Twin tachs

[Jim Burns[_1_]]

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

[Allen[_1_]]

"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

[Jim Burns[_1_]]

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

[Allen[_1_]]

"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

[Jim Burns[_1_]]

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
>
>
>

[Jon Kraus]

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
>
>
>

[Allen[_1_]]

"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

[Kyler Laird]

"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

[Kyler Laird]

"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

[FlyWithTwo]

Jim Burns wrote:
>
> Is there anybody out there with any insight into this dilemma?
>
> Thanks,
> Jim

Hi Jim,
I have a dual needle tach in the 310 with electric tach generators on
each engine - no tach hour recorder. The plane has a hobbs meter that
is activated by a switch. It's not exactly a weight on wheels switch.
It is a microswitch activated by a small stainless steel flap on the
belly that is sensitive to airflow, similar to a stall switch. DC
power goes to the Hobbs, and the ground goes through the switch. It's
supposed to activate at a certain airspeed, but I know it has some
bounce due to airflow from propeller wash when taxiing and running up
the engines.

I previously had a Cessna single with both a Hobbs and Tach hour meter.
When averaged, I found that multiplying 1.15 times the Tach meter was
close to the Hobbs time. I've heard of others with planes on leaseback
that only had tach meters charging something like 1.1 or 1.2 times the
tach time.

Brian

[Jim Burns[_1_]]

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[_1_]]

I've been talking to John at Diamondaire... Rochester totally dropped the
project, he's now working with Westach, but nothing forthcoming. His
solution for now is to use tach generators and electric tachs as the late F
model Aztecs and Barons had.

For now, I'll put in a twin needle mechanical and keep the tach cables
installed. If I blow a cable I'll think about my options once again. I'd
love a dual electronic tach from EI or Horizon... someday... but unless they
come out with a 3 1/8" model I'd have to redo the right panel :(

Jim

"Kyler Laird" > wrote in message
...
> "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

[[email protected]]

Jim Burns > wrote:
> 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?

This may be a totally goofy idea, but here goes. Install the mechanical
dual tach in the panel as above. Then get two Hobbs meters and wire one
to each engine. (I know Hobbs meter time is not tach hour meter time,
but play along.) Now, since you probably don't need to look at the
Hobbs meters every couple of minutes during your flight, you can stick
them in whatever available space you have behind the panel. (An LCD
Hobbs meter is only about 1"x2"x2".) You don't have to mount them so
that the numbers are normally visible; you just have to mount them so
that the numbers are visible when you want them.

If you have enough room, you can mount them on a hinged plate or flap
that can be swung down to read the meters and then swung back up out of
the way. Maybe install a captive thumbscrew or Dzus fastener to hold
the plate in the "stowed" position. Alternatively, mount the meters
without a hinge or flap, and mount small mirrors (like a mechanic's
inspection mirror, or a dental mirror) to bring the numbers out to
where you can see them. As long as you use an even number of mirrors,
you can read the numbers. The mirror closest to your eye probably needs
to be adjustable/removable/coverable, as it might reflect sunlight into
your face in certain situations.

If you believe that there's just no kill like an overkill, mount the
meters behind the panel as above, but also include a small LED or lamp
for illumination, a cheap webcam, and a small single-board computer with
video capture, OCR software, and audio output. Wire the output into an
aux input on your headphone system and wire a pushbutton to the board;
when you push the button it says something like "left engine three six
two point five hours, right engine three six one point seven hours" into
the audio system.

Matt Roberds

[Peter Clark]

On Thu, 24 Aug 2006 00:36:11 GMT, wrote:

>You don't have to mount them so
>that the numbers are normally visible; you just have to mount them so
>that the numbers are visible when you want them.

A Duchess I used to fly had the hobbs thing for the engines mounted in
the aft wall of the luggage compartment........

[Kyler Laird]

Peter Clark > writes:

>A Duchess I used to fly had the hobbs thing for the engines mounted in
>the aft wall of the luggage compartment........

Is there any reason to have them in the cabin at all? Are there
approved clocks that can survive being in the engine compartment? Even
renters only look at them before each flight, right?

--kyler

[Peter Clark]

On Tue, 29 Aug 2006 09:25:05 -0400, Kyler Laird
> wrote:

>Peter Clark > writes:
>
>>A Duchess I used to fly had the hobbs thing for the engines mounted in
>>the aft wall of the luggage compartment........
>
>Is there any reason to have them in the cabin at all? Are there
>approved clocks that can survive being in the engine compartment? Even
>renters only look at them before each flight, right?

Just so it can be read for filling out the tach/hobbs card handed into
the FBO so they know when MX is required.

[[email protected][_1_]]

On Tue, 29 Aug 2006 09:25:05 -0400, Kyler Laird
> wrote:

>Peter Clark > writes:
>
>>A Duchess I used to fly had the hobbs thing for the engines mounted in
>>the aft wall of the luggage compartment........
>
>Is there any reason to have them in the cabin at all? Are there
>approved clocks that can survive being in the engine compartment? Even
>renters only look at them before each flight, right?

Did a pre-buy on a Seminole one time that had 2 recording tachs and 2
independent aircraft hour meters. It had been used at a flight school,
all the "recording" devices had been changed multiple times.

Also, the maintenance records had random references to any/all of
them.

Probably one of the worst sets of logs that I've ever had to dig
through...

TC