Piper Aztec - Alternator Conversion

I have recently bought a 1960 Aztec with generators. Although these
have been overhauled recently, i'd rather have alternators installed.

I see InterAv have a generic kit. Has anyone installed this before?
What is the time to install, and any issues with particular brand?

Any feedback would be appreciated.

Regards,

Dean

Sorry, I have no idea, but you may want to ask he
http://piperchat.com/forum/viewforum.php?f=4
or here http://www.piperapacheclub.com/

Jim

Is there a real need for the switch? The gennies have worked for 45
years... They are reliable... They don't go overvoltage and fry your
radios like an alternator can... Yes, they make less volts/current at
idle and low rpm, but you don't have to have everything turned on until
you roll onto the runway for take off... I have gennies still on Fat
Albert the Apache (1957) and looked hard at the alternator issue and
decided I was well off as is...

cheers ... denny

Denny,

It's not that I particularly wanted to rid of the generators, just that
the existing maintenance company cant get them to work properly!! They
dont have a vested interest as i'm taking the a/c to another mtce
organisation.

The new mtce guy is like you and doesnt think I should be so quick to
dump them, but to troubleshoot the problems on the right generator
first.

Dean

Denny wrote:
Is there a real need for the switch? The gennies have worked for 45
years... They are reliable... They don't go overvoltage and fry your
radios like an alternator can... Yes, they make less volts/current at
idle and low rpm, but you don't have to have everything turned on until
you roll onto the runway for take off... I have gennies still on Fat
Albert the Apache (1957) and looked hard at the alternator issue and
decided I was well off as is...

cheers ... denny

They are reliable...

They are less reliable than alternators. Alternators have solid
commutators; generators have segmented ones - that's how a generator
makes DC. No diodes. Those segmented commutators cause arcing, and
that tends to foul them, get crap between the segments, etc. No big
deal to polish, but not fun either. This goes double if a bit of oil
that leaked from somewhere gets in there.

They don't go overvoltage and fry your radios like an alternator can...

Not true. Your generator can indeed go overvoltage. All it takes is a
failure in the overvoltage cutout on the regulator, or a field short to
ground. If the latter, the field switch will not be able to take the
generator offline. In fact, NOTHING will take it offline short of
pulling the breaker.

On top of that, even pulling the breaker is not a solution when you're
dealing with paralelled generators (and you are). That paralelling
relay system was developed for tractors (so there would not be a need
to built a very few expensive custom oversize generators) not airplanes
(with redundancy in mind). The failure I described (field short to
ground) is one that will take down the entire systems (as the
paralelling relay attempts to balance loads) and really hurts the
redundancy aspects.

Yes, they make less volts/current at
idle and low rpm, but you don't have to have everything turned on until
you roll onto the runway for take off...

Personally, I like to have all my avionics tunred on and set up when
launching into IMC, but that's just me.

In any case - I used to have all sorts of problems with my generator
system, to the point where I kept a spare generator on the shelf. Then
I replaced the 1930's-design vibrating point voltage regulators with a
Zeftronics set ($500 or so for the pair) and all the problems went
away, just like that. On top of that, the system is truly redundant
now - the regulators talk to each other and balance the laod based on
current, not voltage. If one is offline, it can't take down the other.

I suggest that as the real fix - I've had experience with the InterAv
conversion as well (friend had it on his PA-30) and was NOT impressed.
It too is a non-redundant system (master contactor failure takes down
the whole thing). The ideal soluteion would have been a truly
redundant alternator system. I understand Zeftronics was working on
that a couple of years ago - maybe they have it available now. I've
certainly been way more impressed by their stuff than anything InterAv
ever did.

Michael

Then
I replaced the 1930's-design vibrating point voltage regulators with a
Zeftronics set ($500 or so for the pair) and all the problems went
away, just like that. On top of that, the system is truly redundant
now - the regulators talk to each other and balance the laod based on
current, not voltage. If one is offline, it can't take down the other.


Michael,
Could you elaborate more on the Zeftronics system and it's components? I
believe that the regulators on our Aztec need adjustment as our left
alternator has a larger draw on it than the right. I've been told that
adjusting them isn't particularly fun and would be interested in the
Zeftronics system should we find adjusting the regulators does not solve our
output imbalance.
Thanks as always,
Jim Burns

Jim Burns wrote:
Could you elaborate more on the Zeftronics system and it's components? I
believe that the regulators on our Aztec need adjustment as our left
alternator has a larger draw on it than the right.

Unfortunately, I know nothing about their alternator system - only the
generator system.

I've been told that
adjusting them isn't particularly fun and would be interested in the
Zeftronics system should we find adjusting the regulators does not solve our
output imbalance.

I'm familiar with the process. I've never seen anyone get it right
except by luck. The mechanical regulators don't act the same with the
caps on as they do with the caps off.

Michael

Thanks.... I'll hunt them up at OSH tomorrow (hopefully)
Jim

"Michael" wrote in message
oups.com...
Jim Burns wrote:
Could you elaborate more on the Zeftronics system and it's components?
I
believe that the regulators on our Aztec need adjustment as our left
alternator has a larger draw on it than the right.

Unfortunately, I know nothing about their alternator system - only the
generator system.

I've been told that
adjusting them isn't particularly fun and would be interested in the
Zeftronics system should we find adjusting the regulators does not solve
our
output imbalance.

I'm familiar with the process. I've never seen anyone get it right
except by luck. The mechanical regulators don't act the same with the
caps on as they do with the caps off.

Michael

OK Dean, well that's just my opinion... Nothing wrong with either
alternators or gennies, just different methods to convert AC to DC....
Changing the system over to alternators is going to be expensive, and I
personally would do it only if the generators and regulators were
totally shot and needed to be replaced, then I would consider spending
the money for switching... I have to say that all the chargingn
failures I have had in flight over the past 4 decades have been the
alternators... I recognize that is just happenstance... But,
generators tend to give you lots of warning that they are hurting and I
have been lucky enough to recognize the cry for help before failure...
Not so with the alternator failures... Having said that, the RV7 I am
building will have dual alternators...
My suggestion is for you to spend the money for Bob Nucholl's book...
You will be a bunch more aware of the pitfalls of charging systems
after reading it (emminently readable and not loaded down with calculus
equations, etc)... He likes alternators, BTW...

Now, someone made a comment that one generator puts out more than the
other... Let me comment that for the generators to have automatic
selection, one has to have the regulator voltage set higher than the
other, otherwise the selector relay will `hunt'.... As a result of the
higher voltage set point that one will usually show more charging
current than the other when tested separately... I have found that
during local flights, turning off the gennie that always takes the load
(port engine on mine) and allowing the other to work, keeps the
starboard commutator healthy and ready to go if the port gennie does
shut down for real... Also, forget the current meter - it's close to
worthless... What you want is a voltage meter... On my plane the port
engine regulator is adjusted to 14.1 volts and the starboard to 13.8
volts... I don't have problems with the selector relay hunting and the
system works fine...

cheers ... denny

: shut down for real... Also, forget the current meter - it's close to
: worthless... What you want is a voltage meter... On my plane the port
: engine regulator is adjusted to 14.1 volts and the starboard to 13.8
: volts...

Not sure if you're talking of an ammeter or a loadmeter. What one really
needs to know the health of the system is *both* a voltmeter and loadmeter. If I
could only have one or the other, however, I'd agree that a voltmeter is more useful.
Anything under 13 and the alternator is maxing out (for a given RPM). Anything
under 12.5 and the battery is discharging. Anything over 14.4-ish and the battery is
boiling.

-Cory

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************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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