Narrative:

Aircraft is a D328-110, equipped with pw-119B turbo-shaft engines. On departure climb, shortly after flaps up, I noticed both engines were 5-8 percent below their torque 'bug' values. As I adjusted the power levers upward together, the right engine went to the proper value and the left engine surged right off the scale. We contacted our maintenance control via radio and were advised to return to the field. When we checked the exceedance record, it showed a torque spike to 126 percent on the left engine. Itt, nh, and nl support this as being accurate, and not an indication error. It has come to my attention that my company has replaced a number of hydro-mechanical units (hmu's) on our aircraft after over- torques. My understanding is that sections of several different engines were cobbled together to make this unit, ie, EMB120 gear box, ATR compressor, ATP hot section. I have to wonder if all the sub-assemblies are really compatible in line service conditions, and what other exciting modes of operation will pop up as these units age. Callback conversation with reporter revealed the following information: reporter is concerned that with such a new aircraft, they seem to be having an unusual amount of engine problems. And, if problems are already manifesting themselves, what will the future hold? Since submitting the report, he has spoken with a maintenance troubleshooter who believes they have discovered the primary problem causing the spurious engine overspds and hydro-mechanical unit replacements, the cannon plug pins are slightly undersized. Consequently, they become more likely to corrode or get dirt in the connector as well as move. That causes erroneous and spurious signals resulting in overspds, etc. The company came up with a temporary fix by cleaning the cannon plugs and bent the pins slightly to make a tight fit. There is also a new harness assembly being tested by pratt which should also correct the problems. In one of the overspd incidents after landing, the reporter says, had the runway been wet or cluttered, they would not have been able to maintain directional control.

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Original NASA ASRS Text

Title: ACFT EQUIP PROB. ENG OVERSPD OVER-TORQUE.

Narrative: ACFT IS A D328-110, EQUIPPED WITH PW-119B TURBO-SHAFT ENGS. ON DEP CLB, SHORTLY AFTER FLAPS UP, I NOTICED BOTH ENGS WERE 5-8 PERCENT BELOW THEIR TORQUE 'BUG' VALUES. AS I ADJUSTED THE PWR LEVERS UPWARD TOGETHER, THE R ENG WENT TO THE PROPER VALUE AND THE L ENG SURGED RIGHT OFF THE SCALE. WE CONTACTED OUR MAINT CTL VIA RADIO AND WERE ADVISED TO RETURN TO THE FIELD. WHEN WE CHKED THE EXCEEDANCE RECORD, IT SHOWED A TORQUE SPIKE TO 126 PERCENT ON THE L ENG. ITT, NH, AND NL SUPPORT THIS AS BEING ACCURATE, AND NOT AN INDICATION ERROR. IT HAS COME TO MY ATTN THAT MY COMPANY HAS REPLACED A NUMBER OF HYDRO-MECHANICAL UNITS (HMU'S) ON OUR ACFT AFTER OVER- TORQUES. MY UNDERSTANDING IS THAT SECTIONS OF SEVERAL DIFFERENT ENGS WERE COBBLED TOGETHER TO MAKE THIS UNIT, IE, EMB120 GEAR BOX, ATR COMPRESSOR, ATP HOT SECTION. I HAVE TO WONDER IF ALL THE SUB-ASSEMBLIES ARE REALLY COMPATIBLE IN LINE SVC CONDITIONS, AND WHAT OTHER EXCITING MODES OF OP WILL POP UP AS THESE UNITS AGE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR IS CONCERNED THAT WITH SUCH A NEW ACFT, THEY SEEM TO BE HAVING AN UNUSUAL AMOUNT OF ENG PROBS. AND, IF PROBS ARE ALREADY MANIFESTING THEMSELVES, WHAT WILL THE FUTURE HOLD? SINCE SUBMITTING THE RPT, HE HAS SPOKEN WITH A MAINT TROUBLESHOOTER WHO BELIEVES THEY HAVE DISCOVERED THE PRIMARY PROB CAUSING THE SPURIOUS ENG OVERSPDS AND HYDRO-MECHANICAL UNIT REPLACEMENTS, THE CANNON PLUG PINS ARE SLIGHTLY UNDERSIZED. CONSEQUENTLY, THEY BECOME MORE LIKELY TO CORRODE OR GET DIRT IN THE CONNECTOR AS WELL AS MOVE. THAT CAUSES ERRONEOUS AND SPURIOUS SIGNALS RESULTING IN OVERSPDS, ETC. THE COMPANY CAME UP WITH A TEMPORARY FIX BY CLEANING THE CANNON PLUGS AND BENT THE PINS SLIGHTLY TO MAKE A TIGHT FIT. THERE IS ALSO A NEW HARNESS ASSEMBLY BEING TESTED BY PRATT WHICH SHOULD ALSO CORRECT THE PROBS. IN ONE OF THE OVERSPD INCIDENTS AFTER LNDG, THE RPTR SAYS, HAD THE RWY BEEN WET OR CLUTTERED, THEY WOULD NOT HAVE BEEN ABLE TO MAINTAIN DIRECTIONAL CTL.

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.