CGR 30P - Maint Hrs Logging

PilotRPI

PilotRPI

Line Up and Wait
Joined
Jun 21, 2012
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669
Location
MA - 1B9
Display Name
PilotRPI
Home Airfield
1B9 - Mansfield, MA
In short, do you use engine hours or tach hours as shown on the display to log your hours? It seems that tach hours only accrue when your RPM is over 1300 RPM, and engine hours accrue when your RPM is over 300 RPM. Traditional RPM gauges seem to accrue proportionately to a certain cruise RPM, so often under-count compared to clock/hobbs hours unless on a longer flight with very high RPM. I've asked EI if hours accrue proportionately for those two types of hours as well, or are they just hobbs/full hours any time they are being counted. I'll let you know what I hear back. Seems like tach hours might be closer to what was done historically to match a mechanical tach, but engine hours might count more time for any time the engine is running at lower RPM (warm ups, decents, etc).
 
PilotRPI said:
Seems like tach hours might be closer to what was done historically to match a mechanical tach,
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Tach time gets you closer the requirement for time-in-service. For the purists, have seen them go has far to install gear switches to start the TIS recording.

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PilotRPI said:
In short, do you use engine hours or tach hours as shown on the display to log your hours? It seems that tach hours only accrue when your RPM is over 1300 RPM, and engine hours accrue when your RPM is over 300 RPM. Traditional RPM gauges seem to accrue proportionately to a certain cruise RPM, so often under-count compared to clock/hobbs hours unless on a longer flight with very high RPM. I've asked EI if hours accrue proportionately for those two types of hours as well, or are they just hobbs/full hours any time they are being counted. I'll let you know what I hear back. Seems like tach hours might be closer to what was done historically to match a mechanical tach, but engine hours might count more time for any time the engine is running at lower RPM (warm ups, decents, etc).
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I was told by EI “engine” time was used as the name since Honbs could not be used because of trademark
 
Just ran into this recently. Got my plane out of annual and was using ENG time to track time. I was surprised at how much I was flying compared to paste years. Then the lightbulb went off that I should be using TACH instead of ENG. Made the difference of a little under 10 hours.
 
PilotRPI said:
In short, do you use engine hours or tach hours as shown on the display to log your hours?
Click to expand...

Depends on what you mean by "log". Maintenance or flight hours? I've always heard use Tach for maintenance and Hobbs for flight. AFAIK the FAA is agnostic on the subject as long as you are consistent.
 
In reality, neither one is strictly correct. Tach time is engine running time that varies with rpm. Hobbs time starts as soon as there is oil pressure. The FARs say you should log flight time from the first time the aircraft moves with the intention of flight until it comes to a complete stop after flight. If you are a person who waits for the oil to warm up a bit before taxiing, your Hobbs time will not be correct to log as flight time... but close enough.

In the Air Force, we logged takeoff to landing as flight time, and when we got out, we were told we could multiply our hours by 103% to get a civilian equivalent. I didn't bother.
 
What problem are you trying to solve for where you're worried about the very slight variations between historical Tach and Hobbs readings?
 
bradg33 said:
What problem are you trying to solve for where you're worried about the very slight variations between historical Tach and Hobbs readings?
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It's a noticeable difference in the hours.
 
Heard back from EI. Both counters log 1:1 time independent of RPM, so they don't "tick" faster or slower depending on RPM. He made it sound like tach time on their counter is closer to what one would traditionally use for maintenance on a traditional mechanical tach.

Keep in mind per the title I am talking about maintenance hour logging in the books, not flight time. For that I just look at my watch when I start rolling my wheels after the warm up.
 
PilotRPI said:
Heard back from EI. Both counters log 1:1 time independent of RPM, so they don't "tick" faster or slower depending on RPM. He made it sound like tach time on their counter is closer to what one would traditionally use for maintenance on a traditional mechanical tach.

Keep in mind per the title I am talking about maintenance hour logging in the books, not flight time. For that I just look at my watch when I start rolling my wheels after the warm up.
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I need to read post before posting! I wonder how flight schools log time? Probably Hobbs time for billing and tach time for maintenance 100 hour inspections?
 
PilotRPI said:
Keep in mind per the title I am talking about maintenance hour logging in the books, not flight time. For that I just look at my watch when I start rolling my wheels after the warm up.
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You can also use that same watch to track maintenance time as well. Just start the time when the wheels leave the surface and stop the time when the wheels touch the surface again. This method will also give you the most accurate "maintenance time" readings.
 
bonefishpete said:
I need to read post before posting! I wonder how flight schools log time? Probably Hobbs time for billing and tach time for maintenance 100 hour inspections?
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Every flight school I've rented from used Hobbs for charging rental time, and the tach for logging time in the maintenance logs.
 
PART 1—DEFINITIONS

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; or


(2) For a glider without self-launch capability, pilot time that commences when the glider is towed for the purpose of flight and ends when the glider comes to rest after landing.

Time in service, with respect to maintenance time records, means the time from the moment an aircraft leaves the surface of the earth until it touches it at the next point of landing.
 
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