Airframe and Engine Log book times
 

Hi Guys,

I have been brought up to log brakes off/brakes on for airframe logbook and subtract 10 mins per flight for eng logbook (or chocks if you are old school like me).
Taxying over an average grass field probably incurs more stress/wear than in flight.

Now I see many owners are logging airborne times for both airframe and engine.
Is this an easy ar** change, or have I been doing it wrong all these years?
What do you log?

John

You have been doing it wrong.

G

81 Hale Marys said.
3 per year of my sins

G
Could you elaborate please with reference? I too have always done t/o-ldg for both books, but the EASA definition of 'flight time's has made me have second thoughts.

My understanding as far as the UK is concerned (I don't have a reference but it's based on practice, over forty years, at more than twenty different organisations and almost as many maintenance facilities):

Commencing taxy with the intention of flying, the flight time starts when you start to move and finishes when you stop to subsequently shut down. This is time for your personal log book (almost universally rounded to the nearest 5 minutes or a decimal equivalent. (Taxying to or from a fuel station or to load or unload is not logged anywhere except perhaps the airfields own log of movements) If, for any reason, the flight is abandoned before entering the runway no time is logged. If a take off is rejected that should be entered as such in the personal log book.

Only airborne time should be entered in airframe or engine log books.

Custom and practice, from 30+ years in this game, and professional qualifications in most places.

- In the USA flying logbooks are engine start to engine stop, maintenance records are on tacho

- In the UK for microlights only, engine logbooks are from engine start to engine stop, flying logbooks and airframe logbooks are on brakes-off to brakes-on

- In the UK and Europe for civil aeroplanes, flying logbooks are brakes-off to brakes-on, both engine and airframe logbooks are airborne time, except that a few follow the American practice of using tacho.

- In the UK for military aeroplanes, both flying logbooks and maintenance records are for airborne time.

I think it is fair to say that...

Is wrong absolutely everywhere.

It would also be fair to say that when you burrow down it can be hard to find definitive legal documents for any of the above, but generally the definitive answers are somewhere in the maintenance schedule authorising documents.

G

or, to put it another way.
I recorded the correct engine time but was incorrect in adding taxy time to the airframe log.

Like so many things now in light aviation, the majority of us try to do the right thing but regulation, direction and standards have become increasingly complex, obscure and sometimes contradictory. Not helped by the regulator being a key component of contradiction and obscurity.

If I may put my airworthiness engineer hat on for a moment - at the end of the day, it really doesn't matter much anyhow.

The numbers used in most light aircraft maintenance schedules are basically convenient round numbers invented around WW1 when somebody decided we should have a go at something along the lines of regular scheduled maintenance, instead of just waiting for aeroplanes to break then fixing them. They were a best guess then, which have somehow perpetuated for a century or more.

Whilst the basic design engineering done by aircraft and engine manufacturers is pretty good - the predictions of component life and wear on anything much simpler than, say, a Boeing 737, are only marginally better than fag-packet level. Considerable conservatism in basic design work means that mostly this doesn't matter, and anything missed usually gets picked up and solved with Service Bulletins within the first few years a model is in service.

Add to that that there really isn't a common operating environment for light aeroplanes. It stretches credibility to think that a C172 flying student pilots out of Dundee, and another flying tourist flights over the Grand Canyon will see similar wear and load in the same places, at the same rates. Yet both are likely to be being maintained, bar a few minor differences, to the same maintenance schedule.

So, basically - try your best to comply with the regulations, and to be consistent - but where you get it wrong, the chances of it making any real difference to anything, are absolutely tiny.

G

As per Genghis - I have an FAA licence and US registeted airplane I record my time as Hobbs so while the engine is running. For maintenance I use tacho hours.

Which is why, when operating a Cirrus, we use the M2 meter for airborne time and tech logs. It's a very accurate measure of airborne time.

.........since it starts and finishes at around 35 knots.

My Hobbs is connected to a pressure switch on the engine case.