Today's Message Index:
----------------------
1. 03:05 AM - Re: rotax generator without battery (rampil)
2. 04:58 AM - Re: rotax generator without battery (user9253)
3. 05:54 AM - Re: rotax generator without battery (Robert L. Nuckolls, III)
4. 06:03 AM - Re: rotax generator without battery (Robert L. Nuckolls, III)
5. 06:36 AM - Re: rotax generator without battery (user9253)
6. 07:00 AM - Re: rotax generator without battery (GTH)
7. 07:31 AM - Re: Poisonous Battery Vapors? (Eric M. Jones)
8. 08:42 AM - Re: rotax generator without battery (Ken Ryan)
9. 08:56 AM - Re: rotax generator without battery (Robert L. Nuckolls, III)
10. 09:42 AM - Re: Re: Poisonous Battery Vapors? (Carlos Trigo)
11. 01:46 PM - Re: rotax generator without battery (Robert L. Nuckolls, III)
12. 02:00 PM - Re: rotax generator without battery (GTH)
13. 02:01 PM - Re: rotax generator without battery (Ken Ryan)
14. 05:13 PM - Re: rotax generator without battery (Ken Ryan)
Message 1
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Subject: | Re: rotax generator without battery |
If your aux alternator is running off the spline takeoff in the back of
the gearbox, it is never turning at engine RPM and so will never
produce its max rated output of "40" amps. I don't see why you
are planning to just throw away the 15-16 amps from the engine's
alternator.
--------
Ira N224XS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=460998#460998
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Subject: | Re: rotax generator without battery |
Yes, I suggested a momentary push button switch to bypass the oil pressure switch.
A guarded maintained switch could be used instead.
Another option is to automatically energize the fuel pump whenever the starter
is energized.
> Joe, how would I accomplish the engine start? The primary fuel pump needs the
generator and the auxiliary needs oil pressure. Is that what the push button
is for?
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=461000#461000
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Subject: | Re: rotax generator without battery |
At 04:48 PM 10/5/2016, you wrote:
>Thanks Bob.=C2
>
>What would the effect be on the pump if it was
>getting less than ideal amps/volts? Would it
>simply lower the performance of the pump?=C2
If you're talking about and electric,
"thump-thump" pump, you just about cannot
hurt these with any sort of electrical abuse
short of severe over voltage. Pioneered by
Bendix in the 60's, the motor that drives
the pump is simply a solenoid (originally
energized through a set of contacts no unlike
a switch relay) that compresses a spring which
in turn forces fuel out of the pump. As the
fuel flowed out under spring force, a pair
of check valves allowed fuel to be sucked in
behind the piston. When it reached end of
travel, contacts would close, solenoid would
pull the piston back thus re-compressing the
spring.
Modern versions are all solid state. In
the example you see here
http://tinyurl.com/hxwckfr
Figure 10 shows our old friend the 555 timer
used to periodically compress the spring with
a string of short pulses . . . energy applied
irrespective of flow rate through the pump.
This configuration offers an exceedingly
simple, robust design with very long service
life (the contacts would wear out on the
original Bendix design and were not repairable).
>Regarding automatic shut off of the pump, the
>master switch is hardly "automatic." The
>scenario would be one of a crash with injuries.
>We would want the electric fuel pump to shut
>down when the engine shuts down so that it does
>not continue to pump fuel, possibly into a ruptured fuel system.
Electric fuel pumps have been used on aircraft
in various forms almost since day-one. The
POWER source for that device along with all
other electrically driven components offers
a potential ignition source for spilled fuel.
Hence the legacy requirement for crew accessible
control of all electrical sources in the form
of alternator/generator and battery switches.
The idea is that a pilot generally knows when
an off-field landing is imminent and will
shut off those energy sources before the
crash.
This 'new' push by Rotax to dedicate the
built-in PM alternator to running just one
fuel pump is a puzzlement . . .
In he past, this 18A alternator powered
entire airplanes . . . thousands of them. Now
see a suggestion that this capable source be
partitioned off to run one of the smallest
energy-demands in airplane . . . a thump-thump
pump.
Adding a 40A external alternator to the 912/914
engine offers a great opportunity to craft
a Z-13/8 style system in the airplane . . . except
it's a Z-13/18 with about twice the stand-by
power of the original Z-13/8.
This two-layered electrical system is about as
robust with respect to failure modes as you can
get. One pump would run from the battery bus,
the second from the e-bus . . . or main bus . . .
it wouldn't much matter with that large a stand-
by energy source.
This thing Rotax recommends for dedicating an
18A alternator to running just one pump is,
in my not so humble opinion, just silly.
Bob . . .
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Subject: | Re: rotax generator without battery |
At 05:56 PM 10/5/2016, you wrote:
>That may be true, but the Rotax 912iS and the UL Power engines do
>shut off fuel pumps when the engine stops as do all modern
>automobiles. Again, I am not concerned with a forced landing where
>there is time to prepare. I am concerned with a crash, such as
>flipping the aircraft due to soft or rough terrain, or a million
>other things that could conceivably happen (and do happen). In such
>an instance, I would prefer not to have a high pressure fuel pump
>doing its job.
You say "high-pressure" . . . is this no longer
the solenoid driven spring style pump I described
earlier? Is the 912/914 now fuel-injected?
In any case, you can achieve the automatic shut
off in the same way that cars have for decades.
My truck uses an oil pressure switch to keep
the pump running with a bypass relay energized
by the starter switch to get fuel pressure while
cranking. Your 'bypass' could be a simple diode
off the starter engagement line that feeds power
directly to the pump while cranking.
Bob . . .
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Subject: | Re: rotax generator without battery |
The Rotax 912 (with carburetor) has an engine driven fuel pump, so the engine is
not electrically dependent. The Rotax 914iS fuel injected engine is electrically
dependent with two high pressure fuel pumps. It seems that the Rotax engineers
(and lawyers) do not trust aircraft electrical systems to be fail safe.
Thus they have dedicated the flywheel dynamo to powering only a fuel pump.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=461007#461007
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Subject: | Re: rotax generator without battery |
/Le 06/10/2016 14:53, Robert L. Nuckolls, III a crit :
/
> /
> If you're talking about and electric,
> "thump-thump" pump,/
Hi Bob and all,
Just to say that the Rotax 914 pumps are the rotary vane type from
Pierburg, like some German cars.
http://contrails.free.fr/engine_pierburg_en.php
FWIW,
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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Subject: | Re: Poisonous Battery Vapors? |
I wondered if the battery was located in the passenger compartment so I looked it up. https://www.youtube.com/watch?v=d6ZTeFT137Y#t=26.879952
Yes, and it takes three boys and a monkey to swap one. Amazing. When I saw this
I was glad I didn't own one. But I still doubt the Cause Of Death pronouncement.
Cars usually have enough ventilation to avoid the buildup of noxious vapors.
Aircrafts probably do even more.
Recently around here a guy died because he was drunk and sleeping in his car, which
went up to a zillion degrees in the sun. So I'd look for some COD that is
more plausible.
"Wisdom is being aware of the obvious."
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=461010#461010
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Subject: | Re: rotax generator without battery |
Bob, the 914 engine is not fuel injected, but it is turbocharged and there
is a fuel pressure regulator that maintains a constant fuel pressure over
air pressure produced by the turbo. From what I can tell, it works the same
as injection in that a lot of fuel is pumped to the regulator, but most of
that is returned to the tank. I have no idea what a thump-thump pump is,
but I believe the Rotax pumps are the same type as used in fuel injected
automobiles.
Ira, the 40 amp aux is belt driven.
On Thu, Oct 6, 2016 at 5:59 AM, GTH <gilles.thesee@free.fr> wrote:
>
> *Le 06/10/2016 =C3- 14:53, Robert L. Nuckolls, III a =C3=A9crit : *
>
>
> * If you're talking about and electric, "thump-thump" pump,*
>
>
> Hi Bob and all,
>
> Just to say that the Rotax 914 pumps are the rotary vane type from
> Pierburg, like some German cars.
>
> http://contrails.free.fr/engine_pierburg_en.php
>
> FWIW,
> --
> Best regards,
> Gilles
> http://contrails.free.fr
> http://lapierre.skunkworks.free.fr
>
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Subject: | Re: rotax generator without battery |
At 08:59 AM 10/6/2016, you wrote:
>Le 06/10/2016 =E0 14:53, Robert L. Nuckolls, III a =E9crit :
>>
>> If you're talking about and electric,
>> "thump-thump" pump,
>
>Hi Bob and all,
>
>Just to say that the Rotax 914 pumps are the
>rotary vane type from Pierburg, like some German cars.
>
><http://contrails.free.fr/engine_pierburg_en.php>http://contrails.free.fr/e
ngine_pierburg_en.php
Thanks. Okay, on the order of 30psi max. Do we
know what the cracking pressure is for the
fuel return line?
The specs call for not more than 4.3A which
would be at static pressure rating. This
will be reduced in approximate proportion
to the fuel control system pressure relief
settings.
It would be a valuable knowledge-nugget to contribute
to the library if someone made a real-time
measurement of fuel pump current in this system,
The Rotax 912 (with carburetor) has an engine
driven fuel pump, so the engine is not
electrically dependent. The Rotax 914iS fuel
injected engine is electrically dependent with
two high pressure fuel pumps. It seems that the
Rotax engineers (and lawyers) do not trust
aircraft electrical systems to be fail
safe. Thus they have dedicated the flywheel
dynamo to powering only a fuel pump.
Hmmmm . . . I wonder from whence their
discomforts are derived? A study of the aviation
accident reports shows that loss of electrical
power is almost never a contributing factor
in loss of engine . . . and it's an easy task
to craft a failure tolerant system that
insures sources of energy vital to engine
operation.
Z-13/8 evolved out of decades of experience
and observation of aircraft operations in
both TC and OBAM aviation venues. I would
really appreciate it if anyone associated
with Rotax or any other institution could
show by considered FMEA how any aircraft
fitted with Z-13/x is likely to suffer engine
failure due to any single failure within
the system.
Some cultures find comfort in staffing
committees of individuals paid to worry.
All too often, work product of such
committees fails the common sense approach
to failure effects analysis.
I observe that common sense is inversely
proportional to the bureaucratization
of the institution. My last stint in
TC aviation offered me an inside observation
of the merger of Beech/Hawker/Cessna into
one big Textron operation. The very
FIRST field failure problem I was asked
to assist with had a STONE simple, two
week solution made possible by the merger
of the two inventories of qualified
products . . . a foaming at the mouth
field failure on one brand was easily
mittigated by replacement of a decades
old, field proven part from the other
brand. The last meeting I attended before
my consulting contract ran out left me
with a feeling of satisfaction of having
identified a short path to an elegant
solution.
To my dismay, nearly a year later I was
told that there were 'problems' with the
solution having nothing to do with form,
fit, function and everything to do with
differences of opinion from a parade of
bureaucrats with 'worries' and regulatory
barriers . . . I shudder to think of dozens
of customers with million dollar airplanes;
the foam around their mouths getting dried out,
crusty and flaking off. I don't know
they get an airplane built anymore.
Walter, Clyde, Olive Ann, Hedrick,
et. als. would be horrified to see what
we've done to their airplane companies.
My gut feeling is that Rotax is/has
become similarly afflicted with bureaucratic
worriers lacking foundation in physics
and practical experience. This is a
disease that is horribly taxing on one's
ability to offer good value with
un-impeachable confidence. In some instances
it is terminal.
In any case, I'm still unconvinced that the
dedication of a rather capable energy source
to the operation of a single, low energy
task for which a back-up already exists
is a solution seriously lacking elegance.
Bob . . .
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Subject: | Re: Poisonous Battery Vapors? |
Poor engineering, those Porsche guys...
CT
-----Mensagem original-----
De: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] Em nome de Eric M.
Jones
Enviada: Thursday, October 6, 2016 3:03 PM
Para: aeroelectric-list@matronics.com
Assunto: AeroElectric-List: Re: Poisonous Battery Vapors?
--> <emjones@charter.net>
I wondered if the battery was located in the passenger compartment so I
looked it up. https://www.youtube.com/watch?v=d6ZTeFT137Y#t=26.879952
Yes, and it takes three boys and a monkey to swap one. Amazing. When I saw
this I was glad I didn't own one. But I still doubt the Cause Of Death
pronouncement. Cars usually have enough ventilation to avoid the buildup of
noxious vapors. Aircrafts probably do even more.
Recently around here a guy died because he was drunk and sleeping in his
car, which went up to a zillion degrees in the sun. So I'd look for some COD
that is more plausible.
"Wisdom is being aware of the obvious."
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=461010#461010
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Subject: | Re: rotax generator without battery |
At 10:39 AM 10/6/2016, you wrote:
>Bob, the 914 engine is not fuel injected, but it is turbocharged and
>there is a fuel pressure regulator that maintains a constant fuel
>pressure over air pressure produced by the turbo.
Do you know what the pressure setting is?
Bob . . .
Message 12
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Subject: | Re: rotax generator without battery |
/Le 06/10/2016 22:42, Robert L. Nuckolls, III a crit ://
/
> /At 10:39 AM 10/6/2016, you wrote:
> /
>> /Bob, the 914 engine is not fuel injected, but it is turbocharged and
>> there is a fuel pressure regulator that maintains a constant fuel
>> pressure over air pressure produced by the turbo./
> /
> //// Do you know what the pressure setting is?//
> /
Airbox pressure + 0.25 bar (+- 0.10 bar)
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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Subject: | Re: rotax generator without battery |
Per this document
<http://www.rotax-owner.com/en/support-topmenu/technical-information/rotax-
technical-articles/17-understanding-the-rotax-914/file>
:
The fuel regulator is mounted on the airbox and plays a critical role in
maintaining fuel pressure to a minimum 0.15 BAR (2.18 PSI or 4.45=9D)
above
airbox boost pressure. The regulator is calibrated at the factory and
normally no adjustments are required. In the event that the fuel pressure
gets too low, due to a maladjustment or malfunction of the fuel regulator,
the engine would experience fuel starvation due to the higher airbox
pressure sensed in the carburetor float bowls not allowing the fuel supply
to enter. A high fuel pressure can result from regulator maladjustment,
malfunction or restriction in return line.
A properly adjusted fuel regulator will maintain fuel pressure above airbox
pressure within the following parameters:
Maximum fuel pressure is 0.35 BAR (5.08 PSI or 10.36=9D) above airbox
pressure
Minimum fuel pressure is 0.15 BAR (2.18 PSI or 4.45=9D) above airbox
pressure
Normal fuel pressure is 0.25 BAR (3.63 PSI or 7.41=9D) above airbox p
ressure
On Thu, Oct 6, 2016 at 12:42 PM, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 10:39 AM 10/6/2016, you wrote:
>
> Bob, the 914 engine is not fuel injected, but it is turbocharged and ther
e
> is a fuel pressure regulator that maintains a constant fuel pressure over
> air pressure produced by the turbo.
>
>
> Do you know what the pressure setting is?
>
>
> Bob . . .
>
Message 14
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Subject: | Re: rotax generator without battery |
I found this Pressure Switch
<https://www.summitracing.com/parts/crt-a68301> which
seems to be a viable way (combined with a relay) of automatically turning
off the auxiliary fuel pump when the engine stops turning.
On Thu, Oct 6, 2016 at 12:58 PM, GTH <gilles.thesee@free.fr> wrote:
> *Le 06/10/2016 =C3- 22:42, Robert L. Nuckolls, III a =C3=A9crit :*
>
>
> *At 10:39 AM 10/6/2016, you wrote: *
>
> *Bob, the 914 engine is not fuel injected, but it is turbocharged and
> there is a fuel pressure regulator that maintains a constant fuel pressur
e
> over air pressure produced by the turbo.*
>
>
> * Do you know what the pressure setting is?*
>
>
> Airbox pressure + 0.25 bar (+- 0.10 bar)
>
>
> --
> Best regards,
> Gilles
> http://contrails.free.fr
> http://lapierre.skunkworks.free.fr
>
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