PLT OF A PIPER PA44; SEMINOLE; DURING AN IFR FLT IN VFR CONDITIONS; DECLARED AN EMER AND DSNDED TO ANOTHER ARPT FOR LNDG DUE TO HEARING RATTLING NOISES FROM THE ACFT; AND THE MOMENTARY LACK OF BEING ABLE TO CTL THE ACFT PITCH ATTITUDE CAUSING HIM TO BELIEVE THAT THERE WAS A SERIOUS MALFUNCTION IN THE ACFT FLT CTL SYS.

Narrative

ON MAR/XA/99 I DEPARTED CRQ ON AN IFR FLT PLAN TO ELP. THE WX AT DEP WAS CLR WITH LIGHT WINDS RIGHT DOWN THE RWY AND FLT LEVEL WINDS (9000 FT) WERE FORECAST TO BE AROUND 25 KTS. THERE WERE 2 OF US IN THE ACFT; BOTH EXPERIENCED PLTS WITH ABOUT 5000 HRS BTWN US. WE WERE FLYING A PA44 (PIPER SEMINOLE); A LIGHT TWIN ENG PISTON ACFT. ON CLBOUT; WE HEARD AN INTERMITTENT RATTLING NOISE. NEITHER COULD DETERMINE FROM WHERE THE NOISE WAS COMING EXCEPT WE WERE FAIRLY CERTAIN THAT IT WAS NOT COMING FROM THE ENGS. THE ONLY THING THAT WE WERE ABLE TO CORRELATE WAS THAT THE RATTLE WAS MORE PRONOUNCED AND NOTICEABLE WHENEVER THE FLT CTLS WERE REPOSITIONED. PRIOR TO REACHING THE FIRST NAVAID (JLI; JULIAN); WE AGREED THAT THE PRUDENT THING TO DO WAS TO LAND AND CHK OUT THE NOISE. PRIOR TO BEING ABLE TO CANCEL IFR WITH ZLA (BECAUSE OF RADIO TFC) THE ACFT BECAME UNCTLABLE. THE ACFT PITCHED UP ABOUT 15 DEGS AND BEGAN BLEEDING AIRSPD. EVEN WITH THE APPLICATION OF FULL PWR; OUR RATE OF DSCNT EXCEEDED 1000 FPM AND PITCH CTL SEEMED TO NOT MAKE ANY DIFFERENCE AS TO THE ACFT'S ATTITUDE. OUR IMMEDIATE THOUGHT WAS THAT THE RATTLE WE HAD HEARD HAD BEEN A FRAYING FLT CTL CABLE AND THAT IT HAD JUST SEVERED. I DECLARED AN EMER AND WE BEGAN AN IMMEDIATE TURN TOWARDS BORREGO SPRINGS ARPT. DSNDING THROUGH APPROX 5500 FT MSL; WE REGAINED LONGITUDINAL CTL OF THE ACFT AND BEGAN SECOND-GUESSING OUR PREVIOUS PROGNOSIS OF A FLT CTL PROB. NEVERTHELESS; WE DECIDED THAT WE MUST LAND TO CHK OUT THE AIRPLANE. WE THEN THOUGHT THAT WE MAYBE DID NOT HAVE A FLT CTL PROB; BUT WE STILL WERE NOT CERTAIN. FIGHTING OUR WAY DOWN TO AN EXTENDED FINAL APCH SETUP FOR RWY 25 AT BORREGO SPRINGS; I OPTED TO NOT LAND THERE. THE TURB WAS SEVERE IN THE VALLEY AND WHEN POINTED DOWN THE RWY; THE SUN WAS AT SUCH AN ANGLE THAT THE RWY ENVIRONMENT WAS TOTALLY OBSCURED. WE TURNED WNW TOWARDS SALTON SEA BUT CHOSE TO CONTINUE TOWARDS TRM INSTEAD BECAUSE OF THE LONGER RWY AND THE LIKELIHOOD OF HAVING MAINT AVAILABLE AT THE FIELD. WE MADE AN UNEVENTFUL LNDG AT TRM JUST BEFORE SUNSET. ALTHOUGH MOSTLY CONVINCED THAT THERE HAD IN FACT BEEN NO FLT CTL PROB; WE WEREN'T TOTALLY CONVINCED. WE STILL DID NOT KNOW OF THE SOURCE OF THE 'RATTLE.' UPON LNDG; AN A&P INSPECTED THE FLT CTLS; ESPECIALLY THE HORIZ STABILIZER AND ASSOCIATED CABLING; AND COULD FIND NO DISCREPANCIES WITH THE ACFT. SUBSEQUENT TO THE MECH'S INSPECTION; WE CONDUCTED A THOROUGH POSTFLT INSPECTION OF THE ACFT AND COULD DETERMINE NOTHING AS THE SOURCE OF THE RATTLE OR ANY ACFT DISCREPANCY. EVEN CONSIDERING THAT THE MECH COULD FIND NOTHING WRONG WITH THE ACFT; WE ELECTED TO NOT PROCEED THAT NIGHT. SHOULD WE 'REDISCOVER' A PROB INFLT; WE WOULD MUCH PREFER FOR IT TO HAPPEN DURING DAYLIGHT AND VMC. THE NEXT MORNING; WE DEPARTED TRM AND 3 LEGS LATER; RECOVERED UNEVENTFULLY AT PNS. DURING THE 3 FLTS HOME; THE 'RATTLE' NOISE NEVER RECURRED. IN HINDSIGHT; IT WAS MOST LIKELY MOUNTAIN WAVE THAT CAUSED THE 'UNCTLABLE' CONDITION. BASED ON THE WX RPT THAT I HAD RECEIVED; I DID NOT ANTICIPATE MOUNTAIN WAVE. HAD THAT OCCURRED BY ITSELF WITHOUT THE ASSOCIATED 'RATTLING;' WE MAY NOT HAVE CONCLUDED THAT THE FLT CTLS WERE THE ISSUE.