Narrative:

Former manager Y, a&P, and CFI of the company hired me in the capacity of CFI around 1997. Even then, it was customary for Y to maintain, update and safeguard the aircraft logbooks. For the convenience of other pilots, Y created a spreadsheet that automatically calculated maintenance intervals and the time remaining on various aircraft components depending on the tach time entered in the computer. He always preferred to have others refer to that source rather than use the logbooks, unless absolutely necessary. This spreadsheet, together with other paperwork, became part of our 'helicopter book.' at the beginning of this yr it was decided that Y would no longer work for helicopter company and I inherited a number of the responsibilities that Y used to handle. Since I am not an aircraft mechanic, the actual maintenance of the aircraft was shifted from Y to Z. The logbooks also went into Z's care at that time. According to our spreadsheet, the spindles had only a few hours left (5 hours) which prompted me to retrieve the logbooks and doublechk Y's math, making sure that it was indeed about time for maintenance. In doing so, I found a mistake he made in calculating the time remaining on the spindles. The mistake was not apparent. It took me a week or so to find out how the mistake was made. My first guess was that Y had made a simple math error. To calculate the tach time that represents the hour that a given component will come due, you need to take the component's time remaining and add that to the tach reading at the time of installation. Apparently, Y added the tach time at installation to the number of hours flown on the component instead. This result was a number that happened to be about 115 hours too many. Subsequently, we flew on 'borrowed' blades/spindles for about 40 hours, reducing the amount of time that we overflew the spindles to about 75 hours. This number seemed too high though. It did not make sense with other maintenance described in the logbooks. I reported this mistake to the ZZZ FSDO as soon as I found out that it was made. Then, upon closer inspection of the logbooks, I found that the mistake happened for different reasons. It was a case of simply writing down a wrong number on our spreadsheet in the helicopter book. Instead of writing down an interval of 415 hours, he wrote 450. The number 415 was supposed to represent the time left on the spindles at the time that our own blades were reinstalled after the borrowed blades left. By writing down 450 we were 35 hours too 'liberal.' since I found the mistake 5 hours before time was 'supposed' to be up, we overflew the spindles by 30 hours. The mistake was not intentional on my side and I am sure that it wasn't intentional on Y's side either. At the ZZZ FSDO, inspector told me not to fill out a NASA form since this was going to be an airworthiness issue. Rather, I should fill out a disclosure form. This took a few days but ended up being pointless since we were not operating under a part 135 certificate. Finally, the inspector changed his mind and made it a 'flight operations' issue again, leaving me with the option of filling out a NASA form a week or so after the occurrence. I have given a lot of thought on how to avoid a mistake of this sort from happening again. It is puzzling because it seems that the vast majority of pilots that I talk to concur with me, in that it seems customary to ensure airworthiness by looking at the helicopter book and doing a good preflight. It would be unusual for a pilot to scrutinize their employer's logbooks analyzing all the component times before they started flying for that operation. At the same time, it is the PIC's responsibility to determine that the aircraft is airworthy for flight. In the end, I came up with these thoughts: 1) having an 'open logbook policy' is a good idea so that other people can doublechk and possibly find an error of this sort in the future. 2) trusting another person's work blindly is also something that I will avoid from now on. 3) and finally, having a third person, such as a mechanic, go over the logbooks to make sure everything isin order seems to be a good insurance policy.

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Original NASA ASRS Text

Title: INSTRUCTOR MGR OF HELI PLT SCHOOL DISCLOSED THAT THE ROTOR BLADES OF THE ROBINSON R22 HELI HAD EXCEEDED THE TIME REQUIREMENTS IN SVC.

Narrative: FORMER MGR Y, A&P, AND CFI OF THE COMPANY HIRED ME IN THE CAPACITY OF CFI AROUND 1997. EVEN THEN, IT WAS CUSTOMARY FOR Y TO MAINTAIN, UPDATE AND SAFEGUARD THE ACFT LOGBOOKS. FOR THE CONVENIENCE OF OTHER PLTS, Y CREATED A SPREADSHEET THAT AUTOMATICALLY CALCULATED MAINT INTERVALS AND THE TIME REMAINING ON VARIOUS ACFT COMPONENTS DEPENDING ON THE TACH TIME ENTERED IN THE COMPUTER. HE ALWAYS PREFERRED TO HAVE OTHERS REFER TO THAT SOURCE RATHER THAN USE THE LOGBOOKS, UNLESS ABSOLUTELY NECESSARY. THIS SPREADSHEET, TOGETHER WITH OTHER PAPERWORK, BECAME PART OF OUR 'HELI BOOK.' AT THE BEGINNING OF THIS YR IT WAS DECIDED THAT Y WOULD NO LONGER WORK FOR HELI COMPANY AND I INHERITED A NUMBER OF THE RESPONSIBILITIES THAT Y USED TO HANDLE. SINCE I AM NOT AN ACFT MECH, THE ACTUAL MAINT OF THE ACFT WAS SHIFTED FROM Y TO Z. THE LOGBOOKS ALSO WENT INTO Z'S CARE AT THAT TIME. ACCORDING TO OUR SPREADSHEET, THE SPINDLES HAD ONLY A FEW HRS LEFT (5 HRS) WHICH PROMPTED ME TO RETRIEVE THE LOGBOOKS AND DOUBLECHK Y'S MATH, MAKING SURE THAT IT WAS INDEED ABOUT TIME FOR MAINT. IN DOING SO, I FOUND A MISTAKE HE MADE IN CALCULATING THE TIME REMAINING ON THE SPINDLES. THE MISTAKE WAS NOT APPARENT. IT TOOK ME A WK OR SO TO FIND OUT HOW THE MISTAKE WAS MADE. MY FIRST GUESS WAS THAT Y HAD MADE A SIMPLE MATH ERROR. TO CALCULATE THE TACH TIME THAT REPRESENTS THE HR THAT A GIVEN COMPONENT WILL COME DUE, YOU NEED TO TAKE THE COMPONENT'S TIME REMAINING AND ADD THAT TO THE TACH READING AT THE TIME OF INSTALLATION. APPARENTLY, Y ADDED THE TACH TIME AT INSTALLATION TO THE NUMBER OF HRS FLOWN ON THE COMPONENT INSTEAD. THIS RESULT WAS A NUMBER THAT HAPPENED TO BE ABOUT 115 HRS TOO MANY. SUBSEQUENTLY, WE FLEW ON 'BORROWED' BLADES/SPINDLES FOR ABOUT 40 HRS, REDUCING THE AMOUNT OF TIME THAT WE OVERFLEW THE SPINDLES TO ABOUT 75 HRS. THIS NUMBER SEEMED TOO HIGH THOUGH. IT DID NOT MAKE SENSE WITH OTHER MAINT DESCRIBED IN THE LOGBOOKS. I RPTED THIS MISTAKE TO THE ZZZ FSDO AS SOON AS I FOUND OUT THAT IT WAS MADE. THEN, UPON CLOSER INSPECTION OF THE LOGBOOKS, I FOUND THAT THE MISTAKE HAPPENED FOR DIFFERENT REASONS. IT WAS A CASE OF SIMPLY WRITING DOWN A WRONG NUMBER ON OUR SPREADSHEET IN THE HELI BOOK. INSTEAD OF WRITING DOWN AN INTERVAL OF 415 HRS, HE WROTE 450. THE NUMBER 415 WAS SUPPOSED TO REPRESENT THE TIME LEFT ON THE SPINDLES AT THE TIME THAT OUR OWN BLADES WERE REINSTALLED AFTER THE BORROWED BLADES LEFT. BY WRITING DOWN 450 WE WERE 35 HRS TOO 'LIBERAL.' SINCE I FOUND THE MISTAKE 5 HRS BEFORE TIME WAS 'SUPPOSED' TO BE UP, WE OVERFLEW THE SPINDLES BY 30 HRS. THE MISTAKE WAS NOT INTENTIONAL ON MY SIDE AND I AM SURE THAT IT WASN'T INTENTIONAL ON Y'S SIDE EITHER. AT THE ZZZ FSDO, INSPECTOR TOLD ME NOT TO FILL OUT A NASA FORM SINCE THIS WAS GOING TO BE AN AIRWORTHINESS ISSUE. RATHER, I SHOULD FILL OUT A DISCLOSURE FORM. THIS TOOK A FEW DAYS BUT ENDED UP BEING POINTLESS SINCE WE WERE NOT OPERATING UNDER A PART 135 CERTIFICATE. FINALLY, THE INSPECTOR CHANGED HIS MIND AND MADE IT A 'FLT OPS' ISSUE AGAIN, LEAVING ME WITH THE OPTION OF FILLING OUT A NASA FORM A WK OR SO AFTER THE OCCURRENCE. I HAVE GIVEN A LOT OF THOUGHT ON HOW TO AVOID A MISTAKE OF THIS SORT FROM HAPPENING AGAIN. IT IS PUZZLING BECAUSE IT SEEMS THAT THE VAST MAJORITY OF PLTS THAT I TALK TO CONCUR WITH ME, IN THAT IT SEEMS CUSTOMARY TO ENSURE AIRWORTHINESS BY LOOKING AT THE HELI BOOK AND DOING A GOOD PREFLT. IT WOULD BE UNUSUAL FOR A PLT TO SCRUTINIZE THEIR EMPLOYER'S LOGBOOKS ANALYZING ALL THE COMPONENT TIMES BEFORE THEY STARTED FLYING FOR THAT OP. AT THE SAME TIME, IT IS THE PIC'S RESPONSIBILITY TO DETERMINE THAT THE ACFT IS AIRWORTHY FOR FLT. IN THE END, I CAME UP WITH THESE THOUGHTS: 1) HAVING AN 'OPEN LOGBOOK POLICY' IS A GOOD IDEA SO THAT OTHER PEOPLE CAN DOUBLECHK AND POSSIBLY FIND AN ERROR OF THIS SORT IN THE FUTURE. 2) TRUSTING ANOTHER PERSON'S WORK BLINDLY IS ALSO SOMETHING THAT I WILL AVOID FROM NOW ON. 3) AND FINALLY, HAVING A THIRD PERSON, SUCH AS A MECH, GO OVER THE LOGBOOKS TO MAKE SURE EVERYTHING ISIN ORDER SEEMS TO BE A GOOD INSURANCE POLICY.

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.