Tach to Hobbs conversion for logging

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Pilot-To-Be

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Hi,

I fly an airplane that doesn’t have a Hobbs meter. I’ve always used the 1 tach hour equals 1.2 hours of logging time method.

For example, I flew a XC yesterday that was 4.4 tach hours, so I multiplied by 1.2 and I logged 5.3. It more or less matched the approx clock time, so I think it’s a good measure, but I was curious of any thoughts. I am not wanting to misrepresent in anyway, but this seems to be an acceptable method. Thoughts?
 
texasclouds said:
Write down the time you start engine and the time you shut it down, then do the math.
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I’ll do that from now on, but I’m curious about all the time I’ve logged previously using the 1:1.2 method. Like I say, I’m very particular about making sure I record my experience properly for a future airline job.
 
Most Hobbs meters start counting when the master electric switch is on (edit: or via an oil pressure switch…engine running).

Tach x 1.2 may be close or may not be depending on taxi time and other variables.
 
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Pilot-To-Be said:
That doesn’t answer my question. You’re an airline guy , how did the logbook audit go?
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Well they had no questions about the authenticity of my log books. Mine were as legit and accurate as I could make them.

Read up on:

14 CFR § 61.51 - Pilot logbooks.​


And also definitions:

Flight time​

Flight time means:
(1) Pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing
 
Pilot-To-Be said:
I’ll do that from now on, but I’m curious about all the time I’ve logged previously using the 1:1.2 method. Like I say, I’m very particular about making sure I record my experience properly for a future airline job.
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Ain’t nobody going to ask you “Is that tach or Hobbs”. For math’s sake, if you did all 1500 at 1:1.2, that’s only a delta if 250. What school charges by the tach hour though?

IIRC, .mil guys use 1.3 for conversion because how we count time is different than how the FAA does.
 
Usually, you turn on the master switch with the intent to start the engine rather quickly, then shut off the master soon after engine is off. Thus, a hobbs meter gives a pretty accurate representation of “flight time”.
 
When flying our Citation, we logged Out, Off, On, In times with a watch and a pen.

Out - door closed, ready to start engine
Off - wheels up (weight off wheels)
On - wheels down
In - Engine shut down

Out to In is block time which goes in personal logbook.

Off to On time is for the airframe flight time logbook.
 
TCABM said:
Ain’t nobody going to ask you “Is that tach or Hobbs”. For math’s sake, if you did all 1500 at 1:1.2, that’s only a delta if 250. What school charges by the tach hour though?

IIRC, .mil guys use 1.3 for conversion because how we count time is different than how the FAA does.
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Agreed, that single engine time isn’t what a major airline wants to see. Tell me about that Jet PIC time where you signed for the plane as a captain.
 
1.2 is gonna be close… but…

DO NOT use a “conversion factor” unless specifically asked to do so.

There is nothing wrong with going back and relogging.

I needed my total “dual given” to be a chief instructor. Was shy a hundred hours. I mentioned the mil vs civ thing to my fed. Nay nay… but totally legit to go back and relog EVERY military flight as an instructor in a new log book… and guess what I used? Yep, .2 per flight, unless a 4 ship, always had more time marshaling… etc.
 
texasclouds said:
Agreed, that single engine time isn’t what a major airline wants to see. Tell me about that Jet PIC time where you signed for the plane as a captain.
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Well sure, but I’ve gotta get to 1500 first
 
Pilot-To-Be said:
Well sure, but I’ve gotta get to 1500 first
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Look forward, not back. Use the FAAs definition from now on because even at that first interview, ain’t nobody going to question your logbook if it’s remotely legitimate.
 
Pilot-To-Be said:
I’ve always used the 1 tach hour equals 1.2 hours of logging time method.
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Why? Don't you have a watch?

Pilot-To-Be said:
For example, I flew a XC yesterday that was 4.4 tach hours, so I multiplied by 1.2 and I logged 5.3. It more or less matched the approx clock time, so I think it’s a good measure, but I was curious of any thoughts. I am not wanting to misrepresent in anyway, but this seems to be an acceptable method. Thoughts?
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There are too many variables for a "multiplier" to be accurate, even for the same plane. Length of flight, cruise power setting, time spent taxiing, etc will all change it. It's silly.
 
Pilot-To-Be said:
I’ll do that from now on, but I’m curious about all the time I’ve logged previously using the 1:1.2 method. Like I say, I’m very particular about making sure I record my experience properly for a future airline job.
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Keep in mind that you’re actually comparing three different times here…tach, Hobbs, and flight (logbook).
 
FWIW, I just checked my aircraft log for this year. I have 63.8 Hobbs and 59.3 Tach. Ratio is 1.075.
 
Depends a lot on what you are doing...when I was a student and didn't record a clock time my instructor suggested I use a factor of 1.3 for the log...which turned out to be pretty close since most lessons involved a lot of landings. If mostly cross country, I'd use 1.2. I observed later that I could go out and do touch-and-gos for 1.0 hours on the clock, and the tach would just barely turn over to 0.6. Great deal, since the club billed by tach hours, and in the pattern the engine is at comparatively low RPM most of the time.
 
texasclouds said:
When flying our Citation, we logged Out, Off, On, In times with a watch and a pen.

Out - door closed, ready to start engine
Off - wheels up (weight off wheels)
On - wheels down
In - Engine shut down

Out to In is block time which goes in personal logbook.

Off to On time is for the airframe flight time logbook.
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Your Out and In are the goofiest thing I've ever read. You log time when you're buckling your belt and stuff? Nothing in the regulations says that logable time. Out and in refers to the out of the chocks to in to the chocks.
 
NJP_MAN said:
Your Out and In are the goofiest thing I've ever read. You log time when you're buckling your belt and stuff? Nothing in the regulations says that logable time. Out and in refers to the out of the chocks to in to the chocks.
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You start engines before buckling your belt and stuff?
 
MauleSkinner said:
You start engines before buckling your belt and stuff?
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No but he said he start logging time when he closes the door. So that means I'm logging "flight time" when I'm buckling up, getting a clearance, checking the lav or anything that's not "flight".
 
Our partnership logs both tach and Hobbs time. Over 11 years the relationship has consistently been tach time plus .2 equals Hobbs time.
 
NJP_MAN said:
No but he said he start logging time when he closes the door. So that means I'm logging "flight time" when I'm buckling up, getting a clearance, checking the lav or anything that's not "flight".
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if he starts the engine with the brake not set, the airplane moves before he stops it, so buckling up, getting a clearance, and checking the Lav WOULD count as flight time. But with the apparent exception of you, nobody waits until they’re starting engines to do that.
 
Pilot-To-Be said:
I’ll do that from now on, but I’m curious about all the time I’ve logged previously using the 1:1.2 method. Like I say, I’m very particular about making sure I record my experience properly for a future airline job.
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Who's going to be able to contest differently? If you say a flight was 2.0, there's nobody that can say "no, it was only 1.8 because of tach conversion errors, blah blah". I'm not saying to just make up numbers, but if you put down 2.0 due to measuring in a reasonable way, it's 2.0.

But I also agree with others, there's no need to do that whole 1.2x thing anyway going forward. Just use the actual engine times from your watch or other clock. Many logbook apps (I prefer MyFlightBook) will do the math for you. Easy.
 
With FlightAware, just use flight time plus another 0.3 or whatever it is for the airports you started and taxiied, and taxied and shutdown at.
 
MauleSkinner said:
if he starts the engine with the brake not set, the airplane moves before he stops it, so buckling up, getting a clearance, and checking the Lav WOULD count as flight time. But with the apparent exception of you, nobody waits until they’re starting engines to do that.
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Out is out of the blocks. That's it. It's not starting engines. It's not combing your mustache. It's pretty clear. I just decided to start logging when I close the door on my house. I'm headed to the airport to fly so it all counts on according to the logic.
 
NJP_MAN said:
Out is out of the blocks. That's it. It's not starting engines. It's not combing your mustache. It's pretty clear. I just decided to start logging when I close the door on my house. I'm headed to the airport to fly so it all counts on according to the logic.
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Apparently you have both a different definition of “ready to start engines” than most people, and a different definition of loggable “flight time” than the FAA.
 
Pilot-To-Be said:
I’ll do that from now on, but I’m curious about all the time I’ve logged previously using the 1:1.2 method. Like I say, I’m very particular about making sure I record my experience properly for a future airline job.
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You know, no one is ever gonna know if there are discrepancies between hobbs and tach.
 
TommyG said:
You know, no one is ever gonna know if there are discrepancies between hobbs and tach.
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I’d actually be more concerned about saying, “I use xxx method to convert tach to flight time.” If I were an interviewer, my first question would be, “how did you validate that?” As @GaryM noted, there can be huge variability between the two.
 
That’s exactly what I’ve seen at FIVE part 121 airlines. Including American and Delta. Ain’t so weird.

At American Eagle, “in” was recorded by ACARS when parking brake set, transmitted when door opened… so…. Capts would reset parking brake every minute that clicked over before the door opened…
 
MauleSkinner said:
Unlike your previous statement.
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My statement,
"No but he said he start logging time when he closes the door."

His statement
"
Out - door closed, ready to start engine
Off - wheels up (weight off wheels)
On - wheels down
In - Engine shut down"

I reiterate
"Out - door closed, ready to start engine"

So, pretty much exactly what I said. Nice try
 
NJP_MAN said:
My statement,
"No but he said he start logging time when he closes the door."

His statement
"
Out - door closed, ready to start engine
Off - wheels up (weight off wheels)
On - wheels down
In - Engine shut down"

I reiterate
"Out - door closed, ready to start engine"

So, pretty much exactly what I said. Nice try
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I’d suggest a little study of the English language. They’re nowhere near “pretty much exactly” the same.
 
MauleSkinner said:
I’d suggest a little study of the English language.
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Regardless of you being wrong, you still don't log flight time until the aircraft moves under its own power for the purpose of flight. That's the FAAs definition not mine.
 
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