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Operating Limits Seem Conflicting

The recommendation to shut off avionics during engine start is based on an
Old Wives Tale. Click on the link to see what Bob Nuckolls had to say about how that rumor got started. There is no voltage spike during engine start. There is a voltage drop or brownout that does not harm modern avionics. Although brownouts did harm avionics back in the 1960s.
 
The recommendation to shut off avionics during engine start is based on an
Old Wives Tale. Click on the link to see what Bob Nuckolls had to say about how that rumor got started. There is no voltage spike during engine start. There is a voltage drop or brownout that does not harm modern avionics. Although brownouts did harm avionics back in the 1960s.

Thanks for the history-onics Joe. One more old guy learned something today. So, why do RV-12 ELSA's have one?
 
Some people still believe in old wive's tales. :D

No, some people know from experience that other people will try and start the engine regardless of what the voltage says (which once you gain some Rotax knowledge you learn can lead to expensive repairs).

Leaving off everything that can be left off, until the engine is started helps assure the most cranking power possible.
 
Leaving off everything that can be left off, until the engine is started helps assure the most cranking power possible.
Seems like a tradeoff . . . oil pressure verification for more cranking power.
I question . . . just how much more cranking power does that really add up to?

With a Skyview already on, not only do we see oil pressure immediately . . but prior to actual crank, we can see the battery power available.
 
I usually turn on the skyview by holding the "1" button, let it boot up so I have instrumentation for oil P and voltage, turn on the master and ignitions for engine start. Once the RPM's are stable I switch on the avionics,autopilot etc.... I don't see any reason to put extra loads by having the radio, AP, and transponder on during the engine start. Even if it is "old practice".
 
A typical battery is about 25 amp-hours capacity. Cranking power is in the 100 amp range while avionics pull about 7 amps. Seems like the avionics load during a typical start is insignificant.
 
A typical battery is about 25 amp-hours capacity. Cranking power is in the 100 amp range while avionics pull about 7 amps. Seems like the avionics load during a typical start is insignificant.

Rich, Other than a obvious laboring, what indicates/reading shows the battery is about to give up the ghost, per your previous post yesterday? A dip during cranking?
 
No, some people know from experience that other people will try and start the engine regardless of what the voltage says (which once you gain some Rotax knowledge you learn can lead to expensive repairs).

Leaving off everything that can be left off, until the engine is started helps assure the most cranking power possible.

RVBuilder-

What kind of experience? I'd like to avoid expensive repairs? At least those known by others. Thanks!
 
You have to know the details........

Seems like a tradeoff . . . oil pressure verification for more cranking power.
I question . . . just how much more cranking power does that really add up to?

With a Skyview already on, not only do we see oil pressure immediately . . but prior to actual crank, we can see the battery power available.

On the D180 RV-12's, the EFIS was switched by the Avionics switch (which is why it was on during start).

On Skyview RV-12's, the the screen is not controlled by the Avionics switch so the switch can be off for start and still see all necessary engine info...
 
RVBuilder-

What kind of experience? I'd like to avoid expensive repairs? At least those known by others. Thanks!

Cranking the engine with low battery voltage (particularly with early engines that did not have soft start) is hard on the starter sprag clutch and can lead to early failure. It is expensive to repair because of the required engine removal and opening up of the back of the engine.
 
A typical battery is about 25 amp-hours capacity. Cranking power is in the 100 amp range while avionics pull about 7 amps. Seems like the avionics load during a typical start is insignificant.

AMP hour rating is only slightly connect to cranking amps rating.

The cold cranking amps available is directly connected to the actual voltage of a batter at any given moment and the published rating is with the battery fully charged.

With a low battery voltage on your car, it is entirely possible for head lights on or off to mean the difference between whether it will actually start or not.........
 
On the D180 RV-12's, the EFIS was switched by the Avionics switch (which is why it was on during start).

On Skyview RV-12's, the the screen is not controlled by the Avionics switch so the switch can be off for start and still see all necessary engine info...
Got it. Thanks.
 
exceptions, exceptions! Operating legally under sport pilot rules I have flown my RV 12 up to 14,000 feet. It was still climbing 400 fpm when I stopped.
 
Cranking the engine with low battery voltage (particularly with early engines that did not have soft start) is hard on the starter sprag clutch and can lead to early failure. It is expensive to repair because of the required engine removal and opening up of the back of the engine.

Would a 2010-11 ELSA engine have soft start? And what is considered minimum volts to crank?
 
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