AeroElectric-List Digest Archive

Thu 10/06/16


Total Messages Posted: 14



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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    Time: 03:05:18 AM PST US
    Subject: Re: rotax generator without battery
    From: "rampil" <ira.rampil@gmail.com>
    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


    Message 2


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    Time: 04:58:22 AM PST US
    Subject: Re: rotax generator without battery
    From: "user9253" <fransew@gmail.com>
    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


    Message 3


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    Time: 05:54:58 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    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 . . .


    Message 4


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    Time: 06:03:08 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    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 . . .


    Message 5


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    Time: 06:36:12 AM PST US
    Subject: Re: rotax generator without battery
    From: "user9253" <fransew@gmail.com>
    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


    Message 6


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    Time: 07:00:40 AM PST US
    Subject: Re: rotax generator without battery
    From: GTH <gilles.thesee@free.fr>
    /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


    Message 7


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    Time: 07:31:23 AM PST US
    Subject: Re: Poisonous Battery Vapors?
    From: "Eric M. Jones" <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


    Message 8


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    Time: 08:42:09 AM PST US
    From: Ken Ryan <keninalaska@gmail.com>
    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 >


    Message 9


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    Time: 08:56:41 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    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 . . .


    Message 10


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    Time: 09:42:50 AM PST US
    From: "Carlos Trigo" <trigo@mail.telepac.pt>
    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


    Message 11


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    Time: 01:46:11 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    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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    Time: 02:00:09 PM PST US
    Subject: Re: rotax generator without battery
    From: GTH <gilles.thesee@free.fr>
    /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


    Message 13


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    Time: 02:01:44 PM PST US
    From: Ken Ryan <keninalaska@gmail.com>
    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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    Time: 05:13:50 PM PST US
    From: Ken Ryan <keninalaska@gmail.com>
    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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