[AirbusPilot]

Hi,

I have some difference in my RV-8 between Tach and Hobbs time, what do you use to log airframe and engine time???

Happy Building/Flying

 

[sjjonesnz]

Hi,

I have some difference in my RV-8 between Tach and Hobbs time, what do you use to log airframe and engine time???

Happy Building/Flying

I've been told to use tacho. FYI, the Hobbs (in my AF3500 anyway) records time when engine is running (ie above 0 RPM), the Tacho records time when engine RPM is more than 1250RPM.

 

[David-aviator]

Hi,

I have some difference in my RV-8 between Tach and Hobbs time, what do you use to log airframe and engine time???

Happy Building/Flying

I believe the mechanical tach records real time at about 2300 rpm, the Hobbs when it is powered. That's why they are different.

Perhaps you could remove one of the devices and use the other to record time.

 

[dhall_polo]

oil

So..
What do y'all use when reporting time on oil samples? Should be the same answer, I suppose, as what is expected to measure toward tbo.

 

[Walt]

Both

I record both in my airframe log... but tach time is what drives TBO, oil changes etc..

 

[N112B]

I use Hobbs time exclusively. It records time when oil pressure is above 15PSI.

 

[roadrunner20]

I record both in my airframe log... but tach time is what drives TBO, oil changes etc..

I follow this system.
I tend to make more short fun flights so my tach to hobbs ratio is quite different.

 

[Ron Lee]

I use engine start to engine stop.

 

[cfiidon]

Record both

If you have both a tach and hobbs, record both in your maintenance logs. However, most base their maintenance tasks on the tach. The only time the tach will match the hobbs is at "normal cruise". Generally speaking, the Hobbs will be 1.15 (fifteen percent) greater than the tach. This was the rule of thumb we used at a flying club where we billed by Hobbs. If it was inop for some reason we would use the multiplier on the tach.
Some commercial ops have a weight-on-wheels or airspeed switch connected to a meter for maintenance. You can see that this valid method of timing could save 15-20 percent of scheduled maintenance costs (think 100 hour inspection).

Don

 

[Mel]

Generally speaking, the Hobbs will be 1.15 (fifteen percent) greater than the tach. This was the rule of thumb we used at a flying club where we billed by Hobbs.

This delta will vary greatly, depending on mow much continuous flying you do vs. pattern work. During pattern work the engine is running below cruise rpm much more of the time.
Technically "flight time" is when the airplane if OFF the ground and actually in flight.
Generally, most people use tach time for engine maintenance.

 

[dedgemon]

Nope

Sorry, but if its running I'm flying as far I'm concerned.