PLT OF A PIPER PA32 (SEL) ALLEGES A FLAW IN THE STABILATOR TRAVEL-LIMITING BOLT AND NUT DESIGN WHICH CAUSED LIMITING ACFT PITCH CTL DURING FLT.

Narrative

SUBJECT: PIPER STABILATOR TRAVEL-LIMITING BOLTS AND NUTS. THE SKETCH BELOW INDICATES THE AFFECTED PARTS IN THE TAILCONES OF MOST SMALL PIPER ACFT (PA28; PA32; ETC). SOME YRS AGO WHILE CRUISING IN A PA32 ON A FAMILY TRIP I NOTICED THAT THE ELECTRIC TRIM BEGAN WORKING IN REVERSE; IE; NOSE-DOWN TRIM GAVE NOSE-UP PITCH. OBVIOUSLY STABILATOR MOVEMENT HAD BECOME RESTR IN THE PITCH-DOWN DIRECTION SO THE TAB WAS ACTING AS AN ELEVATOR. WE MOVED ALL PAX FORWARD; DSNDED AND LANDED SAFELY; AS FORTUNATELY THE PITCH-UP STABILATOR TRAVEL WAS UNAFFECTED; ENABLING US TO FLARE FOR TOUCHDOWN. EXAMINING THE TRAVEL-LIMITING BOLTS I FOUND THAT ON ONE OF THE LOWER ONES THE STOP NUT HAD LOOSENED; ENABLING THE BOLT TO UNSCREW UNDER VIBRATION AND SO LIMIT THE PITCH-DOWN TRAVEL OF THE STABILATOR. I WROTE THE EPISODE UP AND SENT THE DESCRIPTION OF IT TO THE THEN-EXISTING PIPER COMPANY; THE FAA AND THE NTSB; WITH A SUGGESTION THAT THE BOLTS SHOULD BE SAFETY-WIRED INSTEAD OF MERELY BEING FIXED IN PLACE BY STOP NUTS WITH A DOT OF GLUE. THINKING ABOUT IT AFTERWARD I REALIZED HOW LUCKY WE HAD BEEN THAT THE LOOSE BOLT WAS ONE OF THE LOWER ONES; NOT AN UPPER ONE WHICH IF IT HAD COME LOOSE WOULD HAVE DROPPED DOWN IN TO THE HINGE FITTING AND JAMMED THE STABILATOR PITCH-DOWN. IN THAT CASE THE ONLY HOPE WOULD HAVE BEEN TO ROLL INVERTED OR DO AN OUTSIDE LOOP IN THE HOPE OF EJECTING THE FALLEN BOLT; NOT RECOMMENDED MANEUVERS IN THE PA32 AND PROBABLY NOT ONES I WOULD HAVE HAD THE PRESENCE OF MIND TO TRY AT THE TIME. LATER I READ OF A FATAL PIPER NAVAJO CRASH NEAR LAS VEGAS THAT WAS ATTRIBUTED TO THESE TRAVEL-LIMITING BOLT ASSEMBLIES. NOW TO THE IMMEDIATE REASON FOR THIS ASRS RPT AND LETTER: TODAY I SAW FOR THE FIRST TIME A BRAND-NEW PA32 SARATOGA II HP. LOOKING IN THE TAILCONE I SAW THE SAME ACCIDENT WAITING TO HAPPEN: BOLTS WITH THEIR LOCKING NUTS SECURED ONLY BY GLUE DOTS! WHY NOT SAFETY-WIRE THOSE BOLTS; AS IS ROUTINELY REQUIRED FOR EVERY OTHER CRITICAL NUT OR BOLT ON ANY AIRPLANE? SEVERAL YRS HAVE PASSED SINCE THE EVENTS RECOUNTED ABOVE; YET WHAT SEEMED TO ME TO BE AN EASY AND INEXPENSIVE SAFETY ENHANCEMENT HAS NOT OCCURRED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT WHAT PROMPTED HIS RPT AFTER SO MANY YRS HAD PAST AFTER HIS EXPERIENCE; AND THAT OF AN ACCIDENT HE HAD HEARD HAD RESULTED BY THIS STABILATOR TRAVEL LIMIT DESIGN; WAS THE PRESENT DAY NEW ACFT APPEARED TO HAVE THE SAME DESIGN. SINCE HE BELIEVES THAT A POSITIVE FIX BY SAFETY WIRE IS POSSIBLE AT MINIMUM COST; HE IS SURPRISED TO SEE THAT NOTHING APPARENTLY WAS DONE AFTER HIS RPTS TO THE FAA; NTSB; AND THE MANUFACTURER. HE THINKS THAT THE DESIGN CHANGE MAY HAVE FALLEN THROUGH THE 'CRACKS'!