Twin tachs

One of the tachs in our Aztec has been acting kind of flakey, usually
reading too high when above 2100 rpms, (I've checked it several times with
an optical tach) so I've been contemplating our options of replacing both
tachs with a single dual needle tach. This would open up some panel space
allowing me to spend ludicrous AMU's on another toy.

One option is to simply get a mechanical dual tach and connect both tach
cables to the single tach but I don't know of a dual recording tach that has
dual hour meters. Anybody?

Another option is to get rid of the cables, buy tach generators, and an
electric dual needle tach. But I still don't know of a company that makes a
dual recording tach.

So far, I have not found a company that makes a dual electronic tach.
Neither E.I or Horizon seem to offer a dual tach. Also, due to panel
configuration, I want a 3 1/8" dia tach not the smaller 2 1/4" tachs that EI
or Horizon offer, I have no room for additional 2 1/4" gauges.

Is there anybody out there with any insight into this dilemma?

Thanks,
Jim

"Jim Burns" wrote in message
...
One of the tachs in our Aztec has been acting kind of flakey, usually
reading too high when above 2100 rpms, (I've checked it several times with
an optical tach) so I've been contemplating our options of replacing both
tachs with a single dual needle tach. This would open up some panel space
allowing me to spend ludicrous AMU's on another toy.

One option is to simply get a mechanical dual tach and connect both tach
cables to the single tach but I don't know of a dual recording tach that
has
dual hour meters. Anybody?

I don't believe you need a recording tach. Most twin engine retractable
aircraft only record "flight" time and have a squat switch installed that
powers the Hobbs meter when the aircraft is airborne. Just don't forget to
disconnect the power to it while you have it up on jacks doing MX with the
battery on.

Allen

Yep. Got one of them also, but a previous owner wired it to the master
switch instead of the squat switch. Must have been used as a trainer or
rental at one point. That's little item has been on our "fix it" list for
a long time. I just think it's kind of nice to be able to look at the tachs
and see how many hours are on each engine.
Jim

"Jim Burns" wrote in message
...
Yep. Got one of them also, but a previous owner wired it to the master
switch instead of the squat switch. Must have been used as a trainer or
rental at one point. That's little item has been on our "fix it" list
for
a long time. I just think it's kind of nice to be able to look at the
tachs
and see how many hours are on each engine.
Jim

If you find a dual recording tach it still will not tell you the hours on
"your" engines, you will still need to do the math. I would go with the less
mechanically complex tach and a Hobbs meter. Hobbs meters are cheap and you
could put in a "0" time one at the next engine overhaul so the times
matched.

Allen

The tach shops will run a new or rebuilt tack up to any number you want....
for about the price of a hobbs meter. But I doubt if I'll find a dual
recording tach.
Jim

If you find a dual recording tach it still will not tell you the hours on
"your" engines, you will still need to do the math. I would go with the
less
mechanically complex tach and a Hobbs meter. Hobbs meters are cheap and
you
could put in a "0" time one at the next engine overhaul so the times
matched.

Allen

Isn't engine TBO driven off the engine tach-time and not Hobbs meter
time? Since I don't have a hobbs meter in the Mooney does that mean my
engine is not recording any wear? ;-)

Jon Kraus




Allen wrote:

"Jim Burns" wrote in message
...

Yep. Got one of them also, but a previous owner wired it to the master
switch instead of the squat switch. Must have been used as a trainer or
rental at one point. That's little item has been on our "fix it" list
for
a long time. I just think it's kind of nice to be able to look at the
tachs
and see how many hours are on each engine.
Jim


If you find a dual recording tach it still will not tell you the hours on
"your" engines, you will still need to do the math. I would go with the less
mechanically complex tach and a Hobbs meter. Hobbs meters are cheap and you
could put in a "0" time one at the next engine overhaul so the times
matched.

Allen

"Jon Kraus" wrote in message
. ..
Isn't engine TBO driven off the engine tach-time and not Hobbs meter
time? Since I don't have a hobbs meter in the Mooney does that mean my
engine is not recording any wear? ;-)

Jon Kraus

Heh Heh, if it only worked that way. I have customers come in from Mexico
for overhauls at "TBO" with probably twice the actual hours on the engines.
Not very many twins have the recording tach like the Aztec.

Allen

"Jim Burns" writes:

Yep. Got one of them also, but a previous owner wired it to the master
switch instead of the squat switch.

You have a squat switch?

BTW, we changed our Hobbes meter to run off of the heater.

--kyler

ROFL!
The heater huh? lots of free summer time hours! We actually have
another hobbs on the heater... for the heater

Well, the squat switch is a hydraulic by pass, but the hobbs should be wired
to the gear door switch or the gear up light.

Jim

"Kyler Laird" wrote in message
...
"Jim Burns" writes:

Yep. Got one of them also, but a previous owner wired it to the master
switch instead of the squat switch.

You have a squat switch?

BTW, we changed our Hobbes meter to run off of the heater.

--kyler

"Jim Burns" writes:

One option is to simply get a mechanical dual tach and connect both tach
cables to the single tach but I don't know of a dual recording tach that has
dual hour meters. Anybody?

I probably have the one we pulled from our Aztec in my junk box.

So far, I have not found a company that makes a dual electronic tach.
Neither E.I or Horizon seem to offer a dual tach.

I was told that Horizon would have a dual tach. "soon" when we were
looking in 2001.

Also, due to panel
configuration, I want a 3 1/8" dia tach not the smaller 2 1/4" tachs that EI
or Horizon offer, I have no room for additional 2 1/4" gauges.

The Horizon P-1000 is a larger tach.

Another option is (always) on the horizon...
http://diamondaire.com/aztec.htm

Rochester engine instrumentation.We are currently working with
Rochester Gauges of Texas to introduce new 2-1/4" dual-needle
STC'd backlit gauges. [...] A 3-1/8" dual electric STC'd
tachometer will also be available.
(They've been saying that for awhile now.)

Is there anybody out there with any insight into this dilemma?

It's worth pursuing. I hate mechanical tachs. I've replaced those
damn cables way too many times. It makes no sense to have all that
crap in the plane just to provide a really lousy estimate of engine
speed. In a single it's o.k. but in a twin it's ridiculous. (I recall
the joy of yanking those cable housings out of my plane!)

You will love an electronic tach. I especially like the mag. failure
lights and the mag. drop feature. Having a tach. that always works and
is accurate without constant maintenance is pretty sweet too.

--kyler