Regulator/Rectifier

by Robert J. Dean in 912 / 914 Technical Questions 7 years ago

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Re: Regulator/Rectifier

by James Ott » 7 years ago

James Ott

22 321 357

I would seriously question the advice of Mr. Miller because the Rotax 912 installation manual section 24-00-00 page 19 clearly shows all 3 R, B+, and C terminals tied together before going into the fuse/breaker. Why would the factory recommend this and thousands of us have followed it if it was so bad?

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Re: Regulator/Rectifier

by Adora Kalb » 6 years ago

Adora Kalb

0 1 0

Hi...i am a new user here. As per my knowledge If the voltage to this pin is above three volts there is enough power to turn ON the regulator, once the pin voltage exceeds 14 volts the output is turned OFF.On the RV12, the C pin is connected to the main BUS through the second pole of the master switch.
The typical failure mode for a Rotax regulator is reduced output, or no output, so your regulator is likely good.

percent calculator

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Re: Regulator/Rectifier

by Mike Miller » 6 years ago

Mike Miller

0 41 99

I would seriously question the advice of Mr. Miller because the Rotax 912 installation manual section 24-00-00 page 19 clearly shows all 3 R, B+, and C terminals tied together before going into the fuse/breaker. Why would the factory recommend this and thousands of us have followed it if it was so bad?

Mr. Ott, I’m sorry for the late reply, I missed your comment. Can you find any fault(s) in my statements above? or below? Because Rotax says so is a poor argument in light of the facts. You can wire your aircraft anyway you like, but you should be aware of the consequences. I welcome your peer review.

The Ducati regulator wired according to Rotax’s suggested/mandated wiring will put that aircraft out of compliance with the LSA consensus standards.

To recap, if you wire your aircraft according to Rotax, once the engine is running, the power provided from the alternator will self-excite the regulator. The system will continue to produce power even after the battery has been disconnected. The bus will remain powered, until the engine stops turning. you do NOT have a master switch, you have a “alternator trigger“/“battery disconnect” switch.

Look closely at the disclaimers in the Rotax documentation. Rotax will argue that they make engines and it’s up to the aircraft manufacturer/builder to comply with the regulations.

Please review the following reference documents.

LSA Consensus Standards, From ASTM 2245

8 ) required equipment
8.4.1 ) If installed, an electrical system shall include a master switch and overload protection devices (fuses or circuit breakers.)

The function of a master switch from part 23 (yes I know we are not part 23, but this is the definition the FAA/NTSB will use as a default in the accident report after the inflight fire of an electrical system on a 912ULS that could not of be shutdown.)

§ 23.1361 Master switch arrangement.
(a) There must be a master switch arrangement to allow ready disconnection of each electric power source from power distribution systems, except as provided in paragraph (b) of this section. The point of disconnection must be adjacent to the sources controlled by the switch arrangement. If separate switches are incorporated into the master switch arrangement, a means must be provided for the switch arrangement to be operated by one hand with a single movement.
(b) Load circuits may be connected so that they remain energized when the master switch is open, if the circuits are isolated, or physically shielded, to prevent their igniting flammable fluids or vapors that might be liberated by the leakage or rupture of any flammable fluid system; and
(1) The circuits are required for continued operation of the engine; or
(2) The circuits are protected by circuit protective devices with a rating of five amperes or less adjacent to the electric power source.
(3) In addition, two or more circuits installed in accordance with the requirements of paragraph (b)(2) of this section must not be used to supply a load of more than five amperes.
(c) The master switch or its controls must be so installed that the switch is easily discernible and accessible to a crewmember.

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Re: Regulator/Rectifier

by James Ott » 6 years ago

James Ott

22 321 357

I am certainly not an electrical guru and would never claim to be, so I don't have the qualifications to either verify or dispute what Mr. Miller has said. However, I am smart enough to NEVER trust one opinion from someone I do not know, especially on the "internet". Also I am more inclined to trust the instructions from the engine manufacturer, based on thousands of successful installations. What I would really like to see is a response from Rotax administration regarding Mr. Miller's comment; also from other knowledgeable persons.

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Re: Regulator/Rectifier

by Mike Miller » 6 years ago

Mike Miller

0 41 99

Why trust anyone but yourself, here is a simple test.

If your engine is wired with the C pin jumped to the +B and R pin, next time you do a runup turn “OFF” your master switch. Does your panel go dark? If it doesn’t go dark are you comfortable with that?

When you open the master expect voltage fluxuations.

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Regulator/Rectifier

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