The aircraft was scheduled for a "clean" annual inspection. The aircraft's pristine paint job was only a few years old, and it had a general well-kept look about it. In fact everything about this PA 28-180 seemed to say, "Good condition … no problem." With the engine cowlings and airframe panels removed, the inspection seemed to confirm the initial expectation of an easy annual with only a few minor, easily corrected, discrepancies being found. This being the case, the owners readily agreed to a new set of plugs to replace the worn out set currently installed, and to permit the correction of the few discrepancies noted during the inspection.
However, things began to change during the airworthiness directive (AD) research. The first problem concerned AD 67-12-06. Originally certified on Jan. 27, 1965, this aircraft was subject to the requirements of this AD. Sure enough, an entry in the original logbook dated June 26, 1967 read:
"Complied with AD 67-12-06."
Then, stapled in the back of the logbook in a typical listing was the following entry:
"67-12-06 Tubes, int. Corrosion 6-26-67 C/W by INSP X (recurring).
With this entry was a name and a mechanic's certificate number.
Included in another AD listing at the rear of the same logbook was a typical one liner:
"67-12-06 Balance Horns C/W."
This listing had no name, date, or tach. time recorded.
There was yet another listing in the back of the logbook with an obscure entry reading:
"67-12-06 pre C.W. Tube Chg per AD 70-26-04 see log."
These two ADs are unrelated, though replacement of the stabilator tube in accordance with the instructions in AD 70-26-04, provided it is suitably corrosion proofed internally, would undoubtedly remove any inspection requirements of AD 67-12-06 — but only as far as the stabilator tube is concerned.
Further research found a later listing in the back of the airframe logbook No. 2, which read:
"67-12-06 Rev. date 7-31-68 Internal Corrosion of Tubes 6-27-67 P.C.W."
In another listing also stapled in the back of this logbook read:
"67-12-06 Inspect tubes for internal corrosion/PCW."
Finally, there are two very comprehensive AD listings pertaining to this aircraft generated by a repair station; one is dated 2004 and the other 2005. Both refer to AD 67-12-06 as having been "complied with," the compliance date being given as 6/26/67. (This is the first date associated with the AD mentioned above.)
What does C/W mean?
Now the question is: What does C/W mean? We all know that this common abbreviation stands for the words "complied with." However, even if written out, these words do not in any way indicate how the requirements of an AD were in fact complied with, or exactly which requirements of the AD were met if more than one possible action is specified in the AD instructions.
It is interesting, that in the above entries pertaining to this AD, the first lists it as a recurring AD, while subsequent entries do not. According to the actual instructions contained in the AD we find this paragraph:
(d) Further inspection is not required after accomplishing (c) (1), (c) (2), or (c) (3).
But nowhere in the aircraft maintenance records is there any indication that these conditions were ever met. The all-important question is then, did someone, somewhere, during the period between 1967 and the present, actually comply with this AD? Or could it be that over this long period of time, everyone inspecting this aircraft simply assumed that someone, somewhere, at some time, did in fact do so?
Taking all of the above into consideration, it was decided to treat this AD as if it were a brand new release. Also, it was noted on the discrepancy sheet during the routine inspection that the aileron balance weight tubes were filled with debris, a result of the paint stripping operation accomplished during the repaint done a few years ago. After carefully removing the foreign material from both aileron balance weight tubes, a light trace of internal corrosion was evident in both tubes with no sign of any previous anti-corrosion measures having been implemented. As the corrosion was slight, and replacement of the affected parts not warranted, the internal discoloration was removed and the interior of both left and right tubes painted with zinc oxide.
The rudder tube was then checked using a light and mirror; a very slight trace of corrosion evident therein was removed, and the internal surface of the tube treated with zinc oxide. The original stabilator tube, having been replaced some years previously, had been painted internally with no trace of corrosion being present. Quite confidently, and quite definitely, this AD has now been signed off and now being fully "complied with," has once and for always been laid to rest.
A look at AD 96-09-10 C
The second problem encountered during this AD search concerned AD 96-09-10 C. This AD affects a large number of Lycoming engines and requires the removal of certain oil pump impellers, including both the sintered iron type and those manufactured from aluminum. The notations on the ATP readouts from both 2004 and 2005 — mentioned earlier in conjunction with the previous AD — give a compliance date of 12/13/83 TSMOH 0.0 with the comment: "Complied with at overhaul." This note immediately raised the obvious question: Could an AD issued in 1996 have been complied with at the time of an overhaul done in 1983?
At the beginning of engine logbook No. 2 (the current book) there is a pasted-in entry pertaining to the overhaul mentioned above with the date Dec. 13, 1983. The full description of work done reads exactly as follows:
"Major overhaul engine to manufacturers specifications, comply with all current AD notes and service bulletins at time of overhaul, overhaul or exchange magnetos, carburetor, and fuel pump."
There is no list of the parts used, and therefore no way of telling what oil pump impellers were installed at the time. However, doesn't the statement, "Comply with all current AD notes and service bulletins at time of overhaul," suffice to put any question to rest? Unfortunately it does not! Especially not in a case like this, as the parts in use in 1983 at the time of the overhaul, are in fact the very parts that are subject to removal according to the Lycoming service bulletins cited in AD 96-09-10 C; the very parts condemned by the AD.
What was installed?
While contemplating this dilemma, I began to page through the logbook to see if there was any indication anywhere as to what oil pump impellers were installed in the engine. It was only a few pages on that I found what I was looking for. There I found a pasted-in entry stating that the engine had been removed from the aircraft in 1986 and returned to the overhaul shop for repair. While the nature of the problem that precipitated this repair is not mentioned, a list of the parts installed at the time is. And included within that list are the following:
"…1-#LW13775 Impeller (used), 1-#60746 Impeller (used) …"
It was the first of these two numbers that immediately caught my attention. Somewhere in the back of my mind LW13775 and aluminum seemed to be closely associated. Sure enough, according to the AD, the two impellers now installed in this engine should have been removed "at next engine overhaul (not to exceed the hours specified, for the particular engine model, in Textron Lycoming Service Instruction 1009AJ, dated July 1992), at next oil pump removal, or five years after the effective date of this AD, whichever occurs first." Nowhere in the maintenance records could this requirement be found to have been complied with.
After advising the owner of the problem, the engine was removed from the aircraft, the accessory housing removed from the engine, and the oil pump disassembled. It was with relief that I found the impellors currently installed to be exactly as the above entry stated it. The aluminum (LW13775) impellor made this fact immediately obvious. I say that this was with relief, because even though, given the circumstances it was necessary to ascertain just what parts were in the oil pump, it would have been psychologically difficult to justify the expense involved if legitimate parts had been found installed after all.
The conclusion of this story is quite simple. Lycoming impellor kit 05K19423-5 containing hardened steel impellors LW 18109 and LW18110 was installed along with a new driving shaft 61174. The shaft was also replaced because the one removed was excessively worn. Needless to say, everyone came away from this situation both wiser and happier than would otherwise have been the case — if perchance an unthinkable disaster had resulted from this "previously complied with" AD having never been complied with at all. As the technical representative at Lycoming told me on the phone, "While that plane may have flown for the last 20 years without incident, it is possible that 20 minutes into the next flight …!"
Take a second look
Of course it is not practical to retrace history and double check every AD ever complied with on every aircraft that comes into one's shop for an annual inspection. However, in the interest of safety, it is a good idea to at least look over the AD listings in the logbook, or that may be in the form of a computer readout, with a view to finding something that may bear further investigation. Not too many years ago, hand written AD listings contained very little detailed information as to exactly what was done in compliance with the requirements specified in an AD. In fact, "All ADs complied with" as part of an annual sign off was a fairly common notation. And the PCW that so often appears in an AD listing, is very often an assumption based upon a very scant entry made some years before.
Based upon the experience with the PA 28-180 mentioned above, and a few similar instances encountered over the years, I have found it a good idea to reconsider all the ADs that apply to an aircraft at inspection time, whether previously complied with or not, and taking just a moment of time. Consider the possibility of the subject matter of each AD once more requiring attention. We all know about those recurring ADs, but it's those permanently complied with — so often deemed to be once and for always done — that may in fact through circumstances related to, or unrelated to the ongoing maintenance performed on the aircraft, be due for a second look.
As those of us in the business of maintaining airplanes know, an airworthiness directive is just that. It is a matter of airworthiness, and not just a legal document designed to make life difficult for owners and aircraft inspectors. Therefore, putting legality aside, it behooves us responsible for the safety of those who fly in the aircraft we inspect to make absolutely sure that all the ADs that apply to an aircraft in our care have in fact been complied with. AMT.
Noel Wilton has approximately 15 years experience in aircraft maintenance. He is a repair station inspector at Andrews University FBO, Berrien Springs. MI. He is also a licensed pilot and proud owner of an Ercoupe 415D/0200A. Currently, he's responsible for the maintenance of the Andrews University Flight School fleet of Cessna and Piper aircraft and providing experience for graduates from the Andrews University A&P school.