English is a great big, fat, yeasty language that contains approximately 650,000 words. The average high school graduate in the United States uses 20,000 to 40,000 English words in day-to-day activities and most folks know the meaning of 20,000 more. You might be surprised to find out that of the 650,000 modern English words only 40 percent of them are of Old English origins. Another 40 percent of the words in our dictionary have been borrowed from other languages such as words like: aileron (French), coffee (Turkish), shampoo (Hindu), cigar (Spanish), okra (African), and snorkel (German). The last 20 percent of the words we use to express thoughts and ideas are words we created to satisfy a need such as describing a new technical or medical phenomenon or event.
Examples of brand new English words that owe their genesis to new technology are: Internet, email, bits, and bytes. The medical profession gives birth to scary sounding words every year. Words such as SARS, AIDS, and genome. These are just a few examples of 8,000 to 10,000 new words that are generated each year. It is lucky that we retire approximately the same amount of obsolete words every year as we make up new ones, or we would be up to our clavicle in adjectives, nouns, and verbs.
While the English language is dynamic it is far from perfect. For example, in English, where you place a word in a sentence is crucial. For example, you can plan a table or table a plan, book a place or place a book, lift a thumb or thumb a lift. Another problem with English is that we use words all the time that are spelled the same but used differently. For example the word polish can mean the Slavic language of the Poles, a process meaning to brighten, or it can mean a person refined in manners or upbringing.
Despite its obvious shortcomings, within the last 50 years English has become the language of world politics, commerce, and the Internet.
Need for precision
Where am I going with this? Because English is a very complex language, the need for precision of the written word is paramount. You cannot "assume" anything! Therefore it is in every mechanic's best interest to understand that the meaning of every word used in a logbook must be precise and accurate because if you ever get a letter of investigation from the local FAA FSDO, nine out of 10 times it will reference a logbook entry that you have made.
This need for precise record keeping was not lost on the authors of Part 43. Out of the 12 rules that apply to FAA certificate holders six address record keeping. The most important of these six rules is section 43.2. It talks to the definitions of "overhaul" and "rebuild." You can tell it is a relatively new rule because it has an even number suffix number. It should be noted that the words overhaul and rebuild do not just refer to engines, but also include work performed on aircraft, airframe, propeller, appliance, or component parts.
Paraphrasing the rule, section 43.2 describes the word "overhaul" as using methods, techniques, and practices acceptable to the administrator and the item has been disassembled, cleaned, inspected, repaired as necessary, reassembled, and it has been tested in accordance with standards acceptable to the administrator. The definition of "rebuilt" reads the same as overhaul except that the rebuilt item, instead of just meeting the manufacturer's service limits, must now conform to new part tolerances and limits or to approved oversized or undersized dimensions.
From personal experience I know that mechanics have frequently abused the King's English, especially the definitions of overhaul and rebuild in logbook entries in two ways. First, the most common mistake is that we use the words out of context. We make a logbook entry and use the phrase "overhaul the brakes" when all we did was replace the brake pads, or "rebuild a strut" when all we did was replace a bad quad ring seal and service the strut. The words "replaced or repaired" should have been used to describe these kinds of repairs not overhaul or rebuild.
Perhaps the easiest way to remember when to use the term rebuild or overhaul is whether or not you used a micrometer or any other kind of specialized tool in order to make precise measurements. If you used a micrometer and recorded the dimensions, most likely you are either rebuilding or overhauling the part. If you just used hand tools, you are either repairing or replacing the part and it should be so noted in the logbook entry.
The second way mechanics get in trouble is by assuming a part or engine was overhauled based on the work performed and not what the entry states was done. This sometimes happens when an engine is being repaired. The following are two actual engine logbook entries sent to me. The first entry was dated four years ago. (Please note: dates, times, and names were changed.)
03-15-99 Tach: 1000.1 total time 2000.1, TSMOH 500.1
Engine (S/N 123456) repaired this date. Removed and replaced crankshaft supplied by T.C.M. (S/N 45678). Installed new crankshaft using new rod and main bearings, rod bolts, nuts, oil transfer collar, gaskets, and seals. Installed a recertified starter drive clutch, installed a new piston and rings in No. 2 cylinder. All work done I.A.W. a Continental parts and service manual.
Engine Repair Station
Cert # 98765
The second entry is a description of work performed by a mechanic, 800.1 hours later reads like this:
11/22/02, Tach: 1800.2, total time 2800.2 Top overhauled engine this time and date. Cylinders supplied by XYZ Cylinder Repair Station, see work order No. 7654 dated 9/22/02. Lower engine overhauled by Poteen Engine Repair Station, Cert # 98765. See logbook entry dated 03-15-99. New time since overhaul is now 800.1 hours based on P.Poteen repair station bottom overhaul. All work done I.A.W. a Continental parts and service manual.
A&P 135792468 IA
Obviously, several things were wrong with the second entry. The mechanic assumed that the bottom of the engine was overhauled. That is not the case. The word overhaul was never used in the first entry. The word repaired was. Second thing he did wrong was to piggyback his top overhaul on to the repair station's repair in order to declare the engine new TSMOH. The regulations do not allow for this, and I expect the repair station was a little more than upset to find that it was partners with the mechanic in an overhaul that did not take place. So for the actual time since overhaul for this engine you take the 500.1 hours in the first entry plus the additional 800.1 hours flown between March '99 and November '02 for a grand total of 1300.2 TSMOH.
So what is a good overhaul entry? A good entry meets section 43.9 and it looks something like this for an overhauled engine in its logbook.
06/28.03 Tach time: 1800.2,
TT--2800.3 TTSMO-- 0. This engine has been disassembled, cleaned, inspected, repaired as necessary, and reassembled and tested in accordance with ___________________________ (insert engine manufacturer's overhaul manual/instructions), and complied with the following Airworthiness Directives and service bulletins (list AD and service bulletins). Details of this overhaul can be found on work order No. 1943 that is attached to this maintenance record.
Engine Repair Station
CRS Cert # 98765
On a side note, many mechanics do not rebuild an engine and sign it off as rebuilt because due to section 91.421 they believe that only a manufacturer can rebuild. That is not the case; appropriately rated repair stations and mechanics can rebuild an engine and sign it off as rebuilt if it meets the definition of rebuilt in section 43.2.
What section 91.421 does not allow is for a mechanic or repair station to zero time an engine. Zero time means the operator starts with a brand new logbook. The rule allows only a manufacturer or one of its agencies to sign off an engine as zero time if it meets the requirements of 91.421, "Rebuilt engine maintenance records."
Now you know the difference between the words "rebuild and overhaul" and the importance of proper wording in the logbook entry. So be careful, and know what each word means before you sign it off. After all, it is the King's English.