Menu Sign In Contact FAQ
Banner
Welcome to our forums

When is an engine zero-timed?

This topic has come up many times over many years.

Many years ago, only a manufacturer overhaul could be zero-timed i.e. fresh logbooks starting from 0:00. I don’t know if that restriction is true in any sense today.

My new engine has been overhauled, by Barrett Precision which is the most reputable US engine shop I could find after doing a lot of research in the USA – including asking Lycoming directly! BP also did the SB569 crank swap in 2008. Total time since new (TTSN) is 1125:45 (I have the Israeli Air Force logbooks, in Hebrew, kindly translated by a pilot here ). Total time since overhaul is obviously 0:00. Aircraft total airborne time is 1811:20.

Yesterday we did the first flight, 2:00 airborne.

Should I start the brand new engine logbook like this:

IOW, there is no zero-timing aspect at all going into the logbook.

Incidentally, in both the previous engine logbook and the airframe logbook I never filled in the “tach recording time” because I don’t use the tach time. It is based on anytime the engine is above 1200rpm so on average over-estimates the airborne time by some 10%. Same of course with most “hobbs” devices. I have always worked on pure airborne time. However, one view is that the “tach recording time” in the engine logbook should be the aircraft time.

I would appreciate any views…

BTW the engine is running great

Administrator
Shoreham EGKA, United Kingdom

I remember reading somewhere, probably in John Deakin’s columns on Avweb, that zero-timing has nothing to do with overhaul being “reputable” – it is merely a sign of the pool-based overhaul when the engine is reassembled from other individual major components than it originally consisted of. If every single component has been restored to factory specs but it is still the same engine block, the same crankshaft, etc., then engine time goes on, otherwise it’s reset to zero just because it’s not exactly the same engine.

I have always worked on pure airborne time. However, one view is that the “tach recording time” in the engine logbook should be the aircraft time.

A while ago, Czech CAA issued an official clarification that for the purposes of maintenance records, only airborne time is relevant. Maybe it’s their own opinion, maybe they are repeating after EASA. Not sure what the official situation is for N-reg.

Last Edited by Ultranomad at 03 Apr 07:25
LKBU (near Prague), Czech Republic

Not sure what the official situation is for N-reg.

N-reg is definitely airborne time too.

it is merely a sign of the pool-based overhaul when the engine is reassembled from other individual major components than it originally consisted of

Hmmm, yes, that actually makes a lot of sense, especially as the original mfg (Lyco) would be the only outfit which assembles engines out of a bucket of random bits of unknown origin. Independent engine shops normally overhaul a complete engine.

An interesting tangent here is whether an independent engine shop has the right to build an engine out of a bucket of random bits. What serial number would it be? You would need to get your hands on the sump which has the label on it

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

What serial number would it be? You would need to get your hands on the sump which has the label on it

In all likelihood, such a remanufactured engine would have a new number assigned, too.

LKBU (near Prague), Czech Republic

If the engine S/N is the same, the engine time continues. On a factory overhauled engine AFAIU you will get a new S/N, zero-time and new logbooks.

I am an avid consumer of Savvy videos

Last Edited by Aviathor at 03 Apr 09:35
LFPT, LFPN

It certainly seems logical to me that if the engine has its original serial number, it doesn’t have zero time in service. My Continental was overhauled in 1953 and given a new logbook, put in the plane as replacement engine with total time noted as “unknown”, likely bcause nobody had kept an accurate engine log before that time. It was overhauled again in 1997, with a fairly lousy logbook entry. It still says TT unknown, but for this engine as for many types it makes no significant difference what the total time is as long as you have a pretty good idea that it hasn’t been overhauled a great many times, with correspondingly huge time in service. In that case you might worry about fatigue, particularly of the crankcase.

I still can’t get over making an engine logbook entry after every flight!?!
Last Edited by Silvaire at 03 Apr 14:06

Silvaire wrote:

I still can’t get over making an engine logbook entry after every flight!?!

I have never seen that in Europe (apart from here). Only Journey Log.

Last Edited by Aviathor at 03 Apr 14:09
LFPT, LFPN

Peter wrote:

An interesting tangent here is whether an independent engine shop has the right to build an engine out of a bucket of random bits. What serial number would it be? You would need to get your hands on the sump which has the label on it

Any A&P mechanic can do this for an N-register aircraft engine, IA also required if it’s turbocharged or geared. There is nothing about the components of an engine that tie them to a particular serial number crankcase. As you suggest the engine continues to use the existing data plate and serial number on the crankcase.

If the A&P (or his shop) don’t have the old lookbook he starts a new one, but in that case if the engine is for sale it may not be worth as much depending also on how many yellow tags are available for the overhauled and/or inspected engine components. Many people think that when an engine is field overhauled or overhauled by a ‘no-name’ individual or shop it is those component records that count, more so than than the logbook entry.

Last Edited by Silvaire at 03 Apr 14:32

There is no doubt that most if not all EASA-reg certified planes need to have an airframe log and an engine log. In the UK there is also a propeller logbook. And for sure the Israeli Air Force maintained an engine logbook

The vast majority of owners don’t see these logbooks because their maintenance company retains them.

Re an N-reg, Jeppesen produce all these logbooks too so I am sure they do exist in the USA. They are a widely sold product.

Re having to update them after every flight, I have no idea what the regs are on this (it was on another thread recently; I don’t think anybody commented with a reference) but clearly they have to be updated sometime. The point in time at which most people do this is before each service, so e.g. every 50 or so hours and of course before the Annual – otherwise one can’t sign off the “released to service at xx:yy hours” bit.

It certainly seems logical to me that if the engine has its original serial number, it doesn’t have zero time in service

Yes that makes sense too.

There is nothing about the components of an engine that tie them to a particular serial number crankcase.

I vaguely recall being told that there is some need to maintain a relationship between the engine S/N and the crankshaft S/N otherwise there are possible issues with confirming compliance with the various Lyco crankshaft ADs. I don’t know any more but it does sound plausible. It may be a market value impact only.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

There is no doubt that most if not all EASA-reg certified planes need to have an airframe log and an engine log. In the UK there is also a propeller logbook. And for sure the Israeli Air Force maintained an engine logbook

In the US, all aircraft since the 1940s or so have maintained separate maintenance logs for engine and airframe, with an additional log for the propeller if it is variable pitch. These logs get entries only when maintenance is done, not for individual flights, noting the time when the maintenance was performed as referenced to the recording device on the airframe. No journey log or equivalent is kept unless there is no recording device. If there is no Hobbs meter, only a recording tach, that is used for maintenance log times. Nobody I have ever met personally in the US has worried about the difference between airborne time and recording device time, because the planes are maintained on condition.

Last Edited by Silvaire at 03 Apr 14:41
23 Posts
Sign in to add your message

Back to Top