These logs get entries only when maintenance is done, not for individual flights
OK, but where do you track the accumulating total time? If the journey log (or some other flight log) is sure to exist and to not get lost, one could just transfer the totals from that into the logbooks, before each service.
I suppose you could use a hobbs or similar meter (and enter a single line into the airframe and engine logbooks just before each service) but then you are doing all maintenance too early – probably 10-20% too early depending on the average flight time and taxi time.
Peter wrote:
I suppose you could use a hobbs or similar meter (and enter a single line into the airframe and engine logbooks just before each service)
We do essentially that with the exception that there is no single line entry before each service. Instead each maintenance logbook entry itself gets a TSO and/or TTIS entry as appropriate. Other than that, there is no other record of aircraft time except the airframe recording device.
Nobody cares about the service issue, for private owners subject only to annual inspections the ‘service’ is mostly just an oil change (i.e. not controlled by regulation) and you could stretch it to whatever is right based on tach time. I change my Lycoming oil sometime after 25 hrs tach time, well before before 50, when I have opportunity.
I do have a friend with 20,000 or more hours who draws a little cross on his knee pad for every flight, noting start, stop, takeoff and landing. He does it that way because it used to determine his pay and its ingrained. Later on they paid him from when the aircraft door was closed, until it was reopened.
I guess it matters less if maintenance is on condition, not tied to fixed intervals…
In the flying school I instructed in, we filled in a “technical log” with the individual block and flight times, plus fuel/oil/defects. When the aircraft went in for it 50 hour check, the maintenance organisation got the tech log and copied the entries into the corresponding airframe, engine and prop logbooks. They also did that when some maintenance work required a logbook entry.
I am somewhat confused by the S/N being on the sump.
Isn’t the sump just a thin metal tray that bolts to the bottom. It probably costs a couple of hundred dollars. Why wouldn’t you just buy a new sump?
Or have I misunderstood something?
On a Lycoming, the oil sump is a heavy cast part that includes the intake runners as per this photo. I’d guess it is considered part of the crankcase assembly by Lycoming, although the sump pictured is from a UK website selling used parts. Not cheap.
And while yes one could change the sump and thus change the engine S/N, this is likely to impact the market value of the engine because the S/N will no longer track the history of the rest of the engine. I guess a 145 engine shop could handle this – I know such a shop is able to change the accessory gearbox and thus change the engine P/N – but otherwise you might have fun getting rid of it, IMHO.
There is not necessarily any record if a used sump & data plate are installed on a different engine and the log that stays with the engine is in reality associated only with the sump, not the rest of the engine. The data plate is for the purpose of records the same thing as the engine, and the logbook stays with the data plate. I suppose for it to be legal, although it would clearly be ludicrous, the logbook in this case would include an entry that says in essence that a different engine was installed on the data plate. What would really happen is that the A&P installing the replacement sump on an engine would switch over the data plate matching the logbook for the engine to the used replacement sump, and the data plate removed from the sump would (theoretically at least) stay with the log books and components of another engine. Or maybe (in reality) transfer to his tool box for some future use…
This highlights that nothing in the ‘system’ of light aircraft written records is actually all that rigorous, that’s why the ‘system’ into which the engines are intended to be placed is based largely on periodic evaluation of condition. With that in mind I would caution that you can assume almost nothing based solely on maintenance log books. In reality when evaluating an engine in the field you are relying on a combination of a current physical evalution of condition, a review of the log in which you might try to correlate the log to the physical inspection, the individual character and ethics of previous mechanics and (in particular) previous owners, and your own spider sense with respect to all of the above. Many people buying a used engine have unwittingly ended up with only a core. These are not military owned and operated engines, people are involved 
Going beyond engines, but the situation is identical, I have a 1946 aircraft with an airframe data plate held on with two sheet metal screws by the factory. Six thousand airframes of the type were produced, only a fraction are still flying. Lots of planes were wrecked and lots data plates and parts are floating around. There is no guarantee at all that my data plate and logbooks have lived with my plane since 1946, or in fact that the plane wasn’t at some point assembed out of parts.
I have this additional info from another US engine shop:
Here is how it works, at least legally here in the US:
There are 2 identical serial numbers on the engine. One is the data
plate and the other is on top of the engine towards the back. There are
no rules that say a data plate has to stay with one particular engine.
Example: If a customer has an IO-540 C4D5D and he wants to convert it to
an IO-540 D4A5, but doesn’t have a data plate, if I have all the right
parts along with a D4A5 plate and logs, I can build that engine. IOW,
the data plate is the key to having an engine model.
I’ve just been reading something by Mike Busch, and others, on this.
The engine is just the data plate. You could rebuild an engine and replace every part of it, including the part which the data plate is attached to, and the engine is still the same engine.
And it cannot be given zero-timed logbooks.
So all those engine shops here in Europe, particularly some in the UK, that issue zero timed logbooks, are doing it wrong. But nobody notices, nobody cares, and everybody on the receiving end likes it because their plane sells for more money 
If say Lycoming assemble a “remanufactured” engine, they give it a new data plate, apparently, and this is what entitles them to issue a zeroed logbook. And only Lycoming can manufacture the data plate (being the TC holder).
A great article on this and other stuff is here, written by one of the most experienced US engine builders (his firm did 2 engines for me).
And it is exactly the same with say the “restored” Spitfires. The restorer just needs a data plate, nothing else, to “restore” a genuine original Spitfire.
Interesting article Peter.
And perhaps a bit worrying that 30% of factory new cylinder heads get rejected because they are out of limits.
