOKE EXPERIENCED A VIOLENT PITCH UP.

Narrative: MY COLLEAGUE, MR X, AND I DECIDED WE WOULD SHARE AN INCIDENT THAT OCCURRED DURING AN SMA FLT IN THE HOPE THAT THIS EXPERIENCE MIGHT SHED LIGHT ON YOUR INVESTIGATION OF SMA INFLT BREAKUPS. PRIOR TO LAST SUMMER, WE BOTH PLTED A CORPORATE OWNED 1984 ACFT FOR A NEW JERSEY BASED COMPANY. THE CHIEF EXECUTIVE OFFICER, A RELATIVELY LOW TIME VFR RATED PLT AT THE TIME OF THE INCIDENT, USUALLY FLEW IN THE COCKPIT WITH ONE OF US IN ORDER TO OBTAIN INSTRUMENT TRNING. SINCE I WAS NOT ON BOARD DURING THE FLT IN QUESTION, I AM SURE I WILL MISS SOME OF THE DETAILS. HOWEVER, THE STORY RELATED TO ME THIS EVENING BY MR X IS AS FOLLOWS: THE CEO WAS MANUALLY FLYING THE AIRPLANE DURING CRUISE FLT IN ICING CONDITIONS. THE INSTRUCTOR, MR X, NOTICED THAT THE FLYING PLT WAS REPEATEDLY ADJUSTING THE TRIM UPWARDS TO KEEP THE AIRPLANE FROM DSNDING. HOWEVER, THE MORE THE PLT ADJUSTED THE PITCH TRIM UPWARDS, THE GREATER THE DSNT TENDENCY BECAME. THE PF, WHOLLY UNACCUSTOMED TO FLT IN ICING CONDITIONS AND PERHAPS DENYING THE GRAVITY OF THE SITUATION, SAID NOTHING, BUT APPEARED CONCERNED. FINALLY, THE INSTR FORCED THE YOKE, FREEING THE ELEVATOR. WITH THE PITCH TRIM BY NOW SET ALMOST FULL UP, THE AIRPLANE VIOLENTLY PITCHED UPWARDS, WITH A RESULTANT MARKED G-LOAD INCREASE. I AM NO ENGINEER. BUT, IT OCCURS TO US THAT IF THE ELEVATOR FROZE UP DURING CLB, THEN APPLYING DOWN PITCH TRIM DURING THE TRANSITION TO CRUISE MIGHT HAVE AN OPP EFFECT. THAT IS, AS THE PLT APPLIED DOWN TRIM, THE AIRPLANE WOULD TEND TO CLB. WITH A NOSE DOWN PITCH TRIM SETTING, ONCE SUFFICIENT ELEVATOR PRESSURE WAS APPLIED TO BREAK THE ICE, THE AIRPLANE WOULD VIOLENTLY NOSE DOWN, PERHAPS IMPOSING A SEVERE NEGATIVE G-FORCE ON THE AIRFRAME, WITH CATASTROPHIC RESULTS. THAT, AT LEAST, IS OUR THEORY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. RPTR STATS ONE OF THE PLT PAXS SPOKE WITH MFR REGARDING THIS SITUATION. WHEN RPTR WENT TO TRNING SCHOOL FOR THIS ACFT HE WAS TOLD TO WATCH FOR FREEZING IN THE TAIL ASSEMBLY. STATES THE CREW WAS HAND FLYING THE ACFT AT TIME OF INCIDENT WHICH HELPED THEM REALIZE THE LACK OF MOVEMENT OF THE YOKE. IF ONE WAS ON AUTOPLT HE WOULD NOT NOTICE THIS.

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.