Time Measurement for Inspections

[O. Sami Saydjari]

OK, dumb question. For 100-hour inspections (or 50 hours until oil
change), is this measured in Hobbs time or Tach time?

-Sami
N2057M, Piper Turbo Arrow III

[Dennis O'Connor]

The tach is the instrument for measuring engine hours...
denny

"O. Sami Saydjari" > wrote in message
...
> OK, dumb question. For 100-hour inspections (or 50 hours until oil
> change), is this measured in Hobbs time or Tach time?
>
> -Sami
> N2057M, Piper Turbo Arrow III
>

[G.R. Patterson III]

"O. Sami Saydjari" wrote:
>
> OK, dumb question. For 100-hour inspections (or 50 hours until oil
> change), is this measured in Hobbs time or Tach time?

Everyone I know uses whichever gives them the longest period between inspections.
This is usually tach time, but I know a few people who have wired a Hobbs to the
squat switch on a retract so that they can schedule maintenance based on time spent
in the air.

Me, I use calendar time, since I never log over 50 hours in a 4 month period and have
annual inspections, rather than 100 hour.

George Patterson
This marriage is off to a shaky start. The groom just asked the band to
play "Your cheatin' heart", and the bride just requested "Don't come home
a'drinkin' with lovin' on your mind".

[Jim Weir]

Not a dumb question at all. You can use a sand hourglass if you want, just so
long as you use the same method all the time. That is, use hobbs OR tach OR
wris****ch, just be consistent.

No, the regs do not REQUIRE you to use the same method every time, but you'll
play hell explaining your method to the FAA if they come a'snoopin'.

Jim


"O. Sami Saydjari" >
shared these priceless pearls of wisdom:

->OK, dumb question. For 100-hour inspections (or 50 hours until oil
->change), is this measured in Hobbs time or Tach time?
->
->-Sami
->N2057M, Piper Turbo Arrow III


Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[Rich]

Technically, neither...
In Part I, Definitions,
"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."

As a practical matter, for Part 91 operations, I've never heard of
anybody using anything but tach time.

Rich



O. Sami Saydjari wrote:
> OK, dumb question. For 100-hour inspections (or 50 hours until oil
> change), is this measured in Hobbs time or Tach time?
>
> -Sami
> N2057M, Piper Turbo Arrow III
>

[kage]

There is no tach on a jet. Lots of part 91 operations.

Karl

"Rich" > wrote in message
...
> Technically, neither...
> In Part I, Definitions,
> "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."
>
> As a practical matter, for Part 91 operations, I've never heard of
> anybody using anything but tach time.
>
> Rich
>
>
>
> O. Sami Saydjari wrote:
> > OK, dumb question. For 100-hour inspections (or 50 hours until oil
> > change), is this measured in Hobbs time or Tach time?
> >
> > -Sami
> > N2057M, Piper Turbo Arrow III
> >
>

[[email protected]]

On 3-Apr-2004, "kage" > wrote:

> There is no tach on a jet. Lots of part 91 operations.
>
> Karl
>
> "Rich" > wrote in message
> ...
> > Technically, neither...
> > In Part I, Definitions,
> > "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."
> >
> > As a practical matter, for Part 91 operations, I've never heard of
> > anybody using anything but tach time.
> >
> > Rich


I wonder what they use for sailplanes.

-Elliott Drucker

[d b]

Just did that Saturday. At annual time, I make a single line entry in the
aircraft logs that says "nxyz flew x hours from xx/xx/xx to yy/yy/yy" and
sign my name and date it. After that, the mechanic makes his entries
for the annual.

Some pilots actually log each flight. That is neat because it is interesting
to see what kind of adventures and places the gllider has seen during it's
life.

In article >,
wrote:
>On 3-Apr-2004, "kage" > wrote:
>
>> There is no tach on a jet. Lots of part 91 operations.
>>
>> Karl
>>
>> "Rich" > wrote in message
>> ...
>> > Technically, neither...
>> > In Part I, Definitions,
>> > "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."
>> >
>> > As a practical matter, for Part 91 operations, I've never heard of
>> > anybody using anything but tach time.
>> >
>> > Rich
>
>
>I wonder what they use for sailplanes.
>
>-Elliott Drucker

[Ron Natalie]

"Dennis O'Connor" > wrote in message ...
> The tach is the instrument for measuring engine hours...

Not necessarily. The FAA just wants a consistent reasonably accurate way of
recording time in service. Some aircraft, like late model Bonanza's (and now my
Navion) don't even have a recording tach (no tach time at all). We use the elapsed
time meter (hobbs).

[Tom Sixkiller]

"Ron Natalie" > wrote in message
m...
> Not necessarily. The FAA just wants a consistent reasonably accurate way
of
> recording time in service. Some aircraft, like late model Bonanza's (and
now my
> Navion) don't even have a recording tach (no tach time at all). We use
the elapsed
> time meter (hobbs).

What do you consider "late model Bonanza"? Every one I've looked at (from
1987 onward until they stopped making them in 1994 has one (at least in the
F33A model).

Guessing that Hobbs time is 25% higher than Tach time, I'd put a recording
tach in if it didn't have one already.

[JDupre5762]

>What do you consider "late model Bonanza"? Every one I've looked at (from
>1987 onward until they stopped making them in 1994 has one (at least in the
>F33A model).

How about a 2003 model A36? I service a 1998 A36 and it has no recording tach
only a hobbs meter. All the engine instruments have been reduced to about 1.5"
diameter dials, no room for a tach counter.

John Dupre'

[Ron Natalie]

"JDupre5762" > wrote in message ...
> >What do you consider "late model Bonanza"? Every one I've looked at (from
> >1987 onward until they stopped making them in 1994 has one (at least in the
> >F33A model).
>
> How about a 2003 model A36? I service a 1998 A36 and it has no recording tach
> only a hobbs meter. All the engine instruments have been reduced to about 1.5"
> diameter dials, no room for a tach counter.
>
Yep, that's the ticket. My Navion now has the prop, engine, and engine instruments from
a 2003 A36. Got it with 9 hours total (just enough time to get it from Kansas down to
the conversion shop to put the turboprop on). My old tach wouldn't have worked anyhow.
It was set up for the old Gopher-35 engine which cruises at 2800 RPM. The hours on the
tach weren't the total time anyhow (not the original tach, had to add something like 4000 hours
to the value).

[Michael]

Rich > wrote
> As a practical matter, for Part 91 operations, I've never heard of
> anybody using anything but tach time.

Absence of evidence is not evidence of absence.

My Twin Comanche does not have a recording tach, because it has a
single instrument (dual needle) for both engines. Hobbs time would
have meant inspections at unnecessarily frequent intervals. My
solution was to interface an hourmeter to the squat switch using an
isolation relay. That gives me the real time in service, defined as:

> In Part I, Definitions,
> "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."

The truly hilarious part of this - in order to get the installation
approved, I generated so much paperwork that the weight of the paper
exceeded the weight of the installed components.

Michael

[Russell Kent]

Michael wrote:

> My Twin Comanche does not have a recording tach, because it has a
> single instrument (dual needle) for both engines. Hobbs time would
> have meant inspections at unnecessarily frequent intervals. My
> solution was to interface an hourmeter to the squat switch using an
> isolation relay.

<snip>

> The truly hilarious part of this - in order to get the installation
> approved, I generated so much paperwork that the weight of the paper
> exceeded the weight of the installed components.

In order to reduce the chance of this happening again, I'd suggest using
lighter paper next time. :-)
http://www.xerox.com/Static_HTML/xsis/lwpaper.htm

Russell Kent

[R. Wubben]

On a related note,
I just got a (new to me) 1962 Cessna 172. Are the fuel burn tables in
tach time or hobbs time (I have both) and have been using tach time as
it gives me a slightly higher fuel burn (but is more conservative).

Or am I way off base...?

Ryan Wubben
Madison, WI

[Richard Kaplan]

"R. Wubben" > wrote in message
om...

> On a related note,
> I just got a (new to me) 1962 Cessna 172. Are the fuel burn tables in
> tach time or hobbs time (I have both) and have been using tach time as
> it gives me a slightly higher fuel burn (but is more conservative).

Fuel burn tables are in real (clock) time.

--------------------
Richard Kaplan, CFII

www.flyimc.com