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Dual G5 Questions


jlunseth

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Not sure where you are getting that the 275 is cheaper than a G5.  Its considerably more expensive.  To drive your current autopilot, you need a 275.  The backup battery issue is not really an issue, but if you want to make it one, that's ok.  A vacuum pump isn't going to give you 1 hr notice after the ships battery runs out.  Its just going to quit. 

If you want some upgrade with an attitude indicator backup, you could replace the HSI with a G5.  It will get rid of your gpss and give you a backup AI.  It has an option to switch from the HSI presentation to an attitude indicator.

Then, when you have a problem with the autopilot, you can get the second G5 and the GFC500.

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5 hours ago, jlunseth said:

I called Garmin. The original AI would have to be retained if dual G5's are added, which of course means the vacuum pump would stay, and that eliminates any incentive to put in two G5s as far as I am concerned. Back to the original plan.

Don't think that is correct.  Maybe they meant the T&B must be retained.  Looks like most people with dual G5's keep the airspeed and altimeter also.

I understand your need for backup that would run for hours.  Perhaps a standby alternator from B&C?  Not everyone needs that long lasting backup, just as not everyone needs a turbocharged airplane.  Sounds like you do.

Several months ago, I got a price of a little over $10k  from a nearby shop on installing dual G5's in my plane.  Same shop said dual 275 would be about $3k more.

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21 minutes ago, David Lloyd said:

Don't think that is correct.  Maybe they meant the T&B must be retained.  Looks like most people with dual G5's keep the airspeed and altimeter also.

I understand your need for backup that would run for hours.  Perhaps a standby alternator from B&C?  Not everyone needs that long lasting backup, just as not everyone needs a turbocharged airplane.  Sounds like you do.

Several months ago, I got a price of a little over $10k  from a nearby shop on installing dual G5's in my plane.  Same shop said dual 275 would be about $3k more.

I just had dual G5s installed and the original King AI is gone.  It did not need to be retained.  Still have ASI, altimeter, VSI, and TC.  My vacuum pump doesn't do anything now and will be removed at the next annual.

Edited by ZuluZulu
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15 hours ago, N231BN said:

He needs it to drive his King autopilot.

That’s correct. I need it to drive my King autopilot. There is no ability to add a standby alternator/generator in the 231 because of the way it is driven from the engine. If there were, I would have done it long before now. What Garmin told me about the G5 as an addition to my system confirms what my avionics shop has been saying, that the dual G5 does not provide the information to the AP that it expects fromm the King instruments. There is no point in adding a dual G5 installation if I must keep my King vacuum instruments, the slickest thing is just to add a 275 as a backup. 

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9 minutes ago, jlunseth said:

There is no ability to add a standby alternator/generator in the 231 because of the way it is driven from the engine. If there were, I would have done it long before now.

If you pull the vacuum pump you can add a standby alternator on that pad.  I don't know of an STC'd unit for a 231 but LASAR has gotten it field approved.

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I read the info on the B&C unit. There would be a number of questions, the most important being whether the unit can be driven in the 231. I see it is certified for Pipers and they have other backup units for Bonanzas, the Ovation/Acclaim, and the Cessna 210. You would think, if the unit would work on the 231 they would have an STC for it, but of course there are always reasons they would not invest in that even if they have one that would work. Also, the description says it senses current drop and then steps in. Current drop to a negative buss voltage is very common in the 231 because the drive does not keep the alternator moving fast enough at near idle speeds to put out enough current. We see it at least briefly virtually every time we taxi. I keep the engine speed up above 1100 rpms which avoids that. So the other question is whether that would trigger the second alternator to step in frequently and whether that would create problems. I see it is switched, maybe it could just be kept switched off unless the primary fails.

The output is only 20 amps, would have to check the load and see if that would be enough and what I would be able to run with it. The vacuum of course would go, so the second would have to be a viable backup (enough current to handle the load). 

I have talked to Lasar, they are checking to see if they can add a second, the drive system being the issue.

Thanks for the help.

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Twenty amps will run a lot of modern equipment. These alternators are capable of 40 amps, the regulator blinks a light at you if you exceed 20 amps. I would think it would be an additional bonus to the 231 to add some alternator capability at idle.

Give B&C sales a call as well, they can let you know if they have a copy of a 337 for a 231. I installed one on a 182RG(Lycoming) using a field approval from a 182P(Continental) and it was a piece of cake(other than COVID delays at the FAA).

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12 minutes ago, N231BN said:

Twenty amps will run a lot of modern equipment. These alternators are capable of 40 amps, the regulator blinks a light at you if you exceed 20 amps. I would think it would be an additional bonus to the 231 to add some alternator capability at idle.

Give B&C sales a call as well, they can let you know if they have a copy of a 337 for a 231. I installed one on a 182RG(Lycoming) using a field approval from a 182P(Continental) and it was a piece of cake(other than COVID delays at the FAA).

I agree it will run a lot of equipment. When I first got my aircraft I had incandescent landing light, strobes and nav lights. One night, doing night pattern work, I managed to stall the engine right near the FBO building. All my instructors had to come out and help push me in because the night pattern work (low alternator output, high light draw) had drained the battery and I could not re-start. Now I have all LED lights and the draw is next to nothing. It would be a help to the 231 to add some alternator at idle, I just don't know how that works and if there would be interference of some kind with two alternators charging on the circuit, I will find out. 

I will try B&C. Its the drive, and whether the drive is compatible with the drive for the removed vacuum pump. A significant problem, it seems to me, is whether the drive would be designed to protect the engine if the alternator freezes for some reason (that's what the coupler system does with the main alternator for the 231).

Thanks for the help. Useful ideas.

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Thank you very much. However, I still need to check that out. The punch line in that 337 for us 231 owners is in the third paragraph of part 8. The installation was on an MB engine. So that aircraft maybe was a 262? The serial number is a 231 number (in the 25- series and earlier than mine), but to my knowledge, other than some 262 conversions that can no longer be done (the STC holder is out of business), the MB engine cannot be put into a 231. The engine in the 231 is the significantly different GB or LB. The vacuum pump does come off of the back of the engine on the LB though, so just maybe....

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I talked to Lasar again, they are very friendly. The upshot of the first conversation was not great though. I was told that the 337 process has become complex, especially the changes to the flight manual, and it would not be cost effective for them to do the modification (put the B&C alternator on a 231 as a second). However, in the meantime the above 337 was posted and I sent that to the fellow at Lasar who signed it originally (Robert Brown). He is going to look at that and see if it would make the 337 process easier so it could be done. 

I was also told that B&C may be making an announcement. No idea when or what. They have STC’s for other aircraft, just not the 231....

More to follow...

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34 minutes ago, jlunseth said:

I was also told that B&C may be making an announcement. No idea when or what. They have STC’s for other aircraft, just not the 231....

 

I hope you are right but they have been telling me that at OSH and SnF each year for the last 6 or more years.  I really hope it is true this time.

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2 minutes ago, 201Mooniac said:

I hope you are right but they have been telling me that at OSH and SnF each year for the last 6 or more years.  I really hope it is true this time.

If Lasar decides they can do it then the problem goes away. Cross fingers. Would that maybe work for the J also?

I got the impression Lasar recognizes there is a demand for better electric backup in the older aircraft because of all the glass avionics that are now available.  The current 337 situation is a little daunting, according to them....

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31 minutes ago, jlunseth said:

If Lasar decides they can do it then the problem goes away. Cross fingers. Would that maybe work for the J also?

I got the impression Lasar recognizes there is a demand for better electric backup in the older aircraft because of all the glass avionics that are now available.  The current 337 situation is a little daunting, according to them....

I asked Top Gun to look into and they are checking with the FSDO it but if they can't do it I'll speak with Lasar.

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FWIW, a Peter from EuroGA did a 337 for installing this extra alternator on a TB20 not too long ago; granted that's a Lyco IO-540, not a Conti, but it can be done reasonably. I can look up the thread there if there is interest, but I'd think that the 337 posted above and a friendly FSDO get us Mooney folk well on our way to get this done.

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  • 6 months later...

I have dual G5s as my primary AI and HSI.  The old KI256 is in a secondary position and is retained 1) for backup, 2) to provide pitch and roll to the KFC200 autopilot.  The configuration works great.  In the event of an alternator failure, if I needed to ensure enough battery backup, I can turn one of the G5s off and navigate off of a single G5 (in PDF mode, it provides a course and heading indicator along the top and bottom of the display).  My question is, should I replace the KI256 with the GI275 which can provide attitude information to the KFC200, and then I could remove the vacuum pump.  I get tired of overhauling the old iron instrument every 8-10 years.

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Welcome aboard Pacman...

Many people have come across the same challenge...

The answers are as personal as can be...

Some like the pair of G5s with other support boxes...

Some are enjoying a pair of GI275s...

Others have selected widescreen TVs with a back-up GI275...

All have been tossing the old BK devices on the spare parts rack...

Nobody wants to retain the vac systems...

PP thoughts only, not an instrument guru...

Best regards,

-a-

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