Van's Air Force
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TTSN
- Thread starter prkaye
- Start date
WingsOnWheels
Well Known Member
I would say most are operating time vs flight time. Most hobbs meters run off oil pressure or just the battery master, so taxi and runup time is included. Those with a fancy EFIS etc have flight time (wheels up to wheels down) usually available as well.
indeed, that was my question, when people advertise TTSN for airplanes for sale, do they mean Air Time or Flight Time. There can be quite a difference, of course (my total Hobbs time, for example, is 448 hrs, where my total air time is 359 hrs.). I assume most people would advertise Air Time, since it will be lower, and because that's what gets entered in Journey Logs.
However, engine TBO's are based on Hobbs time, correct? If I were buying an airplane, engine Hobbs would probably be more important to me than Air Time.
However, engine TBO's are based on Hobbs time, correct? If I were buying an airplane, engine Hobbs would probably be more important to me than Air Time.
Auburntsts
Well Known Member
In the US, I don't know anyone who advertises anything based on "Air Time". IMO what matters is the operational time of the unit/system regardless of whether that was in the air or on the ground. YMMV.....
that's interesting, i didn't know it was different in the US. In Canada, for pilot logs we use "flight time" which starts when the A/C begins moving under its own power for the purpose of flight. For Journey and Technical logs, we use Air Time which is wheels-up to wheels-down.
Dan 57
Well Known Member
Yep, I did not think about continental differences... and not a trivial question for anybody interested in TBOs.
We could even divide the times into 3 categories: ground time running, block to block, and airborne.
Is anybody here logging the running time of the engine whilst doing maintenance run-ups, adjustments, etc?
I think (might be wrong...) that the usual practice on the old continent, even in the very restrictive country I'm based in, is to use take-off/landing times for a TSN and TBOs, and block-off/block-on times for one's pilot log.
Auburntsts
Well Known Member
In the US Hobbs time is universal for many logging actions (maintenance and Pilot) with no differentiation. It's admittedly not as accurate but it simplifies the process. The only items I use "clock" time for are things that are a subset of the entire flight like actual IMC and Simulated IMC time.
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WingsOnWheels
Well Known Member
In the US, Tach time is what is commonly used for engine time and maintenance. Tach time clocks slower at lower RPM, so idle time pretty much doesn't count. However, often times in sale adds, hobbs is used for total time. Like you may see a single total time listed if the engine was installed new and has not been to overhaul. In reality, the tach time will be lower.
Jpm757
Well Known Member
Many recording tachometers (whether mechanical or electronic) are calibrated to engine RPM. 1 hour at max rpm (let's say 2700) will equal 1hour of engine time. If you cruise at 2300 rpm your recording tach will indicate less than your Hobbs. For my -7 which spends most of it life at 2300 rpm, the difference is around 15%. So is a 2000 hr. TBO engine based on running that engine for 2000 hrs. at 2700 rpm? My maintenance logs are predicated on tach time, rather than Hobbs. Is an engine that reaches TBO on a Hobbs meter, really at TBO, or are there really a couple of hundred hours left to run? This is why you will see airplanes advertised with a mismatch in Airframe total time versus Engine T.T., despite being installed at the same time.
From a practical standpoint, in the U.S. Experimental world at least, it really doesn;t make much difference. Since we don’t have to abide by factory recommended TBO’s, if you’re looking to buy an airplane, you’re looking at condition - not whatever it says in the logbook. If the advertised time is off by 10%, does it really make any difference if things look good and the engine passes muster with regards to compression and overall condition?
(In our fleet, we log engine start to engine stop time for airframe time, and I generally use that for maintenance as well, since two people flying five airplanes means we frequently get to a calendar limit on oil changes before we get to hours anyway….)
If I’m buying a plane, I would throw the advertised ours into the categories of “very low time”, “mid-time”, and “High time” if shopping. Then I’d inspect!
Paul
(In our fleet, we log engine start to engine stop time for airframe time, and I generally use that for maintenance as well, since two people flying five airplanes means we frequently get to a calendar limit on oil changes before we get to hours anyway….)
If I’m buying a plane, I would throw the advertised ours into the categories of “very low time”, “mid-time”, and “High time” if shopping. Then I’d inspect!
Paul
Oftentimes something like 2500 RPM, or whatever the normal cruise RPM is for that aircraft. Discussed just a few months ago on another thread.
